Arctic sea ice is pulling a Benjamin Button. It’s been getting younger. But while that’s a fate some would relish, it’s not necessarily good news for ice, as it’s youthful appearance could speed its demise.
The National Oceanic and Atmospheric Adminstration has released an animation showing the decline of old sea ice since 1987, the first year for which accurate data is available on ice thickness. It shows a region of change in terms of the long-term trend as well as season-to-season fluctuations.
In 1987, sea ice that was 4 years old or older constituted 26 percent of all sea ice. But fast forward to 2014 and it’s down to about 10 percent. That’s a slight uptick from 2012 and 2013, when old ice comprised just 7 percent of the overal icepack. But as LL Cool J said, don’t call it a comeback.
Ocean currents, water and air temperatures and storms all contribute to year-to-year variability, but the signal outside of that noise points to a clear downward trend over time. Sea ice minimum extent (the low point the ice area hits at the end of each summer) has declined by more than 13 percent per decade since the 1979 compared to the 1981-2010 average. Both the decline in old ice and overall ice extent are due in part to increasing ocean and air temperatures.
The trend towards younger ice and more of it could also be part of a feedback loop, helping accelerate the disappearance of ice across the region. That’s because young ice is more prone to melting in the summer and being broken up by waves compared to older ice.
As darker ocean water takes the place of bright, white ice, more energy is absorbed from the sun, cranking up water temperatures in the region even higher. That’s reflected in ocean temperatures, which have risen by as much as 1°F per decade since the early 1980s according the Arctic Report Card, an annual update on the state of Arctic released this past December.