Heat budget in the North Atlantic subpolar gyre: Impacts of atmospheric weather regimes on the 1995 warming event

In the western subpolar gyre, the 1995 warming event is the decadal, baroclinic ocean response to positive NAO conditions from 1988 to 1995. The latter induced increased surface heat loss in the Labrador Sea that intensified deep convection hence strengthened the meridional overturning circulation and the associated poleward heat transport. In the eastern subregion, a concomittant warming is induced by an interannual, barotropic adjustment of the gyre circulation to an abrupt switch from positive NAO conditions in winter 1995 to negative NAO conditions in winter 1996. Indeed, the gyre response to negative NAO conditions is a cyclonic intergyre-gyre that increases northward volume and heat transports at the southeastern limit of the subpolar gyre. Therefore, the discrepancies found in the literature about the 1995 warming event of the North Atlantic subpolar gyre are reconciled in the present work, which suggests that the atmospheric drivers, the mechanisms at stake and the associated timescales are different to the east and to the west of Reykjanes Ridge.