Deepening of the Atlantic Water Core in the Canada Basin in 2003–11

Abstract

n 2004, a cold mode of Atlantic Water (AW) entered the western Canada basin, replacing the anomalously warm AW that resided in the basin since the 1990s. This slightly colder AW was denser than the 1990s warm mode; it gradually filled most of the western basin by 2009. The enhanced surface stress curl led to the spinup of the Beaufort Gyre and convergence of freshwater. The spinup also resulted in a deepening of the AW core at the center of the gyre and in shoaling of the AW core at the margins of the gyre. The density versus depth relationship revealed in this study shows that the depth of the maximum AW temperature was mainly controlled by the density structure before 2007; thus, it is the case when the denser water was deeper and the case when the lighter water was shallower around the basin. However, this relationship was reversed to become the case when the denser water was shallower and the case when the lighter water was deeper since 2008 inside the Beaufort Gyre. The combined effect of density and sea ice retreat that enhanced surface stress curl determined the depth of the AW inside the Beaufort Gyre since 2008. The deepening of the AW core and expanding of the area where the AW deepening occurred had a profound effect on the large-scale circulation in the Arctic Ocean.