An Integral View of the Hydrographic Development in the Greenland Sea Over a Decade

A thirteen year long time series (1993 to 2005) of basin wide transects is used to analyse the hydrographic development in the Greenland Sea and to identify the processes which are responsible for observed changes. A key feature is the structural change away from a cold water dome to a two layer structure which is related to a fresh water convergence around 1990. The ensuing changes in the upper layer, the interface, and the lower layer are discussed in detail. The upper layer increases continuously in volume and shows no unequivocal trend in any hydrographic property. All observed modifications are reversible. The interface descends steadily with time by more than 1000 m during the investigation and shows constant properties. At the end of the time series, the deep layer volume is reduced to only 50% due to the interface descent. Both temperature and salinity show unambiguous trends in this layer. The temperature increase is mainly caused by vertical advection, the salinity increase by exchange with deep Arctic waters. The observations corroborate the idea that a large single-cell continuous convection scheme dominates the volume changes of both upper and lower layer and the deep water modifications during the 90s. These changes are independent of winter convection. The export from the deep layer is concentrated at the western continental slope of the basin.