Connectivity of the Aleutian North Slope Current and Bering Sea Basin Waters at the Level of the Subsurface Temperature Maximum: A Modeling Study

A 2-km resolution ocean circulation model for the Eastern Bering Sea is utilized to understand whether and where slope-interior exchange along the path of the Aleutian North Slope Current helps maintain the subsurface temperature maximum on the 26.8-kg/m(3) isopycnal surface in the Bering Sea Basin, at approximately 300-400-m depths. A simulation for June-October 2009 shows warmer water advecting westward on this isopycnal along the southern slope of the Aleutian Islands, through Amchitka Pass (180 degrees W), and then eastward along the northern slope as the season progresses, reaching the Bering Canyon. However, Lagrangian particle tracking on this surface shows that very few floats released over the slope south of Amukta Pass (172 degrees W) will end up in the Aleutian North Slope Current. The warming in the Aleutian North Slope Current at the depth of the 26.8-kg/m(3) isopycnal can be explained as resulting from a tidally enhanced downward vertical turbulent flux of warmer water which has been advected eastward in faster flowing waters at shallower depths. This hypothesis is confirmed by the heat equation term balance analysis and Lagrangian particle tracking on the 26.8-kg/m(3) surface and a shallower, 26.4-kg/m(3) surface. The model shows that the warm slope current separates into the basin near several topographical features, particularly at 178 degrees W (just east of Amchitka Pass) and 174 degrees W (Atka Island). North of Amukta Pass, the warmer pattern is strongly modulated at the tidal and fortnightly time scales and is associated with mixing in and transport through the pass. Plain Language Summary An ocean circulation model for the Eastern Bering Sea is utilized to understand whether and where exchange from the Aleutian slope to the interior basin along the path of the Aleutian North Slope Current helps maintain the subsurface temperature maximum on the 26.8-kg/m(3) density surface in the Bering Sea Basin. A simulation for June-October 2009 shows warmer water being transported westward on this density surface along the southern slope of the Aleutian Islands, through Amchitka Pass, and then eastward along the northern slope as the season progresses, reaching the Bering Canyon. However, particle tracking on this surface shows that very few floats released over the southern slope will end up in the Aleutian North Slope Current. The warming in the Aleutian North Slope Current at the depth of the 26.8-kg/m(3) density surface can be explained as resulting from downward vertical mixing of warmer water which has been transported eastward in faster flowing waters at shallower depths. This hypothesis is confirmed by analysis on the heat equation and particle tracking on the 26.8-kg/m(3) surface and a shallower, 26.4-kg/m(3) surface. The model shows that the warm slope current separates into the basin near several topographical features.