Atmospheric conditions in the central Arctic Ocean through the melt seasons of 2012 and 2013: Impact on surface conditions and solar energy deposition into the ice‐ocean system. Issue 3 (5th February 2016) - Wang, Caixin
Abstract: Spectral Radiation Buoys and ice mass balance buoys were deployed on first‐year ice near the North Pole in April 2012 and 2013, collecting in‐band (350–800 nm) solar radiation and ice and snow mass balance data over the complete summer melt seasons. With complementary European ERA‐Interim reanalysis, National Centers for Environmental Prediction (NCEP) Climate forecast system version 2 (CFSv2) analysis and satellite passive microwave data, we examine the evolution of atmospheric and surface melt conditions in the two differing melt seasons. Prevailing atmospheric conditions contributed to a longer and more continuous melt season in summer 2012 than in 2013, which was corroborated by in situ observations. ERA‐Interim reanalysis data showed that longwave radiation likely played a key role in delaying the snowmelt onset in 2013. The earlier melt onset in 2012 reduced the albedo, providing a positive ice‐albedo feedback at a time when solar insolation was high. Due to earlier melt onset and later freeze‐up in 2012, more solar heat was deposited into the ice‐ocean system than in 2013. Summer 2013 was characterized by later melt onset, intermittent freezing events and an earlier fall freeze‐up, resulting in considerably fewer effective days of surface melt and a higher average albedo. Calculations for idealized seasonal albedo evolution show that moving the melt onset just 1 week earlier in mid‐June increases the total absorbed solar radiation by nearly 14% for the summer season. Therefore, the earlier melt onset may have been one of the most important factors driving the more dramatic melt season in 2012 than 2013, though atmospheric circulation patterns, e.g., cyclone in early August 2012, likely contributed as well. Key Points: Autonomous setup measuring sea ice‐albedo and mass balance deployed in high Arctic in 2012 and 2013 Air and surface conditions and their influences on ice‐ocean system examined with different data Earlier melt onset in 2012 was an important factor driving the more dramatic melt in that year