Arctic Ice Ides of March

The monthly average for March represents the annual maximum for Arctic ice extent.  The graph shows the 12-year March average in MASIE is 15M km2, with SII about 200k km2 less.  In this period six years were higher and six lower, including a virtual tie between 2019, 2015 and 2007, slightly higher than 2017 and 2018.  In either MASIE or SII this March is ~330k km2 or 2% below the 12-year average.

As we will see, March 2019 ended with a flash melt that reduced extents dramatically in the final week or so.  First the graph of March comparing the daily extents.

Note that 2019 was close to average as recently as day 79 before dropping well below average and recent years.  As reported previously, most of the decline was due to early melting in Bering Sea, which loses it ice every Spring anyway. Below compares NH ice extents with and without Bering ice.

The gap between the black and green lines shows Bering contributed on average ~600k km2 to overall NH ice extents at the beginning of February, increasing to 800k km2 by end of March.  In 2019, the gap between the cyan and purple lines shows ~500k km2 of Bering Ice starting in February, decreasing to 140k km2 by March, then increasing up to 450k km2, and now back down to 180k km2. When the Bering volatility is set aside, the purple and green lines show Arctic ice excluding Bering was above average most of the month, and only slightly lower at the end.

So what has been happening?  In two words: Polar Vortex.  When cold |Arctic air descends into parts of North America and Euarasia, warm air intrudes into the Arctic to replace it, and ice extents are reduced. For example, see the recently reported balmy weather in UK, and soon to be switched to bitter cold weather. From the Express  UK weather forecast: SHOCK Map shows Britain ENGULFED by freezing Arctic weather front

The cold front is shown in the image, The link underneath goes to the video.

//players.brightcove.net/2540076170001/B1Hli6KCG_default/index.html?videoId=6020946025001#t=12s

The table below shows extents for day 90 comparing 2019 to the 12 year average, and also showing the 600k km2 loss of ice in just 8 days at month end.

Region 2019090 Day 090 
Average
2019-Ave. 2019082 2019090-2019082
 (0) Northern_Hemisphere 13983435 14786570 -803135 14600645 -617210
 (1) Beaufort_Sea 1070498 1070149 348 1070291 207
 (2) Chukchi_Sea 945075 965775 -20700 966006 -20931
 (3) East_Siberian_Sea 1087137 1086034 1103 1087137 0
 (4) Laptev_Sea 897845 896685 1160 897845 0
 (5) Kara_Sea 892123 917893 -25770 926462 -34340
 (6) Barents_Sea 515799 658886 -143086 681050 -165251
 (7) Greenland_Sea 585051 659518 -74467 552178 32873
 (8) Baffin_Bay_Gulf_of_St._Lawrence 1343734 1456673 -112939 1431122 -87388
 (9) Canadian_Archipelago 853337 852817 520 853337 0
 (10) Hudson_Bay 1260903 1253798 7105 1260903 0
 (11) Central_Arctic 3238381 3233007 5374 3227734 10647
 (12) Bering_Sea 178917 803209 -624292 446151 -267235
 (13) Baltic_Sea 25134 68136 -43002 41886 -16752
 (14) Sea_of_Okhotsk 1086939 851929 235010 1150521 -63582

Note that BCE (Beaufort, Chukchi and East Siberian) is rock solid, along with Laptev.  Atlantic metling has begun, with the largest losses in Barents and Baffin Bay.  The major deficit is Bering is there, and while Okhotsk has started melting, it remains 235k km2 above average at this time.

via Science Matters

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April 1, 2019 at 10:31AM

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