Thursday, December 22, 2005

Salt: Its role in preventing global warming

If "Meridional Overturning Circulation" isn't a familiar term, perhaps the more popular concept of the "conveyor belt" describing how the Gulf Stream heats the North Atlantic (and keeps Europe from entering a new ice age) is more familiar. A series in this week's Philadelphia Inquirer examines the crucial role of the Gulf Stream with regard to global warming. While many understand the importance of oceanic circulation, Inquirer staff writer Anthony R. Wood reminds readers: "A critical ingredient in the recipe for climate change is one of the most prosaic and plentiful substances on the planet: salt." He points out that understanding the "subtle but important " differences in the relative densities of salt water and fresh water is "the key to keeping the conveyor belt in motion." The warm Gulf Stream consists of more highly saline water evaporated by the hot sun in the tropics and it eventually sinks below the less dense arctic water in its path. If the salt sinks sooner, the prevailing west winds that transfer the warmth of the Gulf Stream to Europe will have less warmth to transfer and Europe will revert to temperatures more associated with its northerly lattitude. If "global warming" melts the Greenland ice pack, releasing more fresh water, it can affect the rate of salt sinking, perhaps changing the geography of the Gulf Stream itself ... and triggering dramatic cooling in Europe. Whether or not global warming is a short- or long-term phenomenon, experts still debate, but there's no debate that salt plays a crucial role.

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