Friday, October 17, 2008
Arctic on thin ice
Oh dear, start packing those floaties, soon every house will have a water view!
October 17, 2008 - 11:10AM
Autumn temperatures in the Arctic are at record levels, the Arctic Ocean is getting warmer and less salty as sea ice melts, and reindeer herds appear to be declining, researchers have claimed.
"Obviously, the planet is interconnected, so what happens in the Arctic does matter [to the rest of the world]," Jackie Richter-Menge of the Cold Regions Research and Engineering Laboratory said in releasing the third annual Arctic Report Card.
The report, compiled by 46 scientists from 10 countries, looks at a variety of conditions in the Arctic.
The region has long been expected to be among the first areas to show impacts from global warming, which the Intergovernmental Panel on Climate Change says is largely a result of human activities adding carbon dioxide and other gases to the atmosphere.
"Changes in the Arctic show a domino effect from multiple causes more clearly than in other regions," said James Overland, an oceanographer at the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory in Seattle, Washington.
"It's a sensitive system and often reflects changes in relatively fast and dramatic ways."
For example, autumn air temperatures in the Arctic are at a record 5 degrees Celsius above normal.
The report noted that last year was the warmest year on record in the Arctic, leading to a record loss of sea ice. This year's sea ice melt was second only to that of last year.
Rising temperatures help melt the ice, which in turn allows more solar heating of the ocean.
That warming of the air and ocean affects land and marine life and reduces the amount of winter sea ice that lasts into the following summer.
The study also noted a warming trend on Arctic land and an increase in greenness as shrubs move north into areas that were formerly permafrost.
While the warming continues, the rate in this century is less than in the 1990s due to natural variability, the researchers said.
In addition to global warming, natural cycles of warming and cooling occur, and a warm cycle in the 1990s added to the temperature rise.
Now with a cooler cycle in some areas the rise in temperatures has slowed, but Overland said he expects that it will speed up again when the next natural warming cycle comes around.
Asked if an increase in radiation from the sun was having an effect on the Earth's climate, Jason Box of the Byrd Polar Research Centre in Columbus, Ohio, said that, while it was important, increased solar output accounts only for about 10 per cent of global warming.
"You can't use solar to say that greenhouse gases are not a major factor," Overland added.
Other findings from the report include:
- The Arctic Ocean continued to warm and freshen due to ice melt. This was accompanied by an "unprecedented" rate of sea level rise of nearly 0.25 centimetres a year.
- Warming continued around Greenland last year resulting in a record amount of ice melt. The Greenland ice sheet lost 101 cubic kilometres of ice, making it the largest single contributor to global sea level rise.
- Reindeer herds that had been increasing since the 1970s are now showing signs of levelling off or beginning to decline.
- Goose populations are increasing as they expand their range within the Arctic.
- Data on marine mammals is limited, but they seem to have mixed trends. They are adapted to life in a region that is at least seasonally covered in ice. There is concern about the small numbers of polar bears in some regions. The status of many walrus groups is unknown. Some whales are increasing, others declining.
"This is a very complicated system and we are still working diligently to sort out its mysteries," Richter-Menge said.
In addition to Richter-Menge, Overland and Box, lead authors of the report included Michael Simpkin of NOAA and Vladimir Romanovsky of the Geophysical Institute in Fairbanks, Alaska.