The anatomy of the Arctic Frontal Zone in the Greenland Sea

Abstract

From a series of two‐dimensional expendable bathythermograph (XBT) surveys, conductivity‐temperature‐depth (CTD) sections, surface drifters, and acoustic Doppler current profiler (ADCP) observations, the properties and structure of the Arctic Frontal Zone in the Greenland Sea have been determined. The Arctic Frontal Zone appears to be a large‐scale, climatic “multifrontal” frontal zone. The structure of the frontal zone can be discerned from subsurface as well as from surface hydrographic parameters, even in summer, when a seasonal thermocline covers the subsurface hydrographie structure. The Arctic Frontal Zone consists of two semipermanent frontal interfaces with warm, saline Norwegian Atlantic Water to the east and Arctic Water from the Greenland Sea gyre to the west. The two frontal interfaces are bounding a band of shallow cyclonic cold eddies and anticyclonic warm eddies with horizontal scales of the order of 40–50 km. The typical diameter of the eddies can be scaled with the local internal Rossby radius of deformation. The eddy kinetic energy of the surface flow in the frontal zone is of the order of 60 to 85 cm2 s−2. The zonal density gradient in the Arctic Frontal Zone maintains a mean northward geostrophic transport of 3.8 Sv, averaged over a number of cruises. This transport is mainly connected with the frontal interface on the western side of the warm and saline Norwegian Atlantic Water. The estimated cross‐frontal eddy transports of heat and salt appear to be of considerable importance for the conditioning of the Greenland Sea gyre.