Re: [asa] ESA: Wilkins Ice Shelf under threat

On Nov 29, 2008, at 2:04 PM, Lynn Walker wrote:

> Media Hype on "Melting" Antarctic Ignores Record Ice Growth
> http://tomnelson.blogspot.com/2008_10_12_archive.html
> U.S. Senate Committee on Environment and Public Works - Minority Page
>
>
> The media is once again hyping an allegedly dire consequence of man-
> made global warming. This time the media is promoting the ice loss
> of one tiny fraction of the giant ice-covered continent and
> completely ignoring the current record ice growth on Antarctica.
>

The media? I quoted the European Space Agency. You quoted someone from
the Weather Channel. What record ice gain? http://www.sciencedaily.com/releases/2008/01/080123181952.htm
  (More on this later.)

> Ice loss in Antarctica increased by 75 percent in the last 10 years
> due to a speed-up in the flow of its glaciers and is now nearly as
> great as that observed in Greenland, according to a new,
> comprehensive study by NASA and university scientists.

> The team found that the net loss of ice mass from Antarctica
> increased from 112 (plus or minus 91) gigatonnes a year in 1996 to
> 196 (plus or minus 92) gigatonnes a year in 2006. A gigatonne is one
> billion metric tons, or more than 2.2 trillion pounds.

> Contrary to media hype, the vast majority of Antarctica has cooled
> over the past 50 years and ice coverage has grown to record levels
> since satellite monitoring began in the 1979, according to peer-
> reviewed studies and scientists who study the area. (LINK)
>

The pioneer climate modelers Kirk Bryan and Syukuro Manabe took up the
question of the delay of warming in the Southern Hemisphere with a
more detailed model (at the time twenty years ago) that revealed an
additional effect. In the Southern Ocean around Antarctica the mixing
of water went deeper than in Northern waters, so more volumes of water
were brought into play earlier. In their model, around Antarctica
“there is no warming at the sea surface, and even a slight cooling
over the 50-year duration of the experiment.” (1) In the twenty years
since, computer models have improved by orders of magnitude, but they
continue to show that Antarctica cannot be expected to warm up very
significantly until long after the rest of the world’'s climate is
radically changed.

(1) Kirk Bryan et al. (1988). J. Physical Oceanography 18: 851-67.

Now that's what the model says, however we are seeing disturbing
differences from the models in the Arctic and the Antarctic. Not only
did we see the second record smallest ice extent in the Arctic this
year (http://nsidc.org/arcticseaicenews/2008/091608.html) we also are
seeing the decrease in Antarctic ice contrary to the models. What we
are seeing is two parts of Antarctica the Eastern half which is stable
and the Western half where all the "action" is including all these ice
shelf collapses. The last time we had a Wilkins collapse it was
predicted that we wouldn't see any changes until in January. Well it's
November. All the "surprises" have been on the bad side.

http://www.eurekalert.org/pub_releases/2008-01/uob-ail011108.php

> Increasing amounts of ice mass have been lost from West Antarctica
> and the Antarctic peninsula over the past ten years, according to
> research from the University of Bristol and published online this
> week in Nature Geoscience.
>
> Meanwhile the ice mass in East Antarctica has been roughly stable,
> with neither loss nor accumulation over the past decade.
>
> Professor Jonathan Bamber at the University of Bristol and
> colleagues estimated the flux of ice from the ice sheet into the
> ocean from satellite data that cover 85% of Antarctica's coastline,
> which they compared with simulations of snow accumulation over the
> same period, obtained using a regional climate model.
>
> They arrived at a best estimate of a loss of 132 billion tonnes of
> ice in 2006 from West Antarctica – up from about 83 billion tonnes
> in 1996 – and a loss of about 60 billion tonnes in 2006 from the
> Antarctic Peninsula.
>
> Professor Bamber said: “To put these figures into perspective, four
> billion tons of ice is enough to provide drinking water for the
> whole of the UK population for one year."
>
> The authors conclude that the Antarctic ice sheet mass budget is
> more complex than indicated by the evolution of its surface mass
> balance or climate-driven predictions.
>
> Changes in glacier dynamics are significant and may in fact dominate
> the ice sheet mass budget. This conclusion is contrary to model
> simulations of the response of the ice sheet to future climate
> change, which conclude that it will grow due to increased snowfall.
>
> The ice loss is concentrated at narrow glacier outlets with
> accelerating ice flow, which suggests that glacier flow has altered
> the mass balance of the entire ice sheet.
>
> Over the 10 year time period of the survey, the ice sheet as a whole
> was certainly losing mass, and the mass loss increased by 75% during
> this time. Most of the mass loss is from the Amundsen Sea sector of
> West Antarctica and the northern tip of the Peninsula where it is
> driven by ongoing, pronounced glacier acceleration. In East
> Antarctica, the mass balance is near zero, but the thinning of its
> potentially vulnerable marine sectors suggests this may change in
> the near future.
>

>
>
> Former Weather Channel Meteorologist Joe D'Aleo rejected the hype
> surrounding the recent Wilkins Ice Shelf collapse in Western
> Antarctica. "The shattered part of the Wilkins ice sheet was 160
> square miles in area, which is just 0.01% of the total current
> Antarctic ice cover, like an icicle falling from a snow and ice
> covered roof," D'Aleo wrote on March 25. (LINK) "We are very likely
> going to exceed last year's record [for Southern Hemisphere ice
> extent]. Yet the world is left with the false impression
> Antarctica's ice sheet is also starting to disappear," D'Aleo added.
>
>
> Climate scientist Dr. Ben Herman, past director of the Institute of
> Atmospheric Physics and former Head of the Department of Atmospheric
> Sciences at the University of Arizona, stated, "It is interesting
> that all of the AGW (anthropogenic global warming) stories
> concerning Antarctica are always about what's happening around the
> [western] peninsula, which seems to be the only place on Antarctica
> that has shown warming. How about the net 'no change' or 'cooling'
> over the rest of the continent, which is probably about 95% of the
> land mass, not to mention the record sea ice coverage recently."
>
>
>
When Western Antarctica is compared against Eastern Antarctica it's
small but when we melt it it comes to a 5-15m of sea level rise. For
more on this connection see here for West Antarctic Links to Sea-Level
Estimation Initiative: http://www.jsg.utexas.edu/walse This seeks to
correct the underestimates of sea level rise the models are giving.
Record sea ice? NCDC noted:

> Meanwhile, the October 2008 Southern Hemisphere sea ice extent was
> slightly below the 1979-2000 mean. This was the eighth least sea ice
> extent in October (1.02 percent below the 1979-2000 mean) over the
> 30-year historical period.

Rich Blinne
Member ASA

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Received on Sat Nov 29 20:09:22 2008