Impact of Episodic Oceanic Heat Flux Events on the Sea Ice Extent North of Svalbard

The region north of Svalbard is experiencing ice loss and retreat of the ice edge north- and eastwards in all seasons. Short-term variability is thought to be driven mainly by atmospheric circulation redistributing ice floes whereas oceanic heat flux through the inflow of Atlantic Water is a major factor for longer term trends. In this presentation, we discuss the role of episodic large oceanic heat flux events in the development of the winter sea ice north of Svalbard. Since 2012, the A-TWAIN project maintains moorings across the continental slope north of Kvitøya (80°N, 30°E) , Svalbard. We present results from the 2012-2013 deployment. During this period several episodes characterised by strong currents carrying large volumes of Atlantic Water along the slope occurred. The strongest of these events occurred in late November/early December 2012. Prior to the event the ice had moved southward over the moorings as the winter ice cover began to form. However, the heat input associated with the AW pulse reversed the advance of the sea ice. The region around the moorings became ice-free again and remained open until strong southerly and easterly winds promoted import of ice again in mid-January. The oceanic forcing thus led to later development of sea ice north of Svalbard and in the northern Barents Sea, shortening the ice growth season and potentially leading to a thinner and weaker ice cover. Episodic heat flux events along the Atlantic Water inflow could promote further eastward retreat of the winter ice edge along the shelf and slope.