| Summary: | The Laptev Sea shelf is strongly impacted by the Lena River freshwater runoff and is an important ice formation and export region. In 2009, anomalously warm and saline waters likely with basin origin, were distributed over the shelf and changed the hydrography for >1 year. In early 2010, oceanographic moorings recorded the arrival of the anomalies on the inner shelf in form of a near-bottom under-ice gravity current, as a response to offshore winds and ice drift. Sea ice linked with winds and currents, allows insight into the processes leading to cross-shelf and vertical transport. For instance, near-shore polynyas and enhanced ice drift in early winter lead to lateral and vertical buoyancy fluxes, mixing and redistribution of fresher surface waters. Despite ice formation, bottom waters became less dense, which is opposite to the commonly observed dense water formation in other polar regions. Once landfast ice had established, ice drift was limited towards offshore, and currents were governed by near-bottom on-shore flow. Our observations show a vigorous under-ice circulation with implications for heat and nutrient budgets on the Laptev Sea shelf.
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