Tuesday, October 2, 2012

Arctic sea ice extent blows previous record out of the water

This summer was an intense one in Denver.  Denver had 73 days above 90 degrees Fahrenheit this year, which is just one of the many records broken this summer locally and globally.  I spent July and August traveling in Wyoming, Colorado, then east on I70 to Kentucky and northeast to New York City, then to northern Wisconsin before returning to a hot and crispy Colorado. My travels brought me to places much more humid than Denver, so just be thankful for our low heat index values in Colorado, where sweat actually cools you down!  You can see from the image below, not only have temperatures been above normal, we are also quite low in precipitation at Denver International Airport, which hasn't been very helpful after a very poor snow year for the Colorado Rockies last winter.  Colorado and the west in general suffered from awful wild fires this year.  Notable fires for the front range included the High Park fire west of Fort Collins, the small Flagstaff Fire just a mile from my home, and the Waldo Canyon fire near Colorado Springs, which will go down in history as the most horrific fire in Colorado history.
The reason I am writing today, though, is a problem much larger scale than Denver's crispy conditions.  Although this news only made headlines for a day, or a week of you're a reader of the New Yorker, I think it should be the most important story of 2012.
High Noon
2012 set the record for the lowest Arctic sea ice extent ever recorded in the Arctic, by far.  In fact, in 2012, sea ice the size of Texas was lost beyond the previous record set in 2007.  Colleagues at the National Snow and Ice Data Center in Boulder (NSIDC.org) have released the following images to put 2012 into perspective in the instrument record.  http://nsidc.org/arcticseaicenews/

Northwest passages are open all over the place!
Sea ice loss of this magnitude means that new ice formed this winter will be new and thin, making the sea ice even more vulnerable to melt in 2013.  We are headed towards sea ice-free Arctic summers faster than forecasted.  This affects us in a few ways.  First off, the ice will no longer be there to reflect sunlight, allowing the ocean to absorb sunlight, warming the system.  This creates a feedback mechanism that leads to a very warm Arctic.  Second, without sea ice to cap the Arctic Ocean, the whole heat and moisture balance of the northern hemisphere will be different.  This will directly affect the position of our jet stream and weather systems down here in the mid-latitudes.  How?  We're working on figuring that out, but here's two papers that give us some ideas:  Porter et al, 2012 and Francis and Vavrus 2012.

When sea ice melts it does not raise sea levels.  (Just like your Coke doesn't overflow when the ice cubes melt.) This is a huge relief for those of us mile-highers not interested in making room for climate refugees from the lower elevations.  Unfortunately, sea ice's next door neighboor, the Greenland ice sheet, is also melting, and has been since the 90's.  This summer, NASA reported this:
On average in the summer, about half of the surface of Greenland's ice sheet naturally melts. At high elevations, most of that melt water quickly refreezes in place. Near the coast, some of the melt water is retained by the ice sheet and the rest is lost to the ocean. But this year the extent of ice melting at or near the surface jumped dramatically. According to satellite data, an estimated 97 percent of the ice sheet surface thawed at some point in mid-July.
Note that they're reporting surface melt.  Greenland is thick and they are referring to just the top layer here.  Because Greenland's ice is on land, not floating, it most definitely can contribute to sea level rise.  Only time will tell just how much.  The ice sheet, which is 3000 meters (10,000 feet) thick in some places, holds the potential to raise sea levels by 7.3 meters.  Of course this will be a slow process, but one that I would argue is inevitable considering our current path towards unlimited and unregulated carbon dioxide emissions.

If you're interested in learning more about this, come chat with me or take my MTR 1600 course on Global Climate Change.