Arctic sea ice in “unprecedented decline:” study

Summer sea ice in the Arctic hasn’t been lower since nearly 1,500 years ago, a team of scientists have determined. (FILE PHOTO)

Arctic sea ice extent hasn’t been as low as it is now in the summer since 561 A.D..

“Although extensive uncertainties remain, especially before the sixteenth century — both the duration and magnitude of the current decline in sea ice seem to be unprecedented for the past 1,450 years,” a team of an international scientists wrote in the current issue of Nature.

The summer sea ice extent in the Arctic Ocean is now more than two million square kilometres less than it was in the late twentieth century, this has “important consequences for the climate, the ocean and traditional lifestyles in the Arctic,” they noted.

Although observations show a more or less “continuous decline” for the past four or five decades, it’s not easy to see what the situation was before then.

“There are few long-term records [such as satellite images] with which to assess natural sea ice variability,” the scientists wrote.

So they set out to determine whether or not current trends of sea ice decline are potentially unusual.

Before their study, that question “remained unanswerable.”

Using information gathered from glacial ice cores, tree-rings, lake sediments, historical observations and the like, the team of geographers and glacialogists came up with models to show the past sea ice extent.

They found that summer sea ice cover on the Arctic Ocean hasn’t been so low since about the year 561 A.D.

“Heat transfer to the Arctic by warm Atlantic water has been shown recently to be unprecedented over the past 2,000 years and may be the main driver for the sustained loss of Arctic sea ice over recent decades,” they concluded

The rising levels of climate-warming greenhouse gasses is likely responsible for the decline, the scientists said.

“In the present state of knowledge, anthropogenically [man-made] forced (‘greenhouse gases’) warming stands out as a very plausible cause of the record atmospheric and oceanic warmth of the recent decades, which may soon lead to an ice-free Arctic Ocean in summer,” they concluded.

In 2011, satellite data showed the summer sea ice coverage in the Arctic narrowly missed the all-time record low, which was attained in 2007.