Arctic circulation pathways, heat and freshwater fluxes: results from numerical model integrations

Abstract

With increasing attention on Arctic warming and consequent reductions of sea ice, many studies are focusing on the “gateways” to the Arctic Ocean - the regions where water enters and exits the Arctic Basin. The Chukchi Sea is the only pathway for Pacific water to enter the Arctic Ocean. While the Chukchi naturally undergoes large seasonal and interannual variability, currently it is also undergoing larger and rapid changes, which include transition to a longer icefree season. Numerical models are often used to explore this region, due to observational restrictions associated with sea-ice. Most past and current models tend to represent riverine inputs in a non-realistic manner; adding freshwater on or past the shelf break, not accounting for seasonality of the river discharge, and omitting riverine heat content. In addition, in many of these models, buoyant coastal currents are not well resolved. Here, I present a new river discharge and river temperature data set (at 1/6° resolution). Employing this new data set within a high-resolution pan-Arctic model, freshwater content on the Arctic shelves increased by ~3600 km3 and summer heat fluxes increased by 8 TW (compared to previous models), resulting in a reduction of the Arctic-wide September sea ice extent by up to ~10%. With both the improved riverine forcing included in the model calculations, and the model’s ability to resolve the Alaskan Coastal Current, the model suggests an additional 0.25 Sv of flow to the long-term Bering Strait volume transport. This translates to a 64% increase in the heat transport and a 32% increase in freshwater transport (including 4% from sea ice). The model also resolves individual transport pathways in the Chukchi Sea, including that of Bering Sea Water, which could influence species composition and distribution in the eastern Chukchi Sea. Increased computing power and improved observational tools lead to more accurate reproductions of coastal currents and riverine influences in these numerical models. Greater understanding of this near-shore region and its influences is vital to further interpret larger connections between terrestrial and marine ecosystems, as well as Arctic-wide and global oceanic changes.