All in all, I don't think we know enough to warrant the Greenland alarm bells being rung in some corners but that doesn't mean that the bell ringers are not right. There is too much yet to learn for me to have confidence one way or the other.
It's like the laugh the republi-cons have over Al Gore talking about global warming in New York during a New York snow storm. "Global warming, and it was snowing while he was talking! Yuck, yuck!" At any one physical point on the globe you have a thing we call 'the weather'. The weather at any point, any locality, has high variability. It's the global pattern of these variabilities that is so problematic. Greenland may not be the largest Serinus canaria(canary) in the coal mine, but it is surely one of the worst if we lose that ice mass. I can't believe that Greenland would melt without the Antartic also melting. A rise in sea levels of 45 or 50 feet would be devastating.
Dr. Hulbe, will you be addressing the release of frozen methane from the oceans with a rise in sea temperatures?
Posted by phidipides at March 12, 2007 09:18 AMI just read an article about a Polish yacht which recently sailed the fabled Northwest Passage, first negotiated by Roald Amundsen only a hundred years ago (1906--and he was iced in for two years), in a little over a month, with stops enroute for some dogsledding and diving. Check out their website: www.amundsen.pl
Cargo ships sailing London-Tokyo would shave over two thousand miles off their trips using the NW passage in lieu of the Panama Canal.
Greenland may not be the largest Serinus canaria
Well, when I give public talks I often tell folks that if they want to worry about rapid surprises in the cryosphere, Greenland is a good place to envision.
Destabilization of methane clathrates is a murky topic. Estimates of how extensive the deposits are seem to go down every few years. There are times in the past (millions of years ago) when this process might have been a significant driver of rapid climate change though.
Northwest Passage
Changes to sea ice are a different issue than changes to glacier ice, but an important one. During the cold war era, Soviet science had an interest in reducing the albedo of the planet (how reflective it is, thus how much of the incomming solar radiation is reflected right back out to space & not used by the climate system) because the government was interested in ice-free northern ports. It's not only shipping lanes though but also access to mineral resources.
Posted by Christina at March 12, 2007 10:27 AMSo everyone agrees that Greenland is losing ice mass and that glacier speed is increasing. "All the scenarios" for outlet glacier discharge are "linked to global warming".
But the alarm bells aren't ringing? How much more time can we afford for study, professor? And how likely do you think that the conclusions are ultimately going to be that Greenland is not melting as a result of global warming? Or maybe I'm not understanding you.
Posted by euzoius at March 12, 2007 10:40 AMThe alarms bell to which I linked is a "warning," reported here a few weeks ago, of a "dangerous non-linearity" in the glacier mechanics part of the mass loss from Greenland. Until we understand, really understand, the cause for the recent speed ups, we just can't make useful projections for the future. If the recent slowdowns of Kangerdlugssuaq and Helheim indicate a trend toward restabilization, and if they are indicitave of what will happen with other outlet glaciers around the ice sheet, the perturbation may be close to an end. I would argue that it is equally likely, at this point, that the recent slowdowns on those two glaciers could be minor events in a longer-term downwasting. We simply don't know.
The melting, of course, will continue apace as the planet continues to warm.
Whatever change is now underway in Greenland was purchased with fossil fuel burning over the last two centuries. Of that, I have little doubt. But we really do need to understand the mechanics of the glacier speed up events before we can make useful projections about the future. You should be concerned that the models now used in future climate studies are not capable of reproducing the glacier dynamics part of what's going on in Greenland. Those of us who work on these problems certainly are.
There is every reason to be very concerned about global warming and to be working to reduce greenhouse gas emissions, develop mitigation technologies, and plan adaptation strategies. It is my opinion that ill-informed hysteria serves these causes very poorly.
Posted by Christina at March 12, 2007 11:18 AMIn a recent talk in Santa Barbara, James Hansen (who's so well-known in the field of climatology he's almost famous to the public) made two fundamental points on this question:
1) In its latest report, the IPCC was wrong to include an estimate for sea-level rise, because they admitted the science on inland ice melting over Greenland is immature and unreliable. He thinks the IPCC sea level rise estimates may seriously underestimate Greenland's contribution.
2) Hansen added that in his opinion, an ice sheet would soon break up if covered by surface melt.
Do these points make sense to you, Christina?
Posted by Kit Stolz at March 12, 2007 12:23 PMWe need to distinguish between mass loss due to surface melting and mass loss due to changes in ice flow. The former is much easier to get a handle on than the latter, for reasons discussed in this post.
an ice sheet would soon break up if covered by surface melt.
This does not make any sense to me. There is a relationship between pervasive surface melting and the disintegration of floating ice shelves. But relatively thin, floating, coastal ice shelves are very different from thick, grounded, inland ice sheets. We can certainly increase the rate at which ice flows from the interior of the ice sheet to the sea (and that is happening right now in Greenland and in some locations in Antarcitca) but that's different from "breaking up."
Posted by Christina at March 12, 2007 01:01 PMSo Dr. Hulbe, did you get a chance to watch the BBC chanel 4 show recently aired titled The Great Global Warming Swindle? If you haven't Google video has it.
Nice program, well presented with many scientist speaking in opposition. And then there's Penn Professor Bob Giegengach, he works ine the Department of Earth and Evironmental Science. He doesn't hold the Inconvenient Truth too highly. David Bromwich, professor of atmospheric sciences in the Department of Geography, and researcher with the Byrd Polar Research Center at Ohio State University, reported on this work at the annual meeting of the American Association for the Advancement of Science at San Francisco. It's hard to see a global warming signal from the mainland of Antarctica right now.
There seems to be just as many scientist against the idea of man causing any warming as are those saying we are causing it.
Posted by peter at March 12, 2007 08:55 PMFirst, Dr. David Bromwich is a friend of mine and he's not a global warming denier.
Second, I'm not sure why Antarctica comes up in a commentary on Greenland but whatever. There are two issues here, temperature and precipitation. The Antarctic temperature signal is more complicated than the question implies. The Antarcitc Peninsula has warmed a little more than 2.5 degrees Celcius over the last half century, far in excess of the global mean. Surface temperature records in most of the rest of the continent show no statistically significant trend one way or the other. Weather balloon data show that at higher altitude, the Antarctic troposphere is warming. The stratosphere (about 8 km) is cooling, as is theoretically expected in a global warming world.
What David was probably talking about was precipitation (snow). At least, that's something that was on his mind when we talked at a meeting last summer. The spare collection of snow accumulation measurements in East Antarctica don't show an increase in precipitation, as you might expect in a warmer, moister world. David is not saying that the planet is not warming up, he's saying that this one anticipated effect of warming has not been observed in measured snowfall in this region. However, I should add that there has been an observed (via satellite altimetry) increase of surface elevation around the East Antarctic and the Gravity Recovery mission data discussed in my commentary indicates a small increase in mass of the East Antarctic Ice Sheet. The only strong ice flow trend observed is the recent speed-up of one outlet glacier (the Totten Glacier).
Mass balance calculations by Rignot (whose Greenland work is referenced in the commentary) calculates a withdrawal from sea level of about 0.055 mm/year due to mass accumulation in East Antarctica. There is mass loss in West Antarctica due to changes in ice flow.
There is a nice, short statement from the British Antarctic Survey about all of this here.
I can't believe that Greenland would melt without the Antartic also melting.
I missed this the first time. Antarcitca is much colder, in general, than Greenland and somewhat isolated from the rest of the climate system by the circum-antarctic circulation (weterlies) of the atmosphere. We'll be waiting a while if all we have is melting. Indeed, climate-only models predict net withdrawals from sea level due to increased snow accumulation in Antarctica. There are, however, some important reasons to be concerned about large contributions to sea level from Antarctica related to changes in ice flow.
Posted by Christina at March 12, 2007 11:51 PM