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Further evidence of potential THC Slow Down/Shut Down


Guest Viking141

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Posted
  • Location: Sunny Southsea
  • Location: Sunny Southsea

    Good effort, Vikes. The first paper is the only new one on me; I'll check it out when I have time. Suffice it to say that I am happy to follow the general run of scientific opinion when it says a slowdown is much more likely than a complete shutdown, but any changes are likely to result in pattern shifts in the UK, so it is definitely a situation which deserves watching. What is most relevant here is the observed changes in the Southern Oceans, which, up to now, have not been seen as problematic.

    I'd point out, though, that the timespan of shifts between bottom and upper layer water is very long - decades to centuries for the whole 'system' to overturn.

    It might be worth checking when and where the main events for the International Polar Year are due to take place, as there should be a website with link to presentations and abstracts.

    Also worth noting that the EGU publishing arm, Copernicus, has announced a new journal - on the Cryosphere. No articles available yet, though.

    :)P

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    Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

    Thanks Viking!

    The GW Sceptics always harp on about surface (and altitude) temps when trying to pooh,pooh notions of polar change yet it is the waters drifting poleward and the winds driving poleward that bring the conditions for melt. It may be a constant -10c above but if the water is +3c then melt occurs.

    As a solid ice has the potential for catastrophic structural failure of 'undercut' shelves/glacier snouts leading to their breakup (even if temps are sub-zero). The larger surface area of ice presented to the warm waters (relative) then lead to a rapid ablation.

    We don't need plus temps in the pole to melt them just warm water and it's influences on the surface air mass sat over it. When the ice goes then the poles will warm and not the other way around.

    http://www.sciencedaily.com/releases/2007/...70510164044.htm

    In so far as changing deep sea circulation the above makes a worrying read.

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    Posted
  • Location: Cheddar Valley, 20mtrs asl
  • Weather Preferences: Snow and lots of it or warm and sunny, no mediocre dross
  • Location: Cheddar Valley, 20mtrs asl
    Thanks Viking!

    The GW Sceptics always harp on about surface (and altitude) temps when trying to pooh,pooh notions of polar change yet it is the waters drifting poleward and the winds driving poleward that bring the conditions for melt. It may be a constant -10c above but if the water is +3c then melt occurs.

    As a solid ice has the potential for catastrophic structural failure of 'undercut' shelves/glacier snouts leading to their breakup (even if temps are sub-zero). The larger surface area of ice presented to the warm waters (relative) then lead to a rapid ablation.

    We don't need plus temps in the pole to melt them just warm water and it's influences on the surface air mass sat over it. When the ice goes then the poles will warm and not the other way around.

    http://www.sciencedaily.com/releases/2007/...70510164044.htm

    In so far as changing deep sea circulation the above makes a worrying read.

    Could it then be possible that the rise in temps and Co2 we are experiencing are due in a large part to old Co2, now being released from the ocean's depths? There is another article on the same site which says current Co2 sequestered into the oceans from today's atmosphere do not make it to the depths of the ocean's bottom.

    http://www.sciencedaily.com/upi/index.php?...28-00182100-bc-

    Sorry, can't get it to link; here's the body text of the article:

    Oceans' role in climate change limited

    WASHINGTON, April 27 (UPI) -- U.S. and international researchers say carbon dioxide is often recycled in the Pacific Ocean's "twilight zone" instead of sinking into the deep ocean.

    Because the carbon often never reaches the deep ocean, where it can be stored and prevented from re-entering the atmosphere as a greenhouse gas, the oceans may have little impact on climate change, the National Science Foundation said Friday in a release.

    The study, published in the April 27 issue of the journal Science, says carbon dioxide is often consumed by animals and bacteria and recycled in the dimly lit twilight zone located 300 to 3,000 feet below the ocean surface.

    The researchers found that only 20 percent of the total carbon in the ocean surface made it through the twilight zone off Hawaii, while 50 percent did in the northwest Pacific near Japan.

    "Unless the carbon goes all the way down into the deep ocean and is stored there, the oceans will have little impact on climate change," said lead author Ken Buesseler, a biogeochemist at Woods Hole Oceanographic Institution.

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    Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

    Thanks Jethro,

    I find a little 'reading between the lines' is always necessary when trying to absorb 'recent papers'.

    Combining the CO2 'Burps' (18,000yrs and 13,000yrs ago) with Vikings papers on ocean circulation changes and your Woods hole inst. paper leads me to think that any bottom 'freshening' at higher latitudes that leads to a disruption in the B.A.U. circulation could lead to 'upwelling' across many of the ocean basins presenting more CO2 (that would have remained 'buried' in the deep Oceans without the 'warming') to the atmosphere and so further exasperating our warming trend.

    Obviously when the ice has gone/become stable then the 'freshening' will stop and the oceans will settle back down into a new their circulatory 'habits'.

    If you add in the impact of further CO2 from the deep ocean on global temps the the spectre of methane hydrite release from continental shelf 'storage' re-appears as a probable event leading to yet more warming.

    Though 'tipping points' are only slowly becoming acceptable within the scientific community (IMO) there seem to be plenty of them around!!!

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    Posted
  • Location: Cheddar Valley, 20mtrs asl
  • Weather Preferences: Snow and lots of it or warm and sunny, no mediocre dross
  • Location: Cheddar Valley, 20mtrs asl

    That's what I find so disturbing with the stance that "we've got it sussed, 2+3=5, we know what we're doing". I believe we're a very long way from having it sussed, understanding how it all works and interacts. Time will tell I guess.

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    Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......
    That's what I find so disturbing with the stance that "we've got it sussed, 2+3=5, we know what we're doing". I believe we're a very long way from having it sussed, understanding how it all works and interacts. Time will tell I guess.

    Ditto!

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    Guest Viking141
    Good effort, Vikes. The first paper is the only new one on me; I'll check it out when I have time. Suffice it to say that I am happy to follow the general run of scientific opinion when it says a slowdown is much more likely than a complete shutdown, but any changes are likely to result in pattern shifts in the UK, so it is definitely a situation which deserves watching. What is most relevant here is the observed changes in the Southern Oceans, which, up to now, have not been seen as problematic.

    I'd point out, though, that the timespan of shifts between bottom and upper layer water is very long - decades to centuries for the whole 'system' to overturn.

    It might be worth checking when and where the main events for the International Polar Year are due to take place, as there should be a website with link to presentations and abstracts.

    Also worth noting that the EGU publishing arm, Copernicus, has announced a new journal - on the Cryosphere. No articles available yet, though.

    :)P

    Hi P3

    Thanks for that. Only one slight quibble with what you have said. I wouldnt regard "decades" as being long, certainly not on any climactic timescale this is actually quite a rapid period. If, as I suspect and I think you do to, that these changes are already underway and more advanced than current science likes to admit, then "decades" puts it into the "in our lifetime" ballpark so I agree definitely something that needs to be kept an eye on.

    The recent charts Ive looked at re the NAD strength suggests to me at least some interruption going on which could signify slow down or stoppage is already on the cards.

    Mondy

    The lovely lady is Louise Redknapp you philistine!

    :good:

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    Posted
  • Location: Sunny Southsea
  • Location: Sunny Southsea

    Vikes; If you want an idea of my thoughts about CC and timescales, perhaps you'd like to try my 'game': http://fergusbrown.wordpress.com/2007/05/1...t-are-the-odds/

    You can find the answers on Open Mind, where Tamino has given a scientist's opinion; but no peeking!

    :)P

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    Posted
  • Location: Sunny Southsea
  • Location: Sunny Southsea

    Optimus Prime: Would you like some links to papers? They aren't as sensationalist as the articles, but they still paint a picture which causes concern. Where Viking141 ( & others) & I normally disagree is on the matter of when there might be 1. a collapse or rapid acceleration of either the GIS or the WAIS, and 2. What the ARGO bouys and other monitoring devices are telling us currently, and how worried we should be about it.

    The climate models, in general, project as slowdown of between 10% and 85%, depending on circumstances, by 2080, in a 'Business as usual' emissions scenario. There is some evidence that the estimates of both the models and the IPCC are, however, too conservative in terms of timing, if not effect. It's a fair chance, maybe as high as 50/50, that we'll have a confirmed slowing of up to 10% of the AMOC by the 2040's. Worst case scenario might give a 25% slowing as soon as the next decade, however, in spite of the concerns, I'd give this at most a 1/20 chance.

    Regards,

    :)P

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    Posted
  • Location: G.Manchester
  • Location: G.Manchester

    I'm not sure how you can give it a probability when there is no evidence that a North Atlantic Current has ever shut down before and whether it's possible and if it is how, what and even if it'll affect the climate in a major/noticeable way.

    Everything these days that involves warming/current shutdown has to be a doomsday disaster. I don't think there were articles during the 1962/63 winter of an ice-age even though that was basically close to what it was in comparison to our climate.

    In the early 70s when we went through another short warm phase they were on about catastrophes due to a warming world. Then came the winter off 78/79 and a continuation of cold winters in the 80's we were next due an ice-age for the fourthcoming decades....instead were warming fairly promntly.

    The fact is scientists don't know the mechanics of nature because they're so unpredictable in the long term. So IMO we have no basis for these scares of NAC shutdowns.

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    Posted
  • Location: Sunny Southsea
  • Location: Sunny Southsea

    I'm trying quite hard not to be sensationalist or a doom-monger here, O-P; I have never thought it especially constructive.

    On previous instances of THC shut-down, the normally cited reference is the so-called 8.2K year event, which happened 8,200 years ago. Wally Broecker published the definitive paper on this in 1995, though there have been some question marks about the causes of the shut-down; he suggested the most likely cause as a massive 'hosing' of freshwater added to the N. Atlantic by the breaching of an ice dam which allowed the then warming Laurentide Ice sheet to collapse suddenly. Broecker has recently distanced himself a little from this hypothesis. The most recent material I can find is suiggesting a three-fold periodicity in ocean circulation patterns, running at 1000, 1500 and 2500 years; the paper goes on to suggest that, when two of these periodicities combine with other forcing agents, the circulation system experiences relatively rapid changes.

    So; palaeoclimatic evidence suggests not only that a shutdown, or major change in ocean circulation is possible, but also that it has happened on a regular basis in the past.

    Apart from the palaeo data, which also attributes temperature values to matching timeperiods, so inferences can be drawn as to the 'sum effect' of such events in certain locations, or even globally, the other main support for the idea of a circulation pattern shift are the Climate models, which all, under a BAU scenario, show some effect on the THC, almost always negative, and varying in magnitude, depending on the sensitivity of the model to various parameters.

    Nowhere will you find in my posts any suggestion that a THC shutdown will result in an ice age; this is fiction - The Day After Tomorrow - not science. I have enumerated the most commonly cited likely effects several times on these threads. In the scenario into which we are headed, by 2100, even if there was an 85% THC slowdown in the timescale, the cooling effect of this would be overtaken by the warming effect of GW; whilst some parts of the world would be getting much warmer, the UK and Scandinavia would have climates similar to today's.

    Scientist do know quite a lot about many of the mechanics of nature - but the oceans and the icecaps are amongst the least well understood of the components which influence our climate. In terms of long-term predictability, it depends what you mean by 'long term', and by 'predictable'. They can estimate global temperatures for 650,000 years; they can give a reasonably high level of accuracy to temperatures over the last 400 years in particular. They know that the climate changes, and that they don't know all of the reasons why it does, specifically the so-called 'switches' which seem to trip now and again, or the causes for these 'trips'. Theyalso know that the sun's output effects the climate, that the gases in the atmosphere, the aerosols and clouds all play an important role, they know that some of the conditions we are currently in, or are soon very likely to face, are unlike any of the conditions on earth for many thousands of years, and they don't know, for certain, how this will effect any or all of the systems, except insofar as they can apply the laws of physics, the observed data, and a huge computational power so vast it is hard to imagine, into climate models, which attempt to reveal what might happen under certain circumstances. That is quite a lot of knowledge.

    You shouldn't necessarily think of a THC slowdown/shutdown as a 'scare'; this is jumping the gun a bit; if such a thing happens, it will certainly have an impact on the UK's climate. Some people will find that scary, others exciting, others won't care at all.

    I hope this answers some of yourt concerns and helps towards a better understanding of the matter in hand.

    Regards,

    :)P

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    Guest Viking141

    [quote name='parmenides3' date='13 May 2007, 12:28 AM' post='981764'

    Nowhere will you find in my posts any suggestion that a THC shutdown will result in an ice age; this is fiction - The Day After Tomorrow - not science.

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    Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

    Insofar as 'Day after tomorrow' type 'instant' events any partial collapse (physical collapde) of any large section of the GIS or the EAIS or the WAIS would have instantaneous effect in terms of displaced water (if you look at some of the figures of SL impact of some of the larger 'embayment chunks' that have foated free recently).

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    Posted
  • Location: Steeton, W Yorks, 270m ASL
  • Location: Steeton, W Yorks, 270m ASL

    http://www.cru.uea.ac.uk/cru/info/thc/

    UEA tend to be fairly moderate and well reasoned commentators on these things. I think towards the end the assessment is that for the KUK, by the time any NADC slow-down occurred, the downward movement in local temperature would probably be more than offset by the increase brought on by the degree of GW in any case necessary to initiate th shutdown.

    I have seen no evidence in any reasonable source, Viking, to suggest that there is any slowdown ongoing. I think it's rather fanciful, if not wishful thinking, to go looking for it at present. From a cooling perspectivem, things will have to get a lot worse before they have any chance of becoming slightly less worse.

    Found this which may be of interest:

    Science Poles article

    Also this may also be of interest:

    Gulf Stream Shut Down

    Goodbye Gulf Stream?

    Quantative Study

    Got to say Viking that the title of the thread seems to be a bit of a misnomer. There's no evidence that I can see in those papers: they are all just hypothesising WHAT the impact MIGHT be.

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    Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

    I think that the papers showing how and why a slow down would occur need be read with the ongoing AGW in mind.

    NASA's latest offerings on the subject are below

    http://earthobservatory.nasa.gov/Library/G...lWarmingUpdate/

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    Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire
    http://www.cru.uea.ac.uk/cru/info/thc/

    UEA tend to be fairly moderate and well reasoned commentators on these things

    ...which is just as well, because that's where I'll be conducting research, hopefully, over the next three years.

    As it stands, I don't see any evidence of a slowdown at the moment either; the high SSTs around Iceland/Greenland fly somewhat in the face of this idea, given that if a slowdown was to occur, Greenland and Iceland would probably experience the effects first.

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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

    task for you P3

    read, digest and write no more than 150 word accurate summary please?

    many thanks

    John

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    Posted
  • Location: Sunny Southsea
  • Location: Sunny Southsea

    Even simpler; this is from the foreword; it covers the subject matter of the report. Each component of the cryosphere, snow, glaciers, ice sheets and sea ice, are treated separately. The main aim of the report is to encourage increased observation of the system.

    The climate science community, national and international policy makers, the media, and the general

    public are giving considerable attention to the cryosphere for the following reasons:

    • Many glaciers, the Greenland ice sheet, permafrost and frozen ground, snow cover, Arctic sea

    ice, are exhibiting dramatic changes. Melting permafrost and sea ice in the Arctic affect

    ecosystems and the sustainability of human activities. Melting snow and ice are likely to

    contribute to a rise in sea level. The stability of the cryosphere is therefore a matter of significant

    concern for science and international policy, particularly in light of the global warming identified by

    the 2007 reports of the Intergovernmental Panel on Climate Change (IPCC).

    • Adequate knowledge of the cryosphere is important for weather and climate prediction,

    assessment and prediction of sea level rise, availability of fresh water resources, navigation,

    shipping, fishing, mineral resource exploration and exploitation, and in many other practical

    applications.

    • The cryosphere provides indicators of climate change, yet it may be the most under-sampled

    domain in the climate system.

    The Integrated Global Observing Strategy (IGOS) Cryosphere Theme is required to create a

    framework for, and facilitate improved coordination of, cryospheric observations, and to generate the

    data and information needed for both operational services and research. In the polar regions, the cost

    of in situ observations is very high, and satellite monitoring is challenging. Therefore, there is a

    particularly strong need for a close coordination of observations. There is also a need to strengthen

    national and international institutional structures responsible for cryospheric observations, and to

    increase resources for ensuring the transition of research-based projects to sustained observations.

    The likelihood of achieving such goals will be significantly enhanced through the development of a

    comprehensive, coordinated, and integrated approach of the kind represented by an IGOS Theme.

    This report aims to initiate a process that will ultimately result in a more comprehensive, coordinated,

    and integrated cryospheric observing system. The report starts with an Executive Summary that that

    includes major recommendations. Chapters 1 and 2 define the cryosphere and the major applications

    of cryospheric data. Chapters 3-10 describe our current capabilities and requirements for observing

    essential climate variables (ECVs) in the major domains of the cryosphere. Each of these chapters

    contains domain-specific recommendations. Chapter 11 reviews the cryospheric observing system by

    observation types; i.e., in situ, satellite, and airborne. Data management objectives are detailed.

    Chapter 12 presents the Theme implementation considerations and their timeline. Throughout the

    report we will refer to the Cryosphere Theme as CryOS, the Cryosphere Observing System.

    Bottom line; there is an awful lot to be concerned about, an awful lot that requires too mich inference due to inadequacy of data, and a large gap between what we know now, and what we need to know in order to make the best possible decisions for the future. In general, the chapters summarise pretty much what has been reported previously on NW, with the possible exception that we haven't yet paid much attention to the huge dependency of large population groups on snowmelt as a principle source of potable water - for example, in the Western USA, where 75% of all available freshwater originates in the cryosphere.

    It's more a summary of what we've got, and an estimate of what resources we need, as far as understanding the cryosphere goes.

    Will that do?

    :)P

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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

    yeah, I'll let you off with that!

    tks

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    Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet

    The way i calculate it, is that a 1C rise in temperature, has led to a 20% slowdown in the strength of the NAD, however as a complete shutdown would cause a 5C to 8C drop in temperature, if u divide that by 5 (20%) then accounting for a margin of error, the NAD is not slowing down fast enougth to outpace global warming at the current time.

    For the NAD to shutdown and relocate south, it would require another 4C rise in global temperature, and assuming it happened, the temperature drop would be 3C at its worse, meaning that we would still be warmer than we are today.

    I am afraid that while i believe we will see a reduction in the strength of the NAD and maybe even a complete shutdown, we need a large influx of freshwater such as an ice sheet collapse, because at the current time, global warming is not been outpaced.

    Nevertheless, there is some hope, as i believe that the Gliessenburg Minima will subdue global warming, and by that time i expect that the NAD will of weakened by around 40% cancelling out the net rise over this and the last centuary which i expect will be around 1.5C to 2.5C, meaning that the Gliessenburg minima can lower our temperature to little Ice Age standards.

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