Saturday, September 15, 2012

Arctic Ice Melt Now & Winters Ahead

Sea ice in the Arctic Ocean is at record low values, a good chunk below the old record from 2007, as it approaches its annual bottoming out that will occur over the coming weeks as winter begins to set in over the high latitudes.  The record lows in sea ice are part of a continuing trend that has seen the amount of ice drop about a million square kilometers over the last decade at the absolute minimum point in September.

Granted, "good" sea ice records go back only into the late 70's but the recent trend isn't good as far as ice in the Arctic is concerned.  How does this impact our weather?  Well, future winters could become a bit more volatile and fickle as far as winter weather is concerned.

You can see the slight difference in sea ice minimum from last year (below left graphic) to this year, especially to the north of Siberia and Alaska, where there has been a more substantial "dent" in sea ice this year compared to last.  Last year's sea ice was third lowest on record, ahead of this year and 2007.

The impacts of low sea ice are up to some debate -- but one of the chicken/egg arguments is that the additional warmth in ocean temperatures in the high latitudes will fuel additional warmth in the atmosphere over the high latitudes, which in turn limits the potential for deep cold air masses to build up.  The lowering of temperature differential over latitudes could result in more blocking patterns and less progressive jet streams as the jet stream winds slacken off in winters compared to past years.   A study done last year and reiterated in recent days suggests a potential correlation to jet stream blocking patterns with a warming Arctic.

The blocking theory does have some legs -- the US East Coast benefited greatly from the blocking winter pattern in the 2009-10 and 2010-11 winters from a snow standpoint with back-to-back winters of significant snowfall.  Last winter was a dud overall but excessive blocking in October did produce a snowstorm north and west of the city.  Despite a warm winter overall, parts of Europe were rocked by significant snowstorms in February and a significant cold wave gripped a good chunk of Europe from late January into mid February.  

Taking it a step further back, the winter of 2006-2007 is a very good example of "fickle" and "blocky" as we went from record warmth in January to ice storms and our coldest month in years in February, only to bounce to 80 degrees in mid March, followed by three inches of sleet less than 48 hours later.  Such an example may be a bit more extreme but such fickleness in our cold season could be a more frequent "normal" in the future.

Predicting where and how significant those blocking patterns are when they set up is the inexact science in the long range forecasting scheme of things; however, given the increasing amount of open ocean in the Arctic summer it is quite possible we could see more blockiness in our winter weather patterns over the coming winters, with some places getting nailed with storms and snow and others basking in unseasonable warmth.