August Arctic Ice Unalarming

The image above shows ice extents for day 233 from 2007 to 2017. Particularly interesting is the variation in the CAA (Canadian Arctic Archipelago), crucial for the Northwest Passage. (The region is located just north of the words “Ice Extent” in gold.) Note that 2016 was a fine year for cruising with the passage completely open at this date. That was not the case in 2014, and this year is also frozen solid.

The graph of August NH ice extents shows 2017 virtually tied with the decadal average as of yesterday. This year is now 550k km2 greater than 2016 and exceeds 2007 by 250k km2. SII (Sea Ice Index) 2017 is also 400k km2 lower. A previous post Beware the Arctic Storms of August discussed how late summer storms have dramatic impacts, and the graph shows both 2012 and 2016 plummeting in the last five days. By the end of the month in ten days, those two years will go below 4.4M km2.

The Table compares 2017 day 233 ice extents with the decadal average and 2007. it is evident that this year’s extents are in surplus on the Canadian side, offset by deficits on the Pacific side.

Region	2017233	Day 233 Average	2017-Ave.	2007234	2017-2007
(0) Northern_Hemisphere	5634884	5652704	-17820	5388004	246880
(1) Beaufort_Sea	569472	643245	-73773	731647	-162175
(2) Chukchi_Sea	285855	399788	-113934	222895	62959
(3) East_Siberian_Sea	386603	517871	-131268	81989	304614
(4) Laptev_Sea	308812	244158	64655	295384	13428
(5) Kara_Sea	65151	86439	-21288	161780	-96628
(6) Barents_Sea	33482	22883	10599	18656	14826
(7) Greenland_Sea	184582	222908	-38326	335976	-151394
(8) Baffin_Bay_Gulf_of_St._Lawrence	92400	37803	54597	51008	41392
(9) Canadian_Archipelago	494273	353728	140546	325028	169245
(10) Hudson_Bay	34936	43613	-8677	61078	-26141
(11) Central_Arctic	3178159	3079193	98966	3101306	76853

By the way, Barents is still above average and just added some ice.

The black line is average for the last 11 years. 2007 in purple appears close to an average year. 2014 had the highest annual extent in Barents Sea, due to higher and later maximums, holding onto ice during the summer, and recovering quickly. In contrast, 2016 was the lowest annual extent, melting out early and recovering later. 2017 in blue started out way behind, but grew rapidly to reach average, and then persisted longer to exceed even 2014. It will be important to see when the recovery of ice begins.

For more on why Barents Sea matters see Barents Icicles