Global Warming?

[xoxoxoBruce]

The ESA, European Space Agency, just released theresults of an 11 year study on the thickness of the ice sheets in Greenland.

While the edges of the sheets have been thinning was well known, the great interior was a mystery until now.

The result is a mixed picture, with a net increase of 6.4 centimetres per year in the interior area above 1500 metres elevation. Below that altitude, the elevation-change rate is minus 2.0 cm per year, broadly matching reported thinning in the ice-sheet margins. The trend below 1500 metres however does not include the steeply-sloping marginal areas where current altimeter data are unusable.

I'm surprised.

[Undertoad]

I should save it for an IotD, but no.

[Kitsune]

with a net increase of 6.4 centimetres per year

Oh, good, we have nothing to worry about, then. I'm going to burn some coal to celebrate.

Try reading the entire article, people:

The team, led by Professor Ola M. Johannessen of NERSC, ascribe this interior growth of the Greenland Ice Sheet to increased snowfall linked to variability in regional atmospheric circulation known as the North Atlantic Oscillation (NAO). First discovered in the 1920s, the NAO acts in a similar way to the El Niño phenomenon in the Pacific, contributing to climate fluctuations across the North Atlantic and Europe...

Professor Johannessen commented: "This strong negative correlation between winter elevation changes and the NAO index, suggests an underappreciated role of the winter season and the NAO for elevation changes – a wildcard in Greenland Ice Sheet mass balance scenarios under global warming."

He cautioned that the recent growth found by the radar altimetry survey does not necessarily reflect a long-term or future trend. With natural variability in the high-latitude climate cycle that includes the NAO being very large, even an 11-year long dataset remains short.

Modelling studies of the Greenland Ice Sheet mass balance under greenhouse global warming have shown that temperature increases up to about 3ºC lead to positive mass balance changes at high elevations – due to snow accumulation – and negative at low elevations – due to snow melt exceeding accumulation.

Such models agree with the new observational results. However after that threshold is reached, potentially within the next hundred years, losses from melting would exceed accumulation from increases in snowfall – then the meltdown of the Greenland Ice Sheet would be on

[Troubleshooter]

And we still don't have enough accumulated data to build a good long term trend model.

[Cyclefrance]

So, presumably, as more peripheral ice melts, then the ocean waters rise which means that the highest parts of the cap are lower, so there is more land below 1500 feet above sea level, which in turn then means that the ice build up is less and possibly even negative (i.e the build-up becomes a draw-down...) - is that right?

[barefoot serpent]

Originally Posted by Cyclefrance

So, presumably, as more peripheral ice melts, then the ocean waters rise which means that the highest parts of the cap are lower, so there is more land below 1500 feet above sea level, which in turn then means that the ice build up is less and possibly even negative (i.e the build-up becomes a draw-down...) - is that right?

ummm... maybe, yes... as long as you factor in
eustatic sea-level changes

The deal with global warming is that precipitation patterns can change -- some areas will get more, some less. Some of that will be snow.

One thing that happens is that the melting of ice in the areas below 1500 feet makes more free water vapor available in the atmosphere. This has the paradoxical effect of causing snowfall amounts to be greater. However, the warmer temperatures also mean that the snow is more likely to melt off the next spring. If this pattern continues long enough the glacial ice caps will begin a permanent retreat.

[Griff]

Originally Posted by marichiko

If this pattern continues long enough the glacial ice caps will begin a permanent retreat.

As long as by permanent you mean temporary.

Temporary for the next 10,000 years give or take. When I used the word "permanent" that's what I meant - a few thousand years. I figured I'd get called on it, and, sure enough. Sharp crowd around here. First place honors to Griff!

The earth's climate has always undergone natural oscillations. Man's contribution to these oscillations have made the study of chaos theory a fine art.

[xoxoxoBruce]

From barefoot serpent's link

If the Antarctic and Greenland ice sheets were to disappear, cities as far inland as St. Louis (80 m above present sea level) would be inundated, and even decay of the Greenland Ice Sheet alone would drown most coastal cities up to 7 m above modern sea level.

But not to worry, FEMA's on it.