Re: Polar melting may raise sea level sooner than expected


"Carsten Troelsgaard" <carsten.troelsgaardNOSPAM@xxxxxxx> wrote in message
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"George" <george@xxxxxxxxxxxxxxxxxxxxx> skrev i en meddelelse
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Take a look at the maps showing projected sea level rise along several
coasts.

http://www.innovations-report.de/html/berichte/geowissenschaften/bericht-57103.html

Made me think of Bangladesh. I couldn't find a topographic map, but the
clip below says it all

quote
Although Bangladesh is a small country, it has considerable topographic
diversity. It has three distinctive features: (i) a broad alluvial plain
subject to frequent flooding, (ii) a slightly elevated relatively older
plain, and (iii) a small hill region drained by flashy rivers. On the
south, a highly irregular deltaic coastline of about 600 km fissured by
many estuarine rivers and channels flowing into the bay of bengal. The
alluvial plain is part of the larger plain of Bengal, which is sometimes
called the Lower Gangetic Plain. Elevations of the plains are less than
10m above the sea level; elevation furthers decline to a near sea level
in the coastal south.
end quote

http://banglapedia.search.com.bd/HT/T_0194.htm

Carsten

Hi Carsten. If what they are saying here is true, I think a lot of
countries are going to be badly affected.

George

The Earth's warming temperatures are on track to melt the Greenland and
Antarctic ice sheets sooner than previously thought and ultimately lead
to a global sea level rise of at least 20 feet, according to new
research.

If the current warming trends continue, by 2100 the Earth will likely be
at least 4 degrees Fahrenheit warmer than present, with the Arctic at
least as warm as it was nearly 130,000 years ago. At that time,
significant portions of the Greenland and Antarctic Ice Sheets melted,
resulting in a sea level about 20 feet (six meters) higher than present
day.

These studies are the first to link Arctic and Antarctic melting during
the Last Interglaciation, 129,000 to 116,000 years ago. "This is a real
eye-opener set of results," said study co-author Jonathan T. Overpeck of
The University of Arizona in Tucson. "The last time the Arctic was
significantly warmer than present day, the Greenland Ice *** melted
back the equivalent of two to three meters (about six to ten feet) of
sea level."

Contrary to what was previously believed, the research suggests the
Antarctic ice *** also melted substantially, contributing another six
to 10 feet (two to three meters) of sea level rise. The new findings
will be published in the March 24 issue of Science.

Co-author Bette Otto-Bliesner of the National Center for Atmospheric
Research in Boulder, Colo., said, "Although the focus of our work is
polar, the implications are global. These ice sheets melted before and
sea levels rose. The warmth needed isn't that much above present
conditions."

The ice sheets are melting already. The new research suggests the
melting could accelerate, thereby raising sea level as fast, or faster,
than three feet (about one meter) of sea level rise per century.

Although ice *** disintegration and the subsequent sea level rise lags
behind rising temperatures, the process will become irreversible
sometime in the second half of the 21st century, Overpeck said, "unless
something is done to dramatically reduce human emissions of greenhouse
gas pollution.

"We need to start serious measures to reduce greenhouse gases within the
next decade. If we don't do something soon, we're committed to
four-to-six meters (13 to 20 feet) of sea level rise in the future."

As sea levels rise, coastal regions are more susceptible to the impacts
of storm surge. The predicted rise would eventually inundate heavily
populated coastal areas worldwide.

Overpeck, a professor of geosciences and director of Institute for the
Study of Planet Earth at The University of Arizona, Otto-Bliesner and
their colleagues report their new findings in a pair of papers. A
complete list of authors is at the end of this release. The National
Science Foundation funded the research.

The researchers used a computer model that scientists use to predict
future climate, the NCAR-based Community Climate System Model (CCSM),
and combined it with ice *** simulations to estimate what the Earth's
climate was like 129,000 years ago.

The team also cross-checked the computer's estimate of ancient climate
against data from natural recorders of ancient climate such as
sediments, fossils and ice cores.

The CCSM did a good job of estimating past climate changes. That gives
the researchers additional confidence in the model's predictions of
future climate change, Otto-Bliesner said.

The work shows that meltwater from Greenland and other Arctic sources
raised sea level by as much as 10 feet (about three meters) during the
Last Interglaciation. However, coral records indicate that the sea level
actually rose 13 to 20 feet (four to six meters) and sediments under the
West Antarctic Ice *** indicate parts of the ice *** disappeared.

Antarctic melting must have produced the additional sea-level rise,
Overpeck concludes. He said the rise in sea level from melting in the
Arctic could have destabilized parts of the Antarctic ice ***.

In the last few years sea level has begun rising more rapidly, Overpeck
said. He's concerned, because unlike the Greenland Ice ***, the base
of the West Antarctic Ice *** is below sea level. If it starts to
melt, it could go fast, he said. Moreover, during the Last
Interglaciation, most of the warming was in the Arctic and only in
summer. Now the Earth is warming at both poles year round.

"To get rid of Greenland's ice, you have to melt it. In the Antarctic,
all you have to do is break up the ice *** and float it away and that
would raise sea level," he said. "It's just like throwing a bunch of ice
cubes into a full glass of water and watching the water spill over the
top."

Overpeck said the team's next step will be developing a more precise
estimate of the threshold of ice *** and sea level change beyond which
major sea level rise is inevitable.





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