Our grandchildren won't get to see polar bears, at least not in the wild. In the summer of 2007, the Arctic ice surface was about 30% under the long-term average level, a record of all times. Some studies forecast ice-free Arctic summers by 2040; some say that we could even get to see it happening this year.
"The set-up for this summer is disturbing," Mark Serreze of the US National Snow and Ice Data Center (NSIDC) told NewScientist. In September 2007, the retreat of the Arctic sea ice opened
for the first time the North-West passage running from Greenland to Alaska and triggered a competition for the North Pole. In March 2008, the Arctic ice had barely recovered (even if it topped the surface existent a year before), despite a very cold winter; this summer, the melting process could come as another hit (in March, the Arctic ice reaches its annual peak).
Since 1978, the trend has been only downward and the Arctic is annually losing 44,000 km2 (18,000 square miles) on average, as revealed by NSIDC calculations. That is more than the surface of Netherlands.
However, this is not only about surface. The current Arctic ice is thin and young, just one year old, being much more unstable than thick ice that accumulates in several years. "There is this thin first-year ice even at the North Pole at the moment. This raises the specter - the possibility that you could become ice free at the North Pole this year," said Serreze.
The main issue is that the multi-year ice, which doesn't melt in the summer, is accumulating now at a slower pace than the one at which general Arctic ice is melting. In 1989, 80 % of the ice in the Arctic was at least 10 years old. Today, less than 30 % of it is that old. Ice remaining in the Arctic for at least six years represented over 20% of the Arctic area in the mid to late 1980s, but in the winter of 2007-2008, that percentage was down to just 6%.
New ice melts more quickly, and then open water absorbs more sunlight, warming the seas and determining the fall freeze-up to come even later. Usually, 50% of the annual ice formed between September and March melts during the next summer, but in 2007, this percentage was well over 90%.
The situation was also aggravated by a rise of the Arctic atmospheric oscillation this winter, which increased the power and number of winds that pushed multi-year ice out of the Arctic, following the route along the eastern Greenland coast.
"Even if you lost only half of the first-year ice this year - which would be average - you are still in for a very low ice extent this summer," said Serreze. A ray hope does exist though: in the summer of 2007, melting was boosted by warm winds.
"If we have an atmospheric pattern like we had last year, we are going to lose a whole bunch of ice this summer, but if we have a cooler, more cyclonic pattern, that might preserve some of that ice," said Serreze.
Polar bears prefer ice over the shallow continental shelves north because they support a richer food chain. With the melting of last summer, Alaska bears were on ice as much as 600 miles (960 km) north of Barrow, far from their preferred habitat. By 2050, the Alaskan polar bears will have disappeared due to the global warming.
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