Guest post by Steven Goddard
In past years, NSIDC has referred to “declining multi-year ice” as the problem which the Arctic faces. Mark Serreze at NSIDC forecast a possible “Ice Free North Pole” in 2008, based on the fact that it had only first year ice. This year, multi-year ice has increased and NSIDC is now referring to declining “2+ year old” ice as the problem. Note the missing age group (2 year old ice) in the paragraph below from their latest press release .
First-year ice in particular is thinner and more prone to melting away than thicker, older, multi-year ice. This year, ice older than two years accounted for less than 10% of the ice cover at the end of February. From 1981 through 2000, such older ice made up an average of 30% of the total sea ice cover at this time of the year.
Due to the record minimum in 2007, it goes without saying that there isn’t a lot of three year old ice in 2009. Maybe next year they can raise the bar to 3+ year old ice, as the multi-year ice ages one more year?
Multi-year ice has increased from 2008, up to nearly 25%. Compare multi-year ice vs. last year’s map below – upper right corner.
The press has picked up on the 10% figure, based on the new higher standard NSIDC has set.
Ice older than two years once accounted for some 30 to 40 percent of the Arctic’s wintertime cover and made up 25 percent as recently as 2007.
But last year it represented only 14 percent of the maximum. This year the figure fell to 10 percent.
Note too that ice extent is nearly back to normal and has not declined significantly from the winter maximum.