The North Atlantic Current Is Gone

[Methuselah]

Aye, this claim gets made EVERY year, without fail...Given another 2000 years' of blogging, and it might even happen one day?

[knocker]

I don't know if this of interest.

Thermohaline Catastrophes

and the Younger Dryas

During the most recent ice age, the North Atlantic component of the Global Thermohaline Conveyer was partially shut down and the ocean is thought to have operated in a different mode to that of the present day. The northern North Atlantic was considerably cooler and the transport of the North Atlantic current (the northward extension of the Gulf Stream) much reduced. The North Atlantic component of the conveyer was reactivated at the end of the most recent glaciation, at about 14,000 years BP.

Recent research on deep-sea sediment cores has shown that this reactivation of the conveyer was not without hiccups! Part of this conveyer stopped abruptly at about 11,000 BP -a period known as the Younger Dryas^. This led to a catastrophic cooling of the North Atlantic region and caused the build up of small glaciers in the British mountains in what geographers call the Loch Lomond glacial re-advance, This cooling only appears to have lasted a few centuries, but it developed very rapidly over decades. There are several theories about what exactly led to the shut down of the conveyer. One view is that a sudden influx of fresh melt-water from the Laurentide ice sheet into the North Atlantic could have stabilised the vertical stratification and reduced the rate of formation of North Atlantic deep cold water. This, in turn, could have shut down the North Atlantic conveyor circulation, resulting in a cooling of the surface waters of the northern North Atlantic. The effect of changes in fresh water fluctuations on the thermohaline system is an example of positive feedback. The fresh water input weakens the thermohaline circulation, which makes the circulation more susceptible to further weakening. This process has been investigated in recent years using mathematical models of ocean circulation. The models show that there are a number of different states of the thermohaline circulation, some of which are stable. There are, however, transitions between stable states, which occur over periods as short as 40 years. It has been speculated that the present North Atlantic Ocean may be close to one of these transitional states, of which the Younger Dryas is an example. One study has suggested that the transition between states is not necessarily symmetrical. The change from strong to weak thermohaline circulation may be more rapid (40 years) than the re-establishment of the strong circulation (500 years). Further study of the Younger Dryas and similar events in the palaeoclimate record may give us important clues to the likely response of the present-day thermohaline circulation in the North Atlantic to global warming. (Remaining stable or flipping to another state).

Source: Oceanography-an illustrated guide, C.P. Summerhayes and S.A. Thorpe.

To think BP may affect the set up is to my mind laughable.

[Turnedoutniceagain]

To think BP may affect the set up is to my mind laughable.

Where's there's a blame - there's a claim !!

[TonyH]

Where's TC when you need him?

Edited September 9, 2010 by Tonyh

[Cymro]

There's no use one saying this is definitely happening. Because frankly it isn't and nobody can define it as fact or prove it to a justifiable degree, however there is evidence that should be looked at and evaluated. At the same time no scientist or anyone at that matter can say this is not going to happen, never going to happen blah blah, because it has in the past and its more than likely to do so again, when who knows? Near future, in a thousand years? Our climate has a beautiful way of balancing herself out such as the offset of temperatures increasing could be the slowing of the gulf stream etc. We don't know and probably never will so there's no point having certain people trying to forge they're views on others.

[knocker]

From Wikipedia http://en.wikipedia....iki/Gulf_Stream

"Typically, the Gulf Stream is 100 kilometres (62 mi) wide and 800 metres (2,600 ft) to 1,200 metres (3,900 ft) deep. The current velocity is fastest near the surface, with the maximum speed typically about 2.5 metres per second (5.6 mph).^[20] As it travels north, the warm water transported by the Gulf Stream undergoes evaporative cooling. The cooling is wind driven: wind moving over the water cools it and also causes evaporation, leaving a saltier brine. In this process, the water increases in salinity and density, and decreases in temperature. Once sea ice forms, salts are left out of the ice, a process known as brine exclusion.^[21] These two processes produce water that is denser and colder (or, more precisely, water that is still liquid at a lower temperature). In the North Atlantic Ocean, the water becomes so dense that it begins to sink down through less salty and less dense water. (The convective action is not unlike that of a lava lamp.) This downdraft of heavy, cold and dense water becomes a part of the North Atlantic Deep Water, a southgoing stream.^[22] Very little seaweed lies within the current, although seaweed lies in clusters to its east"

Explanations seem to vary slightly

The most prolific producer of deep water in all oceans is a region south of Greenland in the North Atlantic, where several major surface currents converge. Here, the warm salty Gulf Stream converges with the cold, not-so-salty East Greenland and West Greenland Currents. These merging surface waters sink for two reasons. First, "down" is the only place they can go. The second reason is more subtle. Because the lines of constant density on a T-S plot are curved , when waters of the same density but different temperatures and salinities are mixed, the resulting water mass is denser than either of the original waters. So the denser mixture would tend to sink even if it wasn't being forced downward by the convergence. This sinking of merging surface waters is sometimes referred to as caballing. The water mass produced by these converging currents south of Greenland is called North Atlantic Deep Water. It is produced so abundantly that it fills most of the Atlantic Ocean. The North Atlantic Deep Water flows southward beyond the equator and all the way to the Antarctic Circumpolar Current, which mixes with it to produce another water mass, called Common Water. This mixture is carried by the Antarctic Circumpolar Current around the Cape of Good Hope into the Indian Ocean, and around Australia and New Zealand the Pacific, where it fills most of these two oceans as well.

Courtesy “Exploring Ocean Science†by Keith Stowe. (second edition)

I think I would need some compelling evidence to convince me that the status quo is under serious threat.

Edit.

I should have added that as density is dependant on temperature and salinity this can't be ruled out if there is a major change in either of the latter.

Edited September 9, 2010 by weather ship

[Guest]

I don't know if this of interest.

Thermohaline Catastrophes

and the Younger Dryas

During the most recent ice age, the North Atlantic component of the Global Thermohaline Conveyer was partially shut down and the ocean is thought to have operated in a different mode to that of the present day. The northern North Atlantic was considerably cooler and the transport of the North Atlantic current (the northward extension of the Gulf Stream) much reduced. The North Atlantic component of the conveyer was reactivated at the end of the most recent glaciation, at about 14,000 years BP.

Recent research on deep-sea sediment cores has shown that this reactivation of the conveyer was not without hiccups! Part of this conveyer stopped abruptly at about 11,000 BP -a period known as the Younger Dryas^. This led to a catastrophic cooling of the North Atlantic region and caused the build up of small glaciers in the British mountains in what geographers call the Loch Lomond glacial re-advance, This cooling only appears to have lasted a few centuries, but it developed very rapidly over decades. There are several theories about what exactly led to the shut down of the conveyer. One view is that a sudden influx of fresh melt-water from the Laurentide ice sheet into the North Atlantic could have stabilised the vertical stratification and reduced the rate of formation of North Atlantic deep cold water. This, in turn, could have shut down the North Atlantic conveyor circulation, resulting in a cooling of the surface waters of the northern North Atlantic. The effect of changes in fresh water fluctuations on the thermohaline system is an example of positive feedback. The fresh water input weakens the thermohaline circulation, which makes the circulation more susceptible to further weakening. This process has been investigated in recent years using mathematical models of ocean circulation. The models show that there are a number of different states of the thermohaline circulation, some of which are stable. There are, however, transitions between stable states, which occur over periods as short as 40 years. It has been speculated that the present North Atlantic Ocean may be close to one of these transitional states, of which the Younger Dryas is an example. One study has suggested that the transition between states is not necessarily symmetrical. The change from strong to weak thermohaline circulation may be more rapid (40 years) than the re-establishment of the strong circulation (500 years). Further study of the Younger Dryas and similar events in the palaeoclimate record may give us important clues to the likely response of the present-day thermohaline circulation in the North Atlantic to global warming. (Remaining stable or flipping to another state).

Source: Oceanography-an illustrated guide, C.P. Summerhayes and S.A. Thorpe.

To think BP may affect the set up is to my mind laughable.

And as I understand it, (may be wrong) the Laurentide ice sheet was pretty big, covering a fair part of North America and a large proportion of water was held in lakes within the glacier so that when the walls of the glacier finally melted it meant a relatively sudden surge of fresh water with the dam being breached. To get the same amount of fresh water into the Atlantic today would, I presume, melting a good portion of the Greenland ice cap which is likely to take time.

I do wonder though about the start of the Ice Ages in the first place - If the mid Atlantic Ridge were higher, could this possibly have disrupted the currents, then the lowering of it allowed them to resume again bringing more warmth and melting them again? Don't forget that the sea level was some 300 metres lower than what it is today.

Interesting to compare the different depths on the Atlantic current charts and we see that as we drop down about 1,000 metres or so, the continental shelf extends from the British Isles right through to Greenand.

[summer blizzard]

And as I understand it, (may be wrong) the Laurentide ice sheet was pretty big, covering a fair part of North America and a large proportion of water was held in lakes within the glacier so that when the walls of the glacier finally melted it meant a relatively sudden surge of fresh water with the dam being breached. To get the same amount of fresh water into the Atlantic today would, I presume, melting a good portion of the Greenland ice cap which is likely to take time.

I do wonder though about the start of the Ice Ages in the first place - If the mid Atlantic Ridge were higher, could this possibly have disrupted the currents, then the lowering of it allowed them to resume again bringing more warmth and melting them again? Don't forget that the sea level was some 300 metres lower than what it is today.

Interesting to compare the different depths on the Atlantic current charts and we see that as we drop down about 1,000 metres or so, the continental shelf extends from the British Isles right through to Greenand.

The ice age began when the Isthmus Of Panama rose and connected Mexico to South America, this forced the ocean currents to head north providing precipitation which turned to snowat high lattitudes and thus the cycle continued until most of the northern hemisphere was under ice.

[knocker]

As I understand it this isn't about another ice age but whether global warming is affecting the the very important convergence zone south of Greenland. If so it would of course lower temps in north west Europe somewhat. The $64,000 question is this going to happen? Or indeed is happening. It creates circular discussions (elswhere in another thread where one could actually age years reading it) and in my very humble opinion you could yap about this for weeks without as yet coming up with an answer. But it certainly is a possibility.

[Guest]

As I understand it this isn't about another ice age but whether global warming is affecting the the very important convergence zone south of Greenland. If so it would of course lower temps in north west Europe somewhat. The $64,000 question is this going to happen? Or indeed is happening. It creates circular discussions (elswhere in another thread where one could actually age years reading it) and in my very humble opinion you could yap about this for weeks without as yet coming up with an answer. But it certainly is a possibility.

D'accord, but imagination is a wonderful thing and to an extent all this theorising is what drives us.

Edited September 10, 2010 by mike Meehan

[Met4Cast]

I've just come across these links. Perhaps not 100% relevant, but it all ties in all the same.

http://www.rightsandwrongs.co.uk/climate/95-general/2511-climate-little-ice-age-forecast-for-northern-europe

http://www.dailymail.co.uk/sciencetech/article-1267757/Britain-facing-bitterly-cold-winters-drop-solar-winds.html

[weathe20]

I've just come across these links. Perhaps not 100% relevant, but it all ties in all the same.

http://www.rightsand...northern-europe

http://www.dailymail...olar-winds.html

YES! It must be true, this will be the coldest winter for centrys coming up!...........The Daily Mail are always so so right!!!

lol

[johncoolj]

check out this blog what do you think

http://globalcoolingnewiceageuk.blogspot.com/

[Met4Cast]

YES! It must be true, this will be the coldest winter for centrys coming up!...........The Daily Mail are always so so right!!!

lol

Please, quote me where I said "It WAS going to happen" because I don't remember saying it. I simply posted some links which could tie in with what others have been talking about.

P.S. Check your spelling for "Centuries"

[BristolBlizzard]

Please, quote me where I said "It WAS going to happen" because I don't remember saying it. I simply posted some links which could tie in with what others have been talking about.

P.S. Check your spelling for "Centuries"

thanks for the links , would be a dull forum if no one posted :0)

Edited September 10, 2010 by cityatnight2001

[eyeofthestorm]

http://polar.ncep.noaa.gov/ofs/viewer.shtml?-natl-cur-0-large-rundate=latest

Looks like it is weakening further.

http://i82.photobuck...urr20090820.png A reminder of how things looked last year

As someone else pointed out, the 200m charts are irrelevant. It is the surface velocitys which carries the warm waters towards the UK. It is not until it heads back down from the arctic regions does it begin to sink

Type latest in the box for the current run

People who blame BP seem to add the loop current is broken, but if I am reading it right the loop current seems to be functioning fine. It is further up the stream the chaos begins, and of course further down the stream too. It would be good idea to keep a daily eye on the ocean models to see how things play out.

Edited September 11, 2010 by eyeofthestorm

[GulberwickWeather]

Hmmm, certainly seems to peter out south of Greenland. Ive also read somewhere that not only has the NAD halted but so has the Norwegian Coastal Current, any firm news on this?

[blitzen]

Norway current looks a lot 'healthier' on this run. Slight improvement all round I would say?

http://polar.ncep.noaa.gov/ofs/viewer.shtml?-natl-cur-0-large-rundate=latest

Edited September 11, 2010 by Blitzen

[weathe20]

Please, quote me where I said "It WAS going to happen" because I don't remember saying it. I simply posted some links which could tie in with what others have been talking about.

P.S. Check your spelling for "Centuries"

I cant quote you because YOU didnt say it was going to happen. This was not aimed at you..come on get a grip. Its the DAILY MAIL, they do it every year about a dooms day prediction of bad winter weather.

Surely you could tell my comment was about the DAILY MAIL not you...lol. I dont even mention what YOU may think about the subject..drrrr

Thank you for posting the links, the Daily Mail is always good for a laugh.

Edited September 11, 2010 by weathe20

[snowlover2009]

I cant quote you because YOU didnt say it was going to happen. This was not aimed at you..come on get a grip. Its the DAILY MAIL, they do it every year about a dooms day prediction of bad winter weather.

Surely you could tell my comment was about the DAILY MAIL not you...lol. I dont even mention what YOU may think about the subject..drrrr

Thank you for posting the links, the Daily Mail is always good for a laugh.

haha not.... didnt sound like you were laughing when you first responded. (rolles eyes)!

[Turnedoutniceagain]

http://www.dailymail.co.uk/sciencetech/article-1267757/Britain-facing-bitterly-cold-winters-drop-solar-winds.html

From last April ??

[blitzen]

Latest update and it's gone again!

http://polar.ncep.noaa.gov/ofs/viewer.shtml?-natl-cur-0-large-rundate=latest

[The Future]

Latest update and it's gone again!

http://polar.ncep.no...-rundate=latest

Hi everyone, first post.

The temperature seems to be dropping quickly to our north. Is that normal and are we seeing the first signs of the lack of current on SSTs?

Looking at the various depth options, it seems the flow does not want to cross the Atlantic at the moment.

Edited September 11, 2010 by The Future

[blitzen]

Hi everyone, first post.

The temperature seems to be dropping quickly to our north. Is that normal and are we seeing the first signs of the lack of current on SSTs?

Looking at the various depth options, it seems the flow does not want to cross the Atlantic at the moment.

Hi and welcome! Yes, you're right that it's not crossing the Atlantic at the moment. Not sure if it is having any effect on the sea temps tho' There are plenty of more knowledgeable people on here who can advise you about this. Keep watching the thread and the answer will turn up!

[johncoolj]

[thethe chart thats up here from last year and the one up now shows the gulf stream is allmost 90 percent less then it was

is this normal

does it happen from time to time this looks strange to me