CO2 Gas Exchange in the Coastal Gulf of Maine or what have those people with the buoys been doing for the past few years?

James Irish
Research Professor

Ocean Engineering
University of New Hampshire

Friday, Oct. 8, 2010, 3:00pm
Chase 130

UNH is studying CO2 gas exchange and ocean acidification processes in the Western Gulf of Maine with three moored buoys. The first utilizes the NOAA/PMEL MAP-CO2 system and has been successfully deployed for about 85% of the last 4 years. The pCO2 system measures air and surface water dissolved oxygen and CO2 concentrations. Two years ago, the observatory was upgraded with sensors for wind, air temperature, relative humidity and pressure, sea surface temperature, salinity, dissolved oxygen, chlorophyll, CDOM fluorescence and turbidity. This year a pH sensor and duplicate water property sensors were added for ocean acidification studies. A second data system in the buoy controls sensor power, calculates and saves ten minute values and telemeters them to shore via spread spectrum radio.  A SAMI_CO2 system at 36 m depth measures CO2, temperature and oxygen. The CO2 data show that there is a flux of CO2 into the oceans during the summer time, but a nearly equal flux out in the winter, making the coastal (70 m) Gulf of Maine a small source for CO2 . Bacteria on the buoy mounted Optode oxygen sensor created a microclimate where concentrations reached 140% saturation. Cleaning the membrane removed this affect for 50 days. An array of tidbit temperature recorders on the mooring chain provided temperature structure to allow mixed layer depth to be estimated.

The second buoy - a technology-development mooring was deployed for a 1-month test in 2007 and two 3-month tests in 2009. The observational package is centered around a new gas flux measurement approach using a Direct Correlation Flux Sensor (a 3-axis sonic anemometer with 6-axis motion package and fluxgate compass) that samples the wind at 20 Hz for 20 minutes each hour, corrects for buoy motion. The DCFS is paired with an open path Licor Inc., Li-7500 IRGA CO2 sensor that also samples at 20 Hz under control of the DCFS. The buoy has the same basic sensors as the supporting sensors on the CO2 buoy.  An instrument package at 5 m depth has temperature, salinity, dissolved oxygen sensors, a Gas Tension Device, chlorophyll fluorometer, turbidity and a SAMI CO2 sensor. Below this package is a 300 kHz ADCP profiling velocity. The 5 m package also records temperature and oxygen from sensors mounted on the mooring at 12, 24 and 36 m depths. At 50 m depth, an autonomous system measures CO2 , temperature, salinity and oxygen. Both of the observatories use traditional chain catenary moorings with 2:1 scope in about 70 m of water. Analyses of the DCFS and LiCor data show reasonable wind stress and CO2 data, but an average upward wind velocity. This is due to flow disturbance by the buoy. The oxygen sensor array shows the spring and fall plankton blooms, and even a red tide bloom. Further analysis is ongoing.

The third buoy is a Datawell waverider that provides ½ hour measurements of directional waves and sea surface temperature to aid in gas transfer studies. 


Jim Irish has a Ph.D. from Scripps Institution of Oceanography, 1971.

  • Research Professor, Ocean Engineering
  • Oceanographer Emeritus, Woods Hole Oceanographic Institution

Research Areas

Ocean instruments, their calibration, response and the methodology of their use. Buoys, moorings and modeling of moored observing systems. Physical oceanography of the coastal ocean, including waves, tides, currents and water mass property observations and analysis. Acoustic instrumentation for bottom sediment and bedload transport, for remote observations of sediment and for fish surveys.

Research Emphasis

Research involves defining scientific problems in conjunction with other researchers, developing and deploying new instrumentation to collect remote environmental data, understanding instrument calibrations, behavior, and response, and participating in the analysis of these data to improve our understanding of the various processes occurring in the ocean. Specific research activities include:

  • Dynamic processes due to the tides and the associated stress, mixing, and advection of material.
  • Tidal analysis and predictions from bottom pressure and ocean current observations.
  • The generation and propagation of internal waves, internal tides and internal solitary waves.
  • Sea-water heating and cooling, water mass formation, and stability and mixing.
  • Sediment transport processes, particularly in the coastal ocean under wave forcing.
  • Optical and acoustic imaging of suspended sediment, bedload sediment and bedforms in relation to wave and current forcing.
  • Development, deployment and evaluation of new, remote oceanographic instrumentation systems utilizing microprocessors and telemetry.
  • Development of analysis methods and tools to reduce oceanographic observations.
  • A "knowledge-based system" approach to sampling the environment by taking advantage of the power of microprocessors to conditionally sample intermittent oceanic processes.
  • Development and use of acoustic, fiber optics, radio, and satellite telemetry techniques to return data from the field and the control remote instruments in the field.
  • Development of techniques for using new sensors in the ocean, including understanding the calibrations, calibration histories and the sensor behavior and response effects on data.