During Ice Exercise (ICEX) 2018, a 120-kHz echosounder was used to investigate the ocean environment underneath the Arctic ice sheet in the southern Beaufort Sea down to a depth of 200 meters. Returns from the echosounder, coupled with data from an Acoustic Doppler Current Profiler (ADCP) and a Conductivity, Temperature, and Depth (CTD) profiler, suggest the presence of sharp, sound-speed gradients throughout the water column, occurring more often at greater depths. The pattern of returns can be correlated to variations in temperature and salinity common to the development of microstructure, suggesting a mechanism related to the formation of thermohaline staircases at greater depths. The presence of microstructure at shallower depths provides a potential source of detection of submerged objects via their hydrodynamic signature resulting from the disturbance of the microstructure. The current profile from the ADCP, along with the movement of the ice floe, provides evidence of shear at a depth near 20 meters, which allows for water from the lower, warmer mass to penetrate upwards toward the ice, increasing the vertical heat flux and impacting the melting of ice.
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