Winter weather remembers summer's Arctic sea-ice

by John D. Cox | April 15, 2009

Like a boulder in a stream, the consequences to the climate of disappearing summer sea ice in the Arctic will extend far beyond the polar region and are likely to alter large-scale winter weather patterns deep within the Northern Hemisphere, U.S. researchers warn in a new analysis.

The time-lapse between the summertime exposure of the ice-free Arctic Ocean and the distant atmospheric consequences in the following autumn and winter months offers opportunities to give advance warning to affected regions such as the drought-plagued American Southwest.

"By combining satellite measures of sea-ce extent and conventional atmospheric observations, we find that varying summer ice conditions are associated with large-scale atmospheric features during the following autumn and winter well beyond the Arctic's boundary," wrote Jennifer A. Francis of Rutgers University.  Results of the work by Rutgers and University of Delaware scientists was published in the journal Geophysical Research Letters.

This image shows unusually wet and dry areas of the Northern Hemisphere, measured in millimeters per day, following summers of low Arctic sea ice.

The analysis of observed data confirms earlier climate modeling work by Jacob O. Sewall at Virginia Tech and colleagues at the University of California, Santa Cruz, that showed a poleward shift in the winter storm track along the Pacific Coast following the loss of summer Arctic sea ice.

"I'm pleased to see a data-based study that corroborates the modeling work that has been done," Sewall said. "I would expect that the degree to which summer ice extent influences winter conditions is associated with the persistence of the summer ice anomaly...into the winter season."  If ice re-grows quickly, he said, the influence would be lessened.

If the scientists are able to quantify the sea ice loss as well as the likelihood of its persistence, Sewall said, "I think they are accurate in suggesting that long range forecasting of persistent water resource anomalies could be possible."

The climate system "remembers" the summers of lesser Arctic sea ice because heat rising from the exposed ocean warms and destabilizes the lower atmosphere above it, causing more cloudiness and weakening the polar jet stream, the scientists said.

Among the far-flung impacts, Francis and colleagues cited hydropower generation in Scandinavia, where winter precipitation has declined following recent summers of reduced Arctic sea ice.  Similarly, diminished sea-ice aggravates droughts in the southeastern and southwestern U.S.

"If summer sea ice continues on its downward trajectory, which is likely to occur as greenhouse gases accumulate in the atmosphere, then the large-scale atmospheric winter patterns associated with below-normal summer ice cover will also likely continue," the scientists wrote.

- John D. Cox

Image: Geophysical Research Letters

Comments

[Jason]

Downward trajectory? It's been recovering for two years, and is currently highest out of all satellite-imaged years. http://www.ijis.iarc.uaf.edu/seaice/extent/AMSRE_Sea_Ice_Extent.png Notice the tight coupling in May-July, and November - where all years are very close. There is no "remembering".

[Jason]

Also note how the year of least sea ice (2007) leads into the 2nd highest peak level of sea ice (2008). These very plain observations seem to create problems with the credibility of this report.

I didn't expect it to be this simple to invalidate. The authors have some explaining to do.