Mid May 2021 Persistent Arctic Ice

ArcDay135 2007 to 2021

 

Typically in climate observations, averages are referenced without paying attention to the high degree of component variability from year to year, and over longer time periods.  Mid May is when the Spring melt is well underway, but with the Arctic core still frozen solid.  Yet the animation above shows on day 135 over the last 15 years, there are considerable differences as to how much ice is in which regions. 

On the bottom left is Bering Sea which had ice extents on this day ranging from a high of 682k km2 (2012) to a low of 38k km2 (2018).  The day 135 average for Bering is 293k km2, but with a standard deviation of 192k (65%).  Okhotsk center left is the next most variable, from 290k (2012) to 99k (2019), averaging 188k with std. deviation of 63K (33%).  Barents Sea center top has a large variability from 568k km2 (2009) to 223k (2012), averaging 422k km2 +/- 111 k km2.  Other Arctic regions vary little on this day from year to year.  For example, Hudson Bay is close to 1.2M km2 every year on day 135.

The effect on NH total ice extents is presented in the graph below for the period mid April to mid May, comparing the 14-year average with 2021 MASIE and SII, and some other years of interest.

Arctic2021135

Note on average this period shows an ice loss of 1.5M km2.  MASIE 2021 is about 200k km2 below average, 1.6% down, or having the same total extent 3 days ahead of average.  Interestingly, SII shows about 200k higher, matching the MASIE average for day 135.

The table below shows the distribution of sea ice across the Arctic regions.

Region 2021135 Day 135 Average 2021-Ave. 2007135 2021-2007
 (0) Northern_Hemisphere 12490666 12692542  -201876  12431928 58738 
 (1) Beaufort_Sea 1058904 1044067  14837  1057649 1255 
 (2) Chukchi_Sea 926504 921289  5215  953491 -26987 
 (3) East_Siberian_Sea 1083562 1081242  2320  1075314 8248 
 (4) Laptev_Sea 852338 881285  -28948  828738 23600 
 (5) Kara_Sea 858111 882730  -24619  876053 -17942 
 (6) Barents_Sea 396873 421592  -24719  351553 45320 
 (7) Greenland_Sea 669899 618664  51235  564865 105035 
 (8) Baffin_Bay_Gulf_of_St._Lawrence 892167 1093916  -201749  1018780 -126614 
 (9) Canadian_Archipelago 852422 838509  13913  830604 21818 
 (10) Hudson_Bay 1160950 1194448  -33497  1167310 -6360 
 (11) Central_Arctic 3242075 3223985  18089  3234305 7769 
 (12) Bering_Sea 271137 293222  -22085  298268 -27130 
 (13) Baltic_Sea 3752 7215 -3463  6368 -2617 
 (14) Sea_of_Okhotsk 220784 188072  32712  164833 55951 

Overall NH extent March 31 was below average by 200k km2,  equivalent to the deficit in Baffin Bay.  Elsewhere smaller deficits were offset with surpluses. The onset of spring melt is as usual in most regions.

via Science Matters

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May 16, 2021 at 02:42PM

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