Arctic sea ice thinnest in thousands of years

Arctic sea ice is at its record low in the recent geologic history, a major international study has claimed. The first comprehensive history of Arctic ice, carried out by a team of scientists from five countries, found that the recent retreat is the worst in thousands of years.

“The ice loss that we see today — the ice loss that started in the early 20th Century and sped up during the last 30 years — appears to be unmatched over at least the last few thousand years,” said Leonid Polyak, a research scientist at Byrd Polar Research Center at Ohio State University. Polyak is lead author of the research paper which will be published in the upcoming issue of Quarternary Science Reviews.

The sea ice that normally covers huge swaths of the Arctic Ocean has been retreating and thinning over the last few decades, due to the amplified warming at the North Pole, which is a consequence of the buildup of greenhouse gases in Earth’s atmosphere.

The most dramatic sea-ice melt in recent years came in 2007, when sea-ice extent (or the area of ocean covered by the ice) dropped to its lowest level since 1979, when satellite measurements began.

For decades, scientists have strived to collect sediment cores from the difficult-to-access Arctic Ocean floor, to discover what the Arctic was like in the past. Their most recent goal: to bring a long-term perspective to the ice loss we see today.

Now, the team led by Ohio State University has re-examined the data from past and ongoing studies — nearly 300 in all — and combined them to form a big-picture view of the pole’s climate history stretching back millions of years, the university said.

Satellites can provide detailed measures of how much ice is covering the pole right now, but sediment cores are like fossils of the ocean’s history, said Polyak.

To review and combine the data from hundreds of studies, he and his cohorts had to combine information on many different proxies as well as modern observations.

Their conclusion: the current extent of Arctic ice is at its lowest point for at least the last few thousand years. During the summer of 2011, they hope to draw cores from beneath the Chukchi Sea, just north of the Bering Strait between Alaska and Siberia, which can provide a detailed history of interaction between oceanic currents and ice.