Previous posts noted how Arctic ice extents waxed and waned in response to the wavy Polar Vortex this year. The animation above showed how the ice fluctuated over the last two weeks. Okhhotsk upper left steadily lost ~225k km2, while Bering Sea lower left lost ~130k km2 in the first week then waffled around the same extent. Barents at the top lost ~170k km2 early, then in the last 10 days gained back most of it. Greenland Sea middle right waffled down and up with little change up to yesterday. Baffin Bay lower right produced the largest deficit on the Atlantic side ~180k km2.
The effect on NH total ice extents is presented in the graph below.The graph above shows ice extent through April comparing 2021 MASIE reports with the 14-year average, other recent years and with SII. The average April drops about 1.1M km2 of ice extent. This year MASIE showed two sharp drops and two recoveries, the last one coming close to average day 118. SII showed a less than average April loss of ~870k km2. In the end MASIE 2021 matched 2020, and higher then 2007.
The table below shows the distribution of sea ice across the Arctic regions.
|Region||2021120||Day 120 Average||2021-Ave.||2007120||2021-2007|
Overall NH extent March 31 was below average by 240k km2, or 2%. With Bering deficit offset by Okhotsk surplus, the entire difference from average matches the Baffin Bay deficit. The onset of spring melt is as usual in most regions.