I read all of these posts about rising water levels, etc.. The water levels in the Great Lakes has been at its lowest level in recent history for years now.. Why are their levels decreasing, while water elsewhere is rising? I think the largest deposit of fresh water in the world decreasing is just as much of a concern as rising seawater.
Simply put: The ocean sea levels are rising because of the melting of the polar ice caps. Regional river systems and other bodies of water are rising becasue of the same thing though it's more because in certain regions ... there's been a substantial increase in precipitation whereas the additional water cannot be drained fast enough into their repective recevoirs. As for the Great lakes, their water levels are decreasing because: 1) The local annual precipitation hasn't been normal for the last few of years 2) Consumption of fresh water has been higher then usual 3) The Great Lakes primarily drains into the Atlantic Ocean through the St - Lawrence seaway since the lakes are at a higher altitude then the ocean. The lakes only source of new water is from local precipitation and local river systems.
Beware of making this statement. It's true that the Antarctic ice cap contributes to rising sea levels, but the north does not, except for Greenland that is. The ice has to be on land. See the Crushing ants thread in general science for an explanation why. In fact, Saphz here made the definitive explanation in the thread.
Tnx for reminding me, nexus. Ya ... that's what I meant by stating that fact. Maybe I should have been a little more explicit when writing it. Simply put, sea ice only displaces the same amount of water as its weight so it's melting won't contribute in the ovreall rise in sea level ... if it's even noticable. Only ice caps on land will contribute to rising sea level.
Well, talking about Antarctica, the ice is not melting at all: http://www.cnn.com/TECH/science/9812/01/icesheet.yoto/ http://www.greencity.com/globalwarm.htm because Antarctica is cooling http://www.frontpagemag.com/Articles/ReadArticle.asp?ID=4033 however this is a bit course. http://www.secretsoftheice.org/icecore/sealevel.html http://www.secretsoftheice.org/icecore/sealevel.answers.html As Antarctica carries 29 million km3 of ice on a surface of 14 million km2 ( http://www.saburchill.com/facts/facts0001.html ) the average ice height is two kilometres. If it was to melt hypothetically it would raise sea levels with 249 feet (80 meters) when ignoring isostatic effects that would tend to half that figure. So the ratio of sea level rise (80m) to ice height (2000m) is 4% or 1 centimeter ice melting gives 0,4 mm sea level rise, or about 0,2 mm when taking isostatic effects into account. But don't count on it, the coming ten thousends of years. It's not going to happen in that time frame.
Another possible reason is that, if the climate in North America is getting slightly warmer, there will be more evaporation from the Great Lakes. This is not matched by any extra snowfall each winter to replenish the lakes with meltwater. During the last ice age, although the oceans were lower, many inland seas and lakes were larger than they are today, owing to less evaporation: the Caspian and Aral seas, for instance. The Great Salt Lake was about 8 times its current size.
