Recirculation in the Fram Strait and transports of water in and north of the Fram Strait derived from CTD data

Abstract

The volume, heat and freshwater transports in the Fram Strait are estimated from geostrophic computations based on summer hydrographic data from 1984, 1997, 2002 and 2004. In these years, in addition to the usually sampled section along 79° N, a section between Greenland and Svalbard was sampled further north. Quasi-closed boxes bounded by the two sections and Greenland and Svalbard can then be formed. Applying conservation constraints on these boxes provides barotropic reference velocities. The net volume flux is southward and varies between 2 and 4 Sv. The recirculation of Atlantic water is about 2 Sv. Heat is lost to the atmosphere and the heat loss from the area between the sections averaged over the four years is about 10 TW. The net heat (temperature) transport is 20 TW northward into the Arctic Ocean, with large interannual differences. The mean net freshwater added between the sections is 40 mSv and the mean freshwater transport southward across 79° N is less than 60 mSv, indicating that most of the liquid freshwater leaving the Arctic Ocean through Fram Strait in summer is derived from sea ice melt in the northern vicinity of the strait. In 1997, 2001 and 2003 meridional sections along 0° longitude were sampled and in 2003 two smaller boxes can be formed, and the recirculation of Atlantic water in the strait is estimated by geostrophic computations and continuity constraints. The recirculation is weaker close to 80° N than close to 78° N, indicating that the recirculation is mainly confined to the south of 80° N. This is supported by the observations in 1997 and 2001, when only the northern part of the meridional section, from 79° N to 80° N, can be computed with the constraints applied. The recirculation is found strongest close to 79° N.