of June and July this year, causing clear skies and abundant sunshine that was shining on the ice at a time of the year when skies are typically cloudy. The high pressure also favored offshore winds that blow from eastern Siberia into the Arctic Ocean. These winds, which were warmer than the ice, melted the ice and pushed it away from shore --  exposing more dark water to absorb the abundant sunlight of long summer days.  The greatest reduction in summer ice cover has been in the Siberian half of the Arctic Ocean.

 

             The other factor has been recent wind patterns that sweep multi-year ice out of the Arctic into the Atlantic Ocean.  Multi-year ice is thicker and resists complete melting in the summer. Large areas previously covered by multi-year ice now are covered only by 1-year or 2-year-old ice.  This younger ice more often melts away by September.

 

             These natural factors are compounded by a relentless increase in Arctic air temperature since 1979, according to scientist Serreze, who said, “While a number of natural factors have certainly contributed to the overall decline in sea ice, the effects of greenhouse warming are now coming through loud and clear.”

 

             The satellite image released by the Snow and Ice Data Center reveals another feature worth noting:  an ice-free Northwest Passage from the Atlantic Ocean all the way to the Pacific.  The passage winds through the Canadian Arctic islands to the Beaufort Sea off Alaska’s North Slope. This news has been long awaited by international traders, who may well try to ship crude oil and gas from Arctic fields directly to Europe and the East Coast by this shorter route.

 

             While the Northwest Passage did open up in the American Arctic,  the sea route along the northern coast of Russia and Siberia remained firmly closed by ice this year (see inside story). That route “over the top of Asia” was open in 2005 and is often passable in some summers – but not this year.

 

More comparisons of Arctic ice in 2005 and 2007— inside.

CONTENTS

 

Arctic Ice at a Record Low Extent

 

Warming very likely caused by human activities: Highlights of new IPCC Fourth Assessment

          

Hurricanes: Strengthening globally or only locally?          

 Print Newsletter        Previous Issues

          in PDF  format                                 2002 — 2007

 

 Autumn 2007 — #9

Arctic Ice at a Record Low Extent

Center in Boulder, Colorado, and the University of Illinois. By the week of September 16 the Arctic ice covered an area 23% less than it had in 2005, when the previous record was set, and now covers 39% less area (in white, at right) than the long term average extent of ice in September (figure at right).   The conditions that led to the shrinking ice cap this year deserve our attention.

 

             Marc Serreze, senior scientist of the Snow and Ice Data Center, cited two responsible factors, which have added to the melting expected on a warming Earth.  A high pressure cell was parked over the Ocean north of Alaska for most

             The ice cover on the Arctic Ocean had diminished to the smallest area yet observed by August 20 of this year, with one month still left in the summer melting season, according to the National Snow and Ice Data

Extent of sea ice cover (white) at the time of this year’s annual minimum on September 16, 2007. This map may be compared with the earlier (2005) record minimum extent here.   The magenta line is the average location of the ice edge in the period from 1979 to 2000.

Credit: National Snow and Ice Data Center