Turbulent Mixing During Late Summer in the Ice–Ocean Boundary Layer in the Central Arctic Ocean: Results From the MOSAiC Expedition

We examined mixing processes within the ice–ocean boundary layer (IOBL) close to geographic North Pole, with an emphasis on wind-driven sea ice drift. Observations were conducted from late August September 2020, during final leg of international Multidisciplinary drifting Observatory for Study Arctic Climate (MOSAiC) expedition. Measurements motion, and profiles currents, hydrography, microstructure turbulence conducted. The multifarious direct observations upper ocean used quantify transport momentum, heat, salt in IOBL. drift was mostly characterized by inertial oscillation at a semi-diurnal frequency, which forced current mixed layer. Observation-derived heat salinity fluxes interface suggest early termination basal melting transitioning refreezing, resulting rise freezing point temperature presence freshened near-surface water. Based friction velocity, measured dissipation rate (?) turbulent energy can be approximated as 1.4–1.7 times “Law Wall” criterion. also observed spiraling Ekman flow find its vertical extent line estimate ?-based diffusivity. Following passage storm, enhanced oscillatory motions caused trapping near-inertial waves (NIWs) that exclusively propagated through base weakly stratified accounted Holmboe instabilities NIWs distinct peak near bottom