NESMA CPIES Recovery

The physical oceanography at the New England Seamounts (NESM) is dominated by the Gulf Stream. This surface-intensified current, which can reach speeds >4 knots (2 m/s), is a full-water column feature that spans more than 4000-m depth on its approach to the seamount chain. The location where the strongly meandering Gulf Stream crosses the seamount chain can vary by ~900 km. The crossing-location ranges from occasional crossings just north of the Bear Seamount (39°54’N, 67°23’ W) to an extreme southern occurrence near the Nashville Seamount (34°32’N, 57°W). This time-varying crossing-location is expected to have first order effects on: (1) local current-topography interactions at each seamount (e.g., mixing, lee wave generation, etc.) and (2) a range of environmental conditions at the seamounts—including impacts on thermocline depth, mode water thickness, and upper-ocean mixed-layer depth. The meandering current serves as a moving front between the Slope Sea (shallow thermocline and cool, fresh surface waters) to the north and the Sargasso Sea (deep thermocline and warm, salty surface waters) to the south. Since the environmental conditions vary so strongly across the Gulf Stream, just a small shift in Gulf Stream crossing-location at the NESM can be accompanied by a large change in the local environment at a given seamount. To help track the mesoscale variability around Atlantis II seamount, and to record higher frequency variability associated with internal tides, current and pressure sensor equipped inverted echo sounders (CPIESs) were deployed in April 2023 and will be recovered in fall 2024.