Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Arctic ice more vulnerable to sunny weather

22.04.2008
The shrinking expanse of Arctic sea ice is increasingly vulnerable to summer sunshine. Unusually sunny weather contributed to last summer's record loss of Arctic ice, while similar weather conditions in past summers did not appear to have comparable impacts, new research concludes.

"The relative importance of solar radiation in the summer is changing," says Jennifer Kay of the National Center for Atmospheric Research (NCAR) in Boulder, Colo., who is lead author of the study. "The amount of sunshine reaching the Arctic is increasingly influential, as there is less ice to reflect it back into space," she says.

The findings by Kay and colleagues at NCAR and Colorado State University
(CSU) in Fort Collins indicate that the presence or absence of clouds now has greater implications for sea ice loss.

"A single unusually clear summer can now have a dramatic impact," Kay says.

A report on the new results will be published tomorrow 22 April 2008 in Geophysical Research Letters, a journal of the American Geophysical Union (AGU).

Last summer's loss of Arctic sea ice set a modern-day record, with the ice extent shrinking in September to a minimum of about 4.1 million square kilometers (1.6 million square miles). That was 43 percent less ice coverage than in 1979, when accurate satellite observations began.

The soon-to-be-published study draws on observations from new NASA satellite radar and lidar instruments. Lidar devices make measurements using lasers.

Looking at the first two years of satellite data from those sensors, Kay and her colleagues found that total 2007 summertime cloud cover was 16 percent less than the year before, largely because of a strong high-pressure system centered north of Alaska that kept skies clear.

Over a three-month period in the summer, the increased sunshine was strong enough to melt about a foot of surface ice. Over open water, it was sufficient to increase sea-surface temperatures by 2.4 degrees Celsius (4.3 degrees Fahrenheit).

Warmer ocean waters can contribute to sea ice loss by melting the ice from the bottom, thereby thinning it and making it more susceptible to future melt.

"Satellite radar and lidar measurements allow us to observe Arctic clouds in a new way," says CSU's Tristan L'Ecuyer, a co-author of the study. "These new instruments not only provide a very precise view of where clouds exist but also tell us their height and thickness, which are key properties that determine the amount of sunlight clouds reflect back to space."

The research team also examined longer-term records of Arctic cloud and weather patterns, including a 62-year-long record of cloudiness from surface observations at Barrow, Alaska. The scientists found that the 2007 weather and cloud pattern was unusual but not unprecedented. Five other years--1968, 1971, 1976, 1977, and 1991--appeared to have lower summertime cloud cover than 2007, but without the same impact on sea ice.

"In a warmer world, the thinner sea ice is becoming increasingly sensitive to year- to-year variations in weather and cloud patterns," Kay says.

The research suggests that warmth from the sun will increasingly affect Arctic climate in the summer. As the ice shrinks, incoming sunshine triggers a feedback

mechanism: the newly exposed dark ocean waters, much darker than the ice, absorb the sun's radiation instead of reflecting it. This warms the water and melts more ice, which in turn leads to more absorption of radiation and still more warming.

The authors note that, in addition to solar radiation, other factors such as changes in wind patterns and, possibly, shifts in ocean circulation patterns also influence sea ice loss. In particular, strong winds along regions of sea ice retreat were important to last year's loss of ice. The relative importance of these factors, and the precise extent to which global climate change is driving them, are not yet known.

This study was funded by NASA and by the National Science Foundation.

Title:
"The contribution of cloud and radiation anomalies to the 2007 Arctic sea ice extent minimum."
Authors:
Jennifer Kay and Andrew Gettelman: Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, Colorado, USA.; Kay is also with Department of Atmospheric Sciences, Colorado State University, Fort Collins, Colorado, USA.;

Tristan L'Ecuyer, Graeme Stephens, and Chris O'Dell: Department of Atmospheric Sciences, Colorado State University, Fort Collins, Colorado, USA.

Citation:
Kay, J. E., T. L'Ecuyer, A. Gettelman, G. Stephens,and C. O'Dell (2008), The contribution of cloud and radiation anomalies to the 2007 Arctic sea ice extent minimum, Geophys.Res. Lett., 35, L08503, doi:10.1029/2008GL033451.
Contact information for coauthors:
Jennifer Kay, NCAR Scientist (also affiliated with CSU), +1-303-497-1730, jenkay@ucar.edu

Peter Weiss | American Geophysical Union
Further information:
http://www.agu.org
http://www.ucar.edu

More articles from Earth Sciences:

nachricht New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland
19.01.2017 | University of Gothenburg

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>