Atlantic waters inflow north of Svalbard: Insights from IAOOS observations and Mercator Ocean global operational system during N-ICE2015

As part of the N-ICE2015 campaign, IAOOS (Ice Atmosphere Ocean Observing System) platforms gathered intensive winter data at the entrance of Atlantic Water (AW) inflow to the Arctic Ocean north of Svalbard. These data are used to examine the performance of the 1/128 resolution Mercator Ocean global operational ice/ocean model in the marginal ice zone north of Svalbard. Modeled sea-ice extent, ocean heat fluxes, mixed layer depths and AW mass characteristics are in good agreement with observations. Model outputs are then used to put the observations in a larger spatial and temporal context. Model outputs show that AW pathways over and around the Yermak Plateau differ in winter from summer. In winter, the large AW volume transport of the West Spitsbergen Current (WSC) (similar to 4 Sv) proceeds to the North East through 3 branches: the Svalbard Branch (similar to 0.5 Sv) along the northern shelf break of Svalbard, the Yermak Branch (similar to 1.1 Sv) along the western slope of the Yermak Plateau and the Yermak Pass Branch (similar to 2.0 Sv) through a pass in the Yermak Plateau at 80.88N. In summer, the AW transport in the WSC is smaller (similar to 2 Sv) and there is no transport through the Yermak Pass. Although only eddy-permitting in the area, the model suggests an important mesoscale activity throughout the AW flow. The large differences in ice extent between winters 2015 and 2016 follow very distinct atmospheric and oceanic conditions in the preceding summer and autumn seasons. Convection-induced upward heat fluxes maintained the area free of ice in winter 2016.