Update Sept. 20, 2015: 2014 and 2015 Minimums Established, 11 days ago in NOAA, 2 days ago in MASIE
In the annual match of the ocean vs. Arctic ice, Mother Nature has blown the whistle. Results are little confusing, since NOAA shows the lowest extent 11 days ago, and MASIE only 2 days ago. Moreover, MASIE dropped a lot of ice in the recent period and is now showing less ice than NOAA. Usually, MASIE is higher by 2-300k km2.
Still, for the climate record it will be the September average that counts, and the platform is firmed up for that result.
First the daily situation:
September 19 day 262 results from MASIE. 2014 loses a lot while 2015 gains a lot of ice extent.
While 2014 lost 46k of ice, 2015 gained 70k recovering well above the previous annual daily ice minimum..
2015 ice extent now trails 2014 by 10.6%, which is about 538k km2 difference. Day 262 is the 2014 daily ice extent minimum. Day 260 was 2015 minimum, according to MASIE.
Comparing 2014 and 2015 at Annual Minimums
|Ice Extents||Day 2014262||Day 2015260||Ice Extent|
|Region||Ann Min||Ann Min||km2 Diff.|
The table shows the effects of weather in the western Arctic. In August 2015 lost 700k km2 more than 2014, a differential that persisted to the minimum. The reductions occurred in the BCE region and in the near by CAA (Canadian Archipelago). In addition in the east, Barents melted out early and entirely, and nearby Kara become mostly open water.
Elsewhere, on the Canadian side, Hudson and Baffin Bay along with the Greenland Sea had more ice, and the Central Arctic was nearly the same as in 2014.
The first 19 days of September 2015 is in the books, so here is an outlook on the melt season conclusion beyond the daily minimums.
For most of the season, 2015 Arctic sea ice extent was tracking 2014. In fact the July average extent was slightly higher than 2014. Then weather intervened in the last week of August. A large and strong cyclone centered over Chukchi Sea began breaking up ice in the BCE Region and affecting CAA (Canadian Archipelago) and the Central Arctic. In addition, most of the summer the Arctic Oscillation (AO) was in negative phase, meaning fewer clouds, more direct insolation and ice melting. More discussion of these two factors is at the end of this post.
The effects of this storm are seen in the rapid increase in water extent ( 482k km2 in one week) so that August 31 2015 had less ice than did 2014 at minimum September 19. Water extent continued to grow, and then stabilized once the storm abated and the AO went from negative to neutral. Now the ice is growing beyond the daily minimum.
Comparing MASIE and NOAA Ice Extents.
The table shows July 2015 was above 2014 but late August weather caused a drop in monthly averages. The August average is now complete and shows ice extent dropped ~2.7M km2 from July, compared to a 2014 loss of ~2.0M. That difference has persisted up to today. NOAA typically reports a lower extent than MASIE, a difference that averaged ~300k km2. Then in one week MASIE dropped while NOAA plateaued, and now NOAA September extents are quite close to MASIE, some days showing a higher number.
With the September daily ice starting out lower than 2014 the monthly average should end up much smaller. The September first 19 days average is shown, a figure that should rise and end the month near 4.6M km2. This presumes the minimum has definitely occurred, and the recovery is in effect.
In any case, I am not alarmed over open water in the Arctic. Steadily increasing and above average September ice extents signify the coming of the next ice age, a genuine threat to human life and prosperity. Fortunately, that is not the indication this year.
Current and Recent Weather in the Arctic
In addition to the storm, the negative AO has been conducive to accelerating ice melting by increased insolation.
September 16 Arctic Oscillation Forecast from AER:
The AO, which has remained almost consistently in negative territory since late June, has resulted in near record low AO values for July and August. The AO is predicted to first trend positive through the weekend and pop into positive territory early next week. However by midweek the AO is predicted to return back into negative territory and remain negative through early October.
“The positive trend in the AO and the setting sun may have brought an early end to the Arctic sea ice melt season but not before sea ice extent achieved its fourth lowest value since observations began. It is likely that the extremely low AO values observed in July and August are reflective of atmospheric conditions (sunny and warm) that were conducive to rapid sea ice melt.”
The Alaska Dispatch News reported August 27 on the storm effects at Barrow, Alaska:
“The service has issued a coastal flood warning for Barrow until Friday morning, along with a high surf advisory for the western part of the North Slope and a gale warning for much of the Beaufort and Chukchi Seas. Seas up to 14 feet were forecast for Thursday in the Chukchi. . .Thursday’s high waves and flooding are products of a large storm that’s being felt as far as Southcentral Alaska, where high winds are forecast, Metzger said. “It’s a pretty big low-pressure system that’s over the Arctic Ocean,” he said. ”
This storm is reminiscent of the 2012 event that resulted in the lowest ice, greatest water extent this century. The high winds, waves and swells have several effects: Gales push ice floes, opening water between them and pushing them toward warmer waters; Ice pieces are churned and fractured increasing the melt rate; Wave action can flood ice packs or can cause compacting, further reducing extent.