Pbartender
First Post
Hypersmurf said:As I understand it, it's not the melting of floating ice that's supposed to increase sea levels; it's a/ the melting of ice that's on land, meaning that water that wasn't in the ocean in any form ends up in the ocean, and b/ the heating of water that's already in liquid form. Water is densest at about 4 degrees C, right? So if something causes a whole lot of 4 degree water to become 5 degree water, it will take up more space.
If someone says "If the Arctic pack ice melts, seas will rise and we'll all drown!", their physics is out.
But if they say "If the Arctic pack ice melts, it won't be long before the Antarctic and Greenland ice sheets melt too, and then seas will rise and we'll all drown!", they're at least basing their fears on something that makes some sense.
-Hyp.
Even that aside, there isn't nearly as much water froaen into the polar ice caps and glaciers as most people think. From How Stuff Works:
The main ice covered landmass is Antarctica at the South Pole, with about 90 percent of the world's ice (and 70 percent of its fresh water). Antarctica is covered with ice an average of 2,133 meters (7,000 feet) thick. If all of the Antarctic ice melted, sea levels around the world would rise about 61 meters (200 feet). But the average temperature in Antarctica is -37°C, so the ice there is in no danger of melting. In fact in most parts of the continent it never gets above freezing.
At the other end of the world, the North Pole, the ice is not nearly as thick as at the South Pole. The ice floats on the Arctic Ocean. If it melted sea levels would not be affected.
There is a significant amount of ice covering Greenland, which would add another 7 meters (20 feet) to the oceans if it melted. Because Greenland is closer to the equator than Antarctica, the temperatures there are higher, so the ice is more likely to melt.
In other words... Anybody living in coastal cities will have to relocate, but anyone in a town above 200 ft. of elevation would be "safe".
Sorry, the whole scenario in the movie "Waterworld" is a load of








As for thermal exansion of water:
But there might be a less dramatic reason than polar ice melting for the higher ocean level -- the higher temperature of the water. Water is most dense at 4 degrees Celsius. Above and below this temperature, the density of water decreases (the same weight of water occupies a bigger space). So as the overall temperature of the water increases it naturally expands a little bit making the oceans rise.
In 1995 the International Panel on Climate Change issued a report which contained various projections of the sea level change by the year 2100. They estimate that the sea will rise 50 centimeters (20 inches) with the lowest estimates at 15 centimeters (6 inches) and the highest at 95 centimeters (37 inches). The rise will come from thermal expansion of the ocean and from melting glaciers and ice sheets. Twenty inches is no small amount -- it could have a big effect on coastal cities, especially during storms.
It'd make a difference, but not a very big one, geologically speaking.