Sea ice mass balance observations from the North Pole Environmental Observatory

In recent years the periphery of the Arctic sea ice cover has undergone significant changes, with a reduction in summer ice extent, a thinning of the ice, and a shift from multiyear to first year ice. Here we examine sea ice conditions during nine summers between 2000 and 2013 in the interior of the ice pack, using autonomous measurements of sea ice mass balance deployed near the North Pole. Results exhibit no definitive trends. There is large interannual variability, with surface melt ranging from 0.02m to 0.50m and bottom melt from 0.10m to 0.57m. The largest amounts of bottom melt have occurred in the past few years. For all 9 years the ice at the end of the melt season was at least 1.2m thick.