Formation of a dense water cascade in the marginal ice zone in the Barents Sea

In this paper, we examine the origin of a dense water cascade in the marginal ice zone west off the Novaya Zemlya Archipelago in the Barents Sea. We specifically consider how ice advection and melting contribute to the formation of density gradients favourable for cascading. The study is based on three hydrographic surveys taken in December 1987 by Russian research vessels, composite ice maps and meteorological records. A bulk numerical model is applied in order to quantify the dominant physical processes responsible for re-shaping the thermohaline structure, from a state that opposes cascading to one that enhances it. The overall effect of these processes significantly varies depending on the distance from the shore. The most intensive ice production and rapid density increase occurred in the shallow waters, where the salinity increase accounted for almost 90% of the total density increase. The transitional zone, covering the outer shelf and slope waters, is subject to strong freshening by melting ice, which is transported from the production zone. This effect diminishes in the deep water, where the amount of imported ice is small. The opposing trends in salinity in the production and transitional zones caused by the joint effects of freezing/melting and ice mobility play a crucial role in providing the necessary conditions for the onset of cascading. Without ice advection and melting, the density contrast between the shallow and deeper waters at the shelf break would have been -0.10 (kg/m(3)), which would inhibit the formation of dense water cascade. The difference in density fluxes on both sides of the front was 2.1 X 10(-5) (kg/m(2) S), which is comparable with average flux over Arctic polynyas, and resulted in a cross-frontal density difference of 0.06 kg/m(3), which favours dense water cascading. (c) 2005 Elsevier Ltd. All rights reserved.