Last summer's Arctic sea ice minimum was a major record-breaker. It sparked serious thinking about whether the Arctic summer could be ice-free within a decade. This summer's melt now seems likely to be less severe. Does this mean our level of worry should diminish, or is this simply oscillation around a worrying downward trend? It certainly gives ammunition to those who would like to deny that there is a trend at all. In the long run, it probably doesn't matter enormously whether the Arctic melts in ten years or thirty. Where it may matter considerably is insofar as awareness of Arctic melting either prompts the emergence of strong climatic policies or provides fodder for those who want to continue to delay.

Whether it is ice or energy under consideration, the general lesson of shifting baselines is pertinent. We need to see past short term trends and our focus on how the recent past and the present compare, looking onwards to fundamental forces and long-term developments. Of course, when it comes to systems as massive and complex as the global climatic and economic systems, doing so is enormously difficult.

a sibilant intake of breath

"Does ice free mean conveyor free?  And Gulf Stream free?  And a 10 year onset ice age?"

From what I have read, probably not. When people talk about disrupting the thermohaline circulation (THC), they are usually talking about large-scale melting of the Greenland glaciers, not the summer disappearance of the Arctic icecap. That being said, nobody really knows where the threshold for seriously disrupting the THC lies.

a sibilant intake of breath

Joe, why does it always seem you pick the most alarming data?

Take a look at this data:

http://img79.imageshack.us/img79/5952/seaiceextentri5.jpg ...

Or you can read here:

http://wattsupwiththat.wordpress.com/2008/08/15/arctic-ic ...

No way will 2008 be like 2007

http://www.earth-policy.org/Indicators/Ice/2008.htm

"Warmer temperatures are also accelerating ice melt on the nearby Greenland ice sheet, which contains enough ice to raise sea level by seven meters (23 feet). Mass loss in Greenland more than doubled between 1996 and 2005, with loss in the southeast accelerating even further since 2004. The summer of 2007 saw a record area of ice melt on Greenland, 10 percent more than the previous maximum in 2005."

"In 2006, scientists reported that "glacial earthquakes" caused by large masses of ice moving rapidly over bedrock had doubled in frequency in Greenland over the last five years. These earthquakes are associated with meltwater from the glacier surface, which flows to the base of the ice sheet and lubricates it, causing rapid glacial movement. Positive feedback mechanisms such as this meltwater lubrication accelerate the speed with which glaciers react to warmer temperatures; ice sheets once thought to change only over millennia are now seen to be responding to warmer temperatures"

This seems to indicate they are connected.  That the warmer water at the edge of Greenland glaciers where icebergs calve and the higher rainfall from warmer arctic temps, both cause the dobins (glacial lakes) at the edge of glaciers to increase.

Eventually these lakes drain into cracks in the glacier and lubricate the sliding effect at ground level under the glacier.  The increase in the speed of the slide of the glacier connects the warming arctic sea temperature to the glacial melt.

Warmer water at the edge of the glacier causes icebergs to break off quicker too and melt out through the fijords instead of clogging them up and slowing the glacier down.

I think this in turn, dooms the Gulf Stream to end shortly after arctic ice vanishes.

http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin