Giant Ice Sheet Is Safe ... for Now " src="http://www.sciencemag.org/icons/icon.arrow.53859F.lg.r.gif" width=6 border=0>
Historical data and a new model show a long, slow slide for the West Antarctic 18 Mar
http://sciencenow.sciencemag.org/cgi/content/full/2009/318/1
Giant Ice Sheet Is Safe ... for Now
By Phil Berardelli ScienceNOW Daily News 18 March 2009
One of the world's biggest ice masses, the West Antarctic Ice Sheet, could melt over the next few thousand years and raise sea level by as much as 5 meters if nearby ocean temperatures rise by several degrees Celsius, researchers report. Although such a dramatic rise in temperature may seem unlikely in the near term, such conditions are possible based on paleoclimate data and a new computer model, which show that the ice sheet has collapsed multiple times in the past.
Researchers are investigating what warmer temperatures might do to the world's largest ice masses, including the 2-kilometer-thick ice mass that constitutes the West Antarctic Ice Sheet, lying to the southwest of the southern tip of South America. If the ice sheet melts, many of the world's coastal areas, including Bangladesh, southern Florida, and southern Louisiana, could be under water.
Forecasting the ice sheet's behavior has been difficult, however, because over the past million years, global temperatures have been too cool to provide much insight about what might happen in a balmier climate. So, two teams of researchers tried a new approach. One group examined a pristine drill core from sediment below the sea bottom near the ice. In the part of the core that dates back from about 5 million to 3 million years ago, when temperatures and greenhouse gas levels were somewhat higher than they are today, the group found evidence of multiple, 40,000-year cycles of melting and refreezing.
Then the second group compared that data with a new, three-dimensional computer model that simulated the ice sheet's behavior over the past 5 million years. The teams report in two papers tomorrow in Nature that the West Antarctic Ice Sheet could indeed begin to collapse sometime in the next century or so if nearby ocean temperatures increase roughly 5°C--a possibility if current warming trends continue. If that warming occurs, the sheet could totally collapse in a few thousand years but contribute to sea-level rise much sooner.
Geoscientist Richard Alley of Pennsylvania State University, University Park, says the data team has "done an amazing amount of work to reconstruct the history of the [Antarctic] climate and the ice sheet over times that are important, because we may warm to or beyond those conditions under business-as-usual behavior." Likewise, he says, the modelers have "made major advances," though the ice model will need to be combined with an equally sophisticated ocean model to more precisely estimate the melt rate of the ice sheet.
Thanks for your feedback. Please keep it polite and to the point.
R BIndschadler
Thursday, March 19, 2009
As an active researcher in Antarctic ice sheet dynamics, I caution the readers that celebration of a more stable ice sheet is premature. Pollard and DeConto's work is very impressive and help scientists understand the longer-term behavior of the ice sheet. Their model is able to capture the longer term (multi-centennial) behavior of the ice sheet, but the some of the changes might well occur faster than their model is capable of simulating. I take from their result that the ice sheet reacts more sensitively to ocean temperature than other climatic factors. This supports what other scientists are seeing in recent data of the real ice sheet.
Like this comment? [yes] [no] (Score: 0 by 0)
Community assigned karma score: 0 by 0
Mark as offensive[reply] [delete] [edit] [moderate]
Archer
Thursday, March 19, 2009
Between 7 and 6 million year ago the Mediterranean sea was dried out and flooded numerals times. Bore drilling discovered kilometer thick salt deposits.
Like this comment? [yes] [no] (Score: 0 by 0)
Community assigned karma score: 0 by 0
Mark as offensive[reply] [delete] [edit] [moderate]
----GOSH AB LET ME KNOW IF YOU READ ONE FUCKING WORD ABOUT WESTERN ANTARCTICA AND ITS GOD DAMNED ICE SHEET IN THIS STORY.----
New York will bear brunt of uneven sea level rise
* 16:45 16 March 2009 by Anil Ananthaswamy
* For similar stories, visit the Climate Change Topic Guide
Could the Big Apple soon be bobbing in sea water? A new study shows that sea level rise due to climate change in the next 100 years will be disproportionately high around New York and other cities of northeast US.
Today, the sea level along the east coast of the US is lower than elsewhere, whereas further offshore the level rises sharply.
This anomaly is caused by the balance of forces required for the flow of the strong Gulf Stream and North Atlantic Current, both of which contribute to the Atlantic meridional overturning circulation (AMOC).
The AMOC transports warm surface waters to the high northern latitudes, where the currents cool and sink and then flow back southwards across the Equator.
Already, some studies have shown that the AMOC slowed by about 30% between 1957 and 2004, and it is expected to slow down further because of global warming.
This slowdown, besides possibly endangering the mild climate of northwest Europe, will remove the dynamic forces that keep the sea level anomalously low along the US east coast.
Half a metre
Jianjun Yin of Florida State University and colleagues used climate models used by the Intergovernmental Panel on Climate Change (IPCC) to study how changes to the AMOC will affect sea levels.
They found that, for a scenario with high greenhouse gas emissions, the sea level rise solely due to thermal expansion of the oceans could reach 52, 51 and 44 centimetres around Boston, New York and Washington D.C. respectively, by 2100.
This would pose a particular threat to New York, as some parts of lower Manhattan are only about 1.5 metres above sea level.
In contrast, other coastal cities like San Francisco, London and Tokyo will be impacted far less, because of the local ocean conditions.
More from ice sheets
The numbers do not account for the sea level rise that is expected from the melting of the Greenland Ice Sheet.
The melt-water from this is expected to slow down the AMOC even more, thus adding to the sea level rise around New York, as well as putting the cities on the east coast at greater danger during storm surges due to hurricanes.
"The modelling is highly credible," says Stuart Cunningham, an expert on the AMOC at the Southampton Oceanography Centre in Southampton, UK. "It is clear that what they are showing is going to be a robust result. Whether it is absolutely right in all the details remains to be seen."
If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.
"If a nation expects to be ignorant and free, in a state of civilization, it expects what never was and never will be." -- Thomas Jefferson
We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology. - Carl Sagan
I believe that every right implies a responsibility, every opportunity an obligation; every possession, a duty. - John D. Rockefeller, Jr.
* 14:38 10 March 2009 by Catherine Brahic, Copenhagen
* For similar stories, visit the Climate Change Topic Guide
Sea level rises could bust official estimates that's the first big message to come from the climate change congress that kicked off in Copenhagen, Denmark, today.
Researchers, including John Church of the Centre for Australian Weather and Climate Research, presented evidence that Greenland and Antarctica are losing ice fast, contributing to the annual sea-level rise. Recent data shows that waters have been rising by 3 millimetres a year since 1993.
Church says this is above any of the rates forecast by the IPCC models. By 2100, sea levels could be 1 metre or more above current levels, he says. And it looks increasingly unlikely that the rise will be much less than 50 centimetres.
In 2007, the Intergovernmental Panel on Climate Change forecast a rise of 18 cm to 59 cm by 2100. But the numbers came with a heavy caveat that often went unnoticed by the popular press.
Flooding increase
Because modelling how the Greenland and Antarctic ice sheets will react to rising temperatures is fiendishly complicated, the IPCC did not include either in its estimate. It's no small omission: the Greenland ice cap, the smaller and so far less stable of the two, holds enough water that if it all melted, it would raise sea levels by 6 metres on average across the globe.
"As a result of the acceleration of outlet glaciers over large regions, the ice sheets in Greenland and Antarctica are already contributing more and faster to sea level rise than anticipated," says Eric Rignot of the University of California in Irvine and NASA's Jet Propulsion Laboratory. "If this trend continues, we are likely to witness sea level rise 1 metre or more by year 2100", he says.
Church says even 50 cm would have a huge effect on flooding events. "Our study on Australia showed that coastal flooding events that today we expect only once every 100 years will happen several times a year by 2100," he says.
Jason Lowe of the UK Met Office remains cautious. He accepts that recent data shows ice from Greenland and Antarctica is rapidly pushing up sea levels, but says the models simply are not yet sophisticated enough to say how this affects the future.
If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.
"If a nation expects to be ignorant and free, in a state of civilization, it expects what never was and never will be." -- Thomas Jefferson
We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology. - Carl Sagan
I believe that every right implies a responsibility, every opportunity an obligation; every possession, a duty. - John D. Rockefeller, Jr.
March 11, 2009 11:24 AM
Moving beyond the headlines on climate change
Catherine Brahic, environment reporter, Copenhagen
By now you will have seen the headlines: we're all going to have more than just our toes in the water by century-end because sea levels may have risen by as much as 1 metre by then - possibly even more.
Dramatic headlines make big news - we all know that. So yesterday, when a researcher announced here at the Climate Change Congress that the IPCC may have been very wrong in predicting a best estimate sea-level rise of 60cm, all the journalists here knew they had a story.
But talk to other climate scientists and you get a different picture.
As New Scientist mentioned in Tuesday's story, Jason Lowe of the UK Met Office has his reservations regarding the sea-level rise predictions. The group that presented the "new" numbers is reasonably well known for forecasting the upper end of possibilities.
And Lowe also points out that if you add up all of the IPCC's caveats and footnotes, their total best guess including water and ice from the ice sheets came to roughly 80cm by 2100. So one metre would be more than the IPCC forecast, but nowhere near twice as much.
Stefan Rahmstorf and colleagues, who presented the big numbers in Copenhagen, have a new equation to predict sea-level rise which they claim gives more accurate results than previous models did (I'm still trying to find out why, and will tell you if I find out).
Others maintain that glaciologists and climatologists do not know how to model ice dynamics. That is, how a massive sheet of ice slips and slides over continental bedrock when temperatures start to creep up.
So the bottom line, from what I'm able to gather, is this:
1. Since the IPCC was published in 2007 we have new data that shows that Antarctic and Greenland ice sheets are sliding into the oceans faster and faster
2. This will inevitably accelerate sea level rise
3. We still don't have the mathematical know-how to calculate exactly how much
But that doesn't make for a catchy headline.
Categories: Environment
"If a nation expects to be ignorant and free, in a state of civilization, it expects what never was and never will be." -- Thomas Jefferson
We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology. - Carl Sagan
I believe that every right implies a responsibility, every opportunity an obligation; every possession, a duty. - John D. Rockefeller, Jr.
Susan, when evaluating the scientific data you look to see the work, is it from an outlier or does it build on the previous work. In other words if a hypothesis is going to challenge the century old greenhouse theory, then it needs to find a mechanism where the c02 in the atmosphere has a limit to its effect. None of the deniers do that. The cherry pickers who, like AB point out that c02 has been higher in the far past, fail to also factor in the orbital cycle, continental drift and all the other factors that go into climate. When I see a "scientist" cherry picking or a hired PR flack pushing a non-peer reviewed paper I read the work but look to see what they are sweeping under the rug. Its like the recent flap about arctic ice cover, the prediction of historic minimum ice was for summer, the pr flacks hyped an ice sheet that sounded almost as large as that in the 70's ignoring or hiding two facts: It was winter ice and it was not as thick as the 70's ice. Its like saying ice covered the pond in the 70's and the town skated there, look ice is covering the pond now so lets go skating, but the ice now is inches thick and then was feet thick. The preponderance of serious, peer reviewed scientific work supports the fact that human pollution of the atmosphere is a major if not the major contributor to the current warming which if not stopped will lead to climate change. Take a look at the flooded NYC article. The climate changes to the point that a major ocean current is diminished or extinguished. Scientists can quibble about how much how soon, but thermal change in the oceans is documented and absent a change in Human behavior, climate change will follow in the life time of your kids or grandkids. This is not seriously disputed by scientists.
"If a nation expects to be ignorant and free, in a state of civilization, it expects what never was and never will be." -- Thomas Jefferson
We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology. - Carl Sagan
I believe that every right implies a responsibility, every opportunity an obligation; every possession, a duty. - John D. Rockefeller, Jr.
I sure hope this global warming hurries up...this is the coldest winter in decades here on the mid-Atlantic coast! But....if it's cold that's global warming and if it's hot that's global warming....and if there's another ice age then that's because of global warming too! and make damn sure to ignore the solar storms because the sun has nothing to do with the Earth's warming...it's all man's fault, actually American men's fault...American white men's fault...that are rich and have huge houses like Albert "Little Al" Gore Jr.'s house and all drive SUVs (or flying in their Gulfstreams like Algore) when they aren't starving and cheating the minorities...or ruining the world in general... being especially cruel to polar bears and snail darters and while eating whale meat sandwiches as they beat their wives and molest children and don't pay any income taxes!
The language of priorities is the religion of Socialism.....Aneurin Bevan
But....if it's cold that's global warming and if it's hot that's global warming....and if there's another ice age then that's because of global warming too!
No Skip...they have changed the verbage to "Climate Change"...that way they cover all the bases...LOL.
~~life isn't about how to survive the storm but how to dance in the rain~~
When the character of a man is not clear to you, look at his friends.
Japanese Proverb
LOL! It's like how the use of "Liberal" has become "Progressive"...and we all know it's really socialistic! But they only see and believe what they "choose" to believe from a basis of partisan politics and what benefits their half-ass agenda(s) and their constant striving for political power! The irony is that the elitist masters are playing the hamsters like the ones posting their tripe on this BB...and the hamsters refuse to believe it just like they hamsters have always refused to believe it until they are lined up on the wall with the rest of us and shot....look at any country that has deep core leftist governments the machine is oiled with the blood of the hamsters that put that government in place...ala the "Useful Idiots" that they are!
The language of priorities is the religion of Socialism.....Aneurin Bevan
the fact that that process is already in motion, is glaringly obvious to everyone but those worshipers at the altar of "Fairness".....who see freedom as somehow....unfair
nothing could be more fair than freedom...(including the freedom to fail from one's own poor decisions)
This message has been edited by gillis7 on Mar 21, 2009 12:00 PM
