Following a record summer low, Arctic ice has rebounded rapidly this winter but still covers less of the Arctic Ocean than in previous decades. Plus, said NASA scientists, the ice is younger and thinner
Arctic sea ice comes in two types: older, thicker perennial ice that has survived at least one summer melt season and younger, thinner seasonal ice that forms in the winter and melts again in the summer.
Seasonal ice melts more easily because it is thin and salty, and so "it's flexible and crushable and more susceptible to winds and currents," said Seelye Martin of NASA's Cryospheric Sciences Program.
The amount of older, perennial sea ice has substantially decreased over the past few years, and "has reached an all-time minimum," Martin said. This low is in part due to the substantial 2007 summer melt, attributed in part to climate change.
March is the month where Arctic sea ice traditionally hits its highest extent after the Northern Hemisphere winter and Antarctic sea ice reaches its lowest extent. NASA satellites have monitored sea ice coverage over both poles for nearly 40 years.
Arctic sea ice reached a record low this past summer, with 23 percent less sea ice cover than the previous record low and 39 percent less than the average amount that has previously spanned the Arctic Ocean in the summer months.
Whether any perennial sea ice will recover is also uncertain, but "it's not likely that the perennial ice cover will recover [to where it was in the past] in the near future," said Josefino Comiso of NASA's Goddard Space Flight Center in Greenbelt, Maryland.
Source:Xinhua/Agencies
|
Comment
Tell A Friend
Print Format
Save Article