Pacific Arctic dynamics: Results from a High-resolution Ice-ocean Model

The Pacific Arctic Sector is an area of interaction between the North Pacific and Arctic Ocean and it has been a challenging region to observe and model. Understanding its dynamics requires knowledge of the mean circulation and variability upstream, in the northern North Pacific and the Bering Sea. The objective of this research is to synthesize results on the critical processes, mean regional circulation patterns and property fluxes from the northern North Pacific, across the narrow Aleutian Island Passes, into the deep Bering Sea, exchanges across the shelf-break and through Bering Strait into the Chukchi Sea and the western Arctic Ocean. Many local and mesoscale processes controlling the ocean circulation are determined by the Rossby radius of deformation, which is relatively small and further decreases with increasing latitude, necessitating the use of high-resolution modeling. We use a high-resolution, pan-Arctic ice-ocean model forced with realistic atmospheric data to examine the mean transport and temporal and spatial variability within the Alaskan Stream and across the Aleutian Island Passes. Next, we analyze the general ocean circulation as well as spatial and temporal variability in the deep Bering Sea and shelf-basin exchange across the shelf break and the role of mesoscale eddies along the shelf break in eddy-driven shelf-basin fluxes, especially in the major submarine canyons. These exchanges are shown to determine the flow across the shelf towards the Bering Strait.

Dramatic reductions of the Arctic sea ice are a clear indication of change in recent years. However, the underlying causes of this decrease are still not completely understood. While atmospheric forcing plays a role in these changes, it cannot explain all of the variability in the sea ice extent. In fact, large-scale atmospheric patterns have not correlated well with the sea ice variability in recent years. Based on our model results and limited observations, the sea ice changes appear to be also linked to an increased oceanic heat transport into the western Arctic and subsequent lateral melt and under-ice ablation or reduction of ice growth.