Arctic sea ice extent

New Record or Not, the Arctic Sea Ice Alarm Bells Keep Ringing

Credit: National Snow and Ice Data Center

Last week, the National Snow and Ice Data Center came out with the estimate that we did not quite ​set a record for the minimum extent of Arctic sea this year. Rather, 2011 seems to have come in a slight second to 2007.

However, another scientific group does claim that we've hit a new record. Who's right?

I don't know, but I don't think either bit of news is the most important thing to focus on. For as Skeptical Science points out, we also just learned that total sea ice volume reached a new low in 2010 (wonky hide-the-punchline paper here). And that is, to my mind, a much bigger deal than what total sea ice extent is doing on a year by year basis.

Remember, extent is a measure of area covered, and volume is a measure of total ice mass. (More clarification here.)

There is a strong case that volume matters more, because extent can be misleading. Why?

The Annual Arctic Sea Ice Drama Begins

In my last post, I discussed how the increasing risk of devastating heat waves—unlike the worsening of tornadoes—is definitely a phenomenon we can link to global warming. And now, as summer plods on, it’s time to begin paying attention to another one: the continuing decline of Arctic sea ice.

The extent of ice covering the Arctic has been declining for decades, and reached a record low in September of 2007, nearly 40 percent below its long term average. This wasn’t solely the product of global warming—weather patterns also have a lot to do with ice extent, and they contributed to the 2007 record. 

Nevertheless, much like the worsening of heat waves, Arctic ice decline is one of the most obvious  impacts of global warming—and this year, it’s possible that Arctic ice extent might reach a minimum even lower than it did in 2007.

Arctic Sea Ice Still at Lowest Extent Ever

The usual concern for Arctic sea ice crops up in the summertime, when the frightening ice decline results in more open water, and therefore a greater capacity for the dark Arctic Ocean to absorb the 24-hour sun’s heat - rather than reflect it back into space, as was the case when most of the Arctic surface was covered with bright, white ice.

But look at the state of Arctic ice now. Even as we approach the usual winter maximum, the ice extent is lower than at any time in recorded history, according to the National Snow and Ice Data Center in Boulder, Colorado. The Polar Science Center in Seattle reports that ice volume also continues its decline, or should I say, collapse - at unprecedented speed, to unprecedented lows.

Thus, despite the calls from d’oh-headed deniers like Art Horn for a global chill driven by a “super La Nina,” we have a year that wraps up tied as the warmest ever and a continuing trend that indicates the coming summer will feature the effects of redoubling climate feedbacks.

We stand in awe of the DenierGang’s ability to tie themselves up in logical knots and we await their next falacious analysis with unfailing interest.

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