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The timing of snowmelt onset (MO) on Arctic sea ice derived from passive microwave satellite data is examined by determining the melting area (in km2) on a daily basis for the spring and summer melt season months over the 1979 – 2012 data record. The date of MO on Arctic sea ice has important implications for the amount of total solar energy absorbed by the ice-ocean system in a given year. Increasingly early mean MO dates have been recorded over the 34-year data record as evidenced by statistically significant trends of 6.6 days decade-1 over the extent of Arctic sea ice with the largest regional trend (11.8 days decade-1) occurring in the East Siberian Sea. Trends indicate MO is occurring later in the year in the Bering Sea. Temporal and spatial variability in melting events are examined in the time series of daily MO area and daily mapping of MO. Melting events are compared with reanalysis data to investigate the nature of atmospheric conditions inducing MO. The occurrence of transient cyclones tends to produce large, contiguous areas of melting on sea ice within the warm sector of the cyclone. By contrast, high pressure and attendant clear sky conditions tend to produce scattered, discontinuous areas of melting area. This work illustrates the need for a better understanding of the synoptic weather conditions leading to specific patterns in MO area to improve the predictability of early season Arctic sea ice response to a changing climate.
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