6 April 2009
Shed A Tear For The Cryosphere
Posted by Dan Satterfield
A lot of news about the Arctic Sea ice in the past few days. NASA and the National Snow and Ice Data Center issued a report Monday morning that showed the average ice coverage in March was 15.16 million Sq. KM. This is well below the 1979-2000 average for March. The ice is well above the record low in 2006, but the news is generally bad.
Most of the ice is much thinner than it should be. This thin (First year ice), will melt quickly as Summer comes. The Arctic ice reaches it’s maximum extent in late February, or early March. This year the maximum was reached on Feb. 28th, but the ice held steady for most of March.
The thickness of the ice is key to how quickly and how much it will melt in the Summer. The Arctic ice reaches it’s minimum in early September. 2007 saw a record low in the ice. As one scientist put it, “The Arctic Ice has fallen off a cliff”. More importantly, the ice is not following the IPCC forecasts. It’s disappearing much faster!
Greenhouse gases are almost certainly responsible for the rapid decline, but other things control the ice as well. Ocean currents and wind patterns in the atmosphere. This past Winter has been characterized by La Nina conditions. This cold water over a large part of the Pacific actually cools the planet slightly, and it might have been the reason the 2008 melt did not quite reach the drastic levels of 2007.
I read a fascinating paper over the weekend, that is being published in the well respected Science Journal Geophysical Research letters. (GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L07502, doi:10.1029/2009GL037820, 2009) Muyin Wang of the U. of Washington, and James Overland of NOAA Pacific Marine Environmental Laboratory, went back, and looked at the climate models used to forecast the Arctic ice. The IPCC had forecasted most of the ice to disappear by 2100. It’s apparently melting much faster than that.
The way climate modeling works is this. You run the model many times with slightly different initial conditions. You will get an ensemble of different results. A few crazy solutions yes, but the models will cluster around certain values. The average of these clusters is usually the most reliable. I look at ensembles like this daily when making my forecasts for the next 7 days here in Huntsville.
The bright idea here, was to go back and see which of the IPCC models, did the best job over the last 20 years with the ice, and then see what those models predicted for the next 90 years. The answer? Most of the models bring the date of nearly total melt in Summer forward to around 2040. Just 30 years from now, and the North Pole will be water in September, not ice.
You might wonder about how that will affect our weather patterns. How will it change the temperature in the Arctic- North of 60. What kind of changes will we see further South??
A lot of Meteorologists, and Climate scientists are wondering the same thing…