Rate of predicted Arctic warming over land can more than triple during periods of rapid sea ice loss

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Washington, June 11 : A new study has determined that the rate of climate warming and permafrost thaw over northern Alaska, Canada, and Russia could more than triple during periods of rapid sea ice loss.

Conducted by the National Center for Atmospheric Research (NCAR), the study raises concerns about the thawing of permafrost, or permanently frozen soil, and the potential consequences for sensitive ecosystems, human infrastructure, and the release of additional greenhouse gases.

"Our study suggests that, if sea-ice continues to contract rapidly over the next several years, Arctic land warming and permafrost thaw are likely to accelerate," said lead author David Lawrence of NCAR.

Simulations by global climate models show that when sea ice is in rapid decline, the rate of predicted Arctic warming over land can more than triple.

The research was spurred in part by events last summer, when the extent of Arctic sea ice shrank to more than 30 percent below average, setting a modern-day record. From August to October last year, air temperatures over land in the western Arctic were also unusually warm, reaching more than 4 degrees Fahrenheit (2 degrees Celsius) above the 1978-2006 average and raising the question of whether or not the unusually low sea-ice extent and warm land temperatures were related.

To investigate this question, Lawrence and his colleagues analyzed climate change simulations generated by the NCAR-based Community Climate System Model.

The team found that during episodes of rapid sea-ice loss, the rate of Arctic land warming is 3.5 times greater than the average 21st century warming rates predicted in global climate models.

While this warming is largest over the ocean, the simulations suggest that it can penetrate as far as 900 miles inland.

The simulations also indicate that the warming acceleration during such events is especially pronounced in autumn.

The decade during which a rapid sea-ice loss event occurs could see autumn temperatures warm by as much as 9 degrees F (5 degrees C) along the Arctic coasts of Russia, Alaska, and Canada.

Lawrence and his colleagues then used the model to study the influence of accelerated warming on permafrost and found that in areas where permafrost is already at risk, such as central Alaska, a period of abrupt sea-ice loss could lead to rapid soil thaw.

This situation, when summer thaw extends more deeply than the next winter's freeze, can lead to a talik, which is a layer of permanently unfrozen soil sandwiched between the seasonally frozen layer above and the perennially frozen layer below.

A talik allows heat to build more quickly in the soil, hastening the long-term thaw of permafrost.

ANI

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