| Summary: | Over the past three decades of the observed satellite record, there have been significant changes in sea ice cover across the Bering, Chukchi, and Beaufort seas of the Pacific Arctic Region (PAR). Satellite data reveal that patterns in sea ice cover have been spatially heterogeneous, with significant declines in the Chukchi and Beaufort seas, yet more complex multi-year variability in the Bering Sea south of St. Lawrence Island. These patterns in the Chukchi and Beaufort seas have intensified since 2000, indicating a regime shift in sea ice cover across the northern portion of the PAR. In particular, satellite data over 1979–2012 reveal localized decreases in sea ice presence of up to -1.64 days/year (Canada Basin) and -1.24 days/year (Beaufort Sea), which accelerated to up to -6.57 days/year (Canada Basin) and -12.84 days/year (Beaufort Sea) over the 2000–2012 time period. In contrast, sea ice in the Bering Sea shows more complex multi-year variability with localized increases in sea ice presence of up to +8.41 days/year since 2000. The observed increases in sea ice cover since 2000 in the southern Bering Sea shelf region are observed in wintertime, whereas sea ice losses in the Canada Basin and Beaufort Sea have occurred during summer. In this study, we summarize the recent variability in sea ice cover across the broader PAR, including the Bering, Chukchi, and Beaufort seas. We pay particular attention to sea ice using relatively high spatial resolution (6.25 km) sea ice concentrations derived from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) sensor on the Aqua satellite platform . Based on a 15% sea ice concentration threshold to categorize sea ice as being either present or absent, annual sea ice persistence, the timing of sea ice breakup, and the timing of sea ice formation are quantified with AMSR-E data spanning 2003–2011 (up until the point of instrument failure in October 2011).
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