Apologies to Shakespeare and Richard III for the title to this post.

The Arctic ice beast is slouching toward mid-March maximum with some peculiarities from the meandering polar vortex.  More on that from Dr. Judah Cohen later on.

A week ago the ice watch post noted the recovery in Okhotsk which has continued and is now above average for the date.  Bering sea ice is below normal and the main reason for lower overall extent this year.

Ice extents for January appear in the graph below; 2018 is shown to January 15, other years for the full month.  11 year average is 2007 to 2017 inclusive.

Note that 2007 caught and exceeded the 11 year average ending the month tied.  2018 has now matched 2017 though both lag behind average having started the year in deficit. SII 2018 is running about 200k km2 less than MASIE for the month.

Below is the analysis of regions on day 015.  Average is for 2007 to 2017 inclusive.

Region	2018015	Day 015  Average	2018-Ave.	2017015	2018-2017
(0) Northern_Hemisphere	13250556	13887982	-637426	13250750	-194
(1) Beaufort_Sea	1070445	1070178	267	1070445	0
(2) Chukchi_Sea	965971	965842	129	964251	1720
(3) East_Siberian_Sea	1087120	1087134	-14	1087137	-18
(4) Laptev_Sea	897845	897842	3	897845	0
(5) Kara_Sea	918904	911229	7675	866224	52680
(6) Barents_Sea	329631	545176	-215546	334131	-4500
(7) Greenland_Sea	492704	625241	-132536	544015	-51311
(8) Baffin_Bay_Gulf_of_St._Lawrence	1181843	1184801	-2957	1284241	-102397
(9) Canadian_Archipelago	853109	853028	81	853214	-106
(10) Hudson_Bay	1260838	1252263	8575	1260887	-49
(11) Central_Arctic	3182898	3216678	-33780	3164223	18676
(12) Bering_Sea	256467	558895	-302428	253648	2819
(13) Baltic_Sea	18186	51436	-33249	29954	-11768
(14) Sea_of_Okhotsk	701953	615696	86257	617141	84813

The core of the Arctic is frozen solid and for the date 2018 is 4.6% below average.  The difference is mainly due to Bering Sea 64% below average and Barents 40% down. The recovering ice in Okhotsk is now above both the average and the extent last year at this time.

Background:  Updated Winter Forecast by Dr. Judah Cohen, January 15, 2018

Dr. Judah Cohen of AER published his current Arctic Oscillation and Polar Vortex Analysis and Forecast on January 15, 2018. His comments are always enlightening, and particularly so this time. Excerpts in italics with my bolds.

In previous blogs, I have often discussed winter 2013/14 as possibly the best analog for this winter so far. I do believe that the stratospheric PV disruption that occurred in late December and the subsequent response in the tropospheric circulation are similar to what occurred repeatedly in winter 2013/14. However, I think the two winters are now diverging. The single large-scale weather feature that signals to me a divergence from this winter and 2013/14 is the widespread area of below normal temperatures across northern Eurasia beginning this week but predicted to become dominant across the continent next week. The last winter where persistent extensive below normal temperatures where observed across Northern Eurasia was winter 2012/13. That is also the last winter that a mid-winter major warming was observed (where the mean zonal wind reverses at 60°N and at 10hPa), which occurred the second week in January. I do consider that a major warming occurred in 2015/16 but that was in March and subsequently dovetailed into a final warming.

There are signs that a disruption of the stratospheric PV will occur but the timing and magnitude remains uncertain. But based on the anticipated widespread area of below normal temperatures across Northern Eurasia I do believe that the most significant stratospheric PV disruption of the winter is likely in the coming weeks. Our polar vortex forecast model predicts that the PV disruption will peak the second week of February. The model is speculative but a marker to watch. This anticipated stratospheric disruption is likely to differ from the stratospheric PV disruption in late December where the resultant below normal temperatures were focused across North America while much of Eurasia remained relatively mild. If I am correct that a subsequent stratospheric PV disruption will be more significant than the one in December, then I expect the focus of the resultant cold temperatures to be across northern Eurasia, especially Siberia. Temperatures would likely average below normal across much of Siberia and likely elsewhere across northern Eurasia, possibly through the end of February.

The impacts of a more significant stratospheric PV disruption would be less certain across North America. Still I would consider such a PV disruption to increase the probability of cold temperatures following the disruption across eastern North America. Following the mid-winter major warming in January 2013 temperatures initially turned cold across the Western US but the core of below normal temperatures migrated east as the winter progressed. The Global Forecast System (GFS) is predicting the core of below normal temperatures to be focused in Western Canada during the second half of January. However, my expectation would be for the core of the below normal temperatures to slowly migrate southeastward with time and as of now I favor a relatively cold February in southeastern Canada and the Eastern US.

A wild card in North American weather all winter has been ridging/blocking in the North Pacific. For the first half of the winter it was centered in the Gulf of Alaska and along the west coast of North America, contributing to warm temperatures in western North America but cold temperatures in eastern North America. Latest weather model runs are predicting a westward retrogression of this blocking closer to the Aleutians. This position favors cold temperatures in western North America but warm temperatures in eastern North America. And cold temperatures may be focused in western North America for the remainder of the winter if the ridging remains near the Aleutians but I expect that an eventual PV disruption will at least partially offset or cancel warming forced by the central North Pacific ridging.

 

Whichever fork of the road the ice takes, the Polar Bears had a very happy New Years Day.