Feel free to add your questions. Let’s get this problem solved! 
Related: I belive – and please correct me if I am wrong – that current sea level rises are mostly related to temperature, and not directly related to a bunch of ice falling into the sea, thus rasing sea levels.
From the USGS
If all the ice caps melted, including all of Antarctica and Greenland, the total sea level rise would be about 80 meters, or 264 feet. However, even the most extreme projections due to current global warming don’t anticipate the entire melting of the ice caps or anywhere close to it.
Note that the above figures do not include rise due to thermal expansion of the oceans, but that figure would be small in comparison.
No. There have been earlier periods with ice at the poles before the current one, such as one in the Late Paleozoic. During the current period, there seems to be a consensus that a semi-permanent ice cap first developed in Antarctica about the beginning of the Oligocene, or around 35 million years ago.
Thermal expansion: Warmer water takes up more space?? I thought water expands as it cools?
Water behaves like most substances and expands as it warms above 4 C (39 F). It only has the anomalous behavior of expanding when it cools below that temperature (which is why ice floats).
I recall reading that the remains of coniferous forests have been found, beneath the ice cap on Ellesmere Island (in the Canadian arctic). Does anyone know how these trees survived during the dark polar winter? Even though it was a subtropical climate, it is very dark at that latitude, from Novemner to february.
That article’s from 1999, though, so maybe they’ve figured out more about ancient Arctic boreal ecosystems since then.
Just thought I’d add that we had a discussion of sea level rise in this thread recently:
Re the Ellesmere Palms: North America has been rotating and drifting north-northwest for quite some time. I don’t have the link to the regression maps any more, but I suspect that 45 million years ago, Ellesmere Island would be just about at, or a bit south of, the Arctic Circle, not way north of it as at present. Hence while the plants would have to “make hay while the sun shines” nearly 24/7 in the summer, they would get at least a couple hours light most of the time in the winter.
It’s debatable.
One of the more recent (ie last 15 years) discoveries has been the presence of warm-temperrate, broadleafed beech forests in Antarcatica dating from as little as 2 million yeras ago.
This is far more intriguing than the coniferous forests of the Arctic because they are characterised by species that survive in warm temperate climates in South America, Australia and New Zealand. It is also intriguing because Antarctica has been well inside the Antarctic circle for over 100 million years. This removes the probelm that Polycarp raises with interpreting the apparently recent Arctic forests.
There still isn’t any satisfcatory explanation for these. finds. All the usual suspects have been invoked including errors in calculating continental drift, localised tectonic warming, unusual ocean circulation and misdating of the fossils, but at this stage it remains a mystery.
Assuming the fossils really were formed in Antaractica within the last 50 million years then it seems as though the climate has been warm enough in the past to support warm temperate vegetation well wihtin the polars regions, indicating localised temeprature at least 50oC warmer than today.
I…don’t understand. Can someone explain how the temperature could have been high enough that there was little or no ice at the poles? This seems impossible to me. If I’m understanding what Blake is saying, the temperature was 50 degrees C. HIGHER than today??? How could life exist at all in with that much heat? Especially at the equator? They are saying with GW that we are in for a lot more vicious storms, drought and all manner of other disasters…and thats only a few degree’s higher than today in the next century or so.
Unless I’m missing something here.
-XT
50 degrees higher at the poles. Remember the poles are taking the brunt of GW.
How could it be 50 degrees (centigrade!) at the poles without it being higher everywhere else as well??
-XT
You have to remember that the average annual temperature in parts of Antarctica is below -50 C, so that a temperature rise of 50 C doesn’t make things all that warm. Also, I don’t think that it means that Antarctica was entirely ice free, but that localized areas may have been warm enough to permit woody plants to grow.
From here
Average annual temperatures (C):
McMurdo (coastal) = -16.9
South Pole = - 49.4
Vostok = -55.1
The beech tree fossils are from the Transantarctic Mountains, so I assume present conditions are similar to the South Pole station, perhaps a bit warmer.
How warm it would have had to be to allow beech forests to grow is a matter of debate. Some researchers have suggested an average annual temperture of 5 C, which would be a 50 C difference. However, this article suggests an average annual temperature of about -12 C, or similar to conditions in the high Arctic today, or maybe a 30 C difference.
Average annual temperatures are influenced by local conditions. They don’t need to rise to a similar extent around the Earth. There could have been a much lower temperature gradient between the poles and the tropics at the time, as there has been at other times in Earth history.
So…though it was warmer at the poles then (30-50 degrees C), it wasn’t warmer at the equator? Do I have that right? Is there a model to describe this…it seems strange to me. I admit my ignorance on this subject…I thought if it was warmer at the poles it would have to be warmer at the equator too…
-XT
Or, it was a lot warmer at the poles, but only a little warmer at the equator. It’s not as simple as a binary “hot” or “cold”.
As **Chronos ** says, it was probably somewhat warmer in the tropics, but not drastically so. During the Ice Ages, when the north polar regions in particular were substantially colder, the tropics might have dropped by around 5 C. Tropical plants and animals were able to survive even though the Ice Cap extended as far south as New York. There was a much steeper temperature gradient between the poles and the equator than there is today.
Likewise, during extreme greenhouse conditions in the Eocene and Cretaceous, tropical or near tropical conditions prevailed at very high latitudes, but the tropics, while hotter than they are today, were not uninhabitable. The gradient then was much less.
Ok…I think I understand that, though to be honest it doesn’t seem very intuituve to me that its not simply binary. Leaving that aside though, let me see if this part is right. The threat of Global Warming, as opposed to this period when the poles were not covered in (as much) ice, is that the whole planet is warming? And so, even though the poles were warmer, the equator wasn’t a lot warmer than today…so there was less energy in the system? Is that right?
Sorry if this is a hijack btw…I’m trying to wrap my head around this stuff for future considerations of this whole GW issue.
-XT