back to article America haunted by ghost of ice gravity

Canadian researchers have found a gravitational shadow hanging over North America, left over from the last ice age. The work is published in the May 11 edition of the journal Science. Using four years of data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission – a pair of satellites that are measuring the …


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  1. Daniel Grey


    Why does America always think it is the only country to be affected by things? It has been long known that all ice sheets excert a gravitational effect and 'compress the earth' (it's called isostacy).

    Yet again, a group of scientists discover something that every other scientist knew long before them.

  2. Jon McEwen

    Rising Sea, Rising Land

    Is the land rising as fast as the sea level, I wonder?

  3. Tony

    Bottom Line

    Global warming is to blame :)

  4. Colin Jackson


    I blame Bush!

  5. jeremy

    Accuracy required.

    Isostatic Rebound is responsible for the slow uplift of modern northern Europe - as a previous comment probably meant to indicate. This has been known about for some time.

    The mermaid of Copenhagen is slowly being raised higher since it was installed in 1913. Scotland is rising and the south of the UK is sinking. Numerous other examples are known. All are caused by the rebound of the crust that was compressed by the sheer weight of the ice sheets that covered it for so long (Isostaic Rebound). In Europe the rate of rebound has by now decayed to about 1 cm per year.

    While an ice sheet will of course exert a gravitational effect, it is negligable, it is the effect of the Earth's gravity on the mass of the ice sheet that creates its weight which in turn compresses the crust. Once the ice sheet is removed, the crust slowly rebounds towards its previous position at a rate that decays roughly exponentially.

    Curious readers who wish to know more may find useful information here:

  6. Anonymous Coward
    Anonymous Coward

    Canadians not Americans


    Just wanted to point it was Canadian researchers not Americans. If you want to bash Americans stick to foreign policy and obesity, like everybody else.

  7. Anonymous Coward
    Anonymous Coward

    Isostacy metaphor

    My completely splendid Geography teacher described isotacy to us as "rather like a mattress after an orgy", which made an impression on 17 year old brains, I can tell you.

    60 meters of sea level rise rather puts a 1 meter rise due to global warming into perspective, doesn't it ;-) Must have been all those mammoths and their 4x4s...

  8. Anonymous Coward
    Anonymous Coward

    What article did you read Daniel Grey?

    This article says "Canadian" researchers and North America. Last I checked, North America is not a country, so your obvious bias against the United States of America is apparent.

    You ask, "Why does America always think it is the only country to be affected by things?" Please state every time the "country" of America has thought that it is the only country affected by things, so we can judge the validity of your statement. By the way, when did you stop beating your wife? Another statement that implies guilt with no actual proof.

    The article doesn't state that the scientists discovered isostacy, just that "the scientists were able to construct an image of the long-vanished Laurentide ice sheet," so your statement, "Yet again, a group of scientists discover something that every other scientist knew long before them," only shows your ignorance, lack of reading comprehension, and bias.

  9. SImon Hobson Bronze badge

    The AGW police will soon be burying this piece ...

    "... and it is also important for making accurate corrections before we interpret modern climate records."

    Such statements are heresy to the modern religion of Anthropogenic Global Warming - how dare they suggest that any natural process could be involved !

  10. hugo tyson

    Of course the land is rising...

    After all, Baldric and his Time Team pals are always looking down holes for archaeology, not above ground! Old stuff is always buried, ergo the land level is rising.

  11. Anonymous Coward
    Anonymous Coward

    other way 'round

    "...ergo the land level is rising."

    No, it's just that the old stuff is sinking. It just sinks to the bottom more slowly because dirt is thicker than water. I know because the Great Oobleck Diety told me so.

  12. Jason Togneri


    "It just sinks to the bottom more slowly because dirt is thicker than water."

    Just imagine if the world's crust were made of civil servants. Or scientologists ;-)

  13. 4.1.3_U1

    grey goo

    Obviously the ice has been turned by grey goo into water. 60m is nothin' compared to what awaits us.

  14. Jack Stalnaker

    Unjustified, inflammatory post

    As was stated above, I don't believe the original commenter actually read the article. No claim is made that the physics behind the phenomenon are new, only that the imaging of the phenomenon is new. Because, you know, we're always claiming over here to have discovered previously discovered science.

  15. Daniel Grey

    Read the research...

    Actually, yes I was responding to THIS article (in The Register) but was chiefly referring to the research. The work was done by Prof Jerry Mitrovica of the University of Toronto in collaboration with Drs. Mark Tamisiea and James Davis of the Harvard-Smithsonian Center for Astrophysics. Last time *I* checked Harvard was in America. Okay, so I forgot to blame the Canadians too.

    I first heard of the paper after I received a press release by EurekAlert, which is perhaps more complete. It suggests that the phenomenon of rebound was proven using this new method when, in reality, physical methods have been used for a long time (e.g. raised beaches, flooded valleys et.c.). I have yet to fully read the paper (have any of you?) but either the poor researchers were badly quoted in the media or they truly believe they have discovered a new 'phenomenon'.

  16. Caroline Clark

    What are you talking about, don't you knwo about scientific process?

    First, half the webpages I have read on this article tell the story from the American View (Scientists from the Harvard-Smithsonian Center for Astrophysics) and the other half tell it from the Canadian point of view (Scientists from the University of Toronto)... So its understandable that Daniel may have mixed it up...

    Secondly... Have any of you heard of scientific process. Yes there have been theories about the reason for less gravity in this area of the planet. But up untill now there have only been theories. Just because one theory becomes fact doesn't give you that right to throw stones.. Next time your theory might be wrong

  17. Anonymous Coward
    Anonymous Coward

    Do your own research...

    Science reports the current address of Dr. Mark Tamisiea as Proudman Oceanographic Laboratory, 6 Brownlow Street, Liverpool L3 5DA, UK. Last *I* checked, Liverpool, UK is, well, in the UK. This no more makes Dr. Tamisiea a Brit than doing research at Harvard makes Dr. Davis a U.S. citizen. I don't know the nationality of any of the authors of this paper, but if I were responding to this article, since the first two words of the article are "Canadian researchers," I kind of have to go with that.

    You state that your were responding to THIS article, but then go on to say you were referring to the research, which you later explain you actually haven't read, but you received a press release from EurekAlert. The Register article doesn't say these researchers think they have discovered a "new" phenomenon, only that Professor Mitrovica described the phenomenon.

  18. Anonymous Coward
    Anonymous Coward

    Americans thinking nothing is discovered until they finally catch up...

    I agree with the original "inflammatory" poster - the PR on this bit of research is clearly trying to imply some sort of amazingly new ground was broken.

    America *always* does this - no research counts until it has been duplicated by an american, at which point that duplicator becomes a *pioneer*.

    The Wright brothers are a *classic* case: they were not the first people to fly, nor the first to fly in a heavier-than-air craft, not the first to fly in a *powered* heavier-than-air craft. The best they could (rather dubiously) claim was in copying others in doing all the above, but supposedly doing it in a *sustained* way, and filming it (americans usually need pictures).

    - And all this translates in all the modern media as being "Wright brothers were the first to fly" which is incorrect - they were the first *americans* to fly, perhaps.

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  20. Joe Futrelle

    Clearly not a lot of science historians on this thread

    Major new observations supporting an existing theory count as discoveries. For instance gravity probe B is intended to provide major new evidence for frame-dragging in general relativity, and if it succeeds that will be significant discovery, but it will neither "prove" general relativity nor constitute the discovery of general relativity. Journalists often use stories about this kind of data-gathering research as an opportunity to educate the public about the theories the data is intended to support, and if they spin it as the discovery of the theories or readers misinterpret it that way, that's not the scientists' fault--the peer review process (when it works) prevents scientists from taking credit in their journal papers for theories they're only collecting data for.

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