Re: [asa] Subglacial Water System Moving Faster Than Previously Thought

From: Dave Wallace <>
Date: Fri Feb 16 2007 - 17:03:07 EST

Any positive feedback mechanism can produce rapidly changing effects in
an unbelievably short time, expecially one where the degree of feedback
increases. An decrease in snow cover reduces reflectivity thus causing
warming which in turn causes faster melting and so on. Thus both the
Greenland/Artic and Antarctic situations should be getting considerable
attention and close monitoring. While I know little about climate
systems as someone trained in Electrical Engineering I had both course
and practical work experience with feedback in control systems.

In one of this series of notes you mention frustration at people playing
amateur climatologist. I don't want to get into a discussion as to
whether that is good or bad, it simply is a fact of life. A book
similar to the first half of Kenneth Miller's Finding Darwin's God but
on Climate change would be really helpful. Discussion of everything
from the physics to the models and data should be included. Even a
special edition of Scientific Americian devoted to this topic would be
good, maybe I have missed it but I have not seen such.

Dave W (not O or S)

Rich Blinne wrote:
> This is recently discovered. The disturbing part is not the existence of
> this system, but the rapidity of the change and unexpected nature of the
> change over a period of months. The water acts as a lubricant and can
> thus act to accelerate deglaciation. Also, this change can both rapidly
> start and stop,
> see
>> Glaciologist Richard Alley of Pennsylvania State University in State
>> College agrees. "Lots of people were saying we [IPCC authors] should
>> extrapolate into the future," he says, but "we dug our heels in at the
>> IPCC and said we don't know enough to give an answer." Researchers
>> will have to understand how and why glacier speeds can vary so much,
>> he adds, before they can trust their models to forecast the fate of
>> the ice sheets, much less sea level.
> The bottom line is the models for glaciers are not at all good and have
> for the most part underestimated the ice melt. This was why this effect
> got completely pulled from AR4. We simply don't know but it doesn't mean
> we have nothing to fear. Since this is so chaotic we may not know until
> it is too late. What we do know suggests that a rapid and catastrophic
> failure of the arctic (and now antarctic) glaciers is very, very
> possible. We just don't know enough to effectively predict it. Think of
> it this way. The failure mechanism for the New Orleans levees was not
> effectively predicted, yet they did in fact fail catastrophically.
> Glaciers may in an unpredicted fashion deglaciate rapidly in an
> analogous way as a levee failure where the structural integrity of the
> bottom is compromised. Thus, the uh oh.
> On Feb 16, 2007, at 6:27 AM, David Opderbeck wrote:
>> Rich, was this subglacial water system recently formed, or has it been
>> around for a long time and only been recently discovered? It seems
>> that if this is a recent phenomenon, it would perhaps be an "uh oh."
>> If it has been around for a long time and has only been recently
>> discovered, however, couldn't that suggest that some fears about
>> deglaciation are overstated -- that glaciers are always very dynamic
>> systems that aren't likely to collapse catastrophically due to some
>> kind of meltwater feedback loop? I'm thinking of the scenes in An
>> Inconvenient Truth concerning water on top of the glaciers in
>> Antarctica (if I'm remembering this right).
>> On 2/15/07, *Rich Blinne* <
>> <>> wrote:
>> From today's Science Express:
>> An Active Subglacial Water System in West Antarctica Mapped
>> from Space
>> *Helen Amanda Fricker ^1 ^* , Ted Scambos ^2 , Robert Bindschadler
>> ^3 , Laurie Padman ^4 *
>> ^1 Scripps Institution of Oceanography, University of California,
>> San Diego, La Jolla, CA 92093, USA.
>> ^2 National Snow and Ice Data Center, University of Colorado,
>> Boulder, CO 80302, USA.
>> ^ 3 NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
>> ^4 Earth & Space Research, Corvallis, OR 97333, USA.
>> ^* To whom correspondence should be addressed.
>> Helen Amanda Fricker , E-mail:
>> <>
>> Satellite laser altimeter elevation profiles from 2003-2006^
>> collected over the lower parts of Whillans and Mercer ice
>> streams,^ West Antarctica, reveal 14 regions of temporally varying
>> elevation^ which we interpret as the surface expression of
>> subglacial water^ movement. Vertical motion and spatial extent of
>> 2 of the largest^ regions are confirmed by satellite image
>> differencing. A major, ^ previously unknown subglacial lake near
>> the grounding line of^ Whillans Ice Stream is observed to drain
>> 2.0 km^3 of water over^ ~3 years, while elsewhere a similar volume
>> of water is being ^ stored subglacially. These observations reveal
>> a widespread,^ dynamic subglacial water system which may exert an
>> important^ control on ice flow and mass balance.^
>> Fast flowing subglacial ice streams are important indicators of
>> climate change and will be helpful in improving our predictions of
>> sea level rise. The author of this paper was quoted by New
>> Scientist as following:
>> We didn't realise that the water under these ice streams was
>> moving in such large quantities and on such short time scales.
>> We thought these changes took place over years and decades,
>> but we are seeing large changes over months," says Helen
>> Fricker at the University of California San Diego's Scripps
>> Institution of Oceanography in the US, who led the study.
>> Uh, oh. Most of the worry was concerning Greenland and it has been
>> generally assumed that Antarctica would as it has in past
>> deglaciations lag the Northern Hemisphere. This appears to
>> challenge that assumption.
>> --
>> David W. Opderbeck
>> Web:
>> Blog:
>> MySpace (Music):

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Received on Fri Feb 16 17:04:51 2007

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