Internal Waves and Mixing in the Marginal Ice Zone from Ice-Tethered Profilers with Velocity

The transfer of energy in the Arctic Ocean from wind and ice motion to near-inertial currents and internal waves to vertical mixing is affected by the evolving ice cover and air-ice-ocean boundary layers. These dynamics are investigated in the Beaufort Sea using observations from Ice-Tethered Profilers with Velocity, which collect profiles of temperature, salinity, and velocity while drifting with the overlying ice cover. Three systems separated by a few hundred kilometers profiled the upper 250 m every 3 hours while transiting the Beaufort Sea from March to September as part of the Office of Naval Research Marginal Ice Zone Program. Near-inertial motions and the internal-wave field varied on intermittent to seasonal timescales as wind and ice speed changed, the ice cover broke apart, and the mixed layer shoaled. Near-inertial motions were most energetic at intermediate ice concentrations, and were affected by shallow summer mixed layer depths. Variations in velocity shear suggest that the smaller ice floes at intermediate ice concentrations generate internal waves with smaller vertical and horizontal scales than under full ice cover. Several indicators of vertical mixing, including Richardson number, suggest that intermittent events such as internal waves and eddies as well as seasonal modulations due to changes in ice cover and velocity shear affect vertical mixing and water mass properties in the mixed layer and Pacific Water layers. Differences in energy content, timing, and other properties of near-inertial motions between the three systems are explored. The ability to simultaneously observe currents, temperature, and salinity in the upper Arctic Ocean at timescales sufficient to investigate internal-wave dynamics improves our understanding of the links between ice cover, internal waves, and vertical mixing.