photo by Patrick Kelley, U.S. Coast Guard; U.S. Geological Survey (source: Flickr Creative Commons)

Arctic temperatures have risen twice as fast in recent decades as temps in the rest of the world. Melting sea ice – considered part of a positive feedback loop – as well as wind, cloud and ocean current changes have been suspected of driving this rapid warming, known as Arctic amplification.

A positive feedback loop is a system where the cause and effect perpetuate one another, like a vicious circle.

A new study shows that Arctic warming from melting sea ice may be driving a positive feedback loop between rising temperatures and disappearing ice.

From an article in the Guardian:

The concept of Arctic sea ice having a tipping point is still hotly debated. Our results cannot prove whether we have passed a tipping point or not. What we can say is that the emergence of these strong ice-temperature feedbacks can only increase the likelihood of further rapid warming and sea ice loss.

–James Screen, study leader, University of Melbourne, Australia

The global melting of floating ice is also a concern as it threatens to contribute to a rise in sea levels, albeit far less directly than the melting of land ice that then flows into the sea. If floating ice melts it reflects less sunlight and can also unblock glaciers on land, which can in turn fall into the sea. Floating ice has been disappearing at a steady rate over the last 10 years, according to a groundbreaking study. The loss of floating ice has totaled more than ice loss on land from the Greenland and Antarctic ice sheets.

From a Reuters report:

‘It’s a large number,’ said Professor Andrew Shepherd of the University of Leeds, lead author of the paper, estimating the net loss of floating sea ice and ice shelves in the last decade at 7,420 cubic kilometers.

Ironically, some scientists believe that the hole in the ozone over Antarctica – created by mankind’s now-banned use of CFCs – has slowed warming temperatures and ice melt there. However as the ozone hole closes, Antarctic temperatures could increase an average of 3C, causing sea levels to rise by 1.4 meters.

Colin Summerhayes, executive director of SCAR – the Scientific Committee on Antarctic Research – was quoted in a Guardian article back in November of last year regarding the dangers of Antarctic ice melt:

It contains 90% of the world’s ice, 70% of the world’s fresh water and that is enough, if it melts, to raise sea levels by 63m.

by Graham Land

Additional resources:

NASA – Sea Ice Yearly Minimum with Graph Overlay 1979-2008

Yale Environment 360 – The Copenhagen Diagnosis: Sobering Update on the Science