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Author Topic:   Antartic Ice sheets and Sea level rise
Ultima_Squall
Inactive Member


Message 1 of 4 (64140)
11-03-2003 10:31 AM


Hi
I have a question about the tabular icebergs that are breaking off of floating ice shelves around Antartica. Since these icebergs are so large, up to 1km in thickness, does the fact that they are breaking free implies that it will melt and the sea level will rise? Or maybe they are breaking free BECAUSE the sea level is rising. Tx in advance

Replies to this message:
 Message 2 by NosyNed, posted 11-03-2003 11:05 AM Ultima_Squall has not replied
 Message 3 by Coragyps, posted 11-03-2003 12:22 PM Ultima_Squall has not replied

  
NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 2 of 4 (64144)
11-03-2003 11:05 AM
Reply to: Message 1 by Ultima_Squall
11-03-2003 10:31 AM


So far all the ice *shelves* which have rapidly broken up were already floating on the ocean. For this reason when they melt they make no difference at all to the sea level.
Try this. Place water and an ice cube in a glass. Be sure the ice cube is floating freely. mark the water level. check when the ice has all melted. There will be no change.
Ice floats with about 10% of it's volume above the water because it is less dense than water. when it melts and turns to water it loses that 10% in volume.
One concern is that the ice sheets on land behind the ice shelves may flow more freely to the sea if the ice shelves are removed. I understand that there is some evidence that they are accelerating. If this is true and significant then there is real cause for concern. The, apparently, not so stable west antarctic ice sheet has enough water to bring sea levels up about 20 feet! Many cities would disappear, in fact whole countries! I think Florida is in trouble too. (well maybe only half of it so that's not so bad is it? )

This message is a reply to:
 Message 1 by Ultima_Squall, posted 11-03-2003 10:31 AM Ultima_Squall has not replied

  
Coragyps
Member (Idle past 735 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 3 of 4 (64157)
11-03-2003 12:22 PM
Reply to: Message 1 by Ultima_Squall
11-03-2003 10:31 AM


Or maybe they are breaking free BECAUSE the sea level is rising.
Ned answered the part about "already afloat" ice sheets - the big concern seems to be whether the partially grounded ice sheets and the humungous glaciers that feed them are accelerating their journey back into seawater, possibly accelerated by rising sea levels. There's a lot of research activity on the subject, but I'm not knowledgeable enough in it all to evaluate any risks.
Though covering half of Florida might not be all that bad.

This message is a reply to:
 Message 1 by Ultima_Squall, posted 11-03-2003 10:31 AM Ultima_Squall has not replied

Replies to this message:
 Message 4 by Bill Birkeland, posted 11-03-2003 12:45 PM Coragyps has not replied

  
Bill Birkeland
Member (Idle past 2532 days)
Posts: 165
From: Louisiana
Joined: 01-30-2003


Message 4 of 4 (64166)
11-03-2003 12:45 PM
Reply to: Message 3 by Coragyps
11-03-2003 12:22 PM


Coragyps wrote:
"Ned answered the part about "already
afloat" ice sheets - the big concern
seems to be whether the partially
grounded ice sheets and the humungous
glaciers that feed them are accelerating
their journey back into seawater,
possibly accelerated by rising sea
levels. There's a lot of research
activity on the subject, but I'm not
knowledgeable enough in it all to
evaluate any risks."
Some web pages that provide some information in respect to this question are:
1."31 March 2002 , Antarctica Key To Sudden Sea Level Rise"
Antarctica Key To Sudden Sea Level Rise - ScienceAGoGo
"In less than 500 years at the end of
the last Ice Age, this event caused the
Earth's sea level to rise about 70 feet.
That's about four times faster than sea
levels were rising most of the time
during this period, and at least 20
times faster than the sea level is
currently rising."
...text deleted....
"What is very clear, however, is the
importance of Antarctica's huge ice
sheets remaining stable. The West
Antarctic ice sheet is thought to be
potentially unstable, and if it
collapsed sea levels around the world
would rise almost 20 feet. The melting
of the larger and more stable East
Antarctic ice sheet would raise
Earth's sea levels another 200 feet."
++++++++
2. USGS "Estimated Present-Day Area* and Volume* of Glaciers
and Maximum Sea Level Rise Potential" at:
USGS URL Resolution Error Page
Location/Area/Volume/maximum sea level rise (m)
Antarctic/13,586,400(km2)/30,109,800(km3)/73.44 m
East Antarctica/10,153,170(km2)/26,039,200(km3)/64.80 m
West Antarctica/1,918,170(km2)/3,262,000(km3)/8.06 m
Antarctic Peninsula/ 446,690(km2)/227,100(km3)/0.46 m
Ross Ice Shelf/536,070(km2)/229,600(km3)/0.01m
Ronne-Filchner ice sheves/532,200(km2)/351,900(km3)/ 0.11 m
++++++++
"Ice Sheets and Sea Level Rise" By : Claire L. Parkinson,
Oceans and Ice Branch, Code 971, NASA Goddard Space Flight
Center, Greenbelt MD 20771 at:
http://pumas.jpl.nasa.gov/PDF_Examples/02_10_97_1.pdf
"Exercise : Determine the amount
that sea level would rise, averaged
around the globe, in response to the
complete melting of (a) the Greenland
ice sheet, (b) the Antarctic ice sheet,
and (c) both the Greenland and
Antarctic ice sheets."
"The answers are: (a) (2,343,728 cubic
kilometers)/(361,132,000 square kilometers)
= 0.0065 kilometers = 6.5 meters for
the Greenland ice sheet; (b) (26,384,368
cubic kilometers)/(361,132,000 square
kilometers) = 0.0731 kilometers = 73.1
meters for the Antarctic ice sheet;
(c) 6.5 meters + 73.1 meters = 79.6 meters
for Greenland and Antarctica together"
Yours,
Bill Birkeland
[This message has been edited by Bill Birkeland, 11-03-2003]

This message is a reply to:
 Message 3 by Coragyps, posted 11-03-2003 12:22 PM Coragyps has not replied

  
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