Melting Greenland ice sheets may threaten Northeast United States, Canada

May 27, 2009
This visualization, based on new computer modeling, shows that sea level rise may be an additional 10 centimeters (4 inches) higher by populated areas in northeastern North America than previously thought. Extreme northeastern North America and Greenland may experience even higher sea level rise. (Graphic courtesy Geophysical Research Letters, modified by UCAR.)

Melting of the Greenland ice sheet this century may drive more water than previously thought toward the already threatened coastlines of New York, Boston, Halifax, and other cities in the northeastern United States and in Canada, according to new research led by the National Center for Atmospheric Research (NCAR).

The study, which will be published Friday in , finds that if Greenland's ice melts at moderate to high rates, by 2100 may shift and cause sea levels off the northeast coast of North America to rise by about 12 to 20 inches (about 30 to 50 centimeters) more than in other coastal areas. The research builds on recent reports that have found that rise associated with could adversely affect North America, and its findings suggest that the situation is more threatening than previously believed.

"If the Greenland melt continues to accelerate, we could see significant impacts this century on the northeast U.S. coast from the resulting ," says NCAR scientist Aixue Hu, the lead author. "Major northeastern cities are directly in the path of the greatest rise."

A study in Nature Geoscience in March warned that warmer water temperatures could shift ocean currents in a way that would raise sea levels off the Northeast by about 8 inches (20 cm) more than the average global sea level rise. But it did not include the additional impact of Greenland's ice, which at moderate to high melt rates would further accelerate changes in ocean circulation and drive an additional 4 to 12 inches (about 10 to 30 cm) of water toward heavily populated areas in northeastern North America on top of average global sea level rise. More remote areas in extreme northeastern Canada and Greenland could see even higher sea level rise.

Scientists have been cautious about estimating average sea level rise this century in part because of complex processes within ice sheets. The 2007 assessment of the Intergovernmental Panel on Climate Change projected that sea levels worldwide could rise by an average of 7 to 23 inches (18 to 59 cm) this century, but many researchers believe the rise will be greater because of dynamic factors in ice sheets that appear to have accelerated the melting rate in recent years.

The new research was funded by the U.S. Department of Energy and by NCAR's sponsor, the National Science Foundation. It was conducted by scientists at NCAR, the University of Colorado at Boulder, and Florida State University.

How much meltwater?

To assess the impact of Greenland ice melt on ocean circulation, Hu and his coauthors used the Community Climate System Model, an NCAR-based computer model that simulates global climate. They considered three scenarios: the melt rate continuing to increase by 7 percent per year, as has been the case in recent years, or the melt rate slowing down to an increase of either 1 or 3 percent per year.

If Greenland's melt rate slows down to a 3 percent annual increase, the study team's computer simulations indicate that the runoff from its ice sheet could alter ocean circulation in a way that would direct about a foot of water toward the northeast coast of North America by 2100. This would be on top of the average global sea level rise expected as a result of global warming. Although the study team did not try to estimate that mean global sea level rise, their simulations indicated that melt from Greenland alone under the 3 percent scenario could raise worldwide sea levels by an average of 21 inches (54 cm).

If the annual increase in the melt rate dropped to 1 percent, the runoff would not raise northeastern sea levels by more than the 8 inches (20 cm) found in the earlier study in Nature Geoscience. But if the melt rate continued at its present 7 percent increase per year through 2050 and then leveled off, the study suggests that the northeast coast could see as much as 20 inches (50 cm) of sea level rise above a global average that could be several feet. However, Hu cautioned that other modeling studies have indicated that the 7 percent scenario is unlikely.

In addition to sea level rise, Hu and his co-authors found that if the Greenland melt rate were to defy expectations and continue its 7 percent increase, this would drain enough fresh water into the North Atlantic to weaken the oceanic circulation that pumps warm water to the Arctic. Ironically, this weakening of the meridional overturning circulation would help the Arctic avoid some of the impacts of global warming and lead to at least the temporary recovery of Arctic sea ice by the end of the century.

Why the Northeast?

The northeast coast of North America is especially vulnerable to the effects of Greenland ice melt because of the way the meridional overturning circulation acts like a conveyer belt transporting water through the Atlantic Ocean. The circulation carries warm Atlantic water from the tropics to the north, where it cools and descends to create a dense layer of cold water. As a result, sea level is currently about 28 inches (71 cm) lower in the North Atlantic than the North Pacific, which lacks such a dense layer.

If the melting of the Greenland Ice Sheet were to increase by 3 percent or 7 percent yearly, the additional fresh water could partially disrupt the northward conveyor belt. This would reduce the accumulation of deep, dense water. Instead, the deep water would be slightly warmer, expanding and elevating the surface across portions of the North Atlantic.

Unlike water in a bathtub, water in the oceans does not spread out evenly. Sea level can vary by several feet from one region to another, depending on such factors as ocean circulation and the extent to which water at lower depths is compressed.

"The oceans will not rise uniformly as the world warms," says NCAR scientist Gerald Meehl, a co-author of the paper. "Ocean dynamics will push in certain directions, so some locations will experience sea level rise that is larger than the global average."

Source: National Center for Atmospheric Research

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Shootist
3.3 / 5 (12) May 27, 2009
Gotta wonder . . . what was the sealevel in Newfoundland or Nova Scotia 1000 years ago? After all there were thriving Dairy farms in Greenland in 1000AD, which suggests there was less ice then than now. Hmmm? Bueller, anyone, anyone?
vanderMerwe
2.7 / 5 (12) May 27, 2009
It's embarrassing seeing this kind of crap on a "scientific" website. Who did these idiots learn their science from, Trofim Lysenko?
PPihkala
2.7 / 5 (10) May 27, 2009
Not many deny the fact that Arctic ice cover has been melting more that it's accumulated in last decades. And it will continue to do so, because of rising CO2 levels in air. Thus created melt water has to go somewhere and that somewhere is sea. This means rising sea levels, when the melting ice has been on land. Now the only question left is how much melt water there will be in given time, which determines how much the level of sea will rise. And if that extra water also is distributed non-uniformly, that means more trouble for the coastal regions with most rising levels.
RAL
3.2 / 5 (11) May 27, 2009
ooops. The whole "conveyor belt" model is now being questioned.

http://deepseanew...sidered/

Could this impact the "consensus" (stifle laugh here) on which the Even More Dire predictions in this paper is modeled?

The AGW Loop

IF empirical_data contradicts model
AND fewer_people believe Dire_Predictions
THEN
Increment Dire_Predictions
Increment Hysterical_Tone
Loop
Flakk
3 / 5 (8) May 27, 2009


The AGW Loop

IF empirical_data contradicts model

AND fewer_people believe Dire_Predictions

THEN

Increment Dire_Predictions

Increment Hysterical_Tone

Loop



LOL!
dachpyarvile
3.2 / 5 (11) May 27, 2009
Good! Those places need a little population control, anyway. Those places are where most of the enviro-nuts are coming out of the woodwork in this country. :)
dachpyarvile
3.3 / 5 (12) May 27, 2009
Not many deny the fact that Arctic ice cover has been melting more that it's accumulated in last decades. And it will continue to do so, because of rising CO2 levels in air. Thus created melt water has to go somewhere and that somewhere is sea. This means rising sea levels, when the melting ice has been on land. Now the only question left is how much melt water there will be in given time, which determines how much the level of sea will rise. And if that extra water also is distributed non-uniformly, that means more trouble for the coastal regions with most rising levels.



For the umpteenth time, it is not the CO2 that is causing the melt. CO2 levels were much lower 1,000 years ago but the shores and coastlands of Greenland really were green during those times and the global weather was hotter by about 5°C.
Shootist
3 / 5 (12) May 27, 2009
Not many deny the fact that Arctic ice cover has been melting more that it's accumulated in last decades. And it will continue to do so, because of rising CO2 levels in air. Thus created melt water has to go somewhere and that somewhere is sea. This means rising sea levels, when the melting ice has been on land. Now the only question left is how much melt water there will be in given time, which determines how much the level of sea will rise. And if that extra water also is distributed non-uniformly, that means more trouble for the coastal regions with most rising levels.


For the umpteenth time, it is not the CO2 that is causing the melt. CO2 levels were much lower 1,000 years ago but the shores and coastlands of Greenland really were green during those times and the global weather was hotter by about 5C.


As I said above. Dairy farms in Greenland in 1000AD. Yet 200 years later Iceland was surrounded by ice all year long.

Global warming? Global horsesh!t is more likely.

Freeman Dyson. Anyone here at all familiar with Freeman Dyson? Now that Feynman is dead, Dyson may well be the smartest man in the world. Dyson opines that water vapor is several orders of magnitude greater in its greenhouse effect . . . so much stronger than CO2 as to reduce CO2's impact into background noise, so far as the global climate is concerned.

Case closed.
GrayMouser
2.8 / 5 (9) May 28, 2009
Not many deny the fact that Arctic ice cover has been melting more that it's accumulated in last decades.

And this has happened before when the Northwest passage opened up in the 1930s.
The interesting thing is that the last 2 winters have seen more ice accumulate than predicted. It threw the Germans for a loop when they flew over the arctic with their electromagnetic induction probe:
http://wattsupwit...sdicken/
thermodynamics
3.2 / 5 (5) May 28, 2009
Shootist:



You are right about water vapor being a more potent green house gas than carbon dioxide. However, that completely misses the point. What follows is a technical description of heat transfer, not agreement with or argument against AGW.



To better understand why carbon dioxide is important, you have to look at the absorption lines for each of the molecules (water vapor and CO2). There are about a hundred of thousand cataloged lines for each asymmetric molecule that is sensitive to bending or rotation. Water vapor has a broad strong absorption spectra (made up of thousands of lines) in the infrared (which is what keeps the earth habitable). These lines come about by the quantum mechanical absorption of a photon of a specific wavelength causing bending and/or rotation in the molecule. However, there are holes in the water vapor absorption spectra (as there are in all gas spectra). If there were not, then the trace gases would not make a difference. Since there are holes in the spectra it becomes important to understand which molecules have absorption lines in those holes. The most important molecules that do are CO2 and CH4.



The bottom line is that CO2 absorption is relatively independent of H2O because the lines do not overlap in some important areas (or are much stronger for CO2 at a specific line than for H2O). Don't misunderstand, there are overlaps in many areas and there are complicating issues like line broadening that enhance overlap. However, water vapor is not 100% effective in absorbing infrared in the range the earth radiates at. CO2, CH4, and other gases are also not 100% effective. Instead, the trace gases pick up a bit of the energy that H2O misses. Those lines that are picking up missed energy are what makes CO2 and CH4 important even though H2O is the clearly stronger absorber. If you do not understand this very important issue then you need to get a good book on radiative heat transfer. I recommend "Thermal Radiation Heat Transfer" by Siegel and Howell.

Nartoon
3 / 5 (7) May 28, 2009
The really important thing to remember is not CO2, but H2O (as in water vapor). NOT as a GHG, but as a source of clouds, which reflect sunlight and cool the earth. Water vapor has been increasing with the earth warming, then more H2O is evaporated and the clouds reduce heating by reflecting sunlight away from the earth thereby causing global cooling and keeping the earths temperature within a relatively narrow band. This pattern repeats itself about every 30 years -- 30 years of warming followed by 30 years of cooling. Of course there are other factors involved, but CO2 is an infinitesimal part of GW.
mikiwud
2.5 / 5 (11) May 28, 2009
They put their Guestimations and assumtions biased to the result they want into their favourite computer game and come out with the usual answers of "if", "could", "may" etc. Not once did the say WILL HAPPEN. This is not science!
How about factoring in the elevation of most of the ice in Greenland. Most is so high that no matter how hot the lowlands get the temperature drop through altitude would stop the ice melting and considerably slow it down at moderate elevations. Same for Antarctica.
mikiwud
1.5 / 5 (8) May 28, 2009
vos
3 / 5 (5) May 28, 2009
still ... aint no global warming
Velanarris
3.5 / 5 (8) May 28, 2009
Since there are holes in the spectra it becomes important to understand which molecules have absorption lines in those holes. The most important molecules that do are CO2 and CH4.
I truncated a lot of your post but it's quite accurate. Here's the one problem though:

Let's talk satellite images:

If the atmosphere was capturing more heat due to increased CO2 there would be a visible hot spot at the tropopause, most notably where the Ozone is thinnest. This is one of the predictive aspects of the AGW hypothesis. Problem is, there's no hot spot. There isn't even really a deviation outside of instrumental variation.
fhtmguy
3.5 / 5 (6) May 31, 2009
This issue here is man's arrogance to think that we can effect the planets climate, which has been effected by natural causes for millenia. The earth has gone through multiple cycles of warming and cooling. I believe there is evidence for the complete globe covered in ice??? Our contribution to this current cylce is at best minimal considering the percentages of our CO2 output falls withing the propability of error of the tests. Maybe the new plan of the Obama administration to make roofs white to reflect the Sun's energy back into space should be 2 warnings in itself. 1) scientists have their own agenda when it comes to funding for their salaries. and 2) The majority of Americans are unable to understand the science behind the research anyway and thus believe whatever these liberal scientist spew. Is the Earth warming? Yes. Can we as humans effect the outcome? Most likely not, unless we can stop all the volcanoes from erupting, the methane in the ocean from realeasing, and all the other natural processes. The Earth will adapt and control it's own temperature just as is has for billions of years. Remember the other mass extinctions or are we again to arrogant. We may not be around to see the results.
daqman
2.6 / 5 (5) May 31, 2009
It's embarrassing seeing this kind of crap on a "scientific" website. Who did these idiots learn their science from, Trofim Lysenko?
I agree, your comment is crap and embarrassing to see on a scientific web site. On what do you justify your false opinion? This is VERY good science. A theoretical prediction based on current conditions and assumptions about future trends. Now the experimentalists step in and see if it is correct. Nothing crap there.
jonnyboy
2.1 / 5 (7) May 31, 2009
It's embarrassing seeing this kind of crap on a "scientific" website. Who did these idiots learn their science from, Trofim Lysenko?
I agree, your comment is crap and embarrassing to see on a scientific web site. On what do you justify your false opinion? This is VERY good science. A theoretical prediction based on current conditions and assumptions about future trends. Now the experimentalists step in and see if it is correct. Nothing crap there.


Dagman,
You have almost made it to the real world, finish the process and join us my friend!!

The problem, you see, is that the speculators (theorists, if you prefer) continue to deny all the real world evidence that falsifies their man-made GW theories.

That's why it's all crap!!!!!!!!!!

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