Arctic Economics

Are We Headed for a New Record Arctic Ice Low This September?

The National Snow and Ice Data Center reports that there is more ice cover now than last year at this time, but it's melting faster:

April was relatively warm.  Another problem is that this year's ice is unusually young and fragile.  The odds appear good that we'll set a new record low:

The 2008 Melt Season Begins

Arctic sea ice coverage reaches its annual maximum in March, and then begins to shrink, reaching its annual minimum in September.  We're just past the 2008 peak now.  Here's how things are going so far this year:

The ice is more extensive than last year, but still below normal. And it's younger:

It Isn't Just the Arctic That's Changing

Menzie Chinn posts on the ongoing breakup of the Wilkins Ice Shelf in Antarctica, with a link to a Congressional Budget Office presentation from last November on greenhouse gas emissions control policy options: "Antarctic Ice Shelf Disintegration Underscores a Warming World", March 29, Econobrowser). 

Thin Ice

In March the Arctic ice cap reaches its greatest annual extent.   And this year's March ice cover only a little smaller than it's been it the past.

But look at this:  red indicates one-year old seasonal ice.

Mason Inman reports on data from the National Snow and Ice Data Center showing that perennial or multi-year ice has dropped by half since the 80s and early 90s: Shrinking Arctic Sea Ice Thinner, More Vulnerable (National Geographic News, March 18, 2008)

That's important because the seasonal ice is thinner and melts faster.  The ice cap is smallest in September and last September it was as small as we've ever seen it.  We still don't know what will happen this summer, but the ice cap is starting the season with a big strike against it.

First posted at Ben Muse on March 19, 2008.

The Incredible Shrinking Arctic Ice Cap

The Arctic sea ice melt season is over. 

The National Snow and Ice Data Center reports that the arctic ice cap "plummeted to the lowest levels since satellite measurements began in 1979.": Arctic Sea Ice Shatters All Previous Record Lows. Diminished summer sea ice leads to opening of the fabled Northwest Passage . (press release, Oct 1).

Figure 1: This image compares the average sea ice extent for September 2007 to September 2005; the magenta line indicates the long-term median from 1979 to 2000. September 2007 sea ice extent was 4.28, compared to 5.57 in September 2005. This image is from the NSIDC Sea Ice Index.

Figure 2: The updated time series plot puts this summer’s sea ice extent in context with other years. 2007, shown in solid blue, is far below the previous record year of 2005, shown as a dashed line; September 2007 was 36% below where we would expect to be in an average year, shown in solid gray.

Figure 3: September ice extent from 1979 to 2007 shows an obvious decline. The September rate of sea ice decline since 1979 is now approximately 10 percent per decade, or 72,000 square kilometers (28,000 square miles) per year.