Center and NOAA scientists aboard the R/V Atlantis, an oceanographic research vessel operated by the Woods Hole Oceanographic Institution as part of the University-National Oceanographic Laboratory System fleet, are completing a high resolution mapping of the Mendocino Ridge off the California coast using the ship’s 12-kHz multibeam echosounder (MBES) (Figure 1). The scientists, led by Andrew Armstrong, Co-Director of the Joint Hydrographic Center, have been mapping the ocean floor since Sep. 22, 2014 as part of U.S. Extended Continental Shelf effort.

Figure 1 – 3D View of the SW view of a CUBE 100-m resolution grid (5x vertical exaggeration) of the seafloor area surrounding the Mendocino Ridge.

After departing from Astoria, OR (Figure 2), the expedition began the task of completing full-coverage of the Ridge, complementing the existing data collected in 2009 by the NOAA Ship Okeanos Explorer.

Figure 2 – R/V Atlantis moored at Astoria, OR.

In the area surrounding the ridge, the Atlantis’ advanced mapping system is uncovering a feature-rich stretch of seafloor approximately 3200 m deep with small volcanoes and knolls (a knoll is smaller than a seamount, it ranges in height from approximately 500 to 1000 meters). Figure 3 shows one of these features, an almost perfectly round-shaped submarine volcano, and located approximately 400 NM north-west of San Francisco, CA. This volcanic knoll has a 7-km diameter base and a maximum estimated slope of 40 degrees.

Figure 3 – 3D view of the SW side of an unnamed volcano with 40-degree slopes.

The NOAA/UNH team on R/V Atlantis is participating in the work of the U.S. Extended Continental Shelf (ECS) Task Force, a multi-agency project to delimit the outer edges of the U.S. continental shelf. In the ECS project, MBES data are needed to accurately define the foot of the slope and the 2500-m isobath (figure 4).

Figure 4– Close-up view of the western part of the Mendocino Ridge.

Figure 5– Sunset on board the R/V Atlantis.

As always, such a cruise also represents an important learning on-the-job experience for Center students (Figure 6).

Figure 6 – GEBCO fellow Daishi Horiuchi performing an Expendable Bathy Thermograph (XBT) launch for sound speed profiling.