Dynamics of the Near-Inertial Internal Wave Field from a Decade of Ice-Tethered Profiler Observations

Abstract:

The dynamics of wind generated near-inertial internal waves in the Beaufort Gyre region are investigated using the drifting Ice-Tethered Profiler dataset for the years 2005 to 2012. The broad spatial coverage and continuous time series of observations allow for a careful investigation of changes in internal wave energy during a decade when sea-ice extent and thickness decreased dramatically. Near-inertial internal waves are generally most energetic in summer during sea-ice retreat, with a second peak in early winter during the period of maximum wind velocity. This seasonal variability matches the seasonal cycle in `wind factor’, which connects sea-ice drift velocity to wind velocity. The wind factor is related to the ratio of air to water drag coefficients, and is shown to vary with sea-ice extent. An increasing inter-annual trend in near-inertial wave energy is found for the upper ocean, mirroring the pronounced sea-ice decline in the summer months. Following the 2007 sea-ice minimum, the overall variability in the internal wave field increased significantly, with a wider range of wave amplitudes observed in both summer and winter. This is linked to an overall increase in the wind factor, and may indicate a shift in air-ice-ocean dynamics in the Arctic.