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Alarm Over Dramatic Weakening of Gulf Stream

Discussion in 'BBS Hangout: Debate & Discussion' started by MadMax, Dec 1, 2005.

  1. MadMax

    MadMax Contributing Member

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    http://www.guardian.co.uk/science/story/0,3605,1654803,00.html?gusrc=rss

    I'm interested in this...but admittedly it's not something I know much about.

    Alarm over dramatic weakening of Gulf Stream

    · Slowing of current by a third in 12 years could bring more extreme weather
    · Temperatures in Britain likely to drop by one degree in next decade

    Ian Sample, science correspondent
    Thursday December 1, 2005
    The Guardian


    The powerful ocean current that bathes Britain and northern Europe in warm waters from the tropics has weakened dramatically in recent years, a consequence of global warming that could trigger more severe winters and cooler summers across the region, scientists warn today.
    Researchers on a scientific expedition in the Atlantic Ocean measured the strength of the current between Africa and the east coast of America and found that the circulation has slowed by 30% since a previous expedition 12 years ago.

    The current, which drives the Gulf Stream, delivers the equivalent of 1m power stations-worth of energy to northern Europe, propping up temperatures by 10C in some regions. The researchers found that the circulation has weakened by 6m tonnes of water a second. Previous expeditions to check the current flow in 1957, 1981 and 1992 found only minor changes in its strength, although a slowing was picked up in a further expedition in 1998. The decline prompted the scientists to set up a £4.8m network of moored instruments in the Atlantic to monitor changes in the current continuously.

    The network should also answer the pressing question of whether the significant weakening of the current is a short-term variation, or part of a more devastating long-term slowing of the flow.

    If the current remains as weak as it is, temperatures in Britain are likely to drop by an average of 1C in the next decade, according to Harry Bryden at the National Oceanography Centre in Southampton who led the study. "Models show that if it shuts down completely, 20 years later, the temperature is 4C to 6C degrees cooler over the UK and north-western Europe," Dr Bryden said.

    Although climate records suggest that the current has ground to a halt in the distant past, the prospect of it shutting down entirely within the century are extremely low, according to climate modellers.

    The current is essentially a huge oceanic conveyor belt that transports heat from equatorial regions towards the Arctic circle. Warm surface water coming up from the tropics gives off heat as it moves north until eventually, it cools so much in northern waters that it sinks and circulates back to the south. There it warms again, rises and heads back north. The constant sinking in the north and rising in the south drives the conveyor.

    Global warming weakens the circulation because increased meltwater from Greenland and the Arctic icesheets along with greater river run-off from Russia pour into the northern Atlantic and make it less saline which in turn makes it harder for the cooler water to sink, in effect slowing down the engine that drives the current.

    The researchers measured the strength of the current at a latitude of 25 degrees N and found that the volume of cold, deep water returning south had dropped by 30%. At the same time, they measured a 30% increase in the amount of surface water peeling off early from the main northward current, suggesting far less was continuing up to Britain and the rest of Europe. The report appears in the journal Nature today.

    Disruption of the conveyor-belt current was the basis of the film The Day After Tomorrow, which depicted a world thrown into chaos by a sudden and dramatic drop in temperatures. That scenario was dismissed by researchers as fantasy, because climate models suggest that the current is unlikely to slow so suddenly.

    Marec Srokosz of the National Oceanographic Centre said: "The most realistic part of the film is where the climatologists are talking to the politicians and the politicians are saying 'we can't do anything about it'."

    Chris West, director of the UK climate impacts programme at Oxford University's centre for the environment, said: "The only way computer models have managed to simulate an entire shutdown of the current is to magic into existence millions of tonnes of fresh water and dump it in the Atlantic. It's not clear where that water could ever come from, even taking into account increased Greenland melting."

    Uncertainties in climate change models mean that the overall impact on Britain of a slowing down in the current are hard to pin down. "We know that if the current slows down, it will lead to a drop in temperatures in Britain and northern Europe of a few degrees, but the effect isn't even over the seasons. Most of the cooling would be in the winter, so the biggest impact would be much colder winters," said Tim Osborn, of the University of East Anglia climatic research unit.

    The final impact of any cooling effect will depend on whether it outweighs the global warming that, paradoxically, is driving it. According to climate modellers, the drop in temperature caused by a slowing of the Atlantic current will, in the long term, be swamped by a more general warming of the atmosphere.

    "If this was happening in the absence of generally increasing temperatures, I would be concerned," said Dr Smith. Any cooling driven by a weakening of the Atlantic current would probably only slow warming rather than cancel it out all together. Even if a slowdown in the current put the brakes on warming over Britain and parts of Europe, the impact would be felt more extremely elsewhere, he said.
     
  2. Mulder

    Mulder Contributing Member

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    Uh Oh The Guardian??? basso source bashing expected in 3,2,1...
     
  3. lpbman

    lpbman Member

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    I something on this a few years ago on a nerd channel, pretty interesting stuff. I seem to remember the scientists tracking the cooler artic water and dating it back 1000+ years. aaanywho-

    The plain english concern was that the "engine" that helps keep the planets temperature stable is malfunctioning. The concern over Europe having colder winters is only one issue. Another is that warmer water will be trapped in the South, raising the temperature of the already warm Atlantic. Katrina, Rita, Epsilon etc. should remind us why that is a concern.
     
  4. lpbman

    lpbman Member

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    My use of the word concern has me concerned.
     
  5. MadMax

    MadMax Contributing Member

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    Except the NOAA is saying global warming isn't the cause of those storms....

    http://www.magazine.noaa.gov/stories/mag184.htm
     
  6. pirc1

    pirc1 Contributing Member

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    Do they have Bush appointed directors running those agencies these days? If that is the case I would not trust them 100% :p
     
  7. lpbman

    lpbman Member

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    Even if global warming isn't responsible for the wild season this year, the warmer water has everything to do with Katrina, Rita and Wilma being monster storms.
    I shudder to think what happens if the gulf stream stalls and the water temp rises by a signifigant margin. The NOAA is predicting heavy tropical activity for the next 10 to 30+ years.
     
  8. MadMax

    MadMax Contributing Member

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    except that these storms seem to run in cycles. roughly 30 year cycles. for 30 years you have storms that don't crack cat 3, for the most part. for 30 years you'll have killer storms that are cat 4 and 5 more frequently.
     
  9. lpbman

    lpbman Member

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    The previously observed hurricane cycles occured before the dramatic slowing of the gulf stream. What -could- happen is we have this period of normally warm water/active seasons and then you have the warm water that normally travels North, stagnant and getting hotter than we've ever seen.
     
  10. insane man

    insane man Member

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    i know nothing about this topic so feel free to trash me...

    but how exactly do we know and how accurately do we know what the storm cycles were before the last 50-100 years? do we really have good data from a century ago about hurricanes?
     
  11. pirc1

    pirc1 Contributing Member

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    Truth is that no one knows for sure. Scientists can propose theories based on various models, but no one can prove anything.
     
  12. MadMax

    MadMax Contributing Member

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    i know. i say this about ALL climate data. what in the world do we really think we know?

    the most comprehensive climate study was done in Europe. they used all sorts of odd techniques to conclude that the hottest period ever was sometime during the middle ages. whatever. i have no idea how they know that.
     
  13. insane man

    insane man Member

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    well i can understand that somewhat. i'd reckon you could look at ice caps and see the variations and what not. similarly for rain you could look at tree rings and see the growth or such...

    but with hurricanes?

    i guess we should leave science up to scientists. we dont want to become this administration do we? ;)
     
  14. MadMax

    MadMax Contributing Member

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    tree rings!! exactly!! that's what the climatologists used for that big comprehensive study i was mentioning. again, they said the hottest period in history was during the middle ages. i personally blame "Ye Olde Manufactuing Plant."
     
  15. losttexan

    losttexan Contributing Member

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    Middle ages hottest period?

    I just watched a show on the History Channel the other day that was how in the middle ages there was a mini Iceage. So I have no idea either way but that was what the show was about.


    Also something i can't understand about people who say the climate changes are just the usual changes that occur.

    What if you are wrong? You'll look back and say "oops I guess I was wrong,...gee we destroyed the world so a couple of corporations could make a little extra money for a couple of years? that wasn't a good trade off."
     
  16. MadMax

    MadMax Contributing Member

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    i know! i read that the other day, too. it confused me. i'll see if i can google the study.

    this may help some:

    http://www.ncpa.org/pub/st/st279/st279h.html

    A 1,400-year tree ring study in 1990 led by Britain’s Keith Briffa showed little evidence of the Medieval Warming or Little Ice Age.61 In 1992, however, Briffa and several of the same coauthors published another report in Climate Dynamics, noting that “our previously published reconstruction was limited in its ability to represent long-timescale temperature change because of the method used to standardize the original tree-ring data. Here we employ an alternative standardization technique which enables us to capture temperature change on longer timescales.”62 This second report found a cool period from 500 to 700, with 660 an especially cold year. Then it showed generally warm periods from 720 to 1360 (the Medieval Warming) with “peaks of warmth” in the 10th, 11th, 12th and 15th centuries — up to 1430.


    and this was a really interesting article i ran across that's too long to post:

    http://www.longrangeweather.com/article1.asp
     
    #16 MadMax, Dec 1, 2005
    Last edited: Dec 1, 2005
  17. Ottomaton

    Ottomaton Contributing Member
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    For what it's worth there is one scenario that I believe is still considered plausable that I have seen regarding changes in the gulf stream; the gulf stream apparently is believed to be really sensitive to changes in salinity. Were significant chunks of ice to break from Greenland and melt off to the south in the area of the gulf stream, salinity changes could cause significant issues.

    THe International Polar Foundation has a short detailing of this on their site.

    I have some articles similar to this from the early 1980's that come to the conclusion that we'll be under a giant sheet of ice by now. This seems to be a strangly common way to formulate a scientific response against global warming. Too often this has been used as an argument that we should start generating more heat to prevent cooling.

    While eventually destruction of the "chaotic dynamical equilibrium” would indeed result in the “funhouse” state the author claims, it would necessarily follow a prolonged period involving strong sustained pressure in one direction or another to knock the system out of it’s pseudo equilibrium state.

    The mathematical basis for this can be well demonstrated by studying Dynamical Systems

    I'm not trying to attack you or your article, Max, just trying to place the article in some sort of contextual framework. It is not an unreasonable reasonable idea but it seems to have a history of being used as a lever against the idea of global warming.
     
  18. Ubiquitin

    Ubiquitin Contributing Member

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  19. ima_drummer2k

    ima_drummer2k Contributing Member

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    I reckon so, if you take a notion to it...mmmmm....

    [​IMG]

    ;)
     
  20. Invisible Fan

    Invisible Fan Contributing Member

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    Day After Tomorrow was a terrible Hollywood liberal shock movie....

    Random stuff...London is around the same latitude as Boston, but because of the Gulf Stream it's climate is much much warmer. Old Europe would be screwed if the Gulf Stream decided to vanish. Since no one really knows how it works, it could vanish any time w/ or w/o global warming helping it.

    Most interesting thing I learned in a class on Natural Waters... There's been proposals to reduce global warming by adding more iron to the oceans. This would cause more photosynthetic organisms to grow and sequester CO2. It would also increase bioproductivity in the seas. This would never be proven on paper, so the idea of dumping junk into the ocean on purpose and for a purpose is too risky and preposterous....
     

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