Wednesday, 1 April 2015

Large extent of older sea ice in the Beaufort Sea

I have processed images from the Drift Age Model of Fowler/Maslanik/Tschudi to draw attention to the extent of old ice in Beaufort. 2014, like 2013, enters the melt season looking more like a pre-2007 year in the highlighted region.

This amount of older ice is unusual for the post 2007 period, as the following gif animation shows, the area of interest being highlighted. Images from here.

It is possible that this will move further into Chukchi and then into the East Siberian Sea in the next few months. I expect that later in the coming summer this will hold up extent in the region highlighted above.


Anonymous said...

The loss and gain of sea ice in the arctic has been primarily dependent on which way the wind blows. It's been transport with respect to the Beaufort Gyre vs. the Transpolar Drift, not direct melting due to temperature variation. A strong Transpolar Drift and weak Gyre lead to a loss of MYI and significant annual swings because of the prevalence of first year ice. The last two years have seen the return of a strong Gyre with a weak Transpolar Drift--the historically more common condition. Hence, the recent buildup of MYI and its gradual distribution throughout more of the Gyre. So long as the Gyre remains strong MYI, area, and volume will continue to increase.

Chris Reynolds said...

Temperature is bound to show weak influence on melt because summer temperature trends are minimised as melting ice holds temperatures near zero.

Yes, ice is transported to the Beaufort/Chukchi/ESS (BCE) regions due to the Beaufort Gyre. And yes, the transpolar drift drives ice towards Fram where strong pressure differentials between Greenland and the Icelandic low leads to winds which export ice from the Arctic along the coast of Greenland.

Strength of the Beaufort Gyre does not equal ice volume gain and survival of sea ice. 2010 had a strong Beaufort High and resultant gyre over winter. That led to a large export into BCE which, while maintaining extent in the following summer led to a volume loss event as large as 2007, resulting in PIOMAS volume for thick ice collapsing. These conditions ultimately set the stage for the 2011 (equal with 2007) and 2012 (new record) extent lows.

Indeed the failure of the Beaufort Gyre Flywheel has meant that export into Beaufort in recent years has implied loss of that ice. As the pack has thinned increasing open water production efficiency has led to large areas of open water and low ice concentration in the BCE regions. So while ice would once have cycled back into the Transpolar Drift, it now suffers a high degree of loss in the BCE, this has reduced the typical age of the pack.

The recent build up of ice is mainly a result of the 2013 melt season. This was a strikingly poor year for melt. As a result a large volume increase entered the ice/ocean system of the Arctic. In 2014 atmospheric conditions were not unlike other post 2007 years (e.g. 2008, 2011). But the volume increase from 2013 combined with the less than perfect melt weather of 2014 to cause substantially greater ice survival than in almost any other post 1995 year. Hence the increase in volume.