Polar Ice Sheet Melt May Raise Sea Levels Faster Than Anticipated - AFP

[hatrack]

Ice sheets across both the Arctic and Antarctic could melt more quickly than expected this century, according to two studies that blend computer modeling with paleoclimate records. The studies, led by scientists at the National Center for Atmospheric Research (NCAR) and the University of Arizona, show that Arctic summers by 2100 may be as warm as they were nearly 130,000 years ago, when sea levels eventually rose up to 20 feet (6 meters) higher than today.

Bette Otto-Bliesner (NCAR) and Jonathan Overpeck (University of Arizona) report on their new work in two papers appearing in the March 24 issue of Science. The research was funded by the National Science Foundation, NCAR's primary sponsor. The study also involved researchers from the universities of Calgary and Colorado, the U.S. Geological Survey, and The Pennsylvania State University.

Otto-Bliesner and Overpeck base their findings on data from ancient coral reefs, ice cores, and other natural climate records, as well as output from the NCAR-based Community Climate System Model (CCSM), a powerful tool for simulating past, present, and future climates. "Although the focus of our work is polar, the implications are global," says Otto-Bliesner. "These ice sheets have melted before and sea levels rose. The warmth needed isn't that much above present conditions."

The two studies show that greenhouse gas increases over the next century could warm the Arctic by 5-8 degrees Fahrenheit (3-5 degrees Celsius) in summertime. This is roughly as warm as it was 130,000 years ago, between the most recent ice age and the previous one. The warm Arctic summers during the last interglacial period were caused by changes in Earth's tilt and orbit. The CCSM accurately captured that warming, which is mirrored in data from paleoclimate records.

EDIT

http://www.terradaily.com/reports/Arctic_Antarctic_Melting_May_Raise_Sea_Levels_Faster_Than_Expected.html

[flamin lib]

1. Global warming is Bush's answer to Social Security and Medicare.

As the ice sheet gets thinner it will break into more and more ice floes and we need more ice floes to put old people on . . .

[Boomer]

3. I can think of worse ways to go

And many of them involve the conditions on land during an "adjustment" to extreme climate change.

[soothsayer]

2. How come nobody's capturing this runoff for drinking water?

Might as well make the best of it, no?

Now---100 million people globally live within 3 vertical feet of sea level, so those folks are in for a heap o'trouble.

[TreasonousBastard]

4. A lot more than that...

most of the coasts of North and South America, Caribbean and Pacific islands, African and Asian coasts, Indonesia, Japan, Philippines... Places like Bangla Desh, where almost everyone lives on the coast, coastal India... The Netherlands, Denmark... Everything in the Mediterranean.

New York, Los Angeles, Seattle, Boston and Houston and their surrounds are pretty close to a hundred million right there. It'll take a while, but the Great Lakes will rise and there goes Chicago, Toronto, Buffalo...

And don't forget the rivers like the Yalu, Mississippi, and Amazon where a major sea rise will go far inland. Tigris, Euphrates, Nile, Dead Sea, Red Sea, Persian Gulf... The Middle East problem will be solved-- no more Middle East.

It would not be fun. Just think of the mad dash for the hills and the wars over the little remaing land.

[htuttle]

5. Actually, the Great Lakes won't necessarily rise

Only the very bottom of Lake Superior is at or below sea level. All the rest of the lakes are entirely above sea level. Of course, increased rainfall in the Great Lakes basin could easily raise lake levels.

Another problem to consider, however, is salty sea water contaminating regional aquifers. That could effectively wipe out agriculture for many miles farther inland than flooding will submerge.

[TreasonousBastard]

7. Good point, Ontario's surface is...

246' above sea level, and the rest are higher. All but one have their bottoms below sea level, though.

According to the USGS, Lake levels will actually fall maybe 20' or so over the next century if things go the way they are.

[Boomer]

11. Already happening to Tuvulu Islands

They aren't under water yet, but they're losing arable land due to sea water seeping into the island water supplies. The end result is that the population will have to abandon their homes before "official" submersion.

Of course, they could always luck out and have a storm surge sweep them away first.

:sarcasm:

[kestrel91316]

14. Most of the greater Los Angeles area is NOT at risk from rising

sea levels. heck, I am in the San Fernando Valley and I think our elevation is about 750 feet. Only the beach communities in the south bay, and maybe the Long Beach coast are at risk. Our mountains come right down to the sea on the West Coast.

[RaleighNCDUer]

6. Chicken or the egg?

"The warm Arctic summers during the last interglacial period were caused by changes in Earth's tilt and orbit."

Wouldn't another possibility be that melting of polar ice sheets changed the distribution of weight, thus causing changes in the Earth's tilt and orbit?

With such complex systems, we can't really know what caused what effect.

[hatrack]

8. Orbital change likely for long-scale changes - these aren't long-scale

Milankovitch Cycles were the most likely drivers for long-term interglacial changes - i.e. over the last 400,000 years or so. What we're now looking at are changes on timescales so short relative to these natural oscillations that comparing the interglacials to current anthropogenic warming is like trying to emphasize just how similar the life cycles of Galapagos tortoises and mayflies are.

I have serious doubts on melting ice sheets had much of an effect on tilt and orbit - the ice sheets' mass is really, really small compared with the mass of the planet itself.

And to say that "we can't really know" because of complexity is, to my mind, something of a cop-out. Why not just give up the effort entirely if such is the case?

http://www.aip.org/history/climate/cycles.htm

http://www.homepage.montana.edu/~geol445/hyperglac/time1/milankov.htm

http://www.phy6.org/stargaze/Sprecess.htm


See also: Dansgaard-Oeschger Events

http://en.wikipedia.org/wiki/Dansgaard-Oeschger_events

http://www.agu.org/revgeophys/mayews01/node7.html

[phantom power]

9. I would expect orbital changes cannot happen from any earthbound event.

Earth's center of gravity is what orbits the sun. Moving a thin film of mass about the surface does nothing to change that orbit. Even a very large-scale movement would not change the path of earth's center of gravity.

[Dead_Parrot]

10. Not really

Ice makes up 0.0005% of the mass of the Earth - and is is the same orbit as the rest of it, of course. So the orbit would not be affected even if it totally evaporated.

The rate of spin would be affected, and a quick back-of-envelope says it would stretch the length of the year by about about a second - but we typically adjust years by this much anyway, it's in the the same category as other rotational & orbital variations.

It wouldn't affect tilt directly, but it would affect precession, I think: I don't see 7 hours in every 25,000 years as a biggie, though. :)

[Boomer]

12. Either way that's one miserable chicken

[Dead_Parrot]

13. not to mention a poached egg. nt

[Celtic warrior]

15. Arctic pollution

Even more concern that global warming is the high levels of Mercury and heavy metals in Beluga whales and polar bear, animals that do not leave the Arctic!