The Japanese Aerospace Exploration Agency (JAXA: the Japanese version of NASA), which keeps tabs on Arctic sea ice extent from satellites, today released data showing that the extent of Arctic sea ice has reached a new all-time low, breaking the previous record of September 24, 2007.
Today's record (August 24, 2012): 4,189,375 square km.
Previous record (September 24, 2007): 4,254,531 square km.
And that's not the worst of it. Not only is today a record, tomorrow will be too. And the day after that. And the day after that. And the day after that. We still have four weeks left to go in the melt season, and it's likely that every single day will set a new all time low.
Follow below the arabesque to see the graph.
By this time of the year, the ice melt has usually slowed down some, as we head toward the equinox and the beginning of the re-freeze season. Not this year. The decline here at the end of August is still zipping along at rates usually seen only in June and July.
Note that this is sea ice extent. We broke the record for sea ice area a few days ago. The difference is that sea ice looks a lot like swiss cheese around the edges, with a lot of holes. Sea ice area doesn't include the holes, while sea ice extent does.
But the real action is happening in sea ice volume, which continues its decline at and accelerating pace.
For those of us who live at high latitudes and see lakes melt in the spring, it's clear what's going on. Ice melts mostly from below, not from the edges. That's why sea ice volume is going down so sharply: the ice is getting thinner. I see this every year when the lake behind my house melts. The ice gets thinner and thinner, and then very suddenly, the area of ice drops from full-lake to no-lake in a day or two.
We should expect to see the same in Arctic sea ice too. What's going to happen is that sea ice area and extent are headed for a dramatic non-linear collapse, and this year's decline is simply a foreshadowing of that. In the next two to four years, we will see an essentially ice-free Arctic Ocean at the end of summer.