Friday, December 21, 2007

Warming Arctic Surface Water

This article highlights an unexpected consequence of the clearing of sea ice from a huge expanse of surface water. The surface temperature climbs way more than expected because the wind has blown any pack ice far away. This was not so obvious in previous years simply because the open areas developed later and were much smaller.

This indicates that summer surface temperatures in the Arctic Ocean will climb to the same levels once full ice removal is possible and a decent summer season is established. This also suggests that a fair amount of moisture will find its way into the Arctic atmosphere increasing precipitation on the Greenland icecap. So while the edges of the cap will experience greater melting, the cap itself will be adding ice faster.

I used to have a copy of the raw ice core data from back in the nineties when they were not charging for it. I had it because I wanted to get a handle of the precise timing of the Pleistocene Nonconformity and even to confirm it was for real(it was). It now strikes me that that same data may be sensitive enough to pick up those time periods in which the Arctic was ice free in the summer. I hate hard drives.

Note also that a direct result of this is winter ice thicknesses dropping from an average of 80 centimeters to an average an average 25 centimeters thinner or about 55 centimeters. This is a huge effect and it alone means that the sea ice could clear even sooner next season allowing an even earlier attack on the perennial ice. We are clearly well past any tipping point because this is a cumulative effect that will happily clear out all the sea ice over the next several years.

For this process to properly reverse now, something radical has to change and permit a large chilling effect. And since that type of response takes a long time to set up, I suspect that we are in for a few centuries of warmer Arctic climate.

Without Ice Cap, Arctic Waters Warm To As Much As 5C Above Average

Written by The Naib

warming arctic

Record-breaking amounts of ice-free water have deprived the Arctic of more of its natural “sunscreen” than ever in recent summers. The effect is so pronounced that sea surface temperatures rose to 5 C above average in one place this year, a high never before observed, says the oceanographer who has compiled the first-ever look at average sea surface temperatures for the region.

Such superwarming of surface waters can affect how thick ice grows back in the winter, as well as its ability to withstand melting the next summer, according to Michael Steele, an oceanographer with the University of Washington’s Applied Physics Laboratory. Indeed, since September, the end of summer in the Arctic, winter freeze-up in some areas is two months later than usual.

The extra ocean warming also might be contributing to some changes on land, such as previously unseen plant growth in the coastal Arctic tundra, if heat coming off the ocean during freeze-up is making its way over land, says Steele. (who incidentally is speaking Wednesday at the American Geophysical Union meeting in San Francisco)

He is lead author of “Arctic Ocean surface warming trends over the past 100 years,” accepted for publication in AGU’s Geophysical Research Letters. Co-authors are physicist Wendy Ermold and research scientist Jinlun Zhang, both of the UW Applied Physics Laboratory. The work is funded by the National Science Foundation.

“Warming is particularly pronounced since 1995, and especially since 2000,” the authors write. The spot where waters were 5 C above average was in the region just north of the Chukchi Sea. The historical average temperature there is -1 C (the salt in ocean water keeps it liquid at temperatures that would cause fresh water to freeze). This year water in that area warmed to 4 C, for a 5-degree change from the average.

That general area, the part of the ocean north of Alaska and Eastern Siberia that includes the Bering Strait and Chukchi Sea, experienced the greatest summer warming. Temperatures for that region were generally 3.5 C warmer than historical averages and 1.5 C warmer than the historical maximum.

Such widespread warming in those areas and elsewhere in the Arctic is probably the result of having increasing amounts of open water in the summer that readily absorb the sun’s rays, Steele says. Hard, white ice, on the other hand, can work as a kind of sunscreen for the waters below, reflecting rather than absorbing sunlight. The warming also may be partly caused by increasing amounts of warmer water coming from the Pacific Ocean, something scientists have noted in recent years.

The Arctic was primed for more open water since the early 1990s as the sea-ice cover has thinned, due to a warming atmosphere and more frequent strong winds sweeping ice out of the Arctic Ocean via Fram Strait into the Atlantic Ocean where the ice melts. The wind effect was particularly strong in the summer of 2007.

Now the situation could be self-perpetuating, Steele says. For example, he calculates that having more heat in surface waters in recent years means 23 to 30 inches less ice will grow in the winter than formed in 1965. Since sea ice typically grows about 80 inches in a winter, that is a significant fraction of ice that’s going missing, he says.

Then too, higher sea surface temperatures can delay the start of freeze-up because the extra heat must be discharged from the upper ocean before ice can form.

“The effect on net winter growth would probably be negligible for a delay of several weeks, but could be substantial for delays of several months,” the authors write. We are getting very close to the tipping point, or maybe we have already moved past it. Either way these continued warnings from the nations best scientists mean that we need to take much more drastic action, and soon. Without an immediate reduction in green house gas emission we are dooming ourselves to a world with a fever. If only our government could pull it’s head out of it’s ass long enough to realize this we might be alright. I suggest you call up your congress person and bitch at them till they hang up on you, do this every week or until we have change. If they keep voting the way you don’t like, vote for someone else who will vote the way you want.

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