The Role of the Ocean

We have seen previously that the amount of CO2 (carbon dioxide) during peaks of glaciation was 2/3 of the normal levels. Since the ocean is the biggest reservoir of CO2, it is tempting to think that the ocean can play a role in the change of climate. A recent theory, see article in Scientific American , gives the ocean a major role in driving glacial cycles. Here is a summary of it.

A current in the Atlantic moving north at intermediate depths (several hundreds of meters below the air/water interface) reaches the latitude of Iceland and moves toward shallow depth. In doing so, it releases heat. Indeed, this warming effect due to the current is as much as 30% of the solar heat reaching this region of the North Atlantic. As it cools, this water becomes heavy and the current sinks rapidly into the depth of the Atlantic. The amount of water flowing is large, about 20 times the combined flows of all rivers. This "conveyor belt" is responsible for the relatively warm conditions in Western Europe during winters.

A change in the salinity of the water, for example due to changes in the atmospheric pattern of air currents, might produce large effects (example of non-linearity in the atmosphere-ocean system). If the water traveling north in this current that we mentioned above doesn't have enough salinity, it will not sink into the Atlantic and the "conveyor belt" will be shut off. Thus, there won't we an effective transport of heat, and the northern regions will cool followed by the advance of glaciers. Eventually, a change in the average temperature, as due to astronomical causes, could produce, as detailed in the Scientific American article, a change in the salinity of the water and in the restarting of the "conveyor belt".

This page was produced by Gianfranco Vidali.