Recent interannual upper ocean variability in the deep southeastern Bering Sea

Recent seasonal and interannual variability of the upper ocean in the southeast Aleutian Basin of the Bering Sea is related to air sea fluxes, ocean advection, and mixing. Between the winter of 2001/2002 and that of 2002/2003 a warming and freshening of the upper ocean was observed in data from a regional array of profiling Conductivity-Temperature-Depth (CTD) floats. The mild winter of 2002/2003 resulted in an unusually warm, fresh, light, and shallow winter mixed layer and a weakly ventilated temperature minimum layer. These unusual winter conditions contributed to a substantial reduction in the subsurface temperature inversion characteristic of the southeast Aleutian Basin. Heat budget analysis, one-dimensional upper ocean model runs, and altimeter sea-surface height anomalies suggest that a combination of atypical ocean advection and anomalous atmospheric forcing contributed to the unusual upper ocean conditions in 2002/2003. The observed warming and disappearance of the temperature minimum in 2002/2003 appears to have preconditioned the water column toward a similar structure in 2003/2004, despite a return to more normal atmospheric forcing.