Paleoclimate Records Show Rapid Ocean Current Shift, 6C Temp. Increase

[hatrack]

EDIT

Flavia Nunes and Richard Norris of the Scripps Institution of Oceanography at the University of California, San Diego, wondered if the answer might lie in deep-sea sediments. These sediments contain the fossil shells of microscopic organisms, known as foraminifera, and the carbon isotope ratios in the shells can indicate whether water at the sea floor had been deep for long periods of time or had recently sunk from shallow depths.

Up until about 55 million years ago, carbon isotope ratios from samples taken from 14 sites around the globe show that deep sea currents had been generally forming in the Southern Ocean and South Atlantic Ocean and flowing northward to the Pacific Ocean. But less than 5000 years later, the currents seem to have reversed direction, the researchers report 5 January in Nature. This backward flow persisted for at least 40,000 years, and the original pattern didn't completely return for 100,000 years.

The research backs up global climate models that suggest the ancient change in ocean circulation may have warmed so-called gas hydrates on the sea floor, causing massive amounts of methane to bubble into the atmosphere, which would have in turn caused more warming on both sea and land. All told, ocean temperatures spiked by about 6 degrees Celsius. Because modern atmospheric CO2 levels are approaching those seen 55 million years ago, the team warns that people could have a long-lasting effect on deep-ocean circulation.

"Clearly there something going on with deep-sea circulation patterns," says paleoceanographer James Zachos of the University of California, Santa Cruz. But correlating specific time intervals in sediments from different oceans can be very tricky, he says. It is also difficult to say whether the modern ocean will react the same way, he notes, because of differences such as the location of continents and the growth of the Antarctic ice sheet.

EDIT

http://sciencenow.sciencemag.org/cgi/content/full/2006/104/3

Oh, and just FYI - it took 140,000 years to reverse the climate change.

http://news.bbc.co.uk/1/hi/sci/tech/4582872.stm

[glitch]

1. Trouble ahead. nt

[phantom power]

2. Raising all that WATER by 6C??

:wow:

[hatrack]

3. Yeah, that's what I said - DAY-UM!!!!

:wtf:

[Ediacara]

4. I am VERY skeptical of the claims they make

it's pretty much impossible, deep sea sediments or not, to get a resolution as fine as 5,000 years when you're looking at rocks 55 million years old. I actually laughed when I first read it. I will have to check out the paper in Science though and see what they have to say.

[Dead_Parrot]

5. Mid atlantic ridge?

One of the hazier areas of my knowledge, but can't you get fairly accurate dates by looking at changes on either side of the ridge? since it grows constantly, if you find something 100 miles from the ridge, but not 95 miles, you can pin the date down quite well. I think. I might be lying. :(