Thawing Arctic is turning oceans into graveyards

Something is happening to the floating sea ice of the Arctic, other than the well-documented retreat in its surface coverage each summer. Scientists are finding that Arctic sea ice is getting younger and thinner, which is set to continue in March, when US research reveals the winter maximum, and September, when it reveals the summer minimum, making it more vulnerable to a catastrophic and unprecedented break-up.

Nasa researchers have found that the thicker multi-year ice, which has survived several summer melt seasons, is being rapidly replaced by thinner, more ephemeral one-year ice formed over a single winter. This change makes the polar region increasingly vulnerable to storms that could smash their way through the final remnants of thinner, one-year sea ice, making a completely ice-free summer in the Arctic increasingly likely.

An unpublished study of changes to the multi-year ice over the past few decades has revealed that a part of the Arctic that should be a “nursery” for older ice has in recent years turned into a “graveyard”. Instead of multi-year ice forming within the Beaufort Gyre, a huge circular movement of ice off the coast of northern Alaska and Canada, it is now melting away within this critical region.

The result is that while older, multi-year ice typically made up more than 20% of Arctic sea ice in the 1980s, it now comprises just 3% and what little multi-year ice is left behind is behaving like the crushed ice of a cocktail, more prone to being pushed about and melting compared to a solid ice cube.

Now we’re seeing the thicker, multi-year ice melting out completely

The loss of multi-year ice is important because it forms an important bulwark against further ice loss as the region gets warmer, says Walt Meier, a sea ice specialist at Nasa’s Goddard Space Flight Center in Greenbelt, Maryland, who studies the loss of multi-year ice with the help of satellite imagery.

“In the past, the seasonal ice loss in summer would tend to stop when it got to the multi-year ice because it’s three to four metres thick. You couldn’t melt that much ice in summertime, but now what’s happening is that things are getting more broken up,” Meier said.

“Multi-year ice is more fragmented so now you are getting warm water attacking it from all sides. Previously, it was a consolidated ice pack, like a wall of multi-year ice where warm water may melt it a little bit at the edges. But now you are getting big chunks of individual floes sitting there, floating round, surrounded by water that has been warmed by summer sunlight.

“The ice is getting thinner and the winds can more easily break it up. Once broken up, the winds can push it more easily. That just breaks things even further.”

Arctic sea ice, the vital seal-hunting platform of the polar bear, is considered important for the wider climate because it reflects sunlight back into space.  

Read more https://www.theguardian.com/environment/2017/jan/08/arctic-multi-year-sea-ice-break-up-graveyard