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U.S. East Coast a Hotspot of Sea-Level Rise
Harperdog writes "Nature just published this study of sea-level rise and how global warming does not force the it to happen everywhere at the same rate. Interesting stuff about what, exactly, contributes to this uneven rise, and how the East Coast of the U.S., which used to have a relatively low sea level, is now a hotspot in that the sea level there is rising faster than elsewhere."
The TOPEX satellite has been measuring the whole ocean surface for 18 years and found it has risen about two inches at a very even rate of increase. Various scientists attribute about 80% of this to thermal expansion of warmer oceans and the rest to melting ice. Although the ocean surface temperature appears to to have gone up a bit, that may bot be indicative of the total thickness of the ocean. The best proposed temperature experiment- measuring the speed of sound half around the world- has been tied in environmental litigation. The sound source might hurt marine animals hearing is the claim. The sound source is not an explosion, but a distinctive wide-frequency chirp that can be integrated at the receivers over a period of hours. This experiment would be repeated every few years to look for changes in sound travel time, which would show temperature changes of water velocity.
Local tidal guides or GPS would be affected by vagrancies of local land level changes, which are rather common. This ranges from ice age rebound, sediment deposition loading, sediment erosion unloading, and even a bit of tectonic rise in the Appalachians. And this Nature article says the pattern of water circulation in a region can change locally too, contribution to an apparent LOCAL sea level change.
The concept you're having trouble with is known as hysteresis - that is, to oversimplify, a delay between a cause and its effect. In this case, "cause" can be something like "add water to ocean" and effect can be something like "water gets evenly distributed around the globe". Yes, of course gravity wants to equalize out the heights of all of the Earth's oceans (although it hates it when I anthropomorphize it ;) ). But that takes time; it's not instant, no more than is it instant that the water in a mountain river after a rain ends up in the ocean, even though that's where gravity is going to take it eventually. Meanwhile, a localized region can have all kinds of various inputs (such as rivers) and outputs (such as evaporation) which act on it fast enough to be more than noise against the rate at which gravity moves things toward equalization.
Rhetorical questions suck. Why ask a question if you don't want an answer?
The other things that people don't understand is that the original 'New Orleans' city was build ABOVE sea level. The French Quarter is almost 20ft above sea level. It just all the newer development from the last century is in a shitty location. Below sea level shouldn't be rebuilt and the stuff above sea level wasn't flooded much.