Autonomous observations of the spatial variability and temporal evolution of Arctic sea ice mass balance

Observations indicate that the Arctic sea ice cover is undergoing significant decreases in both its thickness and areal extent. The sea ice mass balance provides insights into understanding these changes by attributing them to variations in ice growth, melt season length, snow depth, surface melt, and bottom ablation and thus relating them to atmospheric and ocean forcing. As part of an Arctic Observing Network, we have routinely deployed ice mass balance buoys (IMB) at multiple locations to autonomously monitor the sea ice cover since 2000. Results show considerable spatial variability across the Arctic in a given year. In general, the largest amount of melting has been observed in the Beaufort Sea, while the smallest is observed in ice north of the Canadian Archipelago. There is also interannual variability at a particular location. For example, buoys deployed at the North Pole show year to year values of surface ice melt ranging from 0 to 55 cm. There has been major thinning of ice in the Beaufort Sea primarily due to increases in bottom melting. At the end of summer, peak ocean heat fluxes to the ice in this region have exceeded 100 Watts per square meter.