@article {7568, title = {The GEBCO_2023 Grid - A Continuous Terrain Model of the Global Oceans and Land}, year = {2023}, month = {April 18}, publisher = {NERC EDS British Oceanographic Data Centre NOC}, abstract = {
The GEBCO_2023 Grid is a global continuous terrain model for ocean and land with a spatial resolution of 15 arc seconds. In regions outside of the Arctic Ocean area, the grid uses as a base Version 2.5.5 of the SRTM15_plus data set (Tozer, B. et al, 2019). This data set is a fusion of land topography with measured and estimated seafloor topography. Included on top of this base grid are gridded bathymetric data sets developed by the four Regional Centers of The Nippon Foundation-GEBCO Seabed 2030 Project. The GEBCO_2023 Grid represents all data within the 2023 compilation. The compilation of the GEBCO_2023 Grid was carried out at the Seabed 2030 Global Center, hosted at the National Oceanography Centre, UK, with the aim of producing a seamless global terrain model. Outside of Polar regions, the Regional Centers provide their data sets as sparse grids i.e. only grid cells that contain data are populated. These data sets were included on to the base using a \&$\#$39;remove-restore\&$\#$39; blending procedure. This is a two-stage process of computing the difference between the new data and the base grid and then gridding the difference and adding the difference back to the existing base grid. The aim is to achieve a smooth transition between the new and base data sets with the minimum of perturbation of the existing base data set. The data sets supplied in the form of complete grids (primarily areas north of 60N and south of 50S) were included using feather blending techniques from GlobalMapper software. The GEBCO_2023 Grid has been developed through the Nippon Foundation-GEBCO Seabed 2030 Project. This is a collaborative project between the Nippon Foundation of Japan and the General Bathymetric Chart of the Oceans (GEBCO). It aims to bring together all available bathymetric data to produce the definitive map of the world ocean floor by 2030 and make it available to all. Funded by the Nippon Foundation, the four Seabed 2030 Regional Centers include the Southern Ocean - hosted at the Alfred Wegener Institute, Germany; South and West Pacific Ocean - hosted at the National Institute of Water and Atmospheric Research, New Zealand; Atlantic and Indian Oceans - hosted at the Lamont-Doherty Earth Observatory, Columbia University, USA; Arctic and North Pacific Oceans - hosted at Stockholm University, Sweden and the Center for Coastal and Ocean Mapping at the University of New Hampshire, USA.
\
}, keywords = {elevation, Oceans}, doi = {doi:10.5285/f98b053b-0cbc-6c23-e053-6c86abc0af7b}, url = {https://www.gebco.net/data_and_products/gridded_bathymetry_data/gebco_2023/}, author = {Pauline Weatherall and Michael Bogonko and Caroline Bringensparr and Sheila C{\'a}ceres Ferreras and Sara Cardigos and Boris Dorschel and Hayley Drennon and Simon Dreutter and Vicki L Ferrini and Laura Hehemann and Martin Jakobsson and Paul Johnson and Marcus Karlsson and Juliet Kinney and Kevin Mackay and Sarah M Maher and Tinah V Martin and Larry A Mayer and Jamie McMichael-Phillips and Rezwan Mohammad and Frank O Nitsche and Jaya Roperez and Silvia Salas-Romero and David T Sandwell and Yvonne Schulze Tenberge and Patrick Schwarzbach and Helen Snaith and Sacha Viquerat and GEBCO Bathymetric Compilation Group 2023 and Fynn Warnke} } @article {7541, title = {Mapping Northern Greenland Waters}, volume = {4}, year = {2023}, month = {November 3}, abstract = {An understanding of the interplay between glaciers and the ocean is needed to improve sea-level rise projections. Seafloor mapping is critical in this pursuit, particularly where the ice sheets of Greenland and Antarctica meet the ocean. Northern Greenland\’s marine realm remains one of Earth\’s least explored areas, with completely uncharted fjords. In 2019, one of these fjords was mapped by the Swedish icebreaker Oden, with the next unmapped fjord to the east the target for 2024.
}, url = {https://www.hydro-international.com/content/article/mapping-northern-greenland-waters}, author = {Martin Jakobsson and Larry A Mayer} } @article {7550, title = {Mapping Northern Greenland Waters: A Blank Spot on Nautical Charts in Ice-Infested Waters}, volume = {27,3}, year = {2023}, month = {November 3}, pages = {17-21}, url = {https://www.hydro-international.com/content/article/mapping-northern-greenland-waters}, author = {Martin Jakobsson and Larry A Mayer} } @article {7368, title = {The GEBCO 2022 Grid - A Continuous Terrain Model of the Global Oceans and Land}, year = {2022}, month = {June 22}, publisher = { NERC EDS British Oceanographic Data Centre NOC}, abstract = {The GEBCO_2022 Grid is a global continuous terrain model for ocean and land with a spatial resolution of 15 arc seconds. In regions outside of the Arctic Ocean area, the grid uses as a base Version 2.4 of the SRTM15_plus data set (Tozer, B. et al, 2019). This data set is a fusion of land topography with measured and estimated seafloor topography. Included on top of this base grid are gridded bathymetric data sets developed by the four Regional Centers of The Nippon Foundation-GEBCO Seabed 2030 Project. The GEBCO_2022 Grid represents all data within the 2022 compilation. The compilation of the GEBCO_2022 Grid was carried out at the Seabed 2030 Global Center, hosted at the National Oceanography Centre, UK, with the aim of producing a seamless global terrain model. Outside of Polar regions, the Regional Centers provide their data sets as sparse grids i.e. only grid cells that contain data are populated. These data sets were included on to the base using a remove-restore blending procedure. This is a two-stage process of computing the difference between the new data and the base grid and then gridding the difference and adding the difference back to the existing base grid. The aim is to achieve a smooth transition between the new and base data sets with the minimum of perturbation of the existing base data set. The data sets supplied in the form of complete grids (primarily areas north of 60N and south of 50S) were included using feather blending techniques from GlobalMapper software. The GEBCO_2022 Grid has been developed through the Nippon Foundation-GEBCO Seabed 2030 Project. This is a collaborative project between the Nippon Foundation of Japan and the General Bathymetric Chart of the Oceans (GEBCO). It aims to bring together all available bathymetric data to produce the definitive map of the world ocean floor by 2030 and make it available to all. Funded by the Nippon Foundation, the four Seabed 2030 Regional Centers include the Southern Ocean - hosted at the Alfred Wegener Institute, Germany; South and West Pacific Ocean - hosted at the National Institute of Water and Atmospheric Research, New Zealand; Atlantic and Indian Oceans - hosted at the Lamont-Doherty Earth Observatory, Columbia University, USA; Arctic and North Pacific Oceans - hosted at Stockholm University, Sweden and the Center for Coastal and Ocean Mapping at the University of New Hampshire, USA.
}, keywords = {bathymetric grid, ocean map, terrain model}, url = {https://www.bodc.ac.uk/data/published_data_library/catalogue/10.5285/e0f0bb80-ab44-2739-e053-6c86abc0289c/}, author = {Pauline Weatherall and Caroline Bringensparr and Castro, C.F. and Dorschel, B. and Drennon, H. and Vicki L Ferrini and Harper, H.A. and Laura Hehemann and Martin Jakobsson and Paul Johnson and Juliet Kinney and Mackay, K. and Maher, S.M. and Martin, T.V. and Larry A Mayer and McMichael-Phillips, J. and Mohammad, R. and Nitsche, F.O. and Jaya Roperez and David T Sandwell and Helen Snaith and Tozer, B. and Sacha Viquerat and Fynn Warnke and Yu, Y.} } @article {7270, title = {The International Bathymetric Chart of the Southern Ocean Version 2}, volume = {9(1)}, year = {2022}, month = {June 7}, publisher = {Springer Nature}, abstract = {The Southern Ocean surrounding Antarctica is a region that is key to a range of climatic and oceanographic processes with worldwide effects, and is characterised by high biological productivity and biodiversity. Since 2013, the International Bathymetric Chart of the Southern Ocean (IBCSO) has represented the most comprehensive compilation of bathymetry for the Southern Ocean south of 60\°S. Recently, the IBCSO Project has combined its efforts with the Nippon Foundation \– GEBCO Seabed 2030 Project supporting the goal of mapping the world\’s oceans by 2030. New datasets initiated a second version of IBCSO (IBCSO v2). This version extends to 50\°S (covering approximately 2.4 times the area of seafloor of the previous version) including the gateways of the Antarctic Circumpolar Current and the Antarctic circumpolar frontal systems. Due to increased (multibeam) data coverage, IBCSO v2 significantly improves the overall representation of the Southern Ocean seafloor and resolves many submarine landforms in more detail. This makes IBCSO v2 the most authoritative seafloor map of the area south of 50\°S.
}, doi = {10.1038/s41597-022-01366-7}, author = {Martin Jakobsson and Larry A Mayer and al et} } @article {7298, title = {The International Bathymetric Chart of the Southern Ocean Version 2}, volume = {9, 275}, year = {2022}, month = {June 7}, abstract = {The Southern Ocean surrounding Antarctica is a region that is key to a range of climatic and oceanographic processes with worldwide effects, and is characterised by high biological productivity and biodiversity. Since 2013, the International Bathymetric Chart of the Southern Ocean (IBCSO) has represented the most comprehensive compilation of bathymetry for the Southern Ocean south of 60\°S. Recently, the IBCSO Project has combined its efforts with the Nippon Foundation \– GEBCO Seabed 2030 Project supporting the goal of mapping the world\’s oceans by 2030. New datasets initiated a second version of IBCSO (IBCSO v2). This version extends to 50\°S (covering approximately 2.4 times the area of seafloor of the previous version) including the gateways of the Antarctic Circumpolar Current and the Antarctic circumpolar frontal systems. Due to increased (multibeam) data coverage, IBCSO v2 significantly improves the overall representation of the Southern Ocean seafloor and resolves many submarine landforms in more detail. This makes IBCSO v2 the most authoritative seafloor map of the area south of 50\°S.
}, doi = {https://doi.org/10.1038/s41597-022-01366-7}, author = {Dorschel, B. and Laura Hehemann and Sacha Viquerat and Fynn Warnke and Simon Dreutter and Yvonne Schulze Tenberge and Accettella, D. and Lu An and Barrios, Felipe R and Evgenia Bazhenova and Jenny Black and Fernando Bohoyo and Craig Davey and Laura De Santis and Jennifer Jencks and Hogan, Kelly and Martin Jakobsson and Larry A Mayer and Ivan Ryzhov and al. et} } @article {7374, title = {Polar Region Bathymetry: Critical Knowledge for the Prediction of Global Sea Level Rise}, year = {2022}, month = {January 17}, abstract = {The ocean and the marine parts of the cryosphere interact directly with, and are affected by, the seafloor and its primary properties of depth (bathymetry) and shape (morphology) in many ways. Bottom currents are largely constrained by undersea terrain with consequences for both regional and global heat transport. Deep ocean mixing is controlled by seafloor roughness, and the bathymetry directly influences where marine outlet glaciers are susceptible to the inflow relatively warm subsurface waters - an issue of great importance for ice-sheet discharge, i.e., the loss of mass from calving and undersea melting. Mass loss from glaciers and the Greenland and Antarctic ice sheets, is among the primary drivers of global sea-level rise, together now contributing more to sea-level rise than the thermal expansion of the ocean. Recent research suggests that the upper bounds of predicted sea-level rise by the year 2100 under the scenarios presented in IPCC\’s Special Report on the Ocean and Cryosphere in a Changing Climate (SROCCC) likely are conservative because of the many unknowns regarding ice dynamics. In this paper we highlight the poorly mapped seafloor in the Polar regions as a critical knowledge gap that needs to be filled to move marine cryosphere science forward and produce improved understanding of the factors impacting ice-discharge and, with that, improved predictions of, among other things, global sea-level. We analyze the bathymetric data coverage in the Arctic Ocean specifically and use the results to discuss challenges that must be overcome to map the most remotely located areas in the Polar regions in general.
}, doi = {https://doi.org/10.3389/fmars.2021.788724}, author = {Martin Jakobsson and Larry A Mayer} } @article {7219, title = {Amplified Climate Sensitivity of Northern Greenland Fjords through Sea-Ice Damming}, volume = {2(70)}, year = {2021}, month = {April 12}, abstract = {Record-high air temperatures were observed over Greenland in the summer of 2019 and melting of the northern Greenland Ice Sheet was particularly extensive. Here we show, through direct measurements, that near surface ocean temperatures in Sherard Osborn Fjord, northern Greenland, reached 4\ \°C in August 2019, while in the neighboring Petermann Fjord, they never exceeded 0\ \°C. We show that this disparity in temperature between the two fjords occurred because thick multi-year sea ice at the entrance of Sherard Osborn Fjord trapped the surface waters inside the fjord, which led to the formation of a warm and fresh surface layer. These results suggest that the presence of multi-year sea ice increases the sensitivity of Greenland fjords abutting the Arctic Ocean to climate warming, with potential consequences for the long-term stability of the northern sector of the Greenland Ice Sheet.
}, doi = {https://doi.org/10.1038/s43247-021-00140-8}, author = {Christian Stranne and Johan Nilsson and Adam Ulfsbo and Matt O{\textquoteright}Regan and Helen K. Coxall and Lorenz Merie and Julia Muchowski and Larry A Mayer and Volker Br{\"u}chert and Jonas Fredriksson and Brett Thornton and Julek Chawarski and Gabriel West and Elizabeth Weidner and Martin Jakobsson} } @article {7014, title = {A Deep Scattering Layer Under the North Pole Pack Ice}, volume = {194}, year = {2021}, month = {June}, abstract = {The 3.3 million km\² marine ecosystem around the North Pole, defined as the Central Arctic Ocean (CAO), is a blind spot on the map of the world\’s fish stocks. The CAO essentially comprises the permanently ice-covered deep basins and ridges outside the continental shelves, and is only accessible by ice-breakers. Traditional trawling for assessing fish stocks is impossible under the thick pack ice, and coherent hydroacoustic surveys are unachievable due to ice-breaking noise. Consequently, nothing is known about the existence of any pelagic fish stocks in the CAO, although juveniles of Boreogadus saida richly occur at the surface associated with the sea ice and ice-associated Arctogadus glacialis has been reported as well. We here present a first indication of a possible mesopelagic fish stock in the CAO. We had the opportunity to analyse a geophysical hydroacoustic data set with 13 time windows of usable acoustic data over a transect from 84.4 oN in the Nansen Basin, across the North Pole (90.0 oN), to 82.4 oN in the Canada Basin. We discovered a deep scattering layer (DSL), suggesting the presence of zooplankton and fish, at 300-600 m of depth in the Atlantic water layer of the CAO. Maximum possible fish abundance and biomass was very low; values of ca. 2,000 individuals km$^{-}$\² and ca. 50 kg km$^{-}$\² were calculated for the DSL in the North-Pole area according to a model assuming that all acoustic backscatter represents 15-cm long B. saida and/or A. glacialis. The true abundance and biomass of fish is even lower than this, but cannot be quantified from this dataset due to backscatter originating from pneumatophores of physonect siphonophores that are known to occur in the area. Further studies on the DSL of the CAO should include sampling and identification of the backscattering organisms. From our study we can conclude that if the DSL of the CAO contains fish, their biomass is currently too low for any sustainable fishery.
}, keywords = {acoustics, Arctogadus, Atlantic water layer, Boreogadus, Central Arctic Ocean (CAO), Echosounder, Siphonophore}, doi = {https://doi.org/10.1016/j.pocean.2021.102560}, author = {Snoejis-Leijonmalm, Pauline and Harald Gj{\o}s{\ae}ter and Randi B. Ingvaldsen and Tor Knutsen and Rolf Korneliussen and Egil Ona and Hein Rune Skjoldal and Christian Stranne and Larry A Mayer and Martin Jakobsson and Katarina G{\r a}rdfeldt} } @article {7021, title = {The Holocene Dynamics of Ryder Glacier and Ice Tongue in North Greenland}, volume = {15(8)}, year = {2021}, month = {August 24}, pages = {4073-4097}, publisher = {European Geosciences Union}, abstract = {The northern sector of the Greenland ice sheet is considered to be particularly susceptible to ice mass loss arising from increased glacier discharge in the coming decades. However, the past extent and dynamics of outlet glaciers in this region, and hence their vulnerability to climate change, are poorly documented. In the summer of 2019, the Swedish icebreaker Oden entered the previously unchartered waters of Sherard Osborn Fjord, where Ryder Glacier drains approximately 2 \% of Greenland\&$\#$39;s ice sheet into the Lincoln Sea. Here we reconstruct the Holocene dynamics of Ryder Glacier and its ice tongue by combining radiocarbon dating with sedimentary facies analyses along a 45 km transect of marine sediment cores collected between the modern ice tongue margin and the mouth of the fjord. The results illustrate that Ryder Glacier retreated from a grounded position at the fjord mouth during the Early Holocene (\>10.7 \± 0.4 cal ka BP) and receded more than 120 km to the end of Sherard Osborn Fjord by the Middle Holocene (6.3 \± 0.3 cal ka BP), likely becoming completely land-based. A re-advance of Ryder Glacier occurred in the Late Holocene, becoming marine-based around 3.9 \± 0.4 cal ka BP. An ice tongue, similar in extent to its current position was established in the Late Holocene (between 3.6 \± 0.4 and 2.9 \± 0.4 cal ka BP) and extended to its maximum historical position near the fjord mouth around 0.9 \± 0.3 cal ka BP. Laminated, clast-poor sediments were deposited during the entire retreat and regrowth phases, suggesting the persistence of an ice tongue that only collapsed when the glacier retreated behind a prominent topographic high at the landward end of the fjord. Sherard Osborn Fjord narrows inland, is constrained by steep-sided cliffs, contains a number of bathymetric pinning points that also shield the modern ice tongue and grounding zone from warm Atlantic waters, and has a shallowing inland sub-ice topography. These features are conducive to glacier stability and can explain the persistence of Ryder\’s ice tongue while the glacier remained marine-based. However, the physiography of the fjord did not halt the dramatic retreat of Ryder Glacier under the relatively mild changes in climate forcing during the Holocene. Presently, Ryder Glacier is grounded more than 40 km seaward of its inferred position during the Middle Holocene, highlighting the potential for substantial retreat in response to ongoing climate change.
}, doi = {https://doi.org/10.5194/tc-15-4073-2021}, author = {Matt O{\textquoteright}Regan and Thomas M. Cronin and Brendan Reilly and Aage Kristian Olsen Alstrup and Laura Gemery and Anna Golub and Larry A Mayer and Morlighem, M. and Moros, Matthias and Ole Lajord Munk and Johan Nilsson and Pearce, Christof and Detlef, Henrieka and Christian Stranne and Vermassen, Flor and Gabriel West and Martin Jakobsson} } @article {6742, title = {Glacial Sedimentation, Fluxes and Erosion Rates Associated with Ice Retreat in Petermann Fjord and Nares Strait, North-West Greenland}, volume = {14}, year = {2020}, month = {January 28}, pages = {261-286}, publisher = {Copernicus Publications}, abstract = {Petermann Fjord is a deep (\>1000\ m) fjord that incises the coastline of north-west Greenland and was carved by an expanded Petermann Glacier, one of the six largest outlet glaciers draining the modern Greenland Ice Sheet (GrIS). Between 5 and 70\ m of unconsolidated glacigenic material infills in the fjord and adjacent Nares Strait, deposited as the Petermann and Nares Strait ice streams retreated through the area after the Last Glacial Maximum. We have investigated the deglacial deposits using seismic stratigraphic techniques and have correlated our results with high-resolution bathymetric data and core lithofacies. We identify six seismo-acoustic facies in more than 3500 line kilometres of sub-bottom and seismic-reflection profiles throughout the fjord, Hall Basin and Kennedy Channel. Seismo-acoustic facies relate to bedrock or till surfaces (Facies I), subglacial deposition (Facies II), deposition from meltwater plumes and icebergs in quiescent glacimarine conditions (Facies III, IV), deposition at grounded ice margins during stillstands in retreat (grounding-zone wedges; Facies V) and the redeposition of material downslope (Facies IV). These sediment units represent the total volume of glacial sediment delivered to the mapped marine environment during retreat. We calculate a glacial sediment flux for the former Petermann ice stream as 1080\–1420\ m3\ a\−1 per metre of ice stream width and an average deglacial erosion rate for the basin of 0.29\–0.34\ mm\ a\−1. Our deglacial erosion rates are consistent with results from Antarctic Peninsula fjord systems but are several times lower than values for other modern GrIS catchments. This difference is attributed to fact that large volumes of surface water do not access the bed in the Petermann system, and we conclude that glacial erosion is limited to areas overridden by streaming ice in this large outlet glacier setting. Erosion rates are also presented for two phases of ice retreat and confirm that there is significant variation in rates over a glacial\–deglacial transition. Our new glacial sediment fluxes and erosion rates show that the Petermann ice stream was approximately as efficient as the palaeo-Jakobshavn Isbr\æ at eroding, transporting and delivering sediment to its margin during early deglaciation.
}, doi = {doi.org/10.5194/tc-14-261-2020}, author = {Hogan, Kelly and Martin Jakobsson and Larry A Mayer and Brendan Reilly and Jennings, A. and Stoner, J S and Nielsen, T. and Katrine J. Andresen and Kamla, E. and Kevin Jerram and Christian Stranne and Alan Mix} } @article {6947, title = {A Global Geographic Grid System for Visualizing Bathymetry}, volume = {9(2)}, year = {2020}, month = {October 7}, pages = {375-384}, publisher = {European Geosciences Union}, abstract = {A global geographic grid system (Global GGS) is here introduced to support the display of gridded bathymetric data at whatever resolution is available in a visually seamless manner. The Global GGS combines a quadtree metagrid hierarchy with a system of compatible data grids. Metagrid nodes define the boundaries of data grids. Data grids are regular grids of depth values, coarse grids are used to represent sparse data and finer grids are used to represent high-resolution data. Both metagrids and data grids are defined in geographic coordinates to allow broad compatibility with the widest range of geospatial software packages. An important goal of the Global GGS is to support the meshing of adjacent tiles with different resolutions so as to create a seamless surface. This is accomplished by ensuring that abutting data grids either match exactly with respect to their grid-cell size or only differ by powers of 2. The oversampling of geographic data grids, which occurs towards the poles due to the convergence of meridians, is addressed by reducing the number of columns (longitude sampling) by powers of 2 at appropriate lines of latitude. In addition to the specification of the Global GGS, this paper describes a proof-of-concept implementation and some possible variants.
}, doi = {10.5194/gi-9-375-2020}, url = {https://gi.copernicus.org/articles/9/375/2020/}, author = {Colin Ware and Larry A Mayer and Paul Johnson and Martin Jakobsson and Vicki L Ferrini} } @article {6867, title = {The International Bathymetric Chart of the Arctic Ocean Version 4.0}, volume = {176(2020)}, year = {2020}, month = {June 9}, abstract = {Bathymetry (seafloor depth), is a critical parameter providing the geospatial context for a multitude of marine scientific studies. Since 1997, the International Bathymetric Chart of the Arctic Ocean (IBCAO) has been the authoritative source of bathymetry for the Arctic Ocean. IBCAO has merged its efforts with the Nippon Foundation-GEBCO-Seabed 2030 Project, with the goal of mapping all of the oceans by 2030. Here we present the latest version (IBCAO Ver. 4.0), with more than twice the resolution (200 \× 200\ m versus 500 \× 500\ m) and with individual depth soundings constraining three times more area of the Arctic Ocean (\∼19.8\% versus 6.7\%), than the previous IBCAO Ver. 3.0 released in 2012. Modern multibeam bathymetry comprises \∼14.3\% in Ver. 4.0 compared to \∼5.4\% in Ver. 3.0. Thus, the new IBCAO Ver. 4.0 has substantially more seafloor morphological information that offers new insights into a range of submarine features and processes; for example, the improved portrayal of Greenland fjords better serves predictive modelling of the fate of the Greenland Ice Sheet.
}, doi = {https://doi.org/10.6084/m9.figshare.12369314}, author = {Martin Jakobsson and Larry A Mayer and Caroline Bringensparr} } @article {6791, title = {Links Between Baltic Sea Submarine Terraces and Groundwater Sapping}, volume = {8}, year = {2020}, month = {January 3}, pages = {1-15}, abstract = {Submarine Groundwater Discharge (SGD) influences ocean chemistry, circulation, spreading of nutrients and pollutants, and shapes seafloor morphology. In the Baltic Sea, SGD was linked to the development of terraces and semi-circular depressions mapped in an area of the southern Stockholm Archipelago, Sweden, in the 1990s. We mapped additional parts of the Stockholm Archipelago, areas in Blekinge, southern Sweden, and southern Finland using high-resolution multibeam sonars and sub-bottom profilers to investigate if the seafloor morphological features discovered in the 1990s are widespread and to further address the hypothesis linking SGD to their formation. Sediment coring and seafloor photography conducted with a Remote Operated Vehicle (ROV) and divers add additional information to the geophysical mapping results. We find that terraces, with general bathymetric expressions of about 1 m and lateral extents of sometimes \> 100 m, are widespread in the surveyed areas of the Baltic Sea and are consistently formed in glacial clay. Semi-circular depressions, however, are only found in a limited part of a surveyed area east of the island Ask\ö, southern Stockholm Archipelago. Our study supports the basic hypothesis of terrace formation initially proposed in the 1990s, i.e. groundwater flows through siltier permeable layers in glacial clay to discharge at the seafloor, leading to the formation of a sharp terrace when the clay layers above seepage zones are undermined enough to collapse. By linking the terraces to a specific geologic setting, our study further refines the formation hypothesis and forms the foundation for a future assessment of SGD in the Baltic Sea that may use marine geological mapping as a starting point. We propose that SGD through the sub-marine seafloor terraces is most likely intermittent and linked to periods of higher groundwater levels, implying that to quantify the contribution of freshwater to the Baltic Sea through this mechanism, more complex hydrogeological studies are required.
}, doi = {10.5194/esurf-2019-40}, author = {Martin Jakobsson and Matt O{\textquoteright}Regan and Carl-Magnus M{\"o}rth and Christian Stranne and Elizabeth Weidner and Jim Hansson and Richard Gyllencreutz and Christoph Humborg and Tina Elfwing and Alf Norkko and Joanna Norkko and Bj{\"o}rn Nilsson and Arne Sj{\"o}str{\"o}m} } @article {6937, title = {Ryder Glacier in Northwest Greenland is Shielded from Warm Atlantic Water by a Bathymetric Sill}, volume = {45}, year = {2020}, month = {November 4}, publisher = {Springer Nature}, abstract = {The processes controlling advance and retreat of outlet glaciers in fjords draining the Greenland Ice Sheet remain poorly known, undermining assessments of their dynamics and associated sea-level rise in a warming climate. Mass loss of the Greenland Ice Sheet has increased six-fold over the last four decades, with discharge and melt from outlet glaciers comprising key components of this loss. Here we acquired oceanographic data and multibeam bathymetry in the previously uncharted Sherard Osborn Fjord in northwest Greenland where Ryder Glacier drains into the Arctic Ocean. Our data show that warmer subsurface water of Atlantic origin enters the fjord, but Ryder Glacier\’s floating tongue at its present location is partly protected from the inflow by a bathymetric sill located in the innermost fjord. This reduces under-ice melting of the glacier, providing insight into Ryder Glacier\’s dynamics and its vulnerability to inflow of Atlantic warmer water.
}, doi = {https://doi.org/10.1038/s43247-020-00043-0}, author = {Martin Jakobsson and Larry A Mayer and Johan Nilsson and Christian Stranne}, editor = {Brian R Calder and Matt O{\textquoteright}Regan and John Farell and Thomas M. Cronin and Volker Br{\"u}chert and Julek Chawarski and Bjorn Eriksson and Jonas Fredriksson and Laura Gemery and Anna Glueder and Felicity A. Holmes and Kevin Jerram and Nina Kirchner and Alan Mix and Julia Muchowski and Abhay Prakash and Brendan Reilly and Brett Thornton and Adam Ulfsbo and Elizabeth Weidner and Henning {\r A}kesson and Tamara Handl and Emelie St{\r a}hl and Lee-Gray Boze and Samuel Reed and Gabriel West and June Padman} } @article {6933, title = {Tracking the Spatiotemporal Variability of the Oxic{\textendash}Anoxic Interface in the Baltic Sea with Broadband Acoustics}, year = {2020}, month = {03 November 2020}, abstract = {Anoxic zones, regions of the water column completely devoid of dissolved oxygen, occur in open oceans and coastal zones worldwide. The Baltic Sea is characterized by strong salinity-driven stratification, maintained by occasional water inflows from the Danish Straights and freshwater input from rivers. Between inflow events, the stratification interface between surface and deep waters hinders mixing and ventilation of deep water; consequently, the bottom waters of large regions of the Baltic are anoxic. The onset of the anoxic zone is closely coincident with the depth of the halocline and, as a result, the interface between oxic and anoxic waters corresponds to a strong impedance contrast. Here, we track acoustic scattering from the impedance contrast utilizing a broadband split-beam echosounder in the Western Gotland Basin and link it to a dissolved oxygen level of 2 ml/l using ground truth stations. The broadband acoustic dataset provides the means to remotely observe the spatiotemporal variations in the oxic\–anoxic interface, map out the extent of the anoxic zone with high resolution, and identify several mechanisms influencing the vertical distribution of oxygen in the water column. The method described here can be used to study other systems with applications in ongoing oceanographic monitoring programs.
}, keywords = {anoxia, Baltic Sea, Broadband acoustics, climate change, coastal, hypoxia, stratification}, doi = {10.1093/icesjms/fsaa153}, url = {https://academic.oup.com/icesjms/advance-article/doi/10.1093/icesjms/fsaa153/5952886?guestAccessKey=a0ae8696-7215-4e71-a8c5-bbd38fbb1a77}, author = {Elizabeth Weidner and Christian Stranne and Jonas Henati Sundberg and Thomas C Weber and Larry A Mayer and Martin Jakobsson} } @article {6792, title = {Bathymetric Properties of the Baltic Sea}, volume = {15(4)}, year = {2019}, month = {July 16}, pages = {905-924}, abstract = {Marine science and engineering commonly require reliable information about seafloor depth (bathymetry), e.g. for studies of ocean circulation, bottom habitats, fishing resources, sediment transport, geohazards and site selection for platforms and cables. Baltic Sea bathymetric properties are analysed here using the using the newly released Digital Bathymetric Model (DBM) by the European Marine Observation and Data Network (EMODnet). The analyses include hypsometry, volume, descriptive depth statistics, and km-scale seafloor ruggedness, i.e. terrain heterogeneity, for the Baltic Sea as a whole as well as for 17 sub-basins defined by the Baltic Marine Environment Protection Commission (HELCOM). We compare the new EMODnet DBM with IOWTOPO, the previously most widely used DBM of the Baltic Sea which has served as the primary gridded bathymetric resource in physical and environmental studies for nearly two decades. The area of deep water exchange between the Bothnian Sea and the Northern Baltic Proper across the \Åland Sea is specifically analysed in terms of depths and locations of critical bathymetric sills. The EMODnet DBM provides a bathymetric sill depth of 88 m at the northern side of the \Åland Sea and 60 m at the southern side, differing from previously identified sill depths of 100 and 70 m respectively. High-resolution multibeam bathymetry acquired from this deep water exchange path, where vigorous bottom currents interacted with the seafloor, allows us to assess what we are missing in presently available DBMs in terms of physical characterisation and our ability to then interpret seafloor processes and highlights the need for continued work towards complete high-resolution mapping of the Baltic Sea seafloor.
}, doi = {10.5194/os-2019-18}, author = {Martin Jakobsson and Christian Stranne and Matt O{\textquoteright}Regan and Sarah Greenwood and Bo Gustafsson and Christoph Humborg and Elizabeth Weidner} } @article {6826, title = {Evolving Arctic Bathymetry: The International Bathymetric Chart of the Arctic Ocean (IBCAO) Version 4.0 Compiled Under the Auspices of the Nippon Foundation-GEBCO-Seabed 2030 Project}, year = {2019}, month = {December 9-13}, pages = {San Francisco, CA}, abstract = {The International Bathymetric Chart of the Arctic Ocean (IBCAO) project was initiated in 1997 to meet the need for up-to-date digital portrayals of the Arctic Ocean seafloor. The original international effort assembled all available Arctic bathymetric data and gridded them using a continuous curvature spline under tension at a resolution of 2.5 x 2.5 km to produce a Digital Bathymetric Model (DBM). The resulting DBM, compiled on a Polar Stereographic Projection, was unprecedented in its ability to depict the complexities of Arctic bathymetry and has provided the geospatial context for countless scientific studies. Since the initial IBCAO DBM (Ver. 1.0), two more versions have been published. Ver. 2.0, at 2 x 2 km resolution and Ver. 3 with 500 x 500 m resolution. In all cases, many data sources including multi- and single-beam bathymetry as well as contours and soundings digitized from depth charts were incorporated following the concept developed for IBCAO Ver. 1, where direct depth observations get the highest priority and digitized contours the lowest. Recently the IBCAO project has merged its efforts with the Nippon Foundation-GEBCO-Seabed 2030 Project, an international effort whose goal it is to see the entire world ocean mapped by 2030. Working under the auspices of the Seabed 2030 program (but maintaining the its well-recognized identity) we now introduce IBCAO Ver. 4, compiled using a refined gridding algorithm compared to previous versions and with nearly three times more area of the Arctic Ocean constrained by bathymetric data relative to Ver. 3.0. In preparation for the eventual production of a multi-resolution grid that changes resolution with water depth to reflect achievable resolution from surface vessels, Ver. 4 has been created at a 100\×100 m grid spacing, using a pyramidal scheme of assembling the data considering its native resolution. This results in a degree of oversampling where the native resolution does not justify a 100 m grid, but in those regions where this resolution is achievable (e.g. depths less than say 1500-2000 m) the higher resolution allows analyses and regional uses that previously were not possible, including the depiction of megascale glacial lineations, large pock-marks and the dynamics of newly discovered Arctic submarine channels.
}, url = {https://agu.confex.com/agu/fm19/meetingapp.cgi/Paper/575093}, author = {Martin Jakobsson and Larry A Mayer} } @article {6613, title = {Seafloor Mapping {\textendash} The Challenge of a Truly Global Ocean Bathymetry}, volume = {6(283)}, year = {2019}, month = {June 5}, pages = {283}, abstract = {Detailed knowledge of the shape of the seafloor is crucial to humankind. Bathymetry data is critical for safety of navigation and is used for many other applications. In an era of ongoing environmental degradation worldwide, bathymetry data (and the knowledge derived from it) play a pivotal role in using and managing the world\’s oceans in a way that is in accordance with the United Nations Sustainable Development Goal 14 \– conserve and sustainably use the oceans, seas and marine resources for sustainable development. However, the vast majority of our oceans is still virtually unmapped, unobserved, and unexplored. Only a small fraction of the seafloor has been systematically mapped by direct measurement. The remaining bathymetry is predicted from satellite altimeter data, providing only an approximate estimation of the shape of the seafloor. Several global and regional initiatives are underway to change this situation. This paper presents a selection of these initiatives as best practice examples for bathymetry data collection, compilation and open data sharing as well as the Nippon Foundation-GEBCO (The General Bathymetric Chart of the Oceans) Seabed 2030 Project that complements and leverages these initiatives and promotes international collaboration and partnership. Several non-traditional data collection opportunities are looked at that are currently gaining momentum as well as new and innovative technologies that can increase the efficiency of collecting bathymetric data. Finally, recommendations are given toward a possible way forward into the future of seafloor mapping and toward achieving the goal of a truly global ocean bathymetry.
}, doi = {https://doi.org/10.3389/fmars.2019.00283}, url = {https://www.frontiersin.org/articles/10.3389/fmars.2019.00283/full}, author = {Anne-Cathrin W{\"o}lfl and Helen Snaith and Amirebrahim, Sam and Devey, Colin W. and Dorschel, B. and Vicki L Ferrini and Huvenne, Veerle A.I. and Martin Jakobsson and Jennifer Jencks and Johnston, Gordon and Geoffroy Lamarche and Larry A Mayer and Millar, David and Pedersen, Terje and Picard, Kim and Reitz, Anja and Schmitt, Thierry and Visbeck, Martin and Pauline Weatherall and Rochelle Wigley} } @article {6494, title = {A Wideband Acoustic Method for Direct Assessment of Bubble-Mediated Methane Flux}, volume = {173}, year = {2019}, month = {February 1}, pages = {104-115}, publisher = {Elsevier}, abstract = {The bubble-mediated transport and eventual fate of methane escaping from the seafloor is of great interest to researchers in many fields. Acoustic systems are frequently used to study gas seep sites, as they provide broad synoptic observations of processes in the water column. However, the visualization and characterization of individual gas bubbles needed for quantitative studies has routinely required the use of optical sensors which offer a limited field of view and require extended amounts of time for deployment and data collection. In this paper, we present an innovative method for studying individual bubbles and estimating gas flux using a calibrated wideband split-beam echosounder. The extended bandwidth (16 \– 26 kHz) affords vertical range resolution of approximately 7.5 cm, allowing for the differentiation of individual bubbles in acoustic data. Split-aperture processing provides phase-angle data used to compensate for transducer beam-pattern effects and to precisely locate bubbles in the transducer field of view. The target strength of individual bubbles is measured and compared to an analytical scattering model to estimate bubble radius, and bubbles are tracked through the water column to estimate rise velocity. The resulting range of bubble radii (0.68\–8.40 mm in radius) agrees with those found in other investigations with optical measurements, and the rise velocities trends are consistent with published models. Together, the observations of bubble radius and rise velocity offer a measure of gas flux, requiring nothing more than vessel transit over a seep site, bypassing the need to deploy time-consuming and expensive optical systems.
}, keywords = {Broadband acoustics, Bubble fate, East Siberian Arctic Ocean, Ebullition, Gas flux, Methane gas bubbles, swerus-c3}, doi = {https://doi.org/10.1016/j.csr.2018.12.005}, url = {https://www.sciencedirect.com/science/article/pii/S0278434318303649?via\%3Dihub}, author = {Elizabeth Weidner and Thomas C Weber and Larry A Mayer and Martin Jakobsson and Denis Chemykh and Semiltov, I.} } @article {6345, title = {Acoustic Mapping of Mixed Layer Depth}, volume = {14, 3}, year = {2018}, month = {June 22}, pages = {503-514}, abstract = {The ocean surface mixed layer is a nearly universal feature of the world oceans. Variations in the depth of the mixed layer (MLD) influences the exchange of heat, fresh water (through evaporation), and gases between the atmosphere and the ocean and constitutes one of the major factors controlling ocean primary production as it affects the vertical distribution of biological and chemical components in near-surface waters. Direct observations of the MLD are traditionally made by means of conductivity, temperature, and depth (CTD) casts. However, CTD instrument deployment limits the observation of temporal and spatial variability in the MLD. Here, we present an alternative method in which acoustic mapping of the MLD is done remotely by means of commercially available ship-mounted echo sounders. The method is shown to be highly accurate when the MLD is well defined and biological scattering does not dominate the acoustic returns. These prerequisites are often met in the open ocean and it is shown that the method is successful in 95 \% of data collected in the central Arctic Ocean. The primary advantages of acoustically mapping the MLD over CTD measurements are (1) considerably higher temporal and horizontal resolutions and (2) potentially larger spatial coverage.
}, doi = {10.5194/os-14-503-2018}, url = {https://www.ocean-sci.net/14/503/2018/os-14-503-2018-discussion.html}, author = {Christian Stranne and Larry A Mayer and Martin Jakobsson and Elizabeth Weidner and Kevin Jerram and Thomas C Weber and Andersson, Leif and Johan Nilsson and Bjork, G and Katarina G{\r a}rdfeldt} } @article {6235, title = {Bathymetry and Oceanic Flow Structure at Two Deep Passages Crossing the Lomonosov Ridge}, volume = {14}, year = {2018}, month = {January 2}, pages = {1-13}, publisher = {Copernicus Publications}, abstract = {The Lomonosov Ridge represents a major topographical feature in the Arctic Ocean which has a large effect on the water circulation and the distribution of water properties. This study presents detailed bathymetric survey data along with hydrographic data at two deep passages across the ridge: A southern passage (80\–81\°\ N) where the ridge crest meets the Siberian continental slope and a northern passage around 84.5\°\ N. The southern channel is characterized by smooth and flat bathymetry around 1600\–1700\ m with a sill depth slightly shallower than 1700\ m. A hydrographic section across the channel reveals an eastward flow with Amundsen Basin properties in the southern part and a westward flow of Makarov Basin properties in the northern part. The northern passage includes an approximately 72\ km long and 33\ km wide trough which forms an intra basin in the Lomonosov Ridge morphology (the Oden Trough). The eastern side of Oden Trough is enclosed by a narrow and steep ridge rising 500\–600\ m above a generally 1600\ m deep trough bottom. The deepest passage (the sill) is 1470\ m deep and located on this ridge. Hydrographic data show irregular temperature and salinity profiles indicating that water exchange occurs as midwater intrusions bringing water properties from each side of the ridge in well-defined but irregular layers. There is also morphological evidence that some rather energetic flows may occur in the vicinity of the sill. A well expressed deepening near the sill may be the result of seabed erosion by bottom currents.
}, doi = {doi.org/10.5194/os-2017-14}, author = {Bjork, G and Martin Jakobsson and Assmann, Karen and Andersson, Leif and Johan Nilsson and Christian Stranne and Larry A Mayer} } @article {6329, title = {The Holocene Retreat Dynamics and Stability of Petermann Glacier in Northwest Greenland}, year = {2018}, month = {May 29}, publisher = {Springer Nature}, abstract = {Submarine glacial landforms in fjords are imprints of the dynamic behaviour of marine-terminating glaciers and are informative about their most recent retreat phase. Here we use detailed multibeam bathymetry to map glacial landforms in Petermann Fjord and Nares Strait, northwestern Greenland. A large grounding-zone wedge (GZW) demonstrates that Petermann Glacier stabilised at the fjord mouth for a considerable time, likely buttressed by an ice shelf. This stability was followed by successive backstepping of the ice margin down the GZW\’s retrograde backslope forming small retreat ridges to 680\ m current depth (\∼730\–800\ m palaeodepth). Iceberg ploughmarks occurring somewhat deeper show that thick, grounded ice persisted to these water depths before final breakup occurred. The palaeodepth limit of the recessional moraines is consistent with final collapse driven by marine ice cliff instability (MICI) with retreat to the next stable position located underneath the present Petermann ice tongue, where the seafloor is unmapped.
}, keywords = {Arctic Ocean, cryospheric science, geomorphology}, doi = {10.1038/s41467-018-04573-2}, url = {https://www.nature.com/articles/s41467-018-04573-2}, author = {Martin Jakobsson and Hogan, Kelly and Larry A Mayer}, editor = {Mix, A C and Jennings, A. and Stoner, J S and Bjorn Eriksson and Kevin Jerram and Mohammad, R. and Pearce, Christof and Reilly, B. and Christian Stranne} } @article {6300, title = {The Nippon Foundation-GEBCO Seabed 2030 Project: The Quest to See the World{\textquoteright}s Oceans Completely Mapped by 2030}, volume = {8 (2)}, year = {2018}, month = {February 8}, abstract = {Despite many of years of mapping effort, only a small fraction of the world ocean\’s seafloor has been sampled for depth, greatly limiting our ability to explore and understand critical ocean and seafloor processes. Recognizing this poor state of our knowledge of ocean depths and the critical role such knowledge plays in understanding and maintaining our planet, GEBCO and the Nippon Foundation have joined forces to establish the Nippon Foundation GEBCO Seabed 2030 Project, an international effort with the objective of facilitating the complete mapping of the world ocean by 2030. The Seabed 2030 Project will establish globally distributed regional data assembly and coordination centers (RDACCs) that will identify existing data from their assigned regions that are not currently in publicly available databases and seek to make these data available. They will develop protocols for data collection (including resolution goals) and common software and other tools to assemble and attribute appropriate metadata as they assimilate regional grids using standardized techniques. A Global Data Assembly and Coordination Center (GDACC) will integrate the regional grids into a global grid and distribute to users world-wide. The GDACC will also act as the central focal point for the coordination of common data standards and processing tools as well as the outreach coordinator for Seabed 2030 efforts. The GDACC and RDACCs will collaborate with existing data centers and bathymetric compilation efforts. Finally, the Nippon Foundation GEBCO Seabed 2030 Project will encourage and help coordinate and track new survey efforts and facilitate the development of new and innovative technologies that can increase the efficiency of seafloor mapping and thus make the ambitious goals of Seabed 2030 more likely to be achieved.
}, keywords = {global bathymetry; Seabed 2030; Nippon Foundation/GEBCO; seafloor mapping technologies; seafloor mapping standards and protocols}, doi = {10.3390/geosciences8020063}, url = {http://www.mdpi.com/2076-3263/8/2/63}, author = {Larry A Mayer and Martin Jakobsson and Allen, Graham and Dorschel, B. and Falconer, Robin and Vicki L Ferrini and Geoffroy Lamarche and Helen Snaith and Pauline Weatherall} } @article {6389, title = {Seal Occurrence and Habitat Use during Summer in Petermann Fjord, Northwestern Greenland}, volume = {71(3):334}, year = {2018}, month = {September}, publisher = {Arctic Institute of North America}, abstract = {Ice-associated seals are considered especially susceptible and are potentially the first to modify distribution and habitat use in response to physical changes associated with the changing climate. Petermann Glacier, part of a unique ice-tongue fjord environment in a rarely studied region of northwestern Greenland, lost substantial sections of its ice tongue during major 2010 and 2012 calving events. As a result, changes in seal habitat may have occurred. Seal occurrence and distribution data were collected in Petermann Fjord and adjacent Nares Strait region over 27 days (2 to 28 August) during the multidisciplinary scientific Petermann 2015 Expedition on the icebreaker Oden. During 239.4 hours of dedicated observation effort, a total of 312 individuals were recorded, representing four species: bearded seal (Erignathus barbatus), hooded seal (Crystophora cristata), harp seal (Pagophilus groenlandicus), and ringed seal (Pusa hispida). Ringed seals were recorded significantly more than the other species (\χ2 = 347.4, df = 3, p \< 0.001, n = 307). We found significant differences between species in haul-out (resting on ice) behavior (\χ2 = 133.1, df = 3, p \< 0.001, n = 307). Bearded seals were more frequently hauled out (73.1\% n = 49), whereas ringed seals were almost exclusively in water (93.9\%, n = 200). Differences in average depth and ice coverage where species occurred were also significant: harp seals and bearded seals were found in deeper water and areas of greater ice coverage (harp seals: 663 \± 366 m and 65 \± 14\% ice cover; bearded seals: 598 \± 259 m and 50 \± 21\% ice cover), while hooded seals and ringed seals were found in shallower water with lower ice coverage (hooded seals: 490 \± 163 m and 38 \± 19\% ice cover; ringed seals: 496 \± 235 m, and 21 \± 20\% ice cover). Our study provides an initial look at how High Arctic seals use the rapidly changing Petermann Fjord and how physical variables influence their distribution in one of the few remaining ice-tongue fjord environments.
}, keywords = {Petermann Glacier; marine mammals; ice-tongue fjord; Arctic seals; sea ice; Pusa hispida; Erignathus barbatus; Crystophora cristata; Pagophilus groenlandicus}, doi = {https://doi.org/10.14430/arctic4735}, url = {https://arctic.journalhosting.ucalgary.ca/arctic/index.php/arctic/article/view/4735}, author = {Lomac-MacNair, K. and Martin Jakobsson and Mix, A C and Freire, Francis F and Hogan, Kelly and Larry A Mayer and Smultea, Mari Ann} } @article {6217, title = {Acoustic Mapping of Thermohaline Staircases in the Arctic Ocean}, volume = {7:15192}, year = {2017}, month = {November 9}, pages = {1-9}, publisher = {Springer Nature}, abstract = {Although there is enough heat contained in inflowing warm Atlantic Ocean water to melt all Arctic sea ice within a few years, a cold halocline limits upward heat transport from the Atlantic water. The amount of heat that penetrates the halocline to reach the sea ice is not well known, but vertical heat transport through the halocline layer can significantly increase in the presence of double diffusive convection. Such convection can occur when salinity and temperature gradients share the same sign, often resulting in the formation of thermohaline staircases. Staircase structures in the Arctic Ocean have been previously identified and the associated double diffusive convection has been suggested to influence the Arctic Ocean in general and the fate of the Arctic sea ice cover in particular. A central challenge to understanding the role of double diffusive convection in vertical heat transport is one of observation. Here, we use broadband echo sounders to characterize Arctic thermohaline staircases at their full vertical and horizontal resolution over large spatial areas (100\ s of kms). In doing so, we offer new insight into the mechanism of thermohaline staircase evolution and scale, and hence fluxes, with implications for understanding ocean mixing processes and ocean-sea ice interactions.
}, doi = {10.1038/s41598-017-15486-3}, url = {https://www.nature.com/articles/s41598-017-15486-3}, author = {Christian Stranne and Larry A Mayer and Thomas C Weber and Ruddick, Barry R and Martin Jakobsson and Kevin Jerram and Elizabeth Weidner and Johan Nilsson and Katarina G{\r a}rdfeldt} } @article {6166, title = {BedMachine v3: Complete Bed Topography and Ocean Bathymetry Mapping of Greenland From Multibeam Echo Sounding Combined With Mass Conservation}, volume = {44}, year = {2017}, month = {November 1}, pages = {11}, publisher = {John Wiley and Sons, Inc.}, abstract = {Greenland\&$\#$39;s bed topography is a primary control on ice flow, grounding line migration, calving dynamics, and subglacial drainage. Moreover, fjord bathymetry regulates the penetration of warm Atlantic water (AW) that rapidly melts and undercuts Greenland\&$\#$39;s marine-terminating glaciers. Here we present a new compilation of Greenland bed topography that assimilates seafloor bathymetry and ice thickness data through a mass conservation approach. A new 150\ m horizontal resolution bed topography/bathymetric map of Greenland is constructed with seamless transitions at the ice/ocean interface, yielding major improvements over previous data sets, particularly in the marine-terminating sectors of northwest and southeast Greenland. Our map reveals that the total sea level potential of the Greenland ice sheet is 7.42 \± 0.05 m, which is 7\ cm greater than previous estimates. Furthermore, it explains recent calving front response of numerous outlet glaciers and reveals new pathways by which AW can access glaciers with marine-based basins, thereby highlighting sectors of Greenland that are most vulnerable to future oceanic forcing.
}, doi = {10.1002/2017GL074954}, url = {http://onlinelibrary.wiley.com/doi/10.1002/2017GL074954/abstract;jsessionid=158B0362B92B2C2D0D7ECF2F8104691C.f02t02}, author = {Morlighem, M. and C.N. Williams and Rignot, E. and An, J. and Jan Erik Arndt and Bamber, J.L. and Catania, G. and Chauche, N. and Dowdeswell, J and Dorschel, B. and Fenty, I. and Hogan, K. and Howat, I. and Hubbard, A. and Martin Jakobsson and Thomas Jordan and Kjeldsen, K.K. and Millan, R. and Larry A Mayer and Mouginot, J. and Noel, B.P.Y. and O{\textquoteright}Cofaigh, C. and Palmer, S. and Rysgaard, S. and Seroussi, H. and Siegert, M and Slabon, P. and Straneo, F. and van den Broeke, M.R. and Weinrebe, W. and Wood, M. and Zinglersen, K.B.} } @article {6236, title = {The De Long Trough: A Newly Discovered Glacial Trough on the East Siberian Continental Margin}, volume = {13,9}, year = {2017}, month = {September 28}, pages = {1269-1284}, publisher = {Copernicus Publications}, abstract = {Ice sheets extending over parts of the East Siberian continental shelf have been proposed for the last glacial period and during the larger Pleistocene glaciations. The sparse data available over this sector of the Arctic Ocean have left the timing, extent and even existence of these ice sheets largely unresolved. Here we present new geophysical mapping and sediment coring data from the East Siberian shelf and slope collected during the 2014 SWERUS-C3 expedition (SWERUS-C3: Swedish \– Russian \– US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions). The multibeam bathymetry and chirp sub-bottom profiles reveal a set of glacial landforms that include grounding zone formations along the outer continental shelf, seaward of which lies a \>65m thick sequence of glacio-genic debris flows. The glacial landforms are interpreted to lie at the seaward
end of a glacial trough \– the first to be reported on the East Siberian margin, here referred to as the De Long Trough because of its location due north of the De Long Islands. Stratigraphy and dating of sediment cores show that a drape of acoustically laminated sediments covering the glacial deposits is older than 50 cal kyr BP. This provides direct evidence for extensive glacial activity on the Siberian shelf that predates the Last Glacial Maximum and most likely occurred during the Saalian (Marine Isotope Stage (MIS) 6).
The climate-carbon-cryosphere (C3) interactions in the East Siberian Arctic Ocean and related ocean, river and land areas of the Arctic have been the focus for the SWERUS-C3 Program (Swedish \– Russian \– US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions). This multi-investigator, multi-disciplinary program was carried out on a two-leg 90-day long expedition in 2014 with Swedish icebreaker Oden. One component of the expedition consisted of geophysical mapping and coring of Herald Canyon, located on the Chukchi Sea shelf north of the Bering Strait in the western Arctic Ocean. Herald Canyon is strategically placed to capture the history of the Pacific-Arctic Ocean connection and related changes in Arctic Ocean paleoceanography. Here we present a summary of key results from analyses of the marine geophysical mapping data and cores collected from Herald Canyon on the shelf and slope that proved to be particularly well suited for paleoceanographic reconstruction. For example, we provide a new age constraint of 11 cal ka BP on sediments from the uppermost slope for the initial flooding of the Bering Land Bridge and reestablishment of the Pacific-Arctic Ocean connection following the last glaciation. This age corresponds to meltwater pulse 1b (MWP1b) known as a post-Younger Dryas warming in many sea level and paleoclimate records. In addition, high late Holocene sedimentation rates that range between about 100 and 300 cm kyr-1, in Herald Canyon permitted paleoceanographic reconstructions of ocean circulation and sea ice cover at centennial scales throughout the late Holocene. Evidence suggests varying influence from inflowing Pacific water into the western Arctic Ocean including some evidence for quasi-cyclic variability in several paleoceanographic parameters, e.g. micropaleontological assemblages, isotope geochemistry and sediment physical properties.
}, url = {https://agu.confex.com/agu/fm17/meetingapp.cgi/Paper/214305}, author = {Martin Jakobsson and Anderson, L and Backman, Jan and Barrientos, Natalia and Bjork, G and Helen K. Coxall and Cronin, Tomas and de Boer, A. and Laura Gemery and Kevin Jerram and Johansson, Carina and Kirchner, N. and Larry A Mayer and M{\"o}rth, C-M. and Johan Nilsson and Noormets, R. and O{\textquoteright}Regan, M A and Pearce, Christof and Semiltov, I. and Christian Stranne} } @article {6225, title = {Distribution of an Acoustic Scattering Layer, Petermann Fjord, Northwest Greenland}, year = {2017}, month = {December 11-15}, pages = {New Orleans, LA}, abstract = {The Petermann 2015 Expedition was a comprehensive paleoceanographic and paleoclimatological study of the marine-terminating Petermann Glacier and its outlet system in Northwest Greenland carried out July-August 2015. The purpose was the reconstruction of glacial history and current glacial processes in Petermann Fjord to better understand the fate of the Petermann Glacier and its floating ice tongue that acts as a critical buttressing force to the outlet glacier draining about 4\% of the Greenland Ice Sheet. Seafloor mapping was a critical component of the study and an EM122 multibeam sonar was utilized for this purpose; additionally, water column data were acquired with this sonar and an EK80 split-beam echosounder.
During the expedition, the mapping team noted an acoustic scattering layer in the EK80 and EM122 water column data which was observed to change depth in a spatially consistent manner that appeared to be related to location. Initial onboard processing revealed what appears to be a strong spatial coherence in the layer distribution that corresponds to our understanding of the complex circulation pattern in the study area, including inflow of warmer Atlantic waters and outflow of subglacial waters. This initial processing was limited to observations at 46 discrete locations that corresponded to CTD stations, a very small subset of the 4800 line kilometers of data collected by each sonar. Both sonars were run 24 hours per day over the 30-day expedition, providing continuous time-varying acoustic coverage of the study area.
Post-cruise additional data has been processed to extract the acoustic returns from the scattering layer using a combination of commercial sonar processing software and specialized MATLAB and Python routines. 3-D surfaces have been generated from the extracted points in order to visualize the continuous spatial and temporal distribution of the scattering layer across the entire study area. Multiple crossings of the same location at different times of day address the question of the temporal stability of the scattering layer while the detailed map of the spatial distribution demonstrates the relationship of the scattering layer to the water masses and implies that continuous acoustic coverage may be a powerful proxy for oceanography.
}, keywords = {acoustic, arctic, DSL, EK80, EM122, Petermann, scattering layer}, url = {https://agu.confex.com/agu/fm17/meetingapp.cgi/Paper/287293}, author = {Erin Heffron and Larry A Mayer and Martin Jakobsson and Hogan, Kelly and Kevin Jerram} } @article {6247, title = {A Multi-Frequency Investigation of the Influences of Groundwater Discharge on Hydrocarbon Emission and Transport in the Baltic Sea}, year = {2017}, month = {December 11-15}, pages = {New Orleans, LA}, abstract = {In nearshore coastal regions submarine groundwater discharge is a major component of the hydro-geological cycle: transporting nutrients and pollutants to the ocean, producing up-welling currents through buoyancy effects, and acting as an erosional force at discharge sites. In nearshore regions where biogenic gas production is high, groundwater discharge could potentially act as a control on hydrocarbon emission and transport from the seafloor though the water-column.
In the southern Stockholm Archipelago of the Baltic Sea, terraces and semi-circular depressions on shallow (\<20 meters) seafloor have been linked to the discharge of ground water, traveling along the permeable layers in glacial clay deposits (S\öderberg and Flod\én 1995; Jakobsson et al., 2016). Sub-bottom profiles over the same region have identified widespread areas of subsurface blanking, commonly attributed to gas, as well as water-column seep features, both in spatial proximity to the groundwater discharge sites.
High-resolution multibeam bathymetry and chirp sub-bottom profiles were combined with water-column data sets collected at multiple frequencies (300 kHz, 45-90 kHz, 160-260 kHz) to map the spatial distribution of seeps and investigate their relationship to localized groundwater discharge as determined by seafloor and subsurface morphology. The spatial extent of seep sites appears closely tied to regions of suspected groundwater discharge, suggesting direct or indirect controls on gas emission pathways. Additionally, seep morphology in the broadband data hints at the possibility of groundwater and gas flow mixing.
}, url = {https://agu.confex.com/agu/fm17/meetingapp.cgi/Paper/230878}, author = {Elizabeth Weidner and Martin Jakobsson and Nycander, J and Larry A Mayer} } @article {6237, title = {Post-Glacial Flooding of the Bering Land Bridge Dated to 11 cal ka BP Based on New Geophysical and Sediment records}, volume = {13}, year = {2017}, month = {August 1}, pages = {991-1005}, publisher = {Copernicus Publications}, abstract = {The Bering Strait connects the Arctic and Pacific oceans and separates the North American and Asian landmasses. The presently shallow ( 53 m) strait was exposed during the sea level lowstand of the last glacial period, which permitted human migration across a land bridge today referred to as the Bering Land Bridge. Proxy studies (stable isotope composition of foraminifera, whale migration into the Arctic Ocean, mollusc and insect fossils and paleobotanical data) have suggested a range of ages for the Bering Strait reopening, mainly falling within the Younger Dryas stadial (12.9\–11.7 cal ka BP). Here we provide new information on the deglacial and post-glacial evolution of the Arctic\–Pacific connection through the Bering Strait based on analyses of geological and geophysical data from Herald Canyon, located north of the Bering Strait on the Chukchi Sea shelf region in the western Arctic Ocean. Our results suggest an initial opening at about 11 cal ka BP in the earliest Holocene, which is later than in several previous studies. Our key evidence is based on a well-dated core from Herald Canyon, in which a shift from a near-shore environment to a Pacific-influenced open marine setting at around 11 cal ka BP is observed. The shift corresponds to meltwater pulse 1b (MWP1b) and is interpreted to signify relatively rapid breaching of the Bering Strait and the submergence of the large Bering Land Bridge. Although the precise rates of sea level rise cannot be quantified, our new results suggest that the late deglacial sea level rise was rapid and occurred after the end of the Younger Dryas stadial.
}, doi = {doi.org/10.5194/cp-13-991-2017}, url = {https://www.clim-past.net/13/991/2017/cp-13-991-2017.pdf}, author = {Martin Jakobsson and Pearce, Christof and Cronin, Tomas and Backman, Jan and Anderson, Louise and Barrientos, Natalia and Bjork, G and Helen K. Coxall and de Boer, A. and Larry A Mayer and M{\"o}rth, C-M. and Johan Nilsson and Rattray, J.E. and Christian Stranne and Semiltov, I. and O{\textquoteright}Regan, M A} } @article {5798, title = {Acoustic and Geomorphological Signatures of Gas Seeps on the East Siberian Margin}, year = {2016}, month = {April 11-12}, address = {University of New Hampshire, Durham, NH}, abstract = {Rising hydrocarbon gas concentrations in the atmosphere are strongly linked to global warming. In the next century, significant amounts of hydrocarbons will be transport from the ocean to the atmosphere via thawing of flooded permafrost. The East Siberian Arctic Shelf (ESAS) holds 80\% of the world\’s flooded permafrost and is at risk of massive release due to bottom water warming. Gas released from permafrost is transported by gas seeps through the ocean; however, the magnitude of this gas flux has historically been difficult to quantify.
This research aims to estimate the total gas flux from a region of the ESAS, Herald Canyon, via acoustic and geomorphological characterization of gas seeps in the area. Data was collected with three acoustic systems (EM122 multibeam echosounder, SBP120 subbottom profiler, and EK80 split-beam sonar) onboard the Oden during the Swedish-Russian-US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions (SWERUS-C3) program.
53 seeps have been identified in the vicinity of Herald Canyon. Together, the EM122 high-resolution multibeam bathymetry and SBP120 chirp subbottom profiling data, provide the spatial and geologic context of the gas seeps. The EK80, which makes acoustic measurements over a broad range of frequencies, can identify individual bubble scatters. This enables estimates of bubble size distribution and rise velocity measurements in certain seeps; ultimately providing gas flux estimates. The combination of three data sets offers the opportunity to link seep flux estimates to geomorphological setting. The geomorphological setting can further be linked to local and regional geologic processes determined from seafloor morphology and subsurface structure. These links will help define our knowledge of the transport of hydrocarbon gas from flooded permafrost to the atmosphere.
}, keywords = {acoustic, east siberian margin, gas seeps, geomorphological signatures}, author = {Elizabeth Weidner and Larry A Mayer and Kevin Jerram and Thomas C Weber and Martin Jakobsson and Chernykh, D. and Ananiev, R. and Mohammad, R. and Semiltov, I.} } @article {5814, title = {Evidence for an Ice Shelf Covering the Central Arctic Ocean During the Penultimate Glaciation}, volume = {7}, year = {2016}, month = {January 18}, publisher = {Macmillan Publishers Ltd.}, abstract = {The hypothesis of a km-thick ice shelf covering the entire Arctic Ocean during peak glacial conditions was proposed nearly half a century ago. Floating ice shelves preserve few direct traces after their disappearance, making reconstructions difficult. Seafloor imprints of ice shelves should, however, exist where ice grounded along their flow paths. Here we present new evidence of ice-shelf groundings on bathymetric highs in the central Arctic Ocean, resurrecting the concept of an ice shelf extending over the entire central Arctic Ocean during at least one previous ice age. New and previously mapped glacial landforms together reveal flow of a spatially coherent, in some regions \>1-km thick, central Arctic Ocean ice shelf dated to marine isotope stage 6 (~140\ ka). Bathymetric highs were likely critical in the ice-shelf development by acting as pinning points where stabilizing ice rises formed, thereby providing sufficient back stress to allow ice shelf thickening.
}, keywords = {Arctic Ocean, glaciation, ice shelf}, doi = {doi:10.1038/ncomms10365}, url = {http://www.nature.com/ncomms/2016/160118/ncomms10365/full/ncomms10365.html}, author = {Martin Jakobsson and Johan Nilsson and Anderson, L and Backman, Jan and Bjork, G and Cronin, Tomas and Kirchner, N. and Koshurnikov, Andrey and Larry A Mayer and Noormets, R. and O{\textquoteright}Regan, M A and Christian Stranne and Ananiev, R. and Barrientos, Natalia and Chernykh, D. and Helen K. Coxall and Bjorn Eriksson and Floden, Tom and Laura Gemery and Gustafson, Orjan and Kevin Jerram and Johansson, Carina and Khortov, Alexey and Mohammad, R. and Semiltov, I.} } @article {6003, title = {The Glacimarine Sediment Budget of the Nares Strait-Petermann Fjord Area Since the Last Glacial Maximum}, year = {2016}, month = {December 12-16}, address = {San Francisco, CA}, abstract = {During the Petermann 2015 Expedition of the Swedish icebreaker Oden more than 6500 line-km of high-resolution chirp sub-bottom profiles (2-7 kHz) were acquired in Petermann Fjord and Nares Strait in the area immediately outside of the fjord. The sub-bottom profiles reveal a highly-variable distribution of post-glacial sediment that appears to be largely controlled by the rugged relief of the underlying bedrock. Sediment thicknesses are between 0-60 m above bedrock and comprise predominantly acoustically-stratified, homogeneous to transparent acoustic facies. In Petermann Fjord itself unlithified sediment cover typically comprises two units: an underlying acoustically-transparent unit overlain by an acoustically-stratified unit. Both of these units are conformable over scoured and fairly flat bedrock terrain; small basins are present only locally. Outside of the fjord are a few local sedimentary basins containing up to 40 m of stratified basin-fill deposits, and several areas of stacked mass-flow deposits. Glacial lineations both in the fjord and Nares Strait are formed in an acoustically-homogenous unit that underlies stratified and transparent units. In addition to the sub-bottom profiles, approximately 780 line-km of 2D seismic reflection profiles were acquired using an airgun (210 cu in.) and a 300-m long streamer. These profiles have allowed us to map full unlithified sediment thicknesses down to basement in the area. Here we present the results of this mapping and we calculate the volumes of a prominent grounding-zone wedge at the mouth of Petermann Fjord, and smaller GZWs in Kennedy Channel. These features demarcate former still-stand positions of grounded ice retreating through this system, both towards the present-day grounding line of Petermann Glacier and southwards through Nares Strait. Post-glacial sediment volumes are also calculated and the sedimentary processes responsible for their distribution examined. These data, when combined with chronological information, will provide sediment fluxes through the Petermann system and help us to identify how the system has responded to a past global warming event, namely the last deglaciation. This is particularly important in light of the recent thinning and acceleration of NW Greenland\’s marine-terminating outlet glaciers at present.
}, keywords = {glacial maximum, glacimarine sediment budget, nares strait, petermann fjord}, url = {https://agu.confex.com/agu/fm16/meetingapp.cgi/Paper/172466}, author = {Hogan, K. and Martin Jakobsson and Larry A Mayer and Mix, A C and Kevin Jerram and Nielsen, T. and Kamla, E. and Christian Stranne and Bjorn Eriksson} } @article {6002, title = {The History of Retreat Dynamics of Petermann Glacier Inferred from Submarine Glacial Landforms}, year = {2016}, month = {December 12-16}, pages = {San Francisco, CA}, abstract = {Preserved submarine glacial landforms produced at the base and margin of ice sheets and outlet glaciers comprise records of past ice dynamics complementary to modern glaciological process studies. The Petermann 2015 Expedition on the Swedish icebreaker Oden systematically mapped approximately 3100 km2 of the seafloor in Petermann Fjord and the adjacent Hall Basin of Nares Strait, northwest Greenland, with an EM122 (12 kHz) multibeam and SBP120 (2-7 kHz) chirp sub-bottom profiler. Complete, overlapping mapping coverage permitted compilation of a high-quality (15x15m) digital terrain model (DTM). In addition, the seafloor at the margin of one of the smaller outlet glaciers draining into the Petermann Fjord and selected shallow areas along the coast were mapped using a small survey boat (RV Skidbladner), equipped with an EM2040 (200-300 kHz) multibeam. High-resolution (2 x 2 m) DTMs were compiled from the RV Skidbladner surveys. The seafloor morphology of Petermann Fjord and adjacent Hall Basin is dominated by a stunning glacial landform record comprising the imprints of Petermann Glacier\’s retreat dynamics since the Last Glacial Maximum (LGM). The entrance to Petermann Fjord consists of a prominent bathymetric sill formed by a large well-develop grounding zone wedge that undoubtedly represents a stability point during the glacier\’s retreat history. The deepest entrance to the fjord is 443 m and located on the southern side of this grounding zone wedge. Outside of this grounding zone wedge in Hall Basin, less well developed grounding zones appears to be present. The landform assemblage in between the grounding zones, in particular the lack of retreat ridges, may signify a leap-frog behavior of the glacier\’s retreat; rapid break-up and disintegration of the outlet glacier causing retreat back to the next stability point dictated by the local bedrock geology. While numerous classical glacial landforms characteristic for fast flowing ice streams are identified, the multibeam bathymetry also reveals an enigmatic, toilet bowl-shaped features whose origin is still unclear. The collected data during the Petermann 2015 Expedition will among other things provide new insights into ice shelf-ocean interactions, essential to projecting future climate impacts on Greenland and global sea level changes.
}, keywords = {petermann glacier, retreat dynamics, submarine glacial landforms}, url = {https://agu.confex.com/agu/fm16/meetingapp.cgi/Paper/164992}, author = {Martin Jakobsson and Hogan, K. and Larry A Mayer and Mix, A C and Kevin Jerram and Mohammad, R. and Christian Stranne and Bjorn Eriksson} } @inbook {6238, title = {Mapping Submarine Glacial Landforms Using Acoustic Methods}, booktitle = {Atlas of Submarine Glacial Landforms: Modern, Quaternary and Ancient}, volume = {Memoirs}, number = {46}, year = {2016}, month = {12/2016}, pages = {17-40}, publisher = {Geological Society of London}, organization = {Geological Society of London}, address = {London, UK}, doi = {doi:10.1144/M46.182}, author = {Martin Jakobsson and Gyllencreutz, R. and Larry A Mayer and Dowdeswell, J and Canals, M. and Todd, B J and Dowdeswell, E.K. and Hogan, Kelly and Larter, R.D.} } @article {6000, title = {The Petermann Glacier Experiment, NW Greenland}, year = {2016}, month = {December 12-16}, pages = {San Francisco, CA}, abstract = {The Petermann Glacier Experiment is a comprehensive study on land, ocean, and ice in Northwest Greenland, staged from Swedish Icebreaker Oden in 2015 as a collaboration between the US, Sweden, UK, and Denmark. This talk introduces the strategic goals of the experiment and connects the various scientific results. Petermann Glacier drains a significant marine-based sector of the northern Greenland Ice Sheet and terminates in a floating ice tongue, one of the largest remaining systems of its kind in the northern hemisphere. Records of the modern state of Petermann Glacier and its past variations are of interest to understand the sensitivity of marine terminating outlet glaciers to change, and to constrain the rates and extent of changes that have actually occurred. With this case study we are learning the rules of large scale dynamics that cannot be understood from modern observations alone. Although past behavior is not an simple analog for the future, and no single system captures all possible behaviors, insights from these case studies can be applied through models to better project how similar systems may change in the future. The Petermann Expedition developed the first comprehensive bathymetric maps of the region, drilled through the floating ice tongue to obtain sub-shelf sediment cores near the grounding line and to monitor sub-ice conditions, recovered a broad array of sediment cores documenting changing oceanic conditions in Petermann Fjord, Hall Basin, and Nares Strait, measured watercolumn properties to trace subsurface watermasses that bring heat from the Arctic Ocean into deep Petermann Fjord to melt the base of the floating ice tongue, developed a detailed record of relative sealevel change on land to constrain past ice loads, and recovered pristine boulders for cosmogenic exposure dating of areal ice retreat on land. Together, these studies are shedding new light on the dynamics of past glaciation in Northwest Greenland, and contributing to fundamental understanding of large marine-terminating outlet glacier systems, which are threatened by global warming and poised to contribute to global sealevel rise in the future. Further information in the Petermann Glacier Experiment is available at https://petermannsglacialhistory.wordpress.com
}, keywords = {greenland, petermann glacier}, url = {https://agu.confex.com/agu/fm16/meetingapp.cgi/Paper/139793}, author = {Mix, A C and Martin Jakobsson and Andrews, J.T. and Jennings, A. and Larry A Mayer and Anderson, S.T. and Brook, E. and Ceperley, E. and Cheseby, M. and John E. Hughes Clarke and Dalerum, F. and Dyke, L.M. and Einarsson, D. and Erkisson, D.B. and Frojd, C. and Glueder, A. and Hedman, U. and Heirman, K. and Heuze, C. and Hogan, K. and Padman, J. and Pecnerova, P. and Reilly, B. and Reusche, M. and Ross, A. and Christian Stranne and Marcott, S.A. and Muenchow, A. and Stoner, J S and Andresen, C.S. and Nicholls, K.W. and Holm, C. and Kevin Jerram and Krutzfeld, J. and Nicolas, L. and Par, L. and Lomac-MacNair, K. and Madlener, S. and McKay, J. and Meijer, T. and Meiton, A. and Brian, M. and Mohammad, R. and Molin, M. and Moser, C. and Normark, E. and Trinhammer, P. and Walczak, M.H. and Walczak, P. and Washam, P. and Karasti, M. and Anker, P.} } @article {5999, title = {Quantification of Methane Gas Flux and Bubble Fate on the Eastern Siberian Arctic Shelf Utilizing Calibrated Split-beam Echosounder Data}, year = {2016}, month = {December 12-16}, pages = {San Francisco, CA}, abstract = {On the Eastern Siberian Arctic Shelf (ESAS) subsea permafrost, shallow gas hydrates, and trapped free gas hold an estimated 1400 Gt of methane. Recent observations of methane bubble plumes and high concentrations of dissolved methane in the water column indicate methane release via ebullition. Methane gas released from the shallow ESAS (\<50 m average depth) has high potential to be transported to the atmosphere.
To directly and quantitatively address the magnitude of methane flux and the fate of rising bubbles in the ESAS, methane seeps were mapped with a broadband split-beam echosounder as part of the Swedish-Russian-US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions program (SWERUS-C3). Acoustic measurements were made over a broad range of frequencies (16 to 29 kHz). The broad bandwidth provided excellent discrimination of individual targets in the water column, allowing for the identification of single bubbles. Absolute bubble target strength values were determined by compensating apparent target strength measurements for beam pattern effects via standard calibration techniques. The bubble size distribution of seeps with individual bubble signatures was determined by exploiting bubble target strength models over the broad range of frequencies. For denser seeps, with potential higher methane flux, bubble size distribution was determined via extrapolation from seeps in similar geomorphological settings. By coupling bubble size distributions with rise velocity measurements, which are made possible by split-beam target tracking, methane gas flux can be estimated.
Of the 56 identified seeps in the SWERUS data set, individual bubbles scatterers were identified in more than half (31) of the seeps. Preliminary bubble size distribution results indicate bubble radii range from 0.75 to 3.0 mm, with relatively constant bubble size distribution throughout the water column. Initial rise velocity observations indicate bubble rise velocity increases with decreasing depth, seemingly independent of bubble radius.
}, keywords = {flux and bubble fate, methane gas, siberian arctic}, url = {https://agu.confex.com/agu/fm16/meetingapp.cgi/Paper/122698}, author = {Elizabeth Weidner and Larry A Mayer and Martin Jakobsson and Chernykh, D. and Ananiev, R. and Thomas C Weber and Kevin Jerram and Mohammad, R. and Semiltov, I.} } @article {6001, title = {Towards the Complete Characterization of Marine-Terminating Glacier Outlet Systems}, year = {2016}, month = {December 12-16}, pages = {San Francisco, CA}, abstract = {The Petermann Glacier Experiment was aimed at understanding past variations in Petermann Glacier and their relationship to changes in climatic and oceanographic conditions. A critical component of the experiment was a comprehensive program conducted on the icebreaker Oden to map submarine glacial landforms, offering insight into past ice dynamics and establishing the overall geomorphological context of the region. Concurrent water-column mapping provided remarkable insight into modern glacial, oceanographic, and biological processes suggesting that a carefully designed experiment could provide a near-complete characterization of marine-terminating glacier outlet systems.
Water-column mapping revealed seeps emanating from several seafloor regions. These features appeared along common depth zones and may represent fresh water emanating from a submerged aquifer; initial pore water analyses of cores also imply a fresh water flux into the fjord system. Water-column data also show a spatially consistent but variable distribution of a strong mid-water scattering layer, a biological response possibly tracing the inflow of Atlantic water into the fjord and enhanced by input from local outlet glaciers. The continuous nature of these acoustic records over 30 days offers a complete 4-D picture of the distribution of the scattering layer (and perhaps internal circulation patterns and water-mass interactions) with a spatial and temporal distribution far beyond that achievable by traditional oceanographic stations. Additional, higher-resolution water-column imaging around local outlet glaciers presents a clear picture of subglacial sediment-laden meltwater plumes. Thus in addition to the paleoceanographic information they provided, the acoustic systems deployed captured a 4D-view of many of the modern geological, oceanographic and ecological processes within and adjacent to the Petermann Glacier marine system. With the addition of seafloor and water-column sampling, long-term oceanographic moorings, a much more robust biological program (to understand what we are mapping in the water-column) and, the ability to extend our measurements under the ice sheet, we stand poised to truly characterize and hopefully understand the processes at work in front of marine-terminating outlet glaciers.
}, keywords = {marine-terminating glacier outlet systems, petermann glacier}, url = {https://agu.confex.com/agu/fm16/meetingapp.cgi/Paper/174118}, author = {Larry A Mayer and Martin Jakobsson and Mix, A C and Erin Heffron and Kevin Jerram and Hogan, K. and Muenchow, A.} } @article {5711, title = {Arctic Ocean Bathymetry: A Necessary Geospatial Framework}, volume = {68, No. 5}, year = {2015}, month = {July 2015}, pages = {41-47}, publisher = {Arctic Institute of North America}, address = {Calgary, Canada}, abstract = {Most ocean science relies on a geospatial infrastructure that is built from bathymetry data collected from ships underway, archived, and converted into maps and digital grids. Bathymetry, the depth of the seafloor, besides having vital importance to geology and navigation, is a fundamental element in studies of deep water circulation, tides, tsunami forecasting, upwelling, fishing resources, wave action, sediment transport, environmental change, and slope stability, as well as in site selection for platforms, cables, and pipelines, waste disposal, and mineral extraction. Recent developments in multibeam sonar mapping have so dramatically increased the resolution with which the seafloor can be portrayed that previous representations must be considered obsolete. Scientific conclusions based on sparse bathymetric information should be re-examined and refined. At this time only about 11\% of the Arctic Ocean has been mapped with multibeam; the rest of its seafloor area is portrayed through mathematical interpolation using a very sparse depth-sounding database. In order for all Arctic marine activities to benefit fully from the improvement that multibeam provides, the entire Arctic Ocean must be multibeam-mapped, a task that can be accomplished only through international coordination and collaboration that includes the scientific community, naval institutions, and industry.
Key words: bathymetry; Arctic Ocean; mapping; oceanography;
The glacial history of the vast Siberian continental shelf of the Laptev and East Siberian Seas is poorly known. Most of this shelf area is shallower than 120 m implying that it was exposed land during the Last Glacial Maximum (LGM) as well as during older major Quaternary glaciations. The regional glacial and deglacial history of marine transgression has greatly influenced marine conditions of today\’s Arctic Ocean continental shelves. For example, the present extent of submarine permafrost on the shallow continental shelves is tightly linked to the glacial history, because the submarine permafrost was formed during cold conditions when sea level was low enough for the shelves to be subaerially exposed. Conversely, one explanation for lack of submarine permafrost on some shelf areas is the presence of past ice sheets. Ice sheets extending over parts of the Eastern Siberian continental shelf have been proposed in literature during LGM as well as during older Quaternary glacial periods. However, the sparsely available data from the outer continental shelf and adjacent slope of the Eastern Siberian Arctic Ocean has left the glacial history in this part largely unresolved. Here we present new geophysical mapping and sediment coring data from the shallow East Siberian shelf and adjacent slope collected during the 2014 SWERUS-C3 expedition (SWERUS-C3: Swedish \– Russian \– US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions) with Swedish icebreaker Oden. The mapping, using multibeam sonar, chirp sub-bottom profiler, and electro magnetics, in combination with new sediment cores provide information on past glacial activities, sea-level history and permafrost extent on the Eastern Siberian Arctic Ocean. Combining the new SWERUS-C3 data with previous results from this region raises the question whether an East Siberian-Chukchi ice sheet existed during LGM and/or during older glacial periods.\
}, keywords = {chukchi, ice sheet, swerus-c3}, url = {http://fallmeeting.agu.org/2015/}, author = {Martin Jakobsson and O{\textquoteright}Regan, M A and Kirchner, N. and Ananiev, R. and Bachman, Jan and Barrientos, Natalia and Chernykh, D. and Helen K. Coxall and Cronin, Tomas and Koshurnikov, Andrey and Lobkovsky, Leopold and Larry A Mayer and Noormets, R. and Muschitiello, Francesco and Johan Nilsson and Pearce, Christof and Semiltov, I. and Christian Stranne} } @article {5712, title = {High Resolution Mapping of Offshore and Onshore Glaciogenic Features in Metamorphic Bedrock Terrain, Melville Bay, Northwestern Greenland}, volume = {250}, year = {2015}, month = {December 1}, pages = {29-40}, publisher = {Elsevier}, abstract = {Geomorphological studies of previously glaciated landscapes are important to understand how ice sheets and glaciers respond to rapidly changing climate. Melville Bay, in northwestern Greenland, contains some of the most sensitive but least studied ice sheet sectors in the northern hemisphere, where the bathymetric knowledge previously was restricted to a few sparsely distributed single beam echo soundings. We present here the results of high-resolution, geomorphological mapping of the offshore and onshore landscapes in Melville Bay using multibeam sonar and satellite data, at 5- and 10-m resolutions respectively. The results show a similar areally-scoured bedrock-dominated landscape with a glacially modified cnoc-and-lochan morphology on the inner shelf (150\–500 m depth) and on the nearby exposed coast. This is manifested by the presence of U-shaped troughs, mouton\ée-type elongated landforms, stoss-and-lee forms, and streamlined features. The submarine landscape shows features that are characteristic of bedrock in folded, faulted, and weathered metamorphic terrain, and, to a lesser extent, glacially molded bedforms; while coastal landforms exhibit higher relief, irregular-shaped basins, and more subdued fracture valleys. Although generally similar, the onshore and offshore landscapes contain examples of distinctly different landform patterns, which are interpreted to reflect a longer exposure to long-term deep weathering as well as to more recent periglacial weathering processes on land. The spatial variability in the distribution of landforms across the landscape in both study areas is mostly attributed to differences in lithological properties of the bedrock. The lack of sediment cover on the inner shelf is likely a result of a capacity for sediment erosion and removal by the West Greenland Current flowing northward over the area in combination with limited sediment supply from long sea ice-cover seasons. The distribution and orientation of the landforms in the offshore part indicate ice movement toward the NW, and suggests that this area acted as a tributary or onset region for the major paleo ice stream that formed the present day Melville Bay Trough.
}, keywords = {Combined onshore-offshore mapping, Glacial erosional landforms, High-resolution mapping, Melville Bay, northwest Greenland}, url = {http://www.sciencedirect.com/science/article/pii/S0169555X15301240}, author = {Freire, Francis F and Gyllencreutz, R. and Greenwood, S. and Larry A Mayer and Egilsson, A. and Thorsteinsson, T. and Martin Jakobsson} } @proceedings {5710, title = {Mapping the Surficial Geology of the Arctic Ocean: A Layer for the IBCAO}, year = {2015}, month = {March 23 - 25}, publisher = {Society of Petroleum Engineers}, address = {Copenhagen, Denmark}, abstract = {The purpose of this paper is to show early results of surficial geologic mapping of the Arctic Ocean. Analysis of subbottom profiler and multibeam bathymetric data in conjunction with the regional morphology rendered from the IBCAO data are used to map nine surficial geologic units in the Arctic Ocean. For a relatively small ocean basin, the Arctic Ocean reveals a plethora of margin and basin types reflecting both the complex tectonic origins of the basin and its diverse sedimentation history. Broad and narrow shelves were subjected to a complex ice-margin history in the Quaternary, and bear the sediment types and morphological features as a result. Some shelf areas are heavily influenced by rivers. Extensive deep water ridges and plateaus are isolated from coastal input and have a long history of hemipelagic deposition. The flanks of the basins demonstrate complex sedimentation patterns resulting from mass failures and ice-margin outflow. The deep basins of the Arctic Ocean are filled with turbidites resulting from these mass-flows and are interbedded with hemiplegic deposits.
}, author = {David C Mosher and Courtney, R.C. and Martin Jakobsson and Gebhardt, C. and Larry A Mayer} } @article {5705, title = {A Multi-Frequency Look at Gas Seeps on the East Siberian Margin}, year = {2015}, month = {December 14-18}, address = {San Francisco, CA}, abstract = {The Swedish-Russian-US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions (SWERUS-C3) is a multi-investigator, multi-disciplinary program aimed at increasing our understanding of the climate-cryosphere-carbon system of the Eastern Siberian Arctic Ocean. In 2014 SWERUS-C3 carried out a two-leg field program on the Swedish Icebreaker ODEN. A component of the SWERUS-C3 program focused on water column mapping of the spatial distribution and geologic context of gas seeps using the acoustic systems on board ODEN (12 kHz EM122 multibeam echo sounder, 2-8 kHz SBP120 subbottom profiler, and an 18 kHz EK60 split-beam sonar). On Leg 2 of the 2014 expedition, a new wideband transceiver (EK80) was added to the split-beam echo sounder and calibrated, providing the ability to measure the acoustic response of the gas seeps over a much broader range of frequencies (15-30 kHz). While the broader bandwidth unquestionably provides higher target resolution a further objective of the broadband mapping was to determine whether information on bubble size distribution could be determined so as to help model the flux of gas coming from the seeps. On Leg 2 approximately 34 seeps were mapped, mostly in the vicinity of Herald Canyon. The wide-swath, high-resolution multibeam bathymetry (from the EM122) and high-resolution chirp sub-bottom profiling (from the SBP120 multibeam sub-bottom profiler) combined with water column imaging of seeps collected at both 12 kHz (from the EM122) and 15-30 kHz (from the EK80) offer an important opportunity to understand the spatial distribution of seeps and their relationship to local and regional processes as determined from seafloor and subsurface structure, as well as to explore the potential of extracting quantitative information about the magnitude of gas transport from the seeps.\
}, keywords = {east siberian margin, gas seeps}, url = {http://fallmeeting.agu.org/2015/}, author = {Larry A Mayer and Elizabeth Weidner and Kevin Jerram and Thomas C Weber and Martin Jakobsson and Chernykh, D. and Ananiev, R. and Mohammad, R. and Semiltov, I.} } @article {5799, title = {A Multi-Frequency Look at Gas Seeps on the East Siberian Margin}, year = {2015}, month = {December 14-18 }, publisher = {American Geophysical Union }, address = {San Francisco, CA}, abstract = {The Swedish-Russian-US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions (SWERUS-C3)is a multi-investigator, multi-disciplinary program aimed at increasing our understanding of the climate-cryosphere-carbon system of the Eastern Siberian Arctic Ocean.In 2014, SWERUS-C3 carried out a two-leg field program on the Swedish Icebreaker ODEN. A component of the SWERUS-C3 program focused on water column mapping of the spatial distribution and geologic context of gas seeps using the acoustic systems on board ODEN(12kHzEM122 multibeam echosounder, 2-8kHzSBP120 subbottom profiler, and an 18kHzEK60split-beamsonar). On Leg 2 of the 2014 expedition, a new wide-band transceiver (EK80) was added to the split-beam echosounder and calibrated, providing the ability to measure the acoustic response of the gas seeps over a much broader range of frequencies (15-30kHz). While the broader bandwidth unquestionably provides higher target resolution, a further objective of the broadband mapping was to determine whether information on bubble size distribution could be determined so as to help model the flux of gas coming from the seeps. On Leg2, 53seeps were identified in the vicinity of Herald Canyon.The wide-swath, high-resolution multibeam bathymetry (from the EM122) and high-resolution chirp subbottom profiling (from the SBP120 multibeam subbottom profiler), combined with water column imaging of seeps collected at both 12kHz (from the EM122) and 15-30kHz (from the EK80) offer an important opportunity to understand the spatial distribution of seeps and their relationship to local and regional processes as determined from seafloor and subsurface structure, as well as to explore the potential of extracting quantitative information about the magnitude of gas transportfrom the seeps.
}, keywords = {east siberian margin, gas seeps}, url = {http://ccom.unh.edu/publications/multi-frequency-look-gas-seeps-east-siberian-margin}, author = {Elizabeth Weidner and Larry A Mayer and Thomas C Weber and Martin Jakobsson and Chernykh, D. and Ananiev, R. and Mohammad, R. and Semiltov, I.} } @article {5389, title = {Arctic Ocean Glacial History}, volume = {92}, year = {2014}, pages = {42-67}, author = {Martin Jakobsson and Andreassen, K. and Bjarndottir, L.R. and Dove, D. and Dowdeswell, J and England, J.H. and Funder, S. and Hogan, K. and Ingolfsson, O. and Jennings, A. and Larson, N.K. and Kirchner, N. and Landvik, J.Y. and Larry A Mayer and Mikkelsen, N. and Moller, P and Niessen, F. and Johan Nilsson and O{\textquoteright}Regan, M A and Polyak, Leonid and Norgaard-Pedersen, N. and Stein, R.} } @article {5517, title = {High-resolution Mapping of Offshore and Onshore Glaciogenic Features in Melville Bay, Northwestern Greenland}, year = {2014}, month = {Dec 15 - 19}, address = {San Francisco, CA}, abstract = {This study presents results from high resolution mapping in the northwestern part of Greenland\’s continental shelf, offshore from the Greenland Ice Sheet. The study area is located at about 74o30\’N and 58 o40\’W where high-resolution seafloor imagery were collected from ~200-500 m water depth. These data were analyzed and compared to existing high-resolution satellite imagery of exposed glacial landforms from the nearby coastal areas. Offshore geophysical mapping equipment consisted of a Kongsberg EM2040 multibeam that was bow-mounted on the sailing vessel Explorer of Sweden together with a Seatex MRU5+ motion sensor and GPS antennas. In addition, a GAVIA autonomous underwater vehicle (AUV) from University of Iceland with installed Geoswath interfometric sonar and Marine Sonic side-scan was used. The data from these systems permitted the production of both 5-m (for the EM2040) and 2-m (for the Geoswath) resolution bathymetric grids for landform analyzes. Sediment characterization analysis was also undertaken using the co-registered backscatter data. The exposed onshore landforms were studied using data from the high-res QuickBird satellite images with a 2-m pixel resolution. Geomorphic analysis of the data shows that past tectonic and glacial scouring processes have shaped the present-day landscape in both the offshore and onshore study areas. The terrain consists of glacially eroded bedrock covered with very thin surficial sediments resembling a \‘cnoc-and-lochan\’ terrain, although the degree of erosion varies spatially, probably as a result of local variations in the rock properties. Different glacially influenced features are identified and described in the study. These features have been used to understand and infer past ice-sheet processes, particularly ice-flow direction and the extent of ice-cover on the continental shelves from previous extreme glaciation events. The backscatter information from the high-resolution interferometric sonar show fine-scale sedimentation patterns which are used to infer bottom water circulation. The study highlights that the use of the high-resolution seafloor mapping systems significantly enhance the quality of geomorphologic landform assessment.\
}, author = {Freire, Francis F and Gyllencreutz, R. and Greenwood, S. and Larry A Mayer and Martin Jakobsson} } @article {5518, title = {Mapping the Surficial Geology of the Arctic Ocean}, year = {2014}, month = {Dec 15 - 19}, address = {San Francisco, CA}, abstract = {Surficial geologic mapping of the Arctic Ocean was undertaken to provide a basis for understanding different geologic environments in this polar setting. Mapping was based on data acquired from numerous icebreaker and submarine missions to the polar region. The intent was to create a geologic layer overlying the International Bathymetric Chart of the Arctic Ocean. Analysis of subbottom profiler and multibeam bathymetric data in conjunction with sediment cores and the regional morphology rendered from the IBCAO data were used to map different surficial geologic units. For a relatively small ocean basin, the Arctic Ocean reveals a plethora of margin and basin types reflecting both the complex tectonic origins of the basin and its diverse sedimentation history. Broad and narrow shelves were subjected to a complex ice-margin history in the Quaternary, and bear the sediment types and morphological features as a result. Some shelfal areas are heavily influenced by rivers. Extensive deep water ridges and plateaus are isolated from coastal input and have a long history of hemipelagic deposition. An active spreading ridge and regions of recent volcanism have volcani-clastic and heavily altered sediments. Some regions of the Arctic Ocean are proposed to have been influenced by bolide impact. The flanks of the basins demonstrate complex sedimentation patterns resulting from mass failures and ice-margin outflow. The deep basins of the Arctic Ocean are filled with turbidites resulting from these mass-flows and are interbedded with hemiplegic deposits.\
}, author = {David C Mosher and Martin Jakobsson and Gebhardt, C. and Larry A Mayer} } @proceedings {5168, title = {Arctic Ocean Bathymetry: A required geospatial framework}, year = {2013}, month = {Apr 30 - May 2}, abstract = {Most ocean science relies largely on a geospatial infrastructure that is built primarily from bathymetry data collected underway from ships, archived, and converted into maps and digital grids. Bathymetry, the shape and composition of the seafloor, besides having vital importance to geology and navigation, is a fundamental element of studies of ocean modeling, deep water circulation, tides, tsunami forecasting, upwelling, fishing resources, wave action, sediment transport, environmental baselines, slope stability and risk, paleoceanography, site selection for platforms cables and pipelines, waste disposal, mineral extraction and sampling for environmental research. Recent developments in multibeam sonar mapping have so dramatically increased the resolution with which the seafloor can be portrayed, understood, used by other sciences and interacted with, that previous maps must be considered obsolete and scientific conclusions based on them re-examined and refined. The downside is that only about 10\% of the Arctic Ocean has been mapped with multibeam; the rest of its seafloor area is portrayed through mathematical interpolation using a very sparse depth sounding database. In order for all Arctic marine actives to benefit fully from the order of magnitude improvement that multibeam provides, the entire Arctic Ocean must be ensonified with multibeam data, a task that only can be accomplished through broad international coordination and collaboration, including both the scientific community and industry.
}, author = {Martin Jakobsson}, editor = {Larry A Mayer} } @article {5283, title = {Scientific Discoveries in the Central Arctic Ocean Based on Seafloor Mapping Carried Out to Support Article 76 Extended Continental Shelf Claims}, year = {2013}, month = {9-13 December}, address = {San Francisco, CA}, keywords = {article 76, Extended Continental Shelf}, author = {Martin Jakobsson and Larry A Mayer and Marcussen, C} } @article {4959, title = {The International Bathymetric Chart of the Arctic Ocean (IBCAO) version 3.0}, volume = {39}, year = {2012}, abstract = {The International Bathymetric Chart of the Arctic Ocean (IBCAO) released its first gridded\ bathymetric compilation in 1999. The IBCAO bathymetric portrayals has since supported a wide\ range of Arctic science activities, for example, by providing constraint for ocean circulation models and the means to define and formulate hypotheses about the geologic origin of the Arctic Ocean undersea features. IBCAO Version 3.0 comprises the largest improvement since 1999 taking advantage of new data sets collected by the circum-Arctic nations, opportunistic data collected from fishing vessels, data acquired from US Navy submarines and from research ships of various nations. Built using an improved gridding algorithm, this new grid is on a 500 meter spacing, revealing much greater details of the Arctic seafloor than IBCAO 1.0 (2.5 km) and 2.0 (2.0 km). The area covered by multibeam surveys has increased from ~6 \% in Version 2.0 to ~11\% in Version 3.0.
}, keywords = {Arctic Ocean, bathymetric chart, Bathymetry grids; Arctic; Earth Sciences, ibcoa}, author = {Martin Jakobsson and Larry A Mayer and Coakley, Bernie and Dowdeswell, J and Forbes, S. and Fridman, B. and Hodnesdal, H. and Noormets, R. and James V. Gardner and Andrew A. Armstrong and Pedersen, R. and M. Rebesco and Schenke, H-W. and Zarayskaya, Yulia and Accettella, D. and Anderson, Robert M and Bienhoff, P. and Camerlenghi, A. and Church, I and Edwards, Margo and John K Hall and Hell, B and Hestvik, O. and Kristoffersen, Yngue and Marcussen, C and Mohammad, R. and David C Mosher and Nghiem, S.V. and Pedrosa, M.T. and Travaglini, P.G. and Pauline Weatherall} } @article {, title = {An Arctic Ice Shelf During MIS 6 Constrained by New Geophysical and Geological Data}, volume = {29}, number = {25}, year = {2010}, pages = {3505-3517}, publisher = {Wiley}, keywords = {Other}, author = {Martin Jakobsson and Johan Nilsson and O{\textquoteright}Regan, M A and Backman, Jan and Lowemark, L and Dowdewell, J and Larry A Mayer and Polyak, Leonid and Colleoni, F and Anderson, L and Bjork, G and Darby, D and Eriksson, J and Hanslik, D and Hell, B and Marcussen, C and Sellen, E and Wallin, A} } @article {, title = {Glaciogenic Bedforms on the Chukchi Borderland, Morris Jesup Rise and Yermak Plateau: Three Prolongations of the Arctic Ocean Continental Margin}, year = {2008}, month = {Dec 15 - Dec 19}, address = {San Francisco, CA, USA}, keywords = {Other}, author = {Martin Jakobsson and Larry A Mayer} } @article {, title = {An Improved Bathymetric Portrayal of the Arctic Ocean: Implications for Ocean Modeling and Geological, Geophysical and Oceanographic Analyses}, volume = {35}, year = {2008}, pages = {0-1}, publisher = {American Geophysical Union }, address = {Washington DC, Washington DC, USA}, keywords = {Other}, author = {Martin Jakobsson and Macnab, Ron and Larry A Mayer and Anderson, Robert M and Edwards, Margo and Hatzky, Jorn and Schenke, H-W. and Paul Johnson} } @article {, title = {The Early Miocene Onset of a Ventilated Circulation Regime in the Arctic Ocean}, volume = {447}, year = {2007}, pages = {986-990}, publisher = {Nature Publishing Group}, keywords = {Other}, author = {Martin Jakobsson and Backman, Jan and Rudels, J and Nycander, J and Frank, M and Larry A Mayer and Jokat, W and Sangiorgi, F and O{\textquoteright}Regan, M A and Brinkhuis, H and King, J W and Moran, K} } @article {, title = {The Alpha-Mendeleev Magmatic Province, Arctic Ocean: A New Synthesis}, year = {2006}, month = {May 26 - May 26}, chapter = {Joint Assembly}, address = {Baltimore, MD, USA}, keywords = {Other}, author = {Vogt, Peter R and Jung, W and Martin Jakobsson and Larry A Mayer and Williamson, M} } @article {, title = {On the use of historical bathymetric data to determine changes in bathymetry}, volume = {6}, number = {3}, year = {2005}, pages = {25-41}, publisher = {Geomatics Information \& Trading Center - GITC}, address = {Lemmers, Amsterdam, The Netherlands}, keywords = {Other}, author = {Martin Jakobsson and Andrew A. Armstrong and Brian R Calder and Huff, Lloyd C and Larry A Mayer and Larry G Ward} } @article {, title = {GEBCO: A New 1:35000000 Scale Printed Map}, year = {2005}, month = {Dec 5 - Dec 9}, pages = {0-0}, chapter = {Fall Meeting}, address = {San Francisco, CA, USA}, keywords = {GEBCO}, author = {Anderson, Robert M and Martin Jakobsson and Monahan, Dave and John K Hall and Montoro, Hugo and Mustapha, Abubakar} } @inbook {, title = {Challenges of Collecting Law of the Sea Data in the Arctic: The Arctic and Law of the Sea}, booktitle = {International Energy Policy, the Arctic and the Law of the Sea}, year = {2005}, pages = {125-140}, publisher = {Martinus Nijhoff legacy_publishers}, organization = {Martinus Nijhoff legacy_publishers}, edition = {9}, chapter = {Center for Oceans Law and Policy, 8}, address = {Leiden, South Holland, The Netherlands}, keywords = {Law of the Sea}, author = {Larry A Mayer and Martin Jakobsson and John K Hall} } @article {, title = {Multibeam Bathymetric and Sediment Profiler Evidence for Ice Grounding on the Chukchi Borderland, Arctic Ocean}, volume = {63}, year = {2005}, pages = {150-160}, publisher = {Elsevier}, address = {New York, NY, USA}, keywords = {Other}, author = {Martin Jakobsson and James V. Gardner and Vogt, Peter R and Larry A Mayer and Andrew A. Armstrong and Backman, Jan and Brennan, Rick T and Brian R Calder and John K Hall and Kraft, Barbara J} } @proceedings {, title = {Mapping Paleo-Coastlines and Cultural Resources in Boston Harbor, MA}, year = {2004}, pages = {0-0}, address = {Montreal, Quebec, Canada}, keywords = {Other}, author = {Claesson, S and Huff, Lloyd C and Martin Jakobsson} } @inbook {, title = {Evaluating U.S. data holdings relevant to the definition of continental shelf limits}, booktitle = {Legal and Scientific Aspects of Continental Shelf Limits}, year = {2004}, pages = {313-330}, publisher = {Martinus Nijhoff legacy_publishers}, organization = {Martinus Nijhoff legacy_publishers}, edition = {8}, chapter = {Center for Oceans Law and Policy, 8}, address = {Leiden, South Holland, The Netherlands}, keywords = {Other}, author = {Larry A Mayer and Martin Jakobsson and Andrew A. Armstrong} } @article {, title = {Ice-dammed Lakes and Rerouting of the Drainage of Northern Eurasia during the Last Glaciation}, volume = {23}, year = {2004}, pages = {1313-1332}, publisher = {Wiley InterScience}, keywords = {Other}, author = {Mangerud, Jan and Martin Jakobsson and Alexanderson, H and Astakov, Valery and Clarke, G and Henriksen, M and Hjort, C and Krinner, G and Lunkka, J P and Moller, P and Murray, Andrew and Nikolskaya, O and Saarnisto, M and Svendsen, John I} } @inbook {, title = {Bathymetry and Physiography of the Arctic Ocean and Its Constituent Seas}, booktitle = {Arctic Ocean Organic Carbon Cycle: Present and Past}, year = {2003}, publisher = {Springer Publisher}, organization = {Springer Publisher}, address = {New York, NY, USA}, keywords = {Other}, author = {Martin Jakobsson and Grantz, Arthur and Kristoffersen, Yngue and Macnab, M} } @article {, title = {Physiographic Provinces of the Arctic Ocean Seafloor}, volume = {115}, number = {12}, year = {2003}, pages = {1443-1455}, publisher = {The Geological Society of America (GSA)}, keywords = {Other}, author = {Martin Jakobsson and Grantz, Arthur and Kristoffersen, Yngue and Macnab, M} } @article {, title = {Hypsometry, Volume and Physiography of the Arctic Ocean and Their Paleoceanographic Implications}, year = {2003}, month = {Apr 6 - Apr 11}, pages = {0-0}, address = {Nice, Nice, France}, keywords = {Other}, author = {Martin Jakobsson and Macnab, M and Grantz, Arthur and Kristoffersen, Yngue} } @proceedings {, title = {The International Bathymetric Chart of the Arctic Ocean (IBCAO): An Improved Morphological Framework for Oceanographic Investications}, year = {2003}, month = {Apr 6 - Apr 11}, pages = {0-0}, address = {Nice, Nice, France}, keywords = {Other}, author = {Macnab, M and Martin Jakobsson} } @article {, title = {Analysis of Data Relevant to Extending a Coastal State{\textquoteright}s Continental Margin Under Law of the Sea Article 76}, volume = {4}, number = {1}, year = {2003}, pages = {2-18}, publisher = {Geomatics Information \& Trading Center - GITC}, address = {Lemmers, Amsterdam, The Netherlands}, keywords = {Law of the Sea}, author = {Martin Jakobsson and Larry A Mayer and Andrew A. Armstrong} } @proceedings {, title = {The Grounding of an Ice Shelf in the Central Arctic Ocean: A Modeling Experiment}, year = {2003}, month = {Sep 30 - Oct 3}, pages = {0-0}, edition = {4th}, address = {Halifax, Nova Scotia, Canada}, keywords = {Other}, author = {Martin Jakobsson and Siegert, M and Paton, Mark} } @article {, title = {Is the central Arctic Ocean a sediment-starved basin?}, volume = {5}, year = {2003}, pages = {0-0}, address = {St. Andrews, New Brunswick, Canada}, keywords = {Other}, author = {Backman, Jan and Martin Jakobsson and Lovlie, Reidar and Polyak, Leonid and Febo, L A} } @proceedings {, title = {Impact of Ice-dammed Lakes on the Early Weichselian Climate of Northern Eurasia}, year = {2003}, month = {Jul 23 - Jul 30}, pages = {0-0}, address = {Reno, NV, USA}, keywords = {Other}, author = {Krinner, G and Mangerud, Jan and Martin Jakobsson and Cruicifix, M and Ritz, C and Svendsen, John I and Genthon, C} } @article {, title = {Optically Stimulated Luminescence Dating Supports Central Arctic Ocean CM-scale Sedimentation Rates}, volume = {4}, number = {2}, year = {2003}, pages = {0-11}, publisher = {American Geophysical Union }, address = {Washington DC, Washington DC, USA}, keywords = {Other}, author = {Martin Jakobsson and Backman, Jan and Murray, Andrew and Lovlie, Reidar} } @proceedings {, title = {Central Arctic Ocean Sedimentation: mm/ka-scale or cm/ka-scale Rates?}, year = {2003}, month = {Jul 23 - Jul 30}, pages = {0-0}, address = {Reno, NV, USA}, keywords = {Other}, author = {Backman, Jan and Martin Jakobsson and Lovlie, Reidar and Polyak, Leonid and Febo, L A} } @article {, title = {A Modeling Experiment on the Grounding of an Ice Shelf in the Central Arctic Ocean During MIS 6}, volume = {83}, number = {47}, year = {2003}, month = {Dec 8 - Dec 12}, pages = {0-0}, chapter = {Fall Meeting}, address = {San Francisco, CA, USA}, keywords = {Other}, author = {Martin Jakobsson and Siegert, M and Paton, Mark} } @proceedings {, title = {Paleomagnetic Chronology of Arctic Ocean Sediment Cores: Reversals and Excursions -The Conundrum}, year = {2003}, month = {Apr 6 - Apr 11}, pages = {0-0}, address = {Nice, Nice, France}, keywords = {Other}, author = {Lovlie, Reidar and Martin Jakobsson and Backman, Jan} } @article {, title = {3-D Visualization of IBCAO}, year = {2002}, pages = {40-43}, institution = {University of Hawaii}, keywords = {Other}, author = {Martin Jakobsson and Macnab, M} } @article {, title = {On the Estimation of Errors in Sparse Geophysical Datasets}, volume = {107}, number = {12}, year = {2002}, pages = {14-14}, publisher = {American Geophysical Union }, address = {Washington DC, Washington DC, USA}, keywords = {Other}, author = {Martin Jakobsson and Brian R Calder and Larry A Mayer} } @article {, title = {An Integrated Bathymetric and Topographic Digital Terrain Model of the Canadian Arctic Archipelago}, volume = {83}, number = {47}, year = {2002}, month = {Dec 5 - Dec 9}, pages = {0-0}, chapter = {Fall Meeting}, address = {San Francisco, CA, USA}, keywords = {Other}, author = {Alm, Goran and Macnab, M and Martin Jakobsson and Kleman, Johan and McCracken, Mark} } @proceedings {, title = {Using MGE Applications and Geomedia in Marine Geophysical/Geological Research}, year = {2002}, month = {Mar 31 - Apr 5}, pages = {0-16}, chapter = {Conference on Human Factors in Computing Systems}, address = {New Orleans, LA, USA}, keywords = {Other}, author = {Martin Jakobsson and Larry A Mayer} } @article {, title = {Rates of Sedimentation in the Central Arctic Ocean}, volume = {83}, number = {47}, year = {2002}, month = {Dec 6 - Dec 10}, pages = {0-0}, chapter = {Fall Meeting}, address = {San Francisco, CA, USA}, keywords = {Other}, author = {Backman, Jan and Martin Jakobsson and Lovlie, Reidar and Polyak, Leonid} } @article {, title = {Hypsometry and Volume of the Arctic Ocean and Its Constituent{\textquoteright}s Seas}, volume = {3}, number = {2}, year = {2002}, pages = {1-18}, publisher = {American Geophysical Union }, address = {Washington DC, Washington DC, USA}, keywords = {Other}, author = {Martin Jakobsson} } @article {, title = {Dynamic 3D Visualization of Merged Geophysical and Geological Data Sets from the Arctic}, volume = {83}, number = {47}, year = {2002}, month = {Dec 6 - Dec 10}, pages = {0-0}, chapter = {Fall Meeting}, address = {San Francisco, CA, USA}, keywords = {Other}, author = {Martin Jakobsson} } @article {, title = {The Compilation and Analysis of Data Relevant to a U.S. Claim Under United Nations Law of the Sea Article 76: Maps}, year = {2002}, institution = {U.S. Congress}, keywords = {Law of the Sea}, author = {Martin Jakobsson and Larry A Mayer and Andrew A. Armstrong} } @article {, title = {A Prototype 1:6 Million Map }, year = {2002}, pages = {5-7}, institution = {University of Hawaii}, keywords = {Other}, author = {Martin Jakobsson} } @article {, title = {On the Effect of Random Errors in Gridded Bathymetric Compilations}, volume = {107}, number = {12}, year = {2002}, pages = {1-11}, publisher = {American Geophysical Union }, address = {Washington DC, Washington DC, USA}, keywords = {Other}, author = {Martin Jakobsson and Brian R Calder and Larry A Mayer} } @article {, title = {Paleointensity Confirms cm-scale Sedimentation Rates and Suggests Intervals with Non-uniform Deposition on the Lomonosov Ridge, Central Arctic Ocean}, volume = {83}, number = {47}, year = {2002}, month = {Dec 6 - Dec 10}, pages = {0-0}, chapter = {Fall Meeting}, address = {San Francisco, CA, USA}, keywords = {Other}, author = {Lovlie, Reidar and Martin Jakobsson and Backman, Jan} } @article {3411, title = {Arctic Ocean Physiography}, volume = {83}, number = {47}, year = {2002}, month = {Dec 6 - Dec 10}, pages = {0-0}, chapter = {Fall Meeting}, address = {San Francisco, CA, USA}, keywords = {Other}, author = {Martin Jakobsson and Grantz, Arthur and Kristoffersen, Yngue and Macnab, Ron} } @article {3821, title = {The Compilation and Analysis of Data Relevant to a U.S. Claim Under United Nations Law of the Sea Article 76: A Preliminary Report}, year = {2002}, pages = {75}, institution = {University of New Hampshire (UNH)}, address = {Center for Coastal and Ocean Mapping (CCOM)/Joint Hydrographic Center (JHC)}, keywords = {Law of the Sea}, author = {Larry A Mayer and Martin Jakobsson and Andrew A. Armstrong} } @article {6562, title = {The Compilation and Analysis of Data Relevant to a U.S. Claim Under United Nations Law of the Sea Article 76: Appendices}, year = {2002}, pages = {98}, institution = {University of New Hampshire}, address = {Center for Coastal and Ocean Mapping (CCOM)/Joint Hydrographic Center (JHC)}, author = {Larry A Mayer and Martin Jakobsson and Andrew A. Armstrong} } @article {3975, title = {An Integrated Bathymetric and Topographic Digital Terrain Model of the Canadian Arctic Archipelago}, year = {2002}, month = {December 6-10}, publisher = {American Geophysical Union }, address = {San Francisco, CA}, keywords = {arctic archipelago, digital terrain model}, url = {http://www.agu.org/meetings/fm02/}, author = {Alm, Goran and Macnab, Ron and Martin Jakobsson and Kleman, Johan and McCracken, Mark} } @article {3976, title = {Rates of Sedimentation in the Central Arctic Ocean}, year = {2002}, month = {December 6-10}, publisher = {American Geophysical Union }, address = {San Francisco, CA}, keywords = {Arctic Ocean, sedimentation}, url = {http://www.agu.org/meetings/fm02/}, author = {Backman, Jan and Martin Jakobsson and Lovlie, Reidar and Polyak, Leonid} } @article {, title = {Huge Iceage Lakes in Russia}, volume = {16}, number = {9}, year = {2001}, pages = {773-777}, publisher = {Wiley InterScience}, keywords = {Other}, author = {Mangerud, Jan and Astakov, Valery and Martin Jakobsson and Svendsen, John I} } @article {, title = {Hypsometry and Volume of the Arctic Ocean and It{\textquoteright}s Constituent Seas}, year = {2001}, month = {Nov 5 - Nov 7}, pages = {0-1}, chapter = {Progress in Arctic Ocean Research Over the Past Decades}, address = {Stockholm, Stockholm, Sweden}, keywords = {Other}, author = {Martin Jakobsson} } @article {, title = {On the Estimation of Errors in Sparse Bathymetric Data Sets}, year = {2001}, pages = {0-31}, publisher = {American Geophysical Union }, address = {Washington DC, Washington DC, USA}, keywords = {Other}, author = {Martin Jakobsson and Brian R Calder and Larry A Mayer} } @article {, title = {Manganese, Carbon, and Nitrogen Isotope Composition of Deep Sediments: Tools for Monitoring Paleoceanographic Conditions in Central Arctic Ocean}, year = {2001}, publisher = {Elsevier}, address = {New York, NY, USA}, keywords = {Other}, author = {Al-Hanbali, H and Holm, N and Martin Jakobsson} } @article {, title = {Pleistocene Stratigraphy and Paleoenvironmental Variation from Lomonosov Ridge Sediments Central Artic Ocean}, volume = {31}, number = {1}, year = {2001}, pages = {1-21}, publisher = {Elsevier}, address = {New York, NY, USA}, keywords = {Other}, author = {Martin Jakobsson and Lovlie, Reidar and Arnold, E M and Backman, Jan and Polyak, Leonid and Knutsen, J O and Musatov, E} } @article {, title = {Sedimentation in the Central Arctic Ocean: What We Knew in 1996 and What We Know Today}, year = {2001}, month = {Nov 5 - Nov 7}, pages = {0-0}, address = {St. Andrews, New Brunswick, Canada}, keywords = {Other}, author = {Martin Jakobsson} } @article {, title = {IASC/IOC/IAO Editorial Board for the International Bathymetric Chart of the Arctic Ocean}, year = {2001}, pages = {1-33}, institution = {Geological Survey of Canada (GSC)}, keywords = {Other}, author = {Macnab, M and Martin Jakobsson and Svendsen, John I} } @article {, title = {Improvements to the International Bathymetric Chart of the Arctic Ocean: Updating the database and the grid model}, volume = {84}, year = {2001}, pages = {0-0}, publisher = {American Geophysical Union }, address = {Washington DC, Washington DC, USA}, keywords = {Other}, author = {Martin Jakobsson and I.B.C.A.O Board Members,} } @proceedings {, title = {Implications of Fast Sedimentation Rates in the Central Arctic Ocean}, year = {2001}, month = {Oct 31 - Nov 2}, pages = {0-0}, address = {St. Andrews, New Brunswick, Canada}, keywords = {Other}, author = {Martin Jakobsson and Backman, Jan and Lovlie, Reidar and Murray, Andrew} } @proceedings {2972, title = {Comparing Historical and Contemporary Hydrographic Data Sets: An Example from Great Bay, New Hampshire}, year = {2001}, month = {Sep 24 - Sep 24}, pages = {0-0}, edition = {2nd}, address = {Portsmouth, NH, USA}, keywords = {Great Bay, Other}, author = {Martin Jakobsson and Andrew A. Armstrong and Brian R Calder and Larry A Mayer} } @proceedings {2974, title = {Error Estimation of Bathymetric Grid Models Derived from Historic and Contemporary Data Sets}, year = {2001}, month = {May 21 - May 24}, pages = {0-17}, address = {Norfolk, VA, USA}, keywords = {Other}, author = {Martin Jakobsson and Brian R Calder and Larry A Mayer and Andrew A. Armstrong} } @article {3972, title = {On the Estimation of Errors in Gridded Bathymetric Compilations}, year = {2001}, month = {December 10-14}, publisher = {American Geophysical Union }, address = {San Francisco, CA}, keywords = {estimation of errors, gridded bathymetric compilations}, author = {Martin Jakobsson and Brian R Calder and Larry A Mayer and Andrew A. Armstrong} } @article {3439, title = {On the Estimation of Errors in Sparse Bathymetric Geophysical Data Sets}, volume = {82}, number = {20}, year = {2001}, month = {May 29 - Jun 2}, pages = {0-0}, chapter = {Spring Meeting}, address = {Boston, MA, USA}, keywords = {Other}, author = {Martin Jakobsson and Brian R Calder and Larry A Mayer and Andrew A. Armstrong} } @article {3407, title = {Hypsometry and Volume of the Arctic Ocean and Its Constituent{\textquoteright}s Seas}, year = {2001}, month = {Nov 5 - Nov 7}, pages = {0-0}, address = {St. Andrews, New Brunswick, Canada}, keywords = {Other}, author = {Martin Jakobsson} } @article {3409, title = {Improvement to the International Bathymetric Chart of the Arctic Ocean (IBCAO): Updating the Data Base and the Grid Model}, volume = {84}, year = {2001}, month = {Dec 10 - Dec 14}, pages = {1-5}, chapter = {Fall Meeting}, address = {San Francisco, CA, USA}, keywords = {Other}, author = {Martin Jakobsson and Cherkis, Norman} } @article {3973, title = {The Maximum Extent of the Saalian and Weichselian Glaciations in Eurasis}, year = {2001}, keywords = {Other}, author = {Svendsen, John I and Astakov, Valery and Alexanderson, H and Demidov, I and Dowdeswell, J and Gataulin, V. and Henriksen, M and Hjort, C and Martin Jakobsson} } @article {3405, title = {The STRATAFORM GIS: Interactive Exploration in 2 and 3 Dimensions}, volume = {82}, number = {47}, year = {2001}, month = {Dec 10 - Dec 14}, pages = {0-0}, chapter = {Fall Meeting}, address = {San Francisco, CA, USA}, keywords = {Other}, author = {Larry A Mayer and Fonseca, Luciano and Paton, Mark and McLeod, Pam and Martin Jakobsson} } @article {3408, title = {Volumes and Areas of Early Weichselian Ice Dammed Lakes in Northern Russia}, year = {2001}, month = {Dec 10 - Dec 14}, chapter = {Fall Meeting}, address = {San Francisco, CA, USA}, keywords = {Other}, author = {Martin Jakobsson and Mangerud, Jan and Astakov, Valery and Svendsen, John I} } @article {3404, title = {OSL Dating Supports "High" Sedimentation Rates in Central Arctic Ocean}, volume = {81}, number = {48}, year = {2000}, month = {Dec 6 - Dec 10}, chapter = {Fall Meeting}, address = {San Francisco, CA, USA}, keywords = {Other}, author = {Martin Jakobsson and Murray, Andrew and Backman, Jan and Lovlie, Reidar} }