Fluctuations in the Atlantic Water Transport as a Source for Intra-seasonal Variability in the Barents Sea Ice Cover

During the last few decades, the Arctic has experienced large climatic changes, reflected in its shrinking ice cover. While the most spectacular decline during summer has occurred on the Pacific side of the Arctic, the largest variability and decline during winter has occurred in the Barents Sea on the Atlantic side of the Arctic. Recent studies have shown that the sea-ice cover in the Barents Sea responds to variations in the oceanic heat transport on time scales of years and longer, while variations on time scales of weeks to months have been attributed to wind-driven ice drift, due to the lower advection speed in the ocean as compared with the atmosphere. Here, we utilize both satellite-based observations of sea ice and a numerical model to find evidence that variability in oceanic heat transport impacts the sea-ice cover in the Barents Sea also on intra-seasonal time scales. Ekman divergence caused by positive wind stress curl associated with atmospheric low pressure systems over the northern Barents Sea shelf induces an eastward barotropic current anomaly along-path the Atlantic Water flow through the Barents Sea toward the Arctic. The resulting transport anomalies cause a downstream displacement of the along-path temperature gradient owing to the increased current speed, and subsequently a positive downstream temperature anomaly. During winters with positive wind stress curl over the Barents Sea, the increased availability of oceanic heat causes distinct, negative anomalies in sea ice, especially in the eastern parts. Model results show that such heat transport anomalies represent a robust mode of the climate variability in the Barents Sea region.