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

This is in the overall context of underestimating the ice melt and a
number of unexpected, negative surprises. The IPCC acted
appropriately in the sense there is no consensus on this. The "this"
here is not the consensus that we will have an overall total 7m sea
level rise in the business as usual scenario -- and that could be
worse if there is significant ice melt in Antarctica which is not
included in the 7m. The "this" is how fast we reach the 7m
equilibrium, centuries vs. decades. The effect we are discussing
could speed up that process considerably but we just don't know.

What you suggest as for the "appropriate" reaction to the current
uncertainty reminds me of the reaction to Paul on Mars Hill.
Interesting, let's discuss this some more. I'll take the passionate
"need to know now" vs. the dispassionate "interesting question" any
day. I'm sticking with my uh oh.

On Feb 16, 2007, at 7:35 AM, David Opderbeck wrote:

> Ok - I'm not trying to play the skeptic here, and I confess ignorance
> of the primary literature, but it seems to me that a very recent
> discovery of this magnitude in relation to glacial stability is not
> really supportive of alarmism. On the one hand, you can say "this
> system may be even more fragile than we thought"; but OTOH, you can
> just as well say "this system seems very capable of handling melt
> water and runoff -- it's a much more flexible and dynamic system than
> appears on the surface." If we really don't know where between those
> two responses the truth lies, isn't the appropriate scientific stance
> a dispassionate "interesting question; let's try to find out" rather
> than necessarily an "uh-oh?" (And so the IPCC's stance is indeed
> vindicated at least as far as these data are concerned?)
>
> On 2/16/07, Rich Blinne <rich.blinne@gmail.com> 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 http://
>> sciencenow.sciencemag.org/cgi/content/full/2007/215/2
>>
>>
>>
>> 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 <rich.blinne@gmail.com> wrote:
>> >
>> > From today's Science Express:
>> >
>> > http://www.sciencemag.org/cgi/content/abstract/1136897v1
>> >
>> > 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: hafricker@ucsd.edu
>> >
>> >
>> >
>> >
>> > 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 km3 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: http://www.davidopderbeck.com
>> Blog: http://www.davidopderbeck.com/throughaglass.html
>> MySpace (Music): http://www.myspace.com/davidbecke
>>
>
>
>
> --
> David W. Opderbeck
> Web: http://www.davidopderbeck.com
> Blog: http://www.davidopderbeck.com/throughaglass.html
> MySpace (Music): http://www.myspace.com/davidbecke

To unsubscribe, send a message to majordomo@calvin.edu with
"unsubscribe asa" (no quotes) as the body of the message.
Received on Fri Feb 16 10:13:45 2007