Observations and modeling of dense water cascading from the northwestern Laptev Sea shelf

Abstract

We examine dense water cascading from the northwestern Laptev Sea shelf in the Arctic Ocean. This region is believed to be a potential site of dense water formation through ice freezing and brine ejection. Climate data indicate the presence of saltier/denser water on the shelf all year round. Tongues of dense water spreading from the shelf to the continental slope and reaching a depth of 300–400 m are reported in some historical hydrographic surveys. In this study we recreate dense water cascading from the Laptev Sea shelf by filling a gap between two sequential hydrographic surveys with numerical model output. From October 1984 to April 1985, ice formation over the shelf provided salt input almost 5 times greater than the amount that was accumulated in the shelf waters. This excessive salt was transported off the shelf mainly by baroclinic eddies and also by mean outflow through the bottom boundary layer. Shelf origin dense water would have reached at least 1000‐m depth, but strong stratification prevented it from penetrating deeper than 400 m downslope. Contribution of mean downslope flow to heat and salt exchange between shelf and slope is on the average 4 times smaller than that caused by eddy fluxes. Hence, although the volume transport associated with cascading is relatively small (∼0.02 Sv), heat and salt fluxes are large enough to provide cooling and freshening of Atlantic Water, which propagates along the Siberian continental slope.