Ocean role in the winter sea ice openings north of Svalbard

The winter trend in the sea ice coverage in the Atlantic sector of the Arctic Ocean has been linked to the Atlantic Water heat transport, providing significant skill to decadal prediction (Yeager et al, 2015, Årthun et al., 2019). The Atlantic Water meets the sea ice north of Svalbard where it has the potential to melt significant amounts of ice and contribute to the formation of a cool, fresh surface layer (Rudels et al., 2004). In this study we investigate the origin of the intra-seasonal variability of winter sea ice melt north of Svalbard and evaluate its contribution to recurrent sea ice openings in this region. 

Based on outputs of a simulation with a high resolution regional ice-ocean model over the period 1995-2017, a number of large, short-term ice melt events could be identified in winter which can contribute up to 40% of the total winter ice melt. Most of these events show enhanced signature along the Atlantic Water path. However different types of events have been established depending on the scenario responsible for enhanced sea ice melt. Enhanced melt can happen concomitantly to large ice edge convergence over preexisting warm surface waters, a scenario which predominates during close-up of large ice openings. Large melt rates can also be driven by entrainment of warm water into the mixed layer in response to strong winds or to enhanced advection of warm water during episodes of increased transport in the boundary current. The latter process is however less efficient than entrainment. We conclude that increased southerly winds, which can sustain altogether ice edge retreat and efficient ice melt through entrainment and advection of heat into the region, create optimal conditions for major ice openings such as those observed north of Svalbard.