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

"Hope this helps" ~ Pim 2/18/06

@ I hope this helps you too. :)

ANTARCTIC TEMPERATURES DISAGREE WITH CLIMATE MODEL
PREDICTIONS Source:
<http://www.newswise.com/articles/view/527313//institutions/view/?id=96>Ohio
State University
Released: Tue 13-Feb-2007, 18:00 ET
Embargo expired: Thu 15-Feb-2007, 14:00 ET
http://www.newswise.com/articles/view/527313/

A new report on climate over the world's southernmost continent shows
that temperatures during the late 20th century did not climb as had
been predicted by global climate models. This comes soon after the
latest report by the Intergovernmental Panel on Climate Change that
strongly supports the conclusion that the Earth's climate as a whole
is warming, largely due to human activity.

    It also follows a similar finding from last summer by the same
research group that showed no increase in precipitation over
Antarctica in the last 50 years. Most models predict that both
precipitation and temperature will increase over Antarctica with a
warming of the planet.

    David Bromwich, professor 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," he said. "Part of the reason is that there is
a lot of variability there. It's very hard in these polar latitudes
to demonstrate a global warming signal. This is in marked contrast to
the northern tip of the Antarctic Peninsula that is one of the most
rapidly warming parts of the Earth."

    Bromwich says that the problem rises from several complications.
The continent is vast, as large as the United States and Mexico
combined. Only a small amount of detailed data is available - there
are perhaps only 100 weather stations on that continent compared to
the thousands spread across the U.S. and Europe. And the records that
we have only date back a half-century.

    "The best we can say right now is that the climate models are
somewhat inconsistent with the evidence that we have for the last 50
years from continental Antarctica. "We're looking for a small signal
that represents the impact of human activity and it is hard to find
it at the moment," he said.

    Last year, Bromwich's research group reported in the journal
Science that Antarctic snowfall hadn't increased in the last 50
years. "What we see now is that the temperature regime is broadly
similar to what we saw before with snowfall. In the last decade or
so, both have gone down," he said.

In addition to the new temperature records and earlier precipitation
records, Bromwich's team also looked at the behavior of the
circumpolar westerlies, the broad system of winds that surround the
Antarctic continent.

"The westerlies have intensified over the last four decades of so,
increasing in strength by as much as perhaps 10 to 20 percent," he
said. "This is a huge amount of ocean north of Antarctica and we're
only now understanding just how important the winds are for things
like mixing in the Southern Ocean." The ocean mixing both dissipates
heat and absorbs carbon dioxide, one of the key greenhouse gases
linked to global warming.

~ Janice

At 01:27 PM 2/18/2007, PvM wrote:
>The seems to be some confusion as to what was reported in AR4 versus
>TAR as it pertains to sea level rise due to melting ice.
>
>As I understand it, TAR's estimate included ice dynamics uncertainty
>in their range of estimates, while AR4 removed them because of too
>much uncertainty and the potential to be much larger than originally
>estimated.
>
> From the AR4 SPM
>
><quote>
>Models used to date do not include uncertainties in climate-carbon
>cycle feedback nor do they include the full effects of changes in ice
>sheet flow, because a basis in published literature is lacking. The
>projections include a contribution due to increased ice flow from
>Greenland and Antarctica at the rates observed for 1993-2003, but
>these flow rates could increase or decrease in the future. For
>example, if this contribution were to grow linearly with global
>average temperature change, the upper ranges of sea level rise for
>SRES scenarios shown in Table SPM-2 would increase by 0.1 m to 0.2 m.
>Larger values cannot be excluded, but understanding of these effects
>is too limited to assess their likelihood or provide a best estimate
>or an upper bound for sea level rise.
></quote>
>
>When looking at the effects of warming on sea level, there are various
>relevant components. The first one is expansion because of higher
>temperatures, then there is the increase in melt of sea-ice and the
>increase in melt of ice-sheets
>
><quote>
>Sea ice shrinks in both the arctic and antarctic under all scenarios,
>the reduction is amplified in the arctic where some models predict the
>sea ice to disappear by the latter part of the 21 century.
>
>...
>
>Models suggest that a global average warming of 3 C above present
>levels would cause widespread mass loss of the greenland ice sheet if
>sustained for several centuries, initially contributing up to 0.4 m
>sea level rise per century.
>The melting rate would increase if dynamical processes increase the
>rate of ice flow, as suggested by some recent scenarios.
></quote>
>
>In other words, the largely uncertain effects of dynamical processes
>could add significant increases.
>
><quote>
>The antarctic ice sheet is projected to behave differently from
>Greenland because it is too cold for widespread surface melting. It is
>expected to gain ice through increase snow fall in the 21 century,
>acting to reduce global sea level by 0.1m /century. However, in
>response to weakening of ice shelves by ocean warming or surface
>melting at the margins, ice flow could accelerate. Such effects could
>offset our outweigh increased snowfall but ae uncertain.
></quote>
>
>
>The antarctic in AR4 is described to contribute negatively to sea
>level increases due to increases in precipitation. However at the
>margins, ice flow could accelerate but such effects are still too
>uncertain.
>
>However, Arctic sea ice may very well disappear sooner than later
>(http://www.realclimate.org/index.php/archives/2007/01/arctic-sea-ice-decline-in-the-21st-century/)
>
> From AR4
>During the last interglacial period, about 125,000 years ago, it is
>likely that large scale retreat of the Greenland ice sheet and other
>Arctic ice fields contributed between 2 and 3.5 meters to a sea level
>rise above current levels.
>
>The issues surrounding sea level changes related to ice melt are quite
>interesting and far more complex than initially estimated. However,
>even excluding the dynamic effects, the sea level effects in AR4 are
>similar to TAR with a potential for much larger changes than
>originally expected.
>
>On 2/16/07, Janice Matchett <janmatch@earthlink.net> wrote:
>>
>> At 10:14 AM 2/16/2007, Rich Blinne wrote:
>
>> "This is nice to know, but it has less importance due to the IPCC report
>>downgrading the likeliness of Antarctic ice melting. The current IPCC report
>>(only the executive report (PDF) has been released) notes that Antarctica
>>ice loss should be minimal until after 2100 because the ice is too cold and
>>the models predict increased precipitation in Antarctica. Due to this (and
>>the Greenland ice loss downgrade) most models now only predict a 20 to 50 cm
>>rise in ocean levels due to the seawater heating up and glaciers melting. Al
>>Gore is going to feel sad since his 20 ft sea level rise now looks
>>incredibly unlikely even by the UN. The IPCC report does note that dynamic
>>ice loss events could change this forecast but since they haven't
>>demonstrated any likely candidates yet (perhaps they are in the full report)
>>I would have to assume that they are classifying those types of events in
>>the "what if" category (like what if someone decided to nuke Antarctica 1000
>>times).

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Received on Sun Feb 18 13:59:35 2007