Monday, August 25, 2008

Known unknowns on ice

This time last week I was at Los Alamos National Laboratory for a meeting that discussed building a Community Ice Sheet Model, inspired by the success of the Community Climate System Model. (Eventually CISM will be part of CCSM).

Ice sheets are getting a lot of attention because that's where one of the biggest potential impacts of climate disruption, sea level rise, comes from. The mechanics of ice sheets have some big known unknowns. The biggest is what is happening at the bottom of the ice sheet--at the ice-land interface. Is it sticky or slippery? What can change it? We only have a few observations and some guesses at theory. Another group of "known unknowns" are the processes that control ice sheet calving. Calving is when chunks of the ice sheet edge break off and form icebergs, a very photogenic process whose exact physics are poorly understood. There's lots of theories, but only trial and error in simulations and more observations will help weed out the good from the bad. Both of these processes affect how fast ice sheets can shed mass to the ocean. Its these mechanical processes, rather then simple melting alone, that has the potential to lead to rapid sea level rise. As you might guess from the immaturity of the field, none of this was considered in the last IPCC report. With efforts like CISM, we will hopefully be able to say a little more in the next report, due out in 2013.

4 comments:

S. David Stoney said...

Hi Rob, Thank you for your work with this site. In the 2nd paragraph did you mean to say ice sheet calving causes "icebergs" (not "glaciers")?

Meanwhile, I have started a climate action group in McClellanville, SC, and we have recently launched our website. It's billed as a climate news source for the SC coast. We are the Kitchen Table Climate Study Group - http://www.kitchentableclimatestudygroup.org.

Perhaps you could add us to your list of links.

Cheers,
S. David Stoney, Jr., Ph.D.
Director
Kitchen Table Climate Study Group
POB 523
McClellanville, SC 29458
843 887-3378

Rob said...

Hi David,

Thanks for noticing that error! I've corrected it. I love the idea for "Kitchen Table Climate Study Group". I try to keep my list of links focused on national/international blogs.

Rob

Steve Bloom said...

I just saw the IMPACTS press release, Rob. Congrats on your prominent role!

Anonymous said...

Its these mechanical processes, rather then simple melting alone, that has the potential to lead to rapid sea level rise. As you might guess from the immaturity of the field, none of this was considered in the last IPCC report. With efforts like CISM, we will hopefully be able to say a little more in the next report, due out in 2013.

You don't have to wait until 2013, there are some interesting studies that are yielding results right now. See for yourself. The Christian Haas arctic ice sheet study. As for sea level rise it seems to be holding at 2-3mm per year at present which isn't too alarming really.