North Atlantic Drift

Just to get your thoughts on the possibility of the North Atlantic Drift shutting down.

I've seen a scientic documentary that claims because of the rise in global temperature the big iceflow in Greenland in rapidly shrinking, more & more each year & this is also happening in Siberia to another huge iceflow.

The result of this is millions of litres of fresh water pouring into the northern atlantic. The affects the salinity of the water & prevents something else happening (not entirely sure of the process)

That situation would probably not be very good for Europe but any thoughts on the feasibilty of that? Effects, if any?

If you're talking about the Gulf Stream which keeps places like Ireland and thew island of Britain temperate ... then if it shuts down -it will get rather cooler here - probably quite quickly....

It has happened before, at the end of the last ice age. If I remember correctly there was a large (more like massive) lake of glacial meltwater that collected in the area of the Great Lakes - but which was far larger than all of them combined and then some! When that water finally broke through the remaining ice walls that imprisoned it, it hurtled out to the North Atlantic, carving out parts of the St Lawrence channel at the same time. That amount of cold fresh water would have triggered a shutdown of the Gulf Stream, and the Ice Age had a brief resurgence in the area.
(Shivers) I hate being cold...

But seen as how average temperatures globally have been rising surely it wouldn't cause something as bad as ice reaching down as far as Ireland, would it?

I've seen satellite pictures of northern europe & the reach of winter snowline into Europe seems to be rapidly retreating every year

Darkmind is right - a shut down of the North Atlantic Drift (NAD), due to a sudden influx of fresh water, is thought to have caused or been a contributory factor in both the Younger Dryas (YD) and the '8,200 yrs ago event'.

The latter is perhaps a more realistic indication of what may happen should the NAD switch off again since, at the time of the YD, there were still extensive ice sheets in N America and Europe. There aren't any now. So don't go expecting glaciers in Londin However we could experience similar condition sto the Little Ice Age (LIA) - when the Thames used to freeze over each winter.

Probably we'd be looking at colder winters but with little change to our summer. Given that, in the UK anyway, winters of late have been well on the mild side (perhaps a consequence of Global Warming) then we may even just be looking at a return to the winters of the 70s and 80s - the good ol' days when heavy snow meant more than half an inch.... (I well remember the sea freezing off the Essex coast back in '81/2 )

It wouldn't be catastrophic. But it would be inconvenient.

Originally posted by sepryo
But seen as how average temperatures globally have been rising surely it wouldn't cause something as bad as ice reaching down as far as Ireland, would it?

Making any prediction of the oputcome if the NAD shut down would be pure speculation.

Without the NAD, what happens to the Gulf Stream? The warm water near the equator will certainly mix somehow with the cold water from the north. Whether or not this will form some different current, or system of currents, can't possibly be known. So the direction of flow of the warm and cold waters cannot possibly be known.

Could have glaciers in Ireland, could have temperate beaches (and boat drinks!) there.

I'd agree with the poster that equated the scenario with that of the little ice age. But let's not forget, the little ice age was exceptionally cold. Much colder than the winters of the 70's. The little ice age recalls the winters of Currier and Ives, Saint Nicholas, and the others, that have today shaped the advertising industry's view of the old-time, good-ole, family-time, roasted chestnut and hot toddy Holiday winter. This sort of winter hasn't existed for around a hundred years now.

Probably if it happens, we'll see a shift in ad campaigns, harkening back to the "good ole, homestyle, familytime winters" when we didn't really have to shovel snow every week. You know, the kind that we are fortunate to have today. The kind that people are constantly trying to worry us about today.

Harte

So basically no-one knows for sure what might happen but best bet is colder winters & more snow? Can definitely live with that, was thinking it might get a bit crazy if we started seeing icebergs around the place, especially as polar bears have a tendancy to wander about

The reinsurance industry is starting to run some scenarios about this at the moment. They handle insurance for insurance companies and believe me they have a vested interest in making sure that they lose as little money as possible. At present the worst case scenario is for ice floes in the North Sea. Brrrr.

Should have known they're be an insurance company in there somewhere, suppose they have to keep an eye on future scenarios though. Be interesting to know what factors they took into account

Originally posted by sepryo
Should have known they're be an insurance company in there somewhere, suppose they have to keep an eye on future scenarios though. Be interesting to know what factors they took into account

Reinsurance companies have their eye on a lot of potential threats. Like I said, they have to, otherwise they end up paying large amounts of money. The asbestos crisis nearly killed Lloyd's of London, it was that bad.
As for global warming, Swiss Re is one of the leaders here. You can access what they have at www.swissre.com and look up what they have in the publications section of the website. Or you can go into their media centre and enter 'global warming' into the search function.
They did something very scary on nanotechnology a year and a half back.

These guys really cover the bases, suppose that's their business but still they really go for it.

Thanks for that Darkmind, should keep me occupied for a while.

Originally posted by sepryo
These guys really cover the bases, suppose that's their business but still they really go for it.
Thanks for that Darkmind, should keep me occupied for a while.

You're welcome. I write about the reinsurance market, so I have a great - even if a bit scary at times - job! I write about global warming, natural catastrophes (volcanic, earthquakes, tsunamis, hurricanes etc) and everything else under the sun. The odd thing is that I love my job!

Originally posted by sepryo
But seen as how average temperatures globally have been rising surely it wouldn't cause something as bad as ice reaching down as far as Ireland, would it?

Even if the climate in general is warming, the heat input of the north atlantic drift is greater, for that british isles. So if you shut it down, despite there being global warming, there will still be a large net decrease.

essan
It wouldn't be catastrophic. But it would be inconvenient.

You'd be fundamentally changing the climate in the british isles, making it more like northern canada.

harte
The warm water near the equator will certainly mix somehow with the cold water from the north

Perhaps, but it wouldn't mix at such high lattitudes.

Darkmind - Sounds like a great job, very interesting, I'm just curious about things.


Worst case scenario here:
We'd be snow bound for at least 3 months of the year, ports would be frozen over, inaccessible?
Most native flora & fauna would die including large amounts of people?
Very hostile winters basically.
Something akin to the little ice age awhile back?
Am I being too pesimistic there?

Also how long would these changes need to take place? Badly worded but say the current stops in Spring 2007 would the winter 2007 be worst than anything seen in the last 25-30 years?

So far all the data we're seeing is for a gradual slowdown, but that doesn't mean that we might not get a sudden shut-off. Don't forget, we're at the same latitude as Newfoundland and the southern parts of Alaska, so we might get worse winters but no dramatic cooling over summer.
Sea ice is the area where the scenarios get unpleasant. The North Sea is very shallow, so there is a good chance of more sea ice - not enough to block access to the ports, but certainly enough to be a hazard to shipping, not to mention the oil rigs. Maybe even ice floes as far south as the channel, which would make the place even more of a menace to shipping than it already is.
The ironic thing is that the shut-down of the Gulf Stream would ease fears over the status of the methane hydrate deposits off the coast of Norway. Someone was scannning the sea bed a decade or so ago and discovered these immense holes in the seabed. It turned out that they used to be where methane hydrates had destabilised and rushed to the surface. There are more methane deposits near by. The warmer the sea gets, the more unstable they become - and methane is a far worse greenhouse gas than CO2!