[ProudFossil]

I just watched a program on the International History Channel describing a Saxon sea port of around 1000 AD. The archeologists are now able to examine this area because the sea level, at least at this part of England, is about 6 - 10 feet lower than it was in the days when the Saxons were able to sail into the port. I wonder where the water went. There is no river at this place to have silted up the harbor. Could it be we are still locked in the final stages of an ice age and the Earth is just returning to normal conditions?

[Gunslingr3]

It is suggested that this sheet (about 10% of Antarctic ice) could melt in the "near term" (a usefully vague phrase) and raise sea level 5 to 6 meters.

In case you wondered what that looks like to Florida:

Time to move back to New York, Yankees...

[Gondring]

It's nice to see something that discusses the lag time for ice sheet response, but there are a lot of missing points in this article, too. One very important point, for example, is whether we have a shift from a dry-bed to a wet-bed sheet...the rate of advance of a wet-bed sheet is higher, which leads to ice thinning and more rapid collapse (greatly oversimplifed).

[magellan]

"It is suggested that this sheet (about 10% of Antarctic ice) could melt in the "near term" (a usefully vague phrase) and raise sea level 5 to 6 meters."

This does not quite seem believable.

Using data mostly from Wikipedia:

Water covered area of planet Earth = 361,126,400 km²

Ice covered area of Antarctica = 13,720,000 km²

Therefore 10% of Ice covered area of Antarctica = 1,372,000 km²

Ratio = 263.2 to 1.0

Density of glacier ice compared to sea water = 0.867

Therefore, to raise the sea 6 meters, means the 10% of the ice shelf effectively has to have ice 300 meters thick, almost 1,000 feet thick.

Perhaps 300 meters is the right thickness. But if all of a sudden an ice sheet weighing ALMOST FIVE TRILLION POUNDS slid into the ocean, I think a tsunami would be the bigger immediate threat.

Feel free to check my math.

[ancient_geezer]

"Thresholds for disintegration of the East Antarctic ice sheet by surface melting involve warmings above 20° C (20 C = 68 F)... In that case, the ice sheet would decay over a period of at least 10,000 years." The average temperature in Antarctica is a crisp, or rather, biting -49 C.[31]

Ran into an interesting little study concerning the termination of ice ages that falls right into line with this. Seems the thresholds to terminate the deep glacial ice ages can not be triggered by CO2 concentrations found for those conditions in ice core studies, it take more than 500 times the CO2 present in today's atmosphere to terminate deep ice ages and cause melting of glacial ice.

 

High levels of atmospheric carbon dioxide necessary for the
termination of global glaciation
Raymond T. Pierrehumbert
Department of the Geophysical Sciences, The University of Chicago,
Nature Vol 429 10 June 2004
http://geosci.uchicago.edu/~rtp1/papers/NatureSnowballMelt.pdf

The possibility that the Earth suffered episodes of global glaciation as recently as the Neoproterozoic period, between about 900 and 543 million years ago, has been widely discussed^1–3. Termination of such ‘hard snowball Earth’ climate states has been proposed to proceed from accumulation of carbon dioxide in the atmosphere⁴. Many salient aspects of the snowball scenario depend critically on the threshold of atmospheric carbon dioxide concentrations needed to trigger deglaciation^2,5. Here I present simulations with a general circulation model, using elevated carbon dioxide levels to estimate this deglaciation threshold. The model simulates several phenomena that are expected to be significant in a ‘snowball Earth’ scenario, but which have not been considered in previous studies with less sophisticated models, such as a reduction of vertical temperature gradients in winter, a reduction in summer tropopause height, the effect of snow cover and a reduction in cloud greenhouse effects. In my simulations, the system remains far short of deglaciation even at atmospheric carbon dioxide concentrations of 550 times the present levels (0.2 bar of CO2). I find that at much higher carbon dioxide levels, deglaciation is unlikely unless unknown feedback cycles that are not captured in the model come into effect.

 

Just to get an idea of what 550 times current CO2 is in comparison to levels found in geological history:

 

 

 

Global Surface Temperature and Atmospheric CO2 over Geologic Time 

Late Carboniferous to Early Permian time (315 mya -- 270 mya) is the only time period in the last 600 million years when both atmospheric CO2 and temperatures were as low as they are today (Quaternary Period ).

Temperature after C.R. Scotese
CO2 after R.A. Berner, 1994

•     There has historically been much more CO2 in our atmosphere than exists today. For example, during the Jurassic Period (200 mya), average CO2 concentrations were about 900 ppm or about 2.5 times higher than today. The highest concentrations of CO2 during all of the Paleozoic Era occurred during the Ordovician Period, exceeding 6000 ppm -- more than 16 times higher than today.

•     The Carboniferous Period and the Ordovician Period were the only geological periods during the Paleozoic Era when global temperatures were as low as they are today.
  
  To the consternation of global warming proponents, the Late Ordovician Period was also an Ice Age, with CO2 concentrations nearly 15 times higher than today-- 5500 ppm. According to greenhouse theory, Earth should have been exceedingly hot. Instead, global temperatures were no warmer than today. Clearly, other factors besides atmospheric carbon influence earth temperatures and global warming.