Multi-Year Ice Was 20% Of Arctic Pack In 1980s; Now 3%; Beaufort Gyre Speeding Up
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An unpublished study of changes to the multi-year ice over the past few decades has revealed that a part of the Arctic that should be a “nursery” for older ice has in recent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. 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.
EDIT
https://www.theguardian.com/environment/2017/jan/08/arctic-multi-year-sea-ice-break-up-graveyard
