Failing ocean current raises fears of mini ice age

Discussion in 'Politics, Religion, Social Issues' started by Stella, Nov 30, 2005.

  1. Stella macrumors 604

    Stella

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    #1
    Reminds me of Day After Tomorrow...

    http://www.newscientist.com/article.ns?id=dn8398

    The ocean current that gives western Europe its relatively balmy climate is stuttering, raising fears that it might fail entirely and plunge the continent into a mini ice age.

    The dramatic finding comes from a study of ocean circulation in the North Atlantic, which found a 30% reduction in the warm currents that carry water north from the Gulf Stream.

    The slow-down, which has long been predicted as a possible consequence of global warming, will give renewed urgency to intergovernmental talks in Montreal, Canada, this week on a successor to the Kyoto Protocol.


    What do you think about these dramatic findings?
    Discuss this story >>
    Harry Bryden at the Southampton Oceanography Centre in the UK, whose group carried out the analysis, says he is not yet sure if the change is temporary or signals a long-term trend. "We don’t want to say the circulation will shut down," he told New Scientist. "But we are nervous about our findings. They have come as quite a surprise."

    No one-off

    The North Atlantic is dominated by the Gulf Stream – currents that bring warm water north from the tropics. At around 40° north – the latitude of Portugal and New York – the current divides. Some water heads southwards in a surface current known as the subtropical gyre, while the rest continues north, leading to warming winds that raise European temperatures by 5°C to 10°C.

    But when Bryden’s team measured north-south heat flow last year, using a set of instruments strung across the Atlantic from the Canary Islands to the Bahamas, they found that the division of the waters appeared to have changed since previous surveys in 1957, 1981 and 1992. From the amount of water in the subtropical gyre and the flow southwards at depth, they calculate that the quantity of warm water flowing north had fallen by around 30%.

    When Bryden added previously unanalysed data – collected in the same region by the US government’s National Oceanic and Atmospheric Administration – he found a similar pattern. This suggests that his 2004 measurements are not a one-off, and that most of the slow-down happened between 1992 and 1998.

    The changes are too big to be explained by chance, co-author Stuart Cunningham told New Scientist from a research ship off the Canary Islands, where he is collecting more data. "We think the findings are robust."

    Hot and cold

    But Richard Wood, chief oceanographer at the UK Met Office’s Hadley Centre for climate research in Exeter, says the Southampton team's findings leave a lot unexplained. The changes are so big they should have cut oceanic heating of Europe by about one-fifth – enough to cool the British Isles by 1°C and Scandinavia by 2°C. "We haven’t seen it yet," he points out.

    Though unseasonably cold weather last month briefly blanketed parts of the UK in snow, average European temperatures have been rising, Wood says. Measurements of surface temperatures in the North Atlantic indicate a strong warming trend during the 1990s, which seems now to have halted.

    Bryden speculates that the warming may have been part of a global temperature increase brought about by man-made greenhouse warming, and that this is now being counteracted by a decrease in the northward flow of warm water.

    After warming Europe, this flow comes to a halt in the waters off Greenland, sinks to the ocean floor and returns south. The water arriving from the south is already more saline and so more dense than Arctic seas, and is made more so as ice forms.

    Predicted shutdown

    But Bryden’s study has revealed that while one area of sinking water, on the Canadian side of Greenland, still seems to be functioning as normal, a second area on the European side has partially shut down and is sending only half as much deep water south as before. The two southward flows can be distinguished because they travel at different depths.

    Nobody is clear on what has gone wrong. Suggestions for blame include the melting of sea ice or increased flow from Siberian rivers into the Arctic. Both would load fresh water into the surface ocean, making it less dense and so preventing it from sinking, which in turn would slow the flow of tropical water from the south. And either could be triggered by man-made climate change. Some climate models predict that global warming could lead to such a shutdown later this century.

    The last shutdown, which prompted a temperature drop of 5°C to 10°C in western Europe, was probably at the end of the last ice age, 12,000 years ago. There may also have been a slowing of Atlantic circulation during the Little Ice Age, which lasted sporadically from 1300 to about 1850 and created temperatures low enough to freeze the River Thames in London.
     
  2. cslewis macrumors 6502a

    cslewis

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    #2
    That would be very interesting to see.

    I think that global warming is a part of the natural cycle of global temperature surge and abatement. Of course, we may be contributing to the recent upswing in temperature, but I believe human activites are merely a drop in the bucket in the complex sea of climate change.
     
  3. zimv20 macrumors 601

    zimv20

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    toronto
    #3
    a butterfly flaps its wings in jakarta, and in chicago we get rain instead of snow.

    but man can dump billions of tons of toxins into the environment and have no effect on the weather.

    hm.
     
  4. leekohler macrumors G5

    leekohler

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    Chicago, Illinois
    #4
    Thank you. We can't destroy the Earth, but we can destroy ourselves.
     
  5. Ugg macrumors 68000

    Ugg

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    Penryn
    #5
    The analogy I like to use is that we know we can have a massively adverse impact on local conditions, NY, Houston, Los Angeles, burning rivers, London smog are all clear proof that man has an impact. It doesn't take a huge leap of faith that when magnified by a few thousand times this impact can be global as well. Anyone who fails to grasp such a basic concept better have some good insurance when it impacts their local community.

    History will of course decide who is right and wrong but is it worth gambling our children's future?
     
  6. skunk macrumors G4

    skunk

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    #6
    If we ensure that our children own the world, what will they care? They'll be rich enough to buy their own micro-climate.
     
  7. takao macrumors 68040

    takao

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    #7
    time to go for some mammoth hunting training ... was about time
     
  8. OutThere macrumors 603

    OutThere

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    #8
    Much of this theory was officially published in the scientific, peer-reviewed journal Nature very recently.

    Basically, as the ice caps melt, the northern parts of the ocean will have a relatively fast influx of fresh water. Because of this, the concentration of the salt in the water in those parts of the world will become significantly lower, and the warm currents from the northern parts of the gulf stream will no longer flow properly. When this happens, most of Europe will be put into a localized ice age.

    Now, for everyone who believes that we're just in a naturally occurring global temperature swing, and things will calm down eventually:

    While it may appear at first glance that the pattern right now matches a pattern that occurred many times throughout history. But that's not entirely the case. Right now the average carbon dioxide concentration within the atmosphere is estimated to reach 450ppm, whatever our industrial and environmental actions are in the near future. The highest of the high peaks over the last 500,000 years only reached roughly 280ppm. Right now the global average concentration is somewhere around 350-380ppm.

    From historical evidence, we can see that high levels of carbon dioxide in the atmosphere typically follow, slightly, general global warming trends. What is strange about this time is the fact that the increase in CO2 in the atmosphere preceded the rise in global average temperature. Correlation doesn't necessarily imply causation, but this strange occurrence sheds some light on what is not apparent at first glance.

    People who do not believe that there has been any climate change at all are kidding themselves.

    People who believe that it's a natural occurrence need to take a closer look, and face the reality of the situation.
     
  9. solvs macrumors 603

    solvs

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