Shear and stability at the base of the mixed layer in the Arctic Ocean the role of inertial motions

Abstract

The Arctic environment changed significantly over recent decades and declines in perennial sea ice and thickness concentrations have been frequently observed. Current predictive models providing researchers with conservative estimates of sea ice concentrations, the lack of observations and understanding of the physical processes that promote changes in sea ice create inaccuracies that need to be improved. A fusion of buoy observations, satellite derived ice concentrations, and modeled wind data are made in this thesis to provide a better insight into sea ice inertial motions and its influence on the processes that occur in the Arctic Ocean mixed layer and to investigate whether these processes can be parameterized to improve predictive models. Observations made in the Canadian Basin and the Transpolar Drift by high resolution Autonomous Ocean Flux Buoys (AOFBs), SSMI and AMSR-E satellite derived ice concentrations, and ERA-Interim winds are used to examine the relationships between winds, ice coverage and sea ice inertial oscillations. Data collected from AOFBs and collocated Ice-Tethered Profilers (ITPs) are analyzed to investigate whether ocean mixed layer inertial oscillations contribute to shear instability at the base of the mixed layer, which serves as a mechanism for vertical transport of heat in water masses underlying the mixed layer. Results show that simple linear regression models cannot explain the relationship between inertial sea ice velocities and modeled winds. However, they do indicate that the magnitude of the inertial sea ice velocities during summers is greater when compared to winter. Analysis further reveals a relationship between sea ice inertial oscillations and sea ice concentrations. We conclude that parameterizing the conditions that permit significant inertial motions in terms of changing areal ice conditions is viable. Inertial oscillations generated in the Arctic Ocean mixed layer do contribute significantly to the instability at the base of the mixed layer, especially during summers. However, comparisons of dynamic instability at the base of the mixed layer to satellite derived sea ice concentrations reveal no conclusive relationship.