Steve could we get a new 2009 Sea Ice thread if there’s any interest?

From the WeatherUnderground site, Jeff Master’s blog:

http://www.wunderground.com/blog/JeffMasters/show.html

Latest discussion is on the Arctic ice.

The future of arctic sea ice

Climate models have done a poor job predicting the recent record loss of arctic sea ice. None of the models used to formulate the official word on climate, the 2007 United Nations IPCC report, foresaw the shocking drop of 2007-2008. At the December 2008 AGU meeting, Wieslaw Maslowski of the Navy Postgraduate School hypothesized that the reason for this was the models’ improper handling of ocean currents and how they transport heat. He blamed 60% of the melting during the past decade on heat brought in by ocean currents, and projected that summertime arctic sea ice would completely disappear by 2016.

Dr. Jim Overland of NOAA’s Pacific Marine Environmental Laboratory was more conservative, projecting a 2030 demise of arctic sea ice. He thought we would be “hanging around where we are for a while”, and thought it would take two more unusual summers like the “perfect storm” of 2007 to push the system to an ice-free state.

He further noted that while summertime air temperatures have been near record levels the past few years in the Arctic, there has been one period of comparable warmth, in the 1930s and 1940s. The year 1941 still ranks as the warmest year in the Arctic, though 2007 was virtually tied with it. However, the warmth of the 1930s and 1940s was different than the current warming, and was caused by the Siberian High moving unusually far east over Europe, driving warm, southerly winds over Greenland. The warmth in the past decade, in contrast, is associated with a warming of the entire planet, and is not due to an unusual pressure pattern driving warm air into the region. This means that the current warming is accompanied by much warmer ocean waters, which have helped caused much of the arctic sea ice loss the past two years by melting the ice from beneath.

Used an image credited to: Stroeve et al., 2007 (Arctic sea ice decline: Faster than forecast).

Anbody read the paper he’s referring to?

On a someone what related topic — a bear expert told us that Polar Bears are wondering much further south than typical and are now competing with Brown Bears for territory. She said that the popular theory that diminishing sea ice is causing Polar bears to move south is not supported by the zoology community. They attribute the southern migration to the fact that the berry crop has been quite abundant the past few years causing the population of Polar Bears to swell. It seems that the density of Polar Bears in their native territory is slightly up (including in the sea ice regions), but the total population is up a lot. So the Polar Bears have to move south to avoid competition with other Polar Bears. She then said, “I know that the fact that the Polar bear population is increasing dramatically is disappointing to some of you — but I’m just relating the facts”.

First, you’re best bet for monitoring on-going projections is via our forecasting web page: http://ccar.colorado.edu/arifs/. I will be updating it later this week with a June projection.

Next, the “survival rates” scheme is based on our data, but is run by someone else at NSIDC. If you would like, I can put you in contact with her. But, to quickly answer your question, we have survival rates for age classes one through six, and these are applied to this year’s ice to get that forecast. The average values of 30% and 75% are not used in Figure 4 from http://nsidc.org/arcticseaicenews/2008/050508.html; rather, they are simply average data.

Third, the climate predictors forecast is based on a correlation-weighted scheme. If you want to read about it, this link provides a recent paper: http://ccar.colorado.edu/~drobot/Drobot_RSE.pdf

So, I hope this helps a little! Again, let me know if you want contact info for the person that did the survival rate stuff.

SD

While cheerful enough, I don’t think that I understand it any better after reading the reply, than before. I’ll follow up.

As others have said, ice volume would be even more fundamental, but pretty impossible to measure.

Rich.

And therefore, ice that gets compressed, and thereby thickened, due to a compression event, becomes “old ice” no matter how old it is.

I think most people can conceptualize how thicker ice and whiter ice would melt more slowly than thinner ice and darker ice. Those who don’t will not gain much from the “metric,” “multiyear ice.” “Multiyear ice” mystifies, not clarifies.