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Earth United States Science

U.S. East Coast a Hotspot of Sea-Level Rise 266

Posted by timothy
from the because-of-all-the-sand-pumping-projects dept.
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."
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U.S. East Coast a Hotspot of Sea-Level Rise

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  • Re:Question (Score:4, Informative)

    by Baloroth (2370816) on Tuesday June 26, 2012 @12:46PM (#40453957)
    GPS is nowhere near accurate enough. You are talking about yearly see-level variations of a handful of millimeters a year. GPS is only accurate to a few centimeters, at best, with maximum augmentation (practically the error is in the range of 10 cm or more). Nowhere near good enough.
  • Re:Question (Score:4, Informative)

    by ackthpt (218170) on Tuesday June 26, 2012 @01:01PM (#40454201) Homepage Journal

    GPS is nowhere near accurate enough. You are talking about yearly see-level variations of a handful of millimeters a year. GPS is only accurate to a few centimeters, at best, with maximum augmentation (practically the error is in the range of 10 cm or more). Nowhere near good enough.

    One of the fun things about chasing around with a GPSr, looking for Geodetic Survey markers is you learn a bit about them and the equipment used to place them. How did they get these elevations so darn exact? Well, pull your heads out of your digital-electronic-technology-saviour-for-everything sand pile and realise a very good quality spring with a reference weight and scale can tell you far more accurately what your elevation is, based upon readings taken at nearby sea level. 100 years ago they could tell you within 1 inch the elevation of a marker and to the best of satellite measure, these are still very accurate (using the sort of equipment they have at their disposal.

    So not likely to be so much a case of local gravity fluctuation, try thinking what else could explain it? More fresh water introduced from Greenland Ice cap and Polar melting? Given time it will flow around the continents, but if the melt is happening fast enough that which has flowed to the Pacific and Southerly Atlantic is being replaced at a similar, if not accelating rate.

  • by cpu6502 (1960974) on Tuesday June 26, 2012 @01:05PM (#40454247)

    Wow way to twist a reasonable law into a MSNBC-style rant by Ed Schultz.

    All the law says is that homes will not be eligible for government-paid flood insurance if they are not in the zones that previously recorded flooding (since 1900). Why? Because North Carolina can't afford to provide free insurance to nearly the whole state. MOST people comprehend that the money supply has limits..... others like George "duh" Bush drive-up 10 trillion dollar debts.

  • by peter303 (12292) on Tuesday June 26, 2012 @01:06PM (#40454265)
    The TOPEX satellite has been measuring the whole ocean surface for 18 years and found it has risen about two inches [colorado.edu] 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.
  • by pixelpusher220 (529617) on Tuesday June 26, 2012 @01:19PM (#40454453)

    but in theory shouldn't the entire ocean level rise and fall together?

    "In theory there's no difference between theory and reality...in reality it's the other way around" ;-)

    One of the points made was that salinity levels, localized temperatures and other factors can play regional factors. If a current is flooding in warmer water to an ocean and it goes up by even a little bit there will be a coinciding increase in the volume of that ocean water. If salinity changes, I'm assuming (I don't know) there is likewise a change in volume.

    Now, sure normal temperature and saturation processes will return that to equilibrium eventually, but how long does it take to do that on a scale of an ocean? Could be decades assuming the ongoing current input continues (even without change).

    I also thought parts of the east coast, mid-atlantic I think, were sinking in response to the mid-west area rebounding back from ice age depression. Think about a table tilting with a pivot point somewhere in the middle, as one end goes up the other goes down.

    Also consider that gravity isn't uniform. It does fluxuate minutely from place to place. You obviously don't notice this day to day since it's so small, but again with the scale of an ocean it might be significant enough to cause a lower amount of compression of the water column. And factor in that maybe a gravitational difference is related to how the molten core of the earth is orientated and being molten might change from time to time.

    I don't know any of these things specifically but those are just off the cuff possible reasons that might explain why ocean levels would be different locally.

  • by Rei (128717) on Tuesday June 26, 2012 @01:32PM (#40454665) Homepage

    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.

  • by CaptainLugnuts (2594663) on Tuesday June 26, 2012 @02:31PM (#40455729)
    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.
  • Re:Question (Score:4, Informative)

    by Grishnakh (216268) on Tuesday June 26, 2012 @03:19PM (#40456513)

    You're right, it is wrong. Lots of animals will overfeed their habitat if their population grows too large; of course, then they have a famine, their population dwindles, and the problem is corrected. Humans, OTOH, invent new ways to grow crops to increase yields or find some other way of allowing an ever-increasing population.

    However, what is true is that humans are the only animal known to destroy their own habitat, while being intelligent enough to understand what they're doing. A herd of overpopulated wild deer eating all the available food probably don't actually understand the long-term effects of what they're doing.

  • by steelfood (895457) on Tuesday June 26, 2012 @07:07PM (#40459897)

    Believe it or not, NYC is on fairly high ground. Staten Island, in particular, has hills that are as high as several hundred feet above sea level. Central Park itself is something like forty feet above sea level, and most of Manhattan is fairly high. This is the same with most parts of Brooklyn, Queens, and The Bronx.

    Here's the thing about Manhattan and hurricanes. It's really, really well protected. Any storm surge would have to make its way past Staten Island and Brooklyn (through the Verizano Narrows) to get to Manhattan. New York Harbor is the only large body of water that's directly up against Manhattan, and it's just not that large.

    There's another thing about Manhattan. It's sitting on some crazy hard bedrock. Manhattan Schist, I believe it's called, some of the oldest, hardest rock in the world (it doesn't seem to exist in most of the surrounding area and even in parts of Manhattan). Which means that the island isn't getting washed away anytime soon by a hurricane either. The smaller inhabited islands are mostly situated on the East and Harlem rivers, which are tidal, and thus wouldn't be in any danger of being washed away either.

    Overall, the biggest areas of concern would be the outer boroughs and possibly some of the islands in the harbor, while the area of least concern would be Manhattan island itself. South Brooklyn, south Queens (Far Rockaways), and the eastern part of Staten Island are all at risk of major flooding. But the rest of New York City? Nah. It's about the safest place from a hurricane you can get, safer even than farther inland, where there's a greater chance of the local bodies of water (lakes, rivers, streams, etc.) overflowing and washing out roads, bridges, and even entire houses. Look at what happened during Irene.

    Now, Long Island and New Jersey is a different story, especially the southern shore of Long Island, which has the highest chance of a storm surge. They usually fare much, much worse than the city proper, but that's largely due to the population density or lack thereof.

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