Future of the Gulf stream

[JMP]

I've looked a bit into the theories concerning a possible weakening or shutdown of the Atlantic Gulf stream (wich warms West & North Europe 6-10 degrees Celsius above the average latitude level) caused by excessive amounts of freshwater from melting Greenland glaciers.

Many scientists whose statements I've read seem to be somewhat optimistic on the subject; they claim that the amount of new freshwater is nowhere close enough to shutdown the stream entirely, and that a possible disruption probably would not be that fatal for Europe. Some even say that Europe is warmed more by winds across the Atlantic than by Gulf stream. The pessimists, on the other hand, seem to consist mostly of environmental activists.

If I remember correctly, a recent study by NASA claimed that by the 90's, Gulf stream had already slowed down by 20% (or something), as compared to the 50's and 60's. If that's true, shouldn't Europe already be distinctly colder than it is now (even when considering the mitigating effect of global warming)?

In any case, the Gulf stream is #1 question regarding global warming and its implications for Europe.

Do you have any insights into this debate? Will we face a new ice age?

[skeptik]

If I remember correctly, a recent study by NASA claimed that by the 90's, Gulf stream had already slowed down by 20% (or something), as compared to the 50's and 60's. If that's true, shouldn't Europe already be distinctly colder than it is now (even when considering the mitigating effect of global warming)?

The scientist at NASA, Sirpa Hakkinen, thinks this is cyclical.

"A NASA satellite confirms that overturning in the North Atlantic Ocean?a process where surface water sinks and deep water rises due to varying water densities?speeds up and slows down by 20 to 30 percent over 12- to 14-year cycles. Scientists previously believed that a change of this magnitude would take hundreds of years, rather than close to a decade."

"These kinds of occurrences can be expected every 12 to 14 years," she said. "It appears that in the last 50 years there have been three large-scale changes in the overturning."

http://earthobservatory.nasa.gov/Newsro ... mg_id=5027
http://www.gsfc.nasa.gov/topstory/20010 ... tream.html

I'm not surprised. Every dynamic process in nature seems to have a cyclical component. If the North Atlantic conveyor had turned out to have a constant speed I would have been most surprised.

What does surprise me is that such an enormous mass of water can slow down and speed up in such a short space of time. If you had asked me to guess I would have guessed (from a position of total ignorance) the frequency of the cycles would probably be in the range of hundreds to thousands of years.


A mre recent posting from NASA. A current called the 'sub-polar gyre' is weakening.

http://www.nasa.gov/centers/goddard/new ... 5gyre.html
"The current, known as the sub polar gyre, has weakened in the past in connection with certain phases of a large-scale atmospheric pressure system known as the North Atlantic Oscillation (NAO). But the NAO has switched phases twice in the 1990s, while the subpolar gyre current has continued to weaken. Whether the trend is part of a natural cycle or the result of other factors related to global warming is unknown."

What we do know from the ice core and lakebed records is that the climate in the North Atlantic can change very quickly, over a period of a few decades. Nobody is sure why. A change in the oceans circulatory pattern is an obvious potential culprit. And this could be possibly due to a sudden massive influx of fresh water. The breaking of an enormous morraine dam has been suggested as a source of this water.

A good recent example is the Younger Dryas event, a cold snap which ran from 12,900 ? 11,500 years BP.

http://en.wikipedia.org/wiki/Younger_Dryas
http://www.agu.org/revgeophys/mayews01/node6.html

Will we face a new ice age?

Oh yes. Undoubtedly, if the human race manages to survive for long enough. We are actually in an "Ice Age" - have been in one for 2 million + years - most of the evolutionary priod of genus Homo. We just happen to be in one of the short warm 'interglacial periods' within that ice age. Looking at the Vostok temperature record its fairly obvious hat we could drop back into a glacial period at any minute (geologically speaking). It has been sugested (article in SCIAM earlier this year) that it's only human interference over the last 8000 years or so that has prevented this from happening. The glaciers are already slightly overdue in Boston and London.

[genoxy]

Do you have any insights into this debate? Will we face a new ice age?

http://www.nytimes.com/2005/11/03/inter ... spain.html

The groves that have sustained this region for centuries and helped turn it into the richest source of olive oil in the world have been decimated by circumstances that few here thought possible. A record-breaking freeze last winter was followed by a drought that has been described as the worst to hit Spain in 60 years.

On a slightly different note...

http://education.guardian.co.uk/higher/ ... 43,00.html

Palaeontologists excavating a dump outside Barcelona have found a skull dating back 14m years that could belong to a common ancestor of apes and humans.

Well, what can I say? Our ancestor found in a dump - how symbollic

[genoxy]

Seems like Gulf Stream is shutting down slowly...

http://news.bbc.co.uk/1/hi/sci/tech/4485840.stm

This more or less constitutes a smoking gun

Michael Schlesinger
Changes to ocean currents in the Atlantic may cool European weather within a few decades, scientists say.

Researchers from the UK's National Oceanography Centre say currents derived from the Gulf Stream are weakening, bringing less heat north.

Their conclusions, reported in the scientific journal Nature, are based on 50 years of Atlantic observations.

They say that European political leaders need to plan for a future which may be cooler rather than warmer.

The findings come from a British research project called Rapid, which aims to gather evidence relating to potentially fast climatic change in Europe.

Atmospheric radiator


The north Atlantic conveyor


Enlarge Image

The key is the Gulf Stream. After it emerges from the Caribbean, it splits in two, with one part heading north-east to Europe and the other circulating back through the tropical Atlantic.

As the north-eastern branch flows, it gives off heat to the atmosphere, which in turn warms European land.

"It's like a radiator giving its heat to the atmosphere," said Harry Bryden from the National Oceanography Centre (NOC) at Britain's Southampton University.

"The heat it gives off is roughly equivalent to the output of a million power stations," he told reporters.

By the time it reaches the northern latitudes around Greenland and Iceland, the water has cooled so much that it sinks towards the ocean floor, a process known as "overturning".

This cooler water heads south, forming the return stream of a conveyor belt. The complete cycle sees warm water coming northwards on the ocean's surface, and the cold water returning hundreds or thousands of metres underwater.


The Rapid team monitored at roughly 25 degrees north
Florida-based scientists monitor the northwards-flowing Gulf Stream, and have found it has remained roughly constant over the last 50 years.

The NOC researchers concentrated on the colder water flowing south; and they found that over the last half century, these currents have changed markedly.

"We saw a 30% decline in the southwards flow of deep cold water," said Harry Bryden.

"And so the summary is that in 2004, we have a larger circulating current [in the tropical Atlantic] and less overturning."

And less heat, then delivered to European shores.

First evidence

Computer models of climate have regularly predicted that the north Atlantic conveyor may well reduce in intensity or even turn off altogether, a concept that was pushed beyond credence in the Hollywood blockbuster The Day After Tomorrow.




Arctic: Melting in the heat
Arctic rivers flowing faster
What happens is that as Arctic ice melts and Arctic rivers flow faster - trends which have both been documented - the northern oceans become less saline.

Less salinity means a lower density; the waters then cannot sink, so the conveyor weakens.

Computer models have predicted that if it turned off completely, Europe would cool by perhaps four to six degrees Celsius.

Commenting in Nature, Detlef Quadfasel from the University of Hamburg writes that the NOC experiments provide "...the first observational evidence that such a decrease of the oceanic overturning circulation is well underway."

Natural variation

The NOC researchers admit that the case is not yet proven.

The analysis involves only five sets of measurements, made in 1957, 1981, 1992 and 1998 from ships, and in 2004 from a line of research buoys tethered to the ocean floor.

Even if the trend is confirmed by further data, it could be down to natural variability rather than human-induced global temperature change.

"This issue of variability is very important," said Harry Bryden, "and we do not have any good grasp of it.


In 2004 buoys were deployed from ships onto tethers
"Models can predict it, but we think we ought to go out and measure it."

Michael Schlesinger from the University of Illinois at Urbana-Champaign, a leading expert in models of climate and ocean circulation, believes that even with these caveats, the NOC team has probably come up with a link to human-induced climate change.

"The variability question is the right one to ask," he told the BBC News website, "but the phasing is wrong."

A decade ago Professor Schlesinger showed that the north Atlantic conveyor undergoes a natural 70-year cycle of strengthening and weakening.

"The Bryden measurements are out of phase with this cycle," he said.

"The natural cycle had a northern cooling until the mid-1970s and a warming afterwards, and here we see an apparent cooling."

He is also convinced by other details of the NOC measurements showing that the changes in the southerly underwater flow have occurred at great depths.

"The slowing down of the southward return occurs between 3,000 and 5,000m; and this more or less constitutes a smoking gun," he said.

Choosing policies

So what does all this mean for European weather? Will it necessarily get colder - or will the apparent recent trend of warmer summers continue?


Models can predict variability, but we think we ought to go out and measure it

Harry Bryden
"If this trend persists," said Harry Bryden, "we will see a temperature change in northern latitudes, perhaps of a degree Celsius over a couple of decades."

But climate is a complex phenomenon; other factors could conspire, even so, to produce a net warming.

"The UK government is looking, in terms of mitigating climate change and adapting to it, at a warming scenario," said Phil Newton of the UK's Natural Environment Research Council, which funds the Rapid investigators.

"You might now be asking what sort of mitigation and adaptation they should be looking for."

To answer this question, the Rapid team plans to continue their measurements in the next few years.

Their buoys remain in place, and ships can go to gather their data as often as finance allows.

The findings will have resonance beyond the shores of the UK and Europe, as extra heat left circulating around the tropical Atlantic could have major impacts on weather systems in Africa, the Caribbean and central America.

http://en.wikipedia.org/wiki/Effects_of ... irculation

Recently the hypothesis that the Gulf Stream is switching off received a boost when a retrospective analysis of U.S. satellite data seemed to show a slowing of the North Atlantic Gyre, the northern swirl of the Gulf Stream.NASA: Slowing of North Atlantic Gyre

In May 2005, Peter Wadhams reported to The Times about the results of investigations in a submarine under the Arctic ice sheet measuring the giant chimneys of cold dense water, in which the cold dense water normally sinks down to the sea bed and is replaced by warm water, forming one of the engines of the North Atlantic Drift. He and his team found the chimneys to have virtually disappeared. Normally there are seven to twelve giant columns, but Wadhams found only two giant columns, both extremely weak. [11] [12]

The NewScientist.com news service reported on 30 November 2005 that the Southampton Oceanography Centre in the UK found a 30% reduction in the warm currents that carry water north from the Gulf Stream from the last such measurement in 1992. [13]

[DamianB]

Check out the weather in Calgary, which is what is it suggested that we're in for if the AC stops:

-15C

http://www.weather.ca/weather/cities/ca ... AB0049.htm

[tattercoats]

I caught this issue on the news last night - BBC Radio 4, no less - and it stopped me in my tracks. This is even scarier than the oil and gas situation.

My instant gut response was: skill up. Make yourself such a useful, knowledgeable person that you can earn yourself a place in some community south of here that will need convincing of your worth to let you stay. Or maybe live.

Um, European languages, anyone?

That's assuming Southern Surope isn't scorching while we freeze.

Oh, heck.

[Joe]

I don't think we need to worry about being overrun by glaciers in the UK in the immediate future. Presumably if temperatures in the North Atlantic and Europe dropped significantly, a large amount of the fresh water that's currently lowering salinity levels in the North Atlantic would again become trapped in Glaciers in Greenland, (and possibly Scandinavia and Western Russia) so the gulf stream would start up again (or at least it would act as a brake on the Gulf Stream's deceleration). maybe. please agree with me as I don't want to think about the alternative.

[Totally_Baffled]

Can some of you climate experts help me out with a few questions please ? :

Firstly, are the experts saying that European winters will get worse , or that it will in effect be winter all year around?

Secondly, I've read a few articles suggesting that Europe could warm between 4-6 degrees in some areas (in England for example) if we continue to pump Co2 as we currently do. So will this offset some of the temp decreases from the reduction of the Gulf stream?

Lastly, If the Gulf stream has weakned by 30% , how come the last decade of winters have been the mildest since records began and the summers the warmest? (and the average temp overall is trending upwards?)

Im not doubting the science , I just trying to learn a little more.

I would read/research this further, but I m afraid my eyes are already bleeding from surfing/reading about PO(and other issues)

[SherryMayo]

Regional modelling is a lot more tricky than global modelling. Some models suggest the cooling sure to the weakening of the Gulf stream will merely act to locally offset some of the overall warming for NW Europe.

[skeptik]

Im not doubting the science , I just trying to learn a little more.

I am.

Just points me towards my normal conclusion that climate science is a shite as economics.

[genoxy]

I don't think we need to worry about being overrun by glaciers in the UK in the immediate future. Presumably if temperatures in the North Atlantic and Europe dropped significantly, a large amount of the fresh water that's currently lowering salinity levels in the North Atlantic would again become trapped in Glaciers in Greenland, (and possibly Scandinavia and Western Russia) so the gulf stream would start up again (or at least it would act as a brake on the Gulf Stream's deceleration). maybe. please agree with me as I don't want to think about the alternative.

Sounds good to me - you've got my vote!

Feeling better now?

[genoxy]

Im not doubting the science , I just trying to learn a little more.

I am.

Just points me towards my normal conclusion that climate science is a shite as economics.

Maybe it is, maybe it's not, who knows?

Methane release from melting permafrost peat bogs

Wikinews has news related to this article:
Scientists warn thawing Siberia may trigger global meltdown.

Climate scientists reported in August 2005 that a one million square kilometer region of permafrost peat bogs in western Siberia is starting to melt for the first time since it was formed 11,000 years ago at the end of the last ice age. This will release methane, an extremely effective greenhouse gas, possibly as much as 70,000 million tonnes, over the next few decades. An earlier report in May 2005 reported similar melting in eastern Siberia [40].

http://en.wikipedia.org/wiki/Effects_of ... _peat_bogs

What is it that Gandalf says in Return Of The King? "Things are now in motion that cannot be undone", or something like that... Well, seems to be the case to me.

It should be interesting to see if/how PO will effect global warming and vice versa.

[Blue Peter]

Check out the weather in Calgary, which is what is it suggested that we're in for if the AC stops:

-15C

http://www.weather.ca/weather/cities/ca ... AB0049.htm

Calgary is in the middle of a large continental mass. It would surely make more sense to look at Vancouver, or similar, on or near the Canadian coast. Or does the North Pacific also have adrift?


Peter.

[snow hope]

You are quite correct Peter. More likely the Vancouver example than Calgery.

[genoxy]

You are quite correct Peter. More likely the Vancouver example than Calgery.

What about Kamchatka? That's a peninsula (almost an island), very similar in size and latid-location to UK. Check their "weather forecast" out:

Climate of Kamchatka
The absolute temperature maximum on Kamchatka is +34`C, the absolute minimum is -24:26`C on the islands and -49:60`C in central and northern parts of the peninsula.
The number of days with temperature over +20`C in summer: in coast area 1-6, in the valley of Kamchatka river 35-55.
Maximum amount of precipitation up to 2600 mm a year (south-east seaside).
Maximum wind speed in winter up to 40 m/c (at the seaside).
Volcanoes, glaciers, sea around take part in forming of the Kamchatka's climate.

Brrrrrrrrrrrrr............

By the way, I've decided that my post-PO job is gonna be in the growing panic-mongering industry