the day after tomorrow

[tocqueville]

http://news.bbc.co.uk/2/hi/science/nature/4485840.stm

Ocean changes to cool Europe
By Richard Black
Environment correspondent, BBC News website

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.

[niallmac]

1. A few decades? Or, the day after tomorrow?

(Cue spooky music.) Seriously, what the hell do we really know about the future of our weather or that ribbon of climate creating water, the Gulf Stream? I hope our scientists have a firm grasp on the effects of this flood of melting fresh water into the Atlantic. Pardon the pun but isn't all this simply conjecture about uncharted waters?

[mainegreen]

2. Only to a point.

The drop in salinity in the north atlantic is real and measurable. There is a line that once crossed, the gulf stream will either shut down, or divert to a different path. Most of the people I've talked with who actually have the degrees to talk about this all seem to say not if, but when.

But, until it happens, it's all conjecture.

:shrug:

[niallmac]

3. Egad!

[rman]

10. what makes you think they don't know what they are talking about?

[TallahasseeGrannie]

4. I'M CONFUSED.

This is caused by the greenhouse effect?

So global warming could end up cooling us too much?

[electron_blue]

5. Yes, bcs we lose the gulf-stream in the process, which is

the main reason it's tolerable to live in northwestern europe.

[mcscajun]

6. Yup...for more details on the paradoxical nature of it all, read this

http://www.gbn.com/ArticleDisplayServlet.srv?aid=26231

[Dead_Parrot]

7. Couple more links:

There's a BBC documentary from a few years ago on the subject (the transcript makes a good read, and explains some the research): That page links to a Woods Hole page on abrupt climate change, with some more interesting articles.

[bananas]

8. Europe will get colder, Florida will get hotter

The Gulf Stream carries heat from the Gulf to Europe. Then it cools and sinks and comes back along the bottom of the Atlantic. That cool water then gets heated up again in the Gulf.
As the arctic ice melts, it interferes with the Gulf Stream, slowing it down, so it won't warm Europe as much. And because the Gulf Stream is slower, the water in the Gulf gets hotter, causing bigger hurricanes.

(The Gulf Stream) "makes Western Europe (and especially Northern European winters) considerably warmer than they otherwise would be. For example, in January, the temperature difference between coastal Norway and northern parts of continental Canada is approximately 30 °C on average, even though they are the same latitude." (30°C is 54°F)
http://en.wikipedia.org/wiki/Gulf_stream

[mainegreen]

9. Two visuals that demonstrate the problem

Here are two images that demonstrate the problem. The first shows water density as a matter of temperature and salinity.



As you can see, as temperature increases, density decreases. As salinity increases, so does density. Currently the gulf stream has a higher salinity than artic water, but artic water still is more dense than gulf stream water because it is significantly colder.

Now look at this picture of the artic sea floor:



Notice that the artic ocean is rather like a bowl, with only one exit, denoted by the arrow? The bering straight is way to shallow and narrow to really allow for large amount of water exchange. That leaves the north atlantic, destination of the gulf stream. So all meltwater in the artic reduces the salinity of the artic ocean, and thus the north atlantic. So if the artic ocean warms, or its salinity decreases, the north atlantic will be the outflow destination for the artic currents, and thus one day, the north atlantic will eventually become to warm and/or less salty, and the line will be crossed where the north atlantic waters are less dense than the gulf stream, and will no longer sink below gulf stream waters. Hence, scandinavia is living on borrowed time.

Simple and scary.

[Orrex]

11. NPR's ATC ran a story about this yesterday

Much of the scientific community appears to be of the "we need more data" camp, noting that the samples taken to date are too few and the change between them too small to give a reliable assessment of a trend.

That's absolutely not to suggest that Global Warming isn't a real threat, but simply at present we are not justified in making sweeping predictions based on the info available.