Hydrographic variability during the decade of the 1990s in the Northeast Atlantic and southern Norwegian Sea

Throughout the decade of the 1990s, hydrographic conditions in the Northeast Atlantic have been monitored along standard sections in the Faroe Shetland Channel and at Ocean Weather Station Mike in the southern Norwegian Sea. Transport monitoring has also taken place since 1994 in the Faroe Shetland Channel; series of five semipermanent acoustic Doppler current profiler (ADCP) moorings have been used. The combination of repeat hydrographic sections and ADCP measurements has provided a new description of the annual mean and seasonal variation of temperature, salinity, and along-channel velocity within the Faroe Shetland Channel. These, combined in a simple transport model, have permitted annual mean and seasonal cycles of mass, heat, and salt flux in the poleward flowing Atlantic Water to be estimated for the period 1994-2000. The historical hydrographic data have then been used to set 1994-2000 into the context of decadal variability since 1960. Using recent estimates of Iceland-Scotland overflow variability, it is suggested that the net heat flux towards the Arctic has remained constant during the 1990s, as the observed warming in the inflowing surface waters has been offset by reduced transport. However, salt flux may have reduced, contributing to the freshening tendency in many areas of the Arctic Mediterranean.