sexta-feira, outubro 19, 2007
The Day After Tomorrow?
"Deeper Surface Mixing
Eight episodes of massive iceberg discharge into the
E depois lembrei-me de um outro artigo, da NASA, publicado em 01-10-2007:
“NASA Examines Arctic Sea Ice Changes Leading to Record Low in 2007
A team led by Son Nghiem of NASA's Jet Propulsion Laboratory, Pasadena, Calif., studied trends in Arctic perennial ice cover by combining data from NASA's Quick Scatterometer (QuikScat) satellite with a computing model based on observations of sea ice drift from the International Arctic Buoy Programme. QuikScat can identify and map different classes of sea ice, including older, thicker perennial ice and younger, thinner seasonal ice.
Between winter 2005 and winter 2007, the perennial ice shrunk by an area the size of
The scientists observed less perennial ice cover in March 2007 than ever before, with the thick ice confined to the Arctic Ocean north of
Nghiem said the rapid decline in winter perennial ice the past two years was caused by unusual winds. "Unusual atmospheric conditions set up wind patterns that compressed the sea ice, loaded it into the Transpolar Drift Stream and then sped its flow out of the
"The winds causing this trend in ice reduction were set up by an unusual pattern of atmospheric pressure that began at the beginning of this century," Nghiem said.
The Arctic Ocean's shift from perennial to seasonal ice is preconditioning the sea ice cover there for more efficient melting and further ice reductions each summer. The shift to seasonal ice decreases the reflectivity of Earth's surface and allows more solar energy to be absorbed in the ice-ocean system.
The perennial sea ice pattern change was deduced by using the buoy computing model infused with 50 years of data from drifting buoys and measurement camps to track sea ice movement around the
Results from the buoy model were verified against the past eight years of QuikScat observations, which have much better resolution and coverage. The QuikScat data were verified with field experiments conducted aboard the U.S. Coast Guard icebreaker Healy, as well as by sea ice charts derived from multiple satellite data sources by analysts at the National Oceanic and Atmospheric Administration’s National Ice Center in Suitland, Md.
The new study differs significantly from other recent studies that only looked at the Arctic's total sea ice extent. "Our study applies QuikScat's unique capabilities to examine how the composition of Arctic sea ice is changing, which is crucial to understanding Arctic sea ice mass balance and overall Arctic climate stability," Ngheim said.
Pablo Clemente-Colon of the
Other organizations participating in the study include the