Semidiurnal current dynamics in the Arctic Ocean's eastern Eurasian Basin

<p>In the Arctic Ocean, semidiurnal-band processes including tides and wind-forced inertial oscillations are significant drivers of ice motion, ocean currents and shear contributing to mixing. Two years (2013-2015) of current measurements from seven moorings deployed along 125&#176;E from the Laptev Sea shelf (~50 m) down the continental slope into the deep Eurasian Basin (~3900 m) are analyzed and compared with models of baroclinic tides and inertial motion to identify the primary components of semidiurnal-band current (SBC) energy in this region. The strongest SBCs, exceeding 30 cm/s, are observed during summer in the upper ~30&#160;m throughout the mooring array. The largest upper-ocean SBC signal consists of wind-forced oscillations during the ice-free summer. Strong barotropic tidal currents are only observed on the shallow shelf.&#160; Baroclinic tidal currents, generated along the upper continental slope, can be significant. Their radiation away from source regions is governed by critical latitude effects: the S<sub>2</sub> baroclinic tide (period = 12.000 h) can radiate northwards into deep water but the M<sub>2</sub> (~12.421 h) baroclinic tide is trapped to the continental slope. Baroclinic upper-ocean tidal currents are sensitive to varying stratification, mean flows and sea ice cover.&#160; This time-dependence of baroclinic tides complicates our ability to separate wind-forced inertial oscillations from tidal currents. Since the shear from both sources contributes to upper-ocean mixing that affects the seasonal cycle of the surface mixed layer properties, a better understanding of both, inertial motion and baroclinic tides is needed for projections of mixing and ice-ocean interactions in future Arctic climate states.</p>