"Water, water, everywhere, and all the boards did shrink; Water, water, everywhere, nor any drop to drink."
This short excerpt from Samuel Taylor Coleridge's long poem "The Rime of The Ancient Mariner" evokes an image of the oceans that play such a central role in our planet's weather and climate systems. Just consider the fact that they cover 70 percent of the Earth's surface, with an average depth of about two miles.
After many decades of researching the oceans, scientists are slowly gaining an understanding of this role. Wally Broecker, professor of earth and environmental sciences at Columbia University, developed the concept of ocean circulation called the Great Ocean Conveyor Belt. His book, with the same title, makes for a fascinating read.
He demonstrated that there is a planet-wide circulation of water in the oceans that transports heat. The surface waters warm in the Pacific and continue on the surface to the North Atlantic. Giving up heat, as the water moves north, the surface waters cool and become dense; the cold water then descends to the depths.
This cold, barely above freezing water slowly moves south and east to the North Pacific again, where it slowly warms, rises and starts the whole process over.
This enormous, moving stream of water plays a key role in transporting and storing heat energy. This includes absorbing the extra energy arising from the increased levels of greenhouse gases, primarily carbon dioxide, which is the primary GHG and comes from the consumption of fossil fuels.
We all know how much longer a large pot of water takes to heat up than a small one. The same is true for the oceans. What is happening now is that this huge stream of water is beginning to warm, just a little.