From Science Matters

By Ron Clutz

For ice extent in the Arctic, the bar is set at 15M km2. The average peak in the last 17 years occurs on day 62 at 14.986M km2 before descending, though some years the extent can be above 15M much later.  Ten of the last 17 years were higher than 15M, and recently 2020, 2022 and now 2023 ice extents cleared the bar at 15M km2. The actual day of annual peak ice extent varied between day 59 (2016) to day 82 (2012).

All of this means that 2023 peaked while passing the 15M km2 threshold two days later than average.  The graph below shows the situation evolving over the last four weeks anticipating the annual maximum.

The NH ice extent gap on day 77 is at 269k km2, or 1.8%.  After the day 62 peak, 2023 extents declined sharply until day 71 before recovering to reduce the deficit. (Note that ice extent is affected also by winds piling up drift ice, as well as melting from intrusions of warmer air or water.) SII has shown lower extents throughout this period, averaging 250k km2 less than MASIE.

March monthly average extents in recent years have been below average. While average extents will decline further, we shall see what this year does with only two weeks left to make a difference.

Region	2023077	Day 77 Average	2023-Ave.	2018077	2023-2018
(0) Northern_Hemisphere	14649553	14918812	-269258	14528206	121348
(1) Beaufort_Sea	1070966	1070266	700	1070445	521
(2) Chukchi_Sea	966006	965801	206	966006	0
(3) East_Siberian_Sea	1087137	1087109	29	1087137	0
(4) Laptev_Sea	897845	897837	7	897845	0
(5) Kara_Sea	934539	922767	11771	934807	-268
(6) Barents_Sea	605659	637818	-32159	689702	-84043
(7) Greenland_Sea	835991	617943	218048	514678	321313
(8) Baffin_Bay_Gulf_of_St._Lawrence	1249789	1546282	-296493	1399951	-150162
(9) Canadian_Archipelago	854843	853118	1724	853109	1734
(10) Hudson_Bay	1260903	1259573	1330	1257207	3696
(11) Central_Arctic	3243341	3217827	25514	3131403	111939
(12) Bering_Sea	739914	760728	-20814	445480	294434
(13) Baltic_Sea	67881	80745	-12864	127449	-59568
(14) Sea_of_Okhotsk	822356	982054	-159698	1136990	-314633

The main deficit to average is in Baffin Bay and Sea of Okhotsk, partly offset by a surplus in Greenland Sea. 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 2023 rank in the annual Arctic maximum competition?

Drift ice in Okhotsk Sea at sunrise.

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