Arctic sea ice melts to record low

EarthSkyBlogs by Dan Kulpinski
Published October 8th, 2007 in Arctic, Science, Oceans, Earth, Climate & Weather and Global Warming.

The National Snow and Ice Data Center (NSIDC) announced October 1 that the summer melting of the sea ice at the North Pole hit a new record this year, shrinking to its lowest extent since satellite records started being kept in 1979. The big melt left 23 percent less ice than in 2005, the previous record year, and 39 percent less than the long-term average. This was a significant year.

Scientists say climate change is one of the factors causing the massive melting. According to NASA, however, the primary cause was a large loss of old, thick year-round sea ice during the last two winters.

Other factors included unusually sunny weather in June and July, clouds and water vapor trapping heat near the surface, and also warm winds from Siberia.

Back to that old, thick ice that normally stays frozen year-round. In a NASA press release, scientist Son Nghiem said that "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 Arctic." When the ice reached more southerly latitudes, it melted in the warmer water.

NASA found a 23-percent loss of the perennial sea-ice cover during the last two years. The Arctic is shifting to more seasonal ice cover. The seasonal ice does not grow as thick and thus melts more quickly. NASA said this shift is "preconditioning the sea ice cover there for more efficient melting and further ice reductions each summer." The shrinking ice cap also decreases the reflectivity of Earth's surface and thus allows more solar energy into the ocean-ice system.

Scientists predict the entire ice cap could melt during summer as soon as 2030. One even says 2013!

NSIDC noted the summer melting season lasted four days longer this year, with the five-day running minimum occurring on September 16. The sea ice is also melting earlier in the spring.

Experts cannot find records from Russia, Alaska or anywhere of such a widespread melt in recent times.

The big melt has already affected people and animals. The changing ice affects when people can travel and hunt. Thousands of walruses came ashore in Alaska this summer, because the ice had melted way past their feeding grounds. They used to live on the ice and dive on to the outer continental shelf, to feed on clams and snails. This became impossible this year.

The U.S. government is considering putting polar bears on the endangered species list, because the melting sea ice affects their ability to hunt and feed themselves year-round.

As NSIDC senior scientist Mark Serreze said, "The implications for global climate, as well as Arctic animals and people, are disturbing."

Caption for map graphic: The image below shows the average sea ice extent in September 2007 (in white), compared to the long-term median sea ice extent from 1979-2000 (in magenta) for the end of the melt season.