Ethon brings word of April Fool's Jokes Boulder style
It's pretty hard to keep the irony meter on scale these days. The National Anonymice Academy had no sooner taken up the issue of ice cap rot, when Steve Bloom scurried in from Austin Texas, with news from the parallel meeting of the Western Antarctic Links to Sea Level Estimation (WALSE) Workshop. This proves the power of convening a meeting of the Anonymice Academy for focusing attention on important matters. Word had also run to our friends in Boulder who, if they were the long eared types would be complimented on the wonderful knots they are tying in their ears.
Eli thought it would be a good thing to contrast and compare some of the text from the Hansen Arxiv paper the Academy has been studying, with the consensus statement that emerged from the WALSE group, who presumably had a number of expert glaciologists sitting in.
- Satellite observations show that both the grounded ice sheet and the floating ice shelves of the Amundsen Sea Embayment have thinned over the last decades.
Warming ocean waters are now thinning some West Antarctic ice shelves by several meters per year (Payne et al 2004; Shepherd et al 2004).
- Ongoing thinning in the grounded ice sheet is already contributing to sea-level rise.
- The thinning of the ice has occurred because melting beneath the ice shelves has increased, reducing the friction holding back the grounded ice sheet and causing faster flow.
- Oceanic changes have caused the increased ice-shelf melting. The observed average warming of the global ocean has not yet notably affected the waters reaching the base of the ice shelves. However, recent changes in winds around Antarctica caused by human influence and/or natural variability may be changing ocean currents, moving warmer waters under the ice shelves.
- Our understanding of ice-sheet flow suggests the possibility that too much melting beneath ice shelves will lead to “runaway” thinning of the grounded ice sheet. Current understanding is too limited to know whether, when, or how rapidly this might happen, but discussions at the meeting included the possibility of several feet of sea-level rise over a few centuries from changes in this region.
An important point is that the non-linear response could easily run out of control, because of
positive feedbacks and system inertias.......The nonlinearity of the ice sheet problem makes it impossible to accurately predict sea level change on a specific date.
We leave it as a challenge to find Hansen's opinion on the remaining issues. A good place to start is his slippery slope argument in Climate Change, which, among other things points to problems with ice sheet models.
- The experts agreed that to reduce the very large uncertainties concerning the behavior of the Antarctic ice in the Amundsen Sea Embayment will require new satellite, ground, and ship-based observations coupled to improved models of the ice-ocean-atmosphere system. Issues include:
- The recent changes were discovered by satellite observations; however, continued monitoring of some of these changes is not possible because of a loss of capability in current and funded satellite missions.
- The remoteness of this part of Antarctica from existing stations continues to limit the availability of ground observations essential to predicting the future of the ice sheet.
- No oceanographic observations exist beneath the ice shelves, and other oceanographic sampling is too infrequent and sparse to constrain critical processes.
- Current continental-scale ice sheet models are inadequate for predicting future sea level rise because they omit important physical processes.
- Current global climate models do not provide information essential for predicting ice sheet and oceanic changes in the Amundsen Sea Embayment; for example, ice shelves are not included.
unless someone out there thinks that several feet is substantially different from multi-meter or that a large sea level rise over 1-3 centuries would be a walk in the park. Living a mile or so up may give one a sense of security we at sea level lack. OTOH, there is less O2 up high.
2. There is the "possibility of several feet of sea-level rise over a few centuries from changes in this region." This contrasts strongly with Jim Hansen's assertion that"Spatial and temporal fluctuations are normal, short-term expectations for Greenland glaciers are different from long-term expectations for West Antarctica. Integration via the gravity satellite measurements puts individual glacier fluctuations in proper perspective. The broader picture gives strong indication that ice sheets will, and are already beginning to, respond in a nonlinear fashion to global warming.There is enough information now, in my opinion, to make it a near certainty that IPCC BAU climate forcing scenarios would lead to disastrous multi-meter sea level rise on the century time scale"