Increased Clouds and Humidity Hasten Shrinkage of Arctic Icecap; Clouds Act Like a Blanket Over the Arctic, Rutgers Researchers Say

NEW BRUNSWICK/PISCATAWAY, N.J. A thicker blanket of clouds and water vapor is covering the Arctic in spring and summer, trapping heat and moisture and speeding up the melting of the Arctic icecap, according to Jennifer Francis, an associate research professor at Rutgers, The State University of New Jersey.

Francis and fellow research scientist Elias Hunter of Rutgers Institute of Marine and Coastal Sciences published their findings in the current issue of EOS Transactions (http://www.agu.org/pubs/eos.html), a peer-reviewed journal of the American Geophysical Union. In their paper, New Insight Into the Disappearing Arctic Sea Ice, the researchers report their analysis of 26 years of data about the Arctic climate.

Weve understood that warming of the Earths climate caused the Arctic sea ice cover to shrink, but we havent been sure whether changing winds or heating were the drivers, Francis says. Satellite data extending back over a 26-year period show that increased cloudiness in spring and summer along with increased humidity are causing the dramatic melt.

The mechanism that is shrinking the icecap works in the following way, the researchers say. Increasing cloudiness and atmospheric moisture blanket the Arctic during the spring and summer. The clouds are good absorbers and emitters of infrared energy, and so is the Earth. When the clouds cover the Arctic, they and the Earths surface emit radiation back and forth to each other. If there were less cloud cover and humidity, much of that radiation would escape into space and would not contribute to the warming of the region.

Francis and Hunter analyzed data that stretch back over 26 years from three satellite sensors. Two sensors took measurements of the clouds and atmosphere; the third measured the extent of the ice coverage in the Arctic.

Through the mid-1990s, a climate phenomenon called the North Atlantic Oscillation was in an extended positive phase, which tends to bring more heat and moisture into the Arctic by changing the wind pattern, Francis says. So people thought the sea ice coverage was tied to changes in the NAO index. They thought, if it returns to a neutral or negative phase, the ice will come back. But in recent years, the North Atlantic Oscillation has returned to a more neutral phase, and the ice is shrinking faster. So, we figured something else must be going on.

Using information from satellite sensors, Francis and Hunter measured the varying extent, thickness, and water and ice content of the Arctic cloud cover. One of the instruments also provided atmospheric temperature and winds at various altitudes. Information about the waxing and waning of ice extent was measured each year in six strategically selected areas off the Arctic coasts of Canada, the United States, Scandinavia and Russia.

We monitored ice melt in the spring, and when it reached its maximum distance from the coast, we called that the summer minimum ice extent, Francis explained.

The scientists correlated that information with anomalies in heating and winds to reach their conclusions.

The work described in the paper was funded by the National Science Foundation (NSF), the National Oceanic and Atmospheric Administration (NOAA), the National Aeronautics and Space Administration (NASA), and the United States Department of Defense.

Contact: Ken Branson
732-932-7084, ext. 633
E-mail: kbranson@ur.rutgers.edu