Abstract
"The seasonal and interannual variability of sea ice, current, and freshwater in the Arctic Ocean was studied using a 41-year hindcast simulation by FVCOM over 1978-2018. Not only in seasonal and interannual variability, but also in spatial distribution, simulated sea ice was in good agreement with the observed sea ice extent, concentration, drift velocity, and thickness. The results of the 41-year hindcast simulation show that the BG's major rise in freshwater accumulation began in 2007, and Ekman pumping is a primary physical mechanism for regional interannual fluctuation in freshwater content. The coastal flow over the Arctic shelf and slope has changed substantially in recent decades as a result of increasing freshwater runoff in response to global warming and high variability in ice extent. Increased coastal and slope flows have become a competing supply of freshwater for the region's exceptional freshwater accumulation. The net lateral flux, however, has a modest effect on the freshwater accumulation in the Beaufort Gyre since the freshwater transport induced by the inflow across the slope is substantially smaller than the freshwater outflow from the Beaufort Sea to the Arctic interior. The AO-FVCOM simulation for 2025 and 2050 were conducted to project the impact of global warming on future Arctic Ocean conditions, considering the CESM-RCP8.5-projected increases in air temperature, heat flux, and river runoff. Comparing the 2050 simulations with the 2018 situation, the sea ice extent in the Beaufort Sea will be drastically reduced, with a maximum of -6x106 km2 happening in August and September. The annual mean sea surface temperature will rise by 0.4-0.8 ℃. The Arctic Ocean will become significantly fresher. The highest salinity loss at the sea surface can surpass 2 psu, especially in the summer and autumn. Increased river runoff and a significant drop in sea ice will exacerbate coastal and slope currents up to 10 cm/s. The Beaufort Gyre will be stabilized because of global warming, which will increase the seasonal variability of the circulation in the Arctic Ocean. Freshwater content in the Beaufort Gyre region will increase as a result of net advective freshwater inflow from the slope in the spring and a net Ekman pumping-induced freshwater flux via the lateral freshwater flux from summer to fall." -- Publisher's description.