This blog is to store what I consider to be important - or weird - stories about health and science. To read these, you will need the Adobe Reader; you may download it at: http://www.adobe.com/products/acrobat/readstep2.html Be sure to check out my political blog at: http://larblog.blogspot.com Welcome to my friends from LeftWingRadicals!
Thursday, February 24, 2005
Back in April, 2004, NASA was remarking about the slowdown in the ocean conveyor. For months now, it's been the same refrain, and for months now, I've noted that with the large influx of fresh water that resulted from Lake Ellsmere draining into the North Atlantic and with the warming of the North Atlantic
Now, couple this is a cooling of the Southern oceans and a reduction in their salinity (link), and what you get is a reduction in the energy available to power to ocean conveyor.
It works this way normally: As water warms in the Southern ocean, it rises as it heads toward the North Atlantic. Because the salinity of the two areas is about the same, it rises smoothly (relatively), thus drawing more water with it. As it rounds Florida, heading North (the Gulf Stream), it starts dumping heat, since it is now closer to the surface and a lot warmer than the surrounding water. This salt water column, then cools off as it crosses south of Greenland, and as it now flows past Europe, it dumps the last of its heat and drops. This drop of so many billions of gallons of water acts as a 'pull' to all of that water behind it, and pushes the water in front of it. As it sinks to the ocean bottom and heads south, it carries nutrients and waste down. In the Southern ocean, even though it's at the bottom of the ocean, it starts picking up heat and starts rising, picking up more heat. And the cycle starts again.
However, if the Southern ocean is cooler, it doesn't pick up as much heat, so the water doesn't rise as fast or as powerfully. When the current finally gets to the coast of the U.S., off of Maine, it is not as warm is it previously was, so it doesn't have as much heat to give off. This leaves the northern hempishpere, and in particular, Europe, cooler, since the prevailing winds aren't picking up as much heat to distribute over Europe.
Now, couple this with the fact that the North Atlantic has more fresh water, and thus a lower salinity, and even though the water cools while going around Greenland, the fresh water is not as heavy as salt water, so it doesn't since as fast. (link to salinity article)So, like a train of a slight hill, vs. a train on a steep hill, it doesn't get going as fast downhill, and this reduces the speed of the current. As the current is reduced, and the water stays away from the bottom, as it gets to the Southern hemisphere, it is warmer than before, and this coupled with the cooler ocean, means that it doesn't warm as much - as a percentage of original temperature, so it won't rise as fast, nor will it rise as far, because it is close to the surface.
Eventually, the roller-coaster track of the current becomes level, thus ending the conveyor. This means that no warm water flows North (or very little) and Europe is subject to the might of the cold blasts from the Arctic.
This is what we are already seeing.
The conveyor, even though you don't hear much about it, is coming to a stop, and it is doing so in a time frame that scientists thought could never be.
Can you say, "Brrrr!"
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