Sea Ice Decline – Winter Weather Wild Card
February 29, 2012
We’re getting dumped with a combination of rain, snow, ice and sleet today in the upper midwest. Not entirely unusually for leap-day weather – but just about anyone will tell you that this has been an unusual winter in the US, and around the world. New research strengthens the case that changes in arctic ice may make wild winters, with extremes of warmth AND cold – more common in Eurasia and North America.
A new study led by the Georgia Institute of Technology provides further evidence of a relationship between melting ice in the Arctic regions and widespread cold outbreaks in the Northern Hemisphere. The study’s findings could be used to improve seasonal forecasting of snow and temperature anomalies across northern continents.
Since the level of Arctic sea ice set a new record low in 2007, significantly above-normal winter snow cover has been seen in large parts of the northern United States, northwestern and central Europe, and northern and central China. During the winters of 2009-2010 and 2010-2011, the Northern Hemisphere measured its second and third largest snow cover levels on record.
“Our study demonstrates that the decrease in Arctic sea ice area is linked to changes in the winter Northern Hemisphere atmospheric circulation,” said Judith Curry, chair of the School of Earth and Atmospheric Sciences at Georgia Tech. “The circulation changes result in more frequent episodes of atmospheric blocking patterns, which lead to increased cold surges and snow over large parts of the northern continents.”
The study was published on Feb. 27, 2012 in the online early edition of the journal Proceedings of the National Academy of Sciences. The research was supported by NASA and the National Science Foundation.
You’ve probably heard a lot in recent years about how Arctic sea ice is melting. So what’s the big deal? After all, the Arctic’s a fair distance away and you’re not a polar bear.
Scientists worry that changes in the Arctic will have knock-on effects in other parts of the world, including closer to home. This includes on our winter weather, with three separate scientific studies published this year linking the loss of Arctic sea to cold and snowy winters here in Europe.
The most recent of these studies, published in the journal Proceedings of the National Academy of Sciences, comes from a team of researchers (incidentally including well-known blogging scientist Judith Curry) from Georgia Tech University, the Chinese Academy of Sciences and Columbia University.
The team used observational data along with climate models to examine whether there was a link between Arctic sea ice loss and the unusually large snowfall in Northern Hemisphere winters over recent years.
The research showed that when Arctic sea ice melt is unusually high in summer, the Arctic Ocean, Greenland, and northeastern Canada have a warmer winter, while northern North America, Europe, Siberia, and eastern Asia cool down and experience above average snowfall.
The graphic below is adapted from the University of Bremen sea ice images published on the indispensable Arctic Sea Ice Blog
Carbon Brief continues:
Scientists think that when Arctic sea ice melts more than usual in summer it takes longer for the sea ice to regrow in the autumn, leaving the ocean uncovered by ice for longer than normal.
Because sea ice reflects some of the sun’s energy, more uncovered ocean means the ocean warms more. In turn, this heat escapes from the ocean into the atmosphere, warming the air up and reducing the temperature difference between the Arctic and lower latitudes.
This affects weather systems, allowing more ‘blocking patterns’ to develop – where high pressure air masses sit over the European continent, ‘blocking’ other air masses and bringing cold, snowy conditions to the continent.
It was a large ‘blocking pattern’ that is thought to have caused the unusually cold and snowy weather experienced by much of Europe at the start of February 2012, neatly shown in this satellite image:
These changes could also lead to more snowfall, as the study’s lead author Dr Jiping Liu, a senior research scientist in the School of Earth and Atmospheric Sciences at Georgia Tech, explains:
“We think the recent snowy winters could be caused by the retreating Arctic ice altering atmospheric circulation patterns … and increasing the amount of moisture in the atmosphere. These pattern changes enhance blocking patterns that favor more frequent movement of cold air masses to middle and lower latitudes, leading to increased heavy snowfall in Europe and the Northeast and Midwest regions of the United States.”
Retreating Arctic sea ice, according to the researchers, helps alter the atmosphere in two ways.
First, scientists found that less ice is causing a change in atmospheric circulation patterns, weakening the westerly winds that blow across the northern Pacific and Atlantic oceans. That weakened jet stream, in turn, allows more frequent surges of bitter cold Arctic air not only into the U.S., but also in Europe and east Asia.
“We have more cold air outbreaks,” said Jiping Liu, a senior research scientist in the School of Earth and Atmospheric Sciences at Georgia Tech, and a co-author of the new study released today.
The second factor, Liu said, is that more water is evaporating into the air as Arctic ice at the ocean’s surface melts away.
“This greatly enhances the transfer of moisture from the ocean to the atmosphere,” Liu said. That humidity, he says, essentially acts as fuel to help supercharge “Snowmageddon”-type storms like the ones that paralyzed parts of the northeastern U.S. in 2010. A more recent, deadly deep freeze in Eastern Europe left 650 people dead.
“The record decline in Arctic sea ice is at least a critical contributor to recent snowy winters in northern continents,” Liu said.
The disinformers have repeatedly suggested that big snowstorms disprove (!) climate science. They can’t stand the fact that actual science says that the Snowpocalypses we’ve been seeing can be directly linked to global warming, which, of course, wasn’t news to anyone who actually reads the scientific literature or talks to real climatologists (see “An amazing, though clearly little-known, scientific fact: We get more snow storms in warm years!“).
This study is probably particularly annoying to the disinformers since it was co-authored by (climate scientist and favorite of denial fringe Judith) Curry, who has transformed herself from climate science advocate into a promoter of many long-debunked disinformers (see “The curious incident of Curry with the fringe“).
Below, see my annual Arctic ice wrap-up video from this past September, 2011: