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

From: Janice Matchett <>
Date: Fri Feb 16 2007 - 12:41:03 EST

At 10:14 AM 2/16/2007, Rich Blinne wrote:

>"..I'm sticking with my uh oh." ~ Rich

@ Almost as if he anticipated a response such as
yours, we have this comment (and one other one I like below it):

"Since we've only observed this recently, we
should assume that it's a new phenomenon, rather
than something that's been going on for millions
of years." [ :) ] ~ 3 posted on 02/15/2007
7:20:06 PM EST by

"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
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).

I can't wait until the full IPCC report comes out
because I am trying to figure out what they are
talking about with the 1.6 W/mē radiative forcing
(with 1-sigma ranges apparently from 0.6 W/mē to
2.4 W/mē). It appears to me that their 2-sigma
values would overlap 0 W/mē which is probably
from where the 90% probability that they listed
comes from (with 10% less than 0 W/mē). If this
is the case then they are dramatically
overstating the importance of the calculated
radiative forcing in the same way that stating
that the gravitational acceleration was 9.8 m/sē
(with 1 sigma values from 4.0 m/sē to 16.0 m/sē)
would be too imprecise a measurement of g to be
of great use." ~ 4 posted on 02/15/2007 8:21:39 PM EST by burzum

~ Janice :)

NASA Study Reveals Leaks In Antarctic 'Plumbing System'
Science Daily ^ | 2-15-2007 | NASA/Goddard
Posted on 02/15/2007 7:09:51 PM EST by blam
Source: NASA/Goddard Space Flight Center
Date: February 15, 2007

Science Daily ­ Scientists using NASA satellites
have discovered an extensive network of waterways
beneath a fast-moving Antarctic ice stream that
provide clues as to how "leaks" in the system
impact sea level and the world's largest ice
sheet. Antarctica holds about 90 percent of the
world's ice and 70 percent of the world's reservoir of fresh water.

[click above link to see the pictures above this caption]:
 From December 2003 to December 2005, MODIS
captured these two images showing a draw down of
water in a subglacial lake (left)and the rise of
water in the same subglacial lake (right). Color
coded ICESat tracks across both images indicate
rises and falls in the elevation of the lake's water. (Credit: NASA)

With data from NASA satellites, a team of
scientists led by research geophysicist Helen
Fricker of the Scripps Institution of
Oceanography, La Jolla, Calif., detected for the
first time the subtle rise and fall of the
surface of fast-moving ice streams as the lakes
and channels nearly a half-mile of solid ice
below filled and emptied. Results were presented
Thursday at the annual meeting of the American
Association for the Advancement of Science (AAAS)
in San Francisco. The study will be published in
the Feb. 16 issue of Science magazine.

"This exciting discovery of large lakes
exchanging water under the ice sheet surface has
radically altered our view of what is happening
at the base of the ice sheet and how ice moves in
that environment," said co-author Robert
Bindschadler, chief scientist of the Laboratory
for Hydrospheric and Biospheric Sciences at
NASA's Goddard Space Flight Center, Greenbelt, Md.

"NASA's state-of-the-art satellite instruments
are so sensitive we are able to capture an
unprecedented three-dimensional look at the
system beneath the thick ice sheet and measure
from space changes of a mere 3 feet in its
surface elevation. That is like seeing an
elevation change in the thickness of a paperback
book from an airplane flying at 35,000 feet."

The surface of the ice sheet appears stable to
the naked eye, but because the base of an ice
stream is warmer, water melts from the basal ice
to flow, filling the system's "pipes" and
lubricating flow of the overlying ice. This web
of waterways acts as a vehicle for water to move
and change its influence on the ice movement.
Moving back and forth through the system's
"pipes" from one lake to another, the water
stimulates the speed of the ice stream's flow a
few feet per day, contributing to conditions that
cause the ice sheet to either grow or decay.
Movement in this system can influence sea level and ice melt worldwide.

"There's an urgency to learning more about ice
sheets when you note that sea level rises and
falls in direct response to changes in that ice,"
Fricker said. "With this in mind, NASA's ICESat,
Aqua and other satellites are providing a vital public service."

In recent years, scientists have discovered more
than 145 subglacial lakes, a smaller number of
which composes this "plumbing system" in the
Antarctic. Bindschadler and Fricker; Ted Scambos
of the National Snow and Ice Data Center in
Boulder, Colo.; and Laurence Padman of Earth and
Space Research in Corvallis, Ore.; observed water
discharging from these under-ice lakes into the
ocean in coastal areas. Their research has
delivered new insight into how much and how
frequently these waterways "leak" water and how many connect to the ocean.

The study included observations of a subglacial
lake the size of Lake Ontario buried under an
active area of west Antarctica that feeds into
the Ross Ice Shelf. The research team combined
images from the Moderate Resolution Imaging
Spectroradiometer (MODIS) instrument aboard
NASA's Aqua satellite and data from the
Geoscience Laser Altimeter System (GLAS) on
NASA's Ice Cloud and Land Elevation Satellite
(ICESat) to unveil a multi-dimensional view of
changes in the elevation of the icy surface above
the lake and surrounding areas during a
three-year period. Those changes suggest the lake
drained and that its water relocated elsewhere.

MODIS continuously takes measurements of
broad-sweeping surface areas at three levels of
detail, revealing the outline of under-ice lakes.
ICESat's GLAS instrument uses laser altimetry
technology to measure even the smallest of
elevation changes in the landscape of an ice
sheet. Together, data from both have been used to
create a multi-year series of calibrated surface
reflectance images, resulting in a new technique
called satellite image differencing that
emphasizes where surface slopes have changed.

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Received on Fri Feb 16 12:42:45 2007

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