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A temperature color mapping of the effects of a closed Bering Strait. The northern Pacific cools while the northern Atlantic warms significantly enough to bully Norther American climate.  (Source: Nature/UCAS)

The unassuming 53 mile Bering Strait hardly seems like the type of geological formation that would cause this kind of trouble.  (Source: Wikipedia commons)
It comes down to one little strait and some really big sheets of ice.

The Bering Strait, spanning a distance of approximately 53 miles between Alaska and Russia, looks like an unassuming place for temperature regulation for the entire North American region (including Greenland), but recently published NCAR/UCAR findings seem to indicate that it may be very geologically important.

The strait serves as a gate for cooler, less salinized water from the Pacific to flow to the warmer and saltier Atlantic. Their simulations found that without this flow, the climate of North America fluctuates much more rapidly – in the span of a few thousand years rather than some tens of thousands – and helps explain constant temperature and ice sheet modulation between 116,000 and 34,000 years ago, a time of constant ice sheet advance and retreat.

In the past, this pattern was often attributed to the Earth’s position along its 95,000 year orbital pattern, but the NCAR researchers found that when correlated with the temperature and ice data, the orbit could not explain the rapid fluctuations. Instead, it occurred to them that changes to the Bering Strait itself could have a large impact on the entire region due to the changes it would bring to the Pacific and Atlantic ocean currents. Their models indicate that a slight change in the strait would adversely affect the meridional overturning circulation, an ocean current which helps drive the Atlantic tropics-to-polar heat pump.

In the simulation, they show that around 110 to 115 thousand years ago, the northern climate cooled sufficiently to create giant ice sheets over the northern regions of North America and all of Greenland. As these ice sheets sucked up water from the global oceans, sea levels dropped by as much as 100 feet. Eventually a vast amount of the strait was no longer able to pass water – the average depth of the strait is 100 - 190 feet. The new land bridge cut off a vast portion of the ocean flow between the Pacific and Atlantic. This, in turn, caused the Pacific ocean to become even cooler and cleaner, but allowed the now saltier waters of the Atlantic to push the meridional overturning circulation into overdrive, warming the regional ocean, North America and Greenland by as much as 1.5C over a few thousand years.

Next, the regional warming caused the iced sheets to melt over another few thousand years, returning the oceans to their previous depth and reopening the Bering Strait. With the Atlantic’s access to cooler and cleaner water from the Pacific restored, the cycle started all over again.

These temperature oscillations went on like a driver overcompensating for an icy road fishtail until finally, around 34,000 years ago, the Earth’s distance from the sun was so great that it literally froze the fluctuation in place. About 10,000 years ago, the Earth had finally gotten close enough to the sun again to warm up the northern hemisphere to the point where the strait reopened slowly and the temperature variations settled into a much more docile animal.

This study helps to provide convincing data for two things: that a significant change in something even so geographically small can adversely affect the climate of an entire quadrant of hemisphere, if not an even greater area, and that the planet has its own regulatory devices to deal with such things. However, it remains to be seen how long the cycle would have gone on if not for the fortuitous position in the orbital cycle. Too, this study reflects nothing at all of man’s influence on these climate systems in current times. The key to understanding these things lies in first understanding the basic driving forces behind climate systems and the NCAR study has shown us how one such small system may operate.



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RE: Makes sense to me
By porkpie on 1/12/2010 9:30:56 PM , Rating: 4
"Modern humans" haven't existed for the blink of an eye as far as the planet is concerned. Your comment is pointless. Plenty of other life existed on the planet when CO2 levels were 5 or even 10 times higher than today. In fact, those periods were the most fertile and ecologically diverse ones in the planet's history. CO2 is good for the environment.

Saying that we "can't compare climate" between the Devonian and today is just a way of sticking your head in the sand. The fact is that CO2 has never before caused runaway warming , no matter how high its been.


RE: Makes sense to me
By ArcliteHawaii on 1/13/2010 4:04:53 AM , Rating: 2
Porkie, thanks for making my point for me. Exactly, plenty of life existed when CO2 levels were higher, but not HUMAN life. As for the claim that the world was more fertile and diverse 200m years ago, back it up with cites. Temps on average were higher, Pangaea meant that temps were more evenly distributed and much of the land was covered in jungle. That's all well and good. The Amazon has the most diversity on the planet. However, jungle soil is among the poorest to grow in:

http://users.rcn.com/jkimball.ma.ultranet/BiologyP...

Also, explain what you mean by the phrase "runaway global warming". Define it with metrics, or else no one knows if you mean that temps will rise by 5 degress or 500 (the Venus scenario).


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