by Frank
www.teresi.us/writing


I’ve always been sympathetic to the phenomenon of global warming. I’ve always been pro-environment, and have always tuned in closely to the possible dangers looming as a result of our bad environmental practices. But as science better understands the dangers of global warming, it seems that all they’ve done is improved their ability to showcase how horrible it can be, how quickly it can happen, and illustrate some details of how its already happening. Its pretty depressing and scary to watch those shows, so I often switch off the channel. It seems global warming was more of a vague concept a few years ago.

Nevertheless, I was watching this neat show on ocean currents the other day. I was pulled in and fascinated. Ever since people began sailing, we’ve known about surface currents. But it has only been recently that people have understood deep sea currents.

One of the most famous surface currents is the one in the North Atlantic. Between Europe and America and as far down as the Caribbean and Africa’s “arm,” there is a large, clockwise circling current which shoots warm water northward and keeps England from looking like Siberia, even though they are at the same latitude. Norway, too.

Interestingly enough, when this warm water shoots up by Greenland and hits the icebergs, there is a neat process that occurs: The warm water hits the icebergs, slides under them, cools off and because of some differences in salinity it causes a process whereby huge channels of water shoot downward like huge waterfalls in the middle of the ocean! I guess as water freezes and attaches itself to the icebergs, then you can literally see shoots of pure salt running off the iceberg, and this denser water falls downward and cools off.

Once it hits the ocean bottom, it kind of creeps along and ends up (somehow) in a belt 60 miles wide that is very near the coast of North America and continues down to South America all the way to Antarctica at a speed of like 4 inches an hour, or some amazingly slow speed. There, it picks up more water that came shooting down from Antarctic icebergs and they circle around Antarctica. Eventually, these deep sea currents split off—one travels north toward the region between India and Saudi Arabia, and the other keeps creeping and goes north just a little east of New Zealand. At some point, this cold, salty bottom water falls into those deep Pacific trenches that are several miles deep. As they go north in the Pacific Ocean, eventually their momentum dissipates in the deep trenches and the salinity differences (I think) cause the bottom and surface water to eventually mix, so this cool water comes to the surface around the equator and keeps that region from becoming too hot. Eventually, it gets caught up in surface currents that drive this water westward around India, rounding the cape in Africa, and eventually back up to the North Atlantic. I think the whole cycle can take like 2,000 years. Scientists think it’s like a huge conveyor belt, and it keeps northern regions temperate, and equatorial regions from becoming limitlessly hot.

Looking back in history, they claim there have been wild fluctuations in earth’s climate over the earth’s history... but over the last 10,000 years the climate has been virtually a straight line—very little differences. They think this fragile ocean current system is the cause.

So here’s the deal: As the earth warms up due to greenhouse gases, icebergs will be fewer in the north, or they will break up and be sparser, and as a result the whole phenomenon of water hitting them and shooting downward will spread out or at least lessen. It could be that as icebergs retreat northward, the same phenomenon could still occur, but it might disrupt the conveyor belt enough that maybe the global mixing would not occur. New currents might emerge that wouldn’t accomplish the task that currents now accomplish, or there will at least be less water driver down (due to less icebergs creating these downward watershoots). If this conveyor stopped, what would happen is that northern regions would get colder and equatorial regions would get hotter.

Scientists believe the disruption of these currents could actually bring about an ice age! There’s a twist. I guess as the second-to-last ice age was retreating, it created a phenomenally huge freshwater lake in the middle of Canada, held in place by glaciers. As glaciers retreated, there came a day when this dam eventually broke, and they claim there was a global flooding of unbelievable proportions as this lake came gushing into the oceans. They think this flooding broke up these ocean currents by sheer force and through the differences in salinity it brought—and disrupted them enough, so that we ended up with another ice age afterwards. Whoa, dude.

Fascinating stuff, I think.