TORONTO, ON- JULY 25 – Derek Drouin wins the men’s high jump at the Pan Am Track and Field competition at CIBC Athletics Stadium at York University in Toronto. July 25, 2015. Steve Russell/Toronto Star

As anticipated in the previous post reprinted below, Arctic ice extent appears to have peaked under the 15M km2 threshold.  An earlier discussion at 2020 year end noted that March actually ends up with less ice extent than end of February, so the rest of the month is not likely to add any more ice.  Here is the graph for March including yesterday.

The graph shows this year did recover from a 400k km2 deficit to the 14-year average, to about 100k by day 70, and has now fallen back to almost 300k km2 down (2%).  It is also apparent that extent will likely decline in the next two weeks, by about 300k km2 on average, already matched by 2021.  Climatology uses SII March monthly average as the annual maximum, so that will come out lower as well.

Interestingly, both Okhotsk and Barents Seas peaked well above 2020, and are now starting to retreat, along with other marginal basins.  The central Arctic, Siberian and Canadian regions remain solidly frozen.

Background previous post Arctic Ice Moment of Truth 2021

For ice extent in the Arctic, the bar is set at 15M km2. The average peak in the last 14 years occurs on day 62 at 15.04M km2 before descending, though the average can still be above 15M at late as day 73.  Nine of the last 14 years were able to clear 15M, but recently only 2016 and 2020 ice extents cleared the bar at 15M km2; the others came up short. The actual annual peak ice extent day varied between day 59 (2016) to day 82 (2012).

The animation shows in two weeks how this year’s ice extents contracted and then regrew greater than before, coincidental with the wavy Polar Vortex (PV) first admitting warmer southern air and then keeping the cold air in.

As reported previously, most of the action was firstly in the Pacific, especially Sea of Okhotsk upper left, ice shrinking one week by 200k km2 and rapidly growing back 210k km2 ice extent the next.  Okhotsk ice is now 1.1M km2, 96% of 2020 max.  On the Atlantic side, Barents sea upper right lost 100k km2 retreating from Svalbard, then gained 120k km2 back.  Greenland Sea ice middle right lost 100k km2, and then gained 150k km2.  Barents now has 3% more ice than 2020 max, while Greenland sea ice is 85% of last year’s max.

All of this means that 2021 will be hard pressed to pass the 15M km2 threshold.  The graph below shows the situation evolving over the last two weeks anticipating the annual maximum to appear within the fortnight.

Note that Sea Ice Index (SII) went offline day 51 so the MASIE record alone shows the loss of ice extent ending day 56 and climbing up to the present.  The NH ice extent gap is at 244k km2, or 1.6%.  Since the 14 year average has already peaked, further growth will narrow the margin.  (Note that ice extent is affected also by winds piling up drift ice, as well as melting from intrusions of warmer air or water.)

Last year surpassed the average while other recent years were lower.  We shall see what this year does with only 10 days or so to make a difference.

Region2021063Day 063 Average2021-Ave.20070632021-2007
 (0) Northern_Hemisphere1477261715016830-24421414665491107126
 (1) Beaufort_Sea107068910702544351069711978
 (2) Chukchi_Sea96600696411818889660060
 (3) East_Siberian_Sea10871201087134-141087137-17
 (4) Laptev_Sea897827897842-15897845-18
 (5) Kara_Sea93500692965053569320672939
 (6) Barents_Sea805710649490156220626044179666
 (7) Greenland_Sea6696516250854456661684152809
 (8) Baffin_Bay_Gulf_of_St._Lawrence12245081553901-32939312205133995
 (9) Canadian_Archipelago85459785314814508527671830
 (10) Hudson_Bay12604711260567-9612567183753
 (11) Central_Arctic31976273222365-247383229824-32197
 (12) Bering_Sea631115686765-55650660726-29612
 (13) Baltic_Sea6514697873-32727104884-39738
 (14) Sea_of_Okhotsk1090295108459357031129107-38812

The main deficit to average is in Baffin Bay, partly offset by a surplus in Barents.  Smaller pluses and minuses are found in other regions.

Typically, Arctic ice extent loses 67 to 70% of the March maximum by mid September, before recovering the ice in building toward the next March.

What will the ice do this year?  Where will 2020 rank in the annual Arctic Ice High Jump competition?

Drift ice in Okhotsk Sea at sunrise.

For more on the Pacific basins see post Meet Bering and Okhotsk Seas

via Science Matters

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March 15, 2021 at 09:18AM