Response of the Arctic Ocean Near-Inertial Internal Wave Field to Changing Sea-Ice Conditions

The internal wave field in the Arctic Ocean is dominantly driven by the wind, and modulated by the sea-ice cover. Internal waves provide an important link between the atmosphere and the ocean interior, and potentially drive mixing and vertical exchanges of ocean properties. Seasonal and interannual connections between wind, sea-ice properties, and the internal wave field in the Western Arctic are quantified using data from 27 drifting Ice-Tethered Profilers. Seasonally, near-inertial internal waves are found to be most energetic during the summer months. Average wave amplitudes are 16% higher in summer and peak in September when sea-ice concentration is lowest and ice drift speed is high. Near-inertial waves are least energetic during late winter when sea ice responds minimally to wind forcing. Over the last decade, the seasonality and variability of the near-inertial internal wave field have increased as sea ice has dramatically declined. Between 2012 and 2014, unusually large waves were generated over 50% more frequently than between 2005 and 2007. These waves, many of which are predicted to cause mixing through shear instability above the Atlantic Water temperature maximum, now comprise over 10% of the near-inertial internal wave field. The continuing transition from thick multiyear to thin first-year ice in the Western Arctic Ocean appears to be affecting the fate of wind energy carried into the ocean interior through its impact on internal wave generation.