Synoptic sections of the Denmark Strait Overflow

Abstract

We report on a rapid high‐resolution survey of the Denmark Strait overflow (DSO) as it crosses the sill, the first such program to incorporate full‐water‐column velocity profiles in addition to conventional hydrographic measurements. Seven transects with expendable profilers over the course of one week are used to estimate volume transport as a function of density. Our observations reveal the presence of a strongly barotropic flow associated with the nearly‐vertical front dividing the Arctic and Atlantic waters. The seven‐section mean transport of water denser than σ θ =27.8 is 2.7±0.6Sv, while the mean transport of water colder than 2.0°C is 3.8±0.8 Sv. Although this is larger than the 2.9 Sv of θ < 2°C water measured by a 1973 current meter array, we find that a sampling of our sections equivalent to the extent of that array also measures 2.9Sv of cold water. Both the structure and magnitude of the measured flow are reproduced well by a high‐resolution numerical model of buoyancy‐driven exchange with realistic topography.