Arctic Ice Is Younger, Thinner, and Disappearing

If there were such a thing, now would not be a good time to buy shares in Arctic sea ice.

First, on September 15, the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado announced that the sea ice of the Arctic Ocean region had reached its annual minimum -- i.e. its lowest extent after a summer of melting, before beginning to rebuild for the fall and winter. At 1.84 million square miles (4.76 million square kilometers), that minimum was the third-lowest on record, behind only 2007 and 2008.

Then, on September 27, NSIDC posted an update. After appearing to begin its winter recovery, the sea ice extent began contracting again, settling in at a revised minimum of 1.78 million square miles (4.6 million square kilometers). 

Now the organization has provided a more in-depth analysis with more bad news. As scientists have been warning for years, the bigger, underlying problem is not just that Arctic sea ice is diminishing in area, it is also decreasing significantly in volume. The ice that remains is younger and thus thinner:

Researchers often look at ice age as a way to estimate ice thickness. Older ice tends to be thicker than younger, one- or two-year-old ice. Last winter, the wind patterns associated with the negative phase of the Arctic Oscillation transported a great deal of multiyear ice from the coast of the Canadian Arctic into the Beaufort and Chukchi seas. Scientists speculated that much of this ice, some five years or older, would survive the summer melt period. Instead, it mostly melted away. At the end of the summer 2010, under 15% of the ice remaining [in] the Arctic was more than two years old, compared to 50 to 60% during the 1980s. There is virtually none of the oldest (at least five years old) ice remaining in the Arctic (less than 60,000 square kilometers [23,000 square miles] compared to 2 million square kilometers [722,000 square miles] during the 1980s).

The problem with ice being younger and thinner, of course, is that deeper cold is required each winter to build it up, and less warmth is required each summer to melt it.

Since NSIDC began satellite measurements of sea ice extent, the trend in the Arctic has been one of decline. (Click on this link for a Quicktime movie of annual maximums and minimums). For the first twelve years, the decline was a somewhat arresting one: a year of melt followed by one of at least partial recovery. (The line in the image to left is the median minimum extent from 1979 to 2000). That changed in 2002, when the sea ice minimum fell to a then-record 2.3 million square miles, more than 66,000 square miles below the previous low; the rebound the following year, such as it was, added a mere 7,700 square miles. In 2005, sea ice extent fell to another low, 2.15 million square miles, and then, in 2007, it underwent a massive drop, to 1.65 million square miles, the lowest yet.

There are some possibly encouraging signs. While the very oldest ice has all but disappeared,there has been an increase in two- and three-year-old ice, which could potentially thicken and slow the decline at least for a while.

"While the total coverage of multiyear ice is the third lowest on record, the amount of younger multiyear ice has rebounded somewhat over the last two years. A key question is whether this ice will continue to survive over the next couple of summers, perhaps slowing the overall decline in multiyear ice area," said James Maslanik, a research professor in the Department of Aerospace Engineering Sciences at the University of Colorado.

But, according to NSIDC director Mark Serreze, the underlying trend is abundantly clear.