Science

The Atlantic Conveyor

It is a scientific fact that the Earth’s climate is in a state of flux between Ice Ages and warmer periods. The warm period that we are experiencing now began some 15,000 years ago. There is still some debate among the scientific community as to how gradual the change between Ice Age and warm period is and also some scientists are now theorizing that the global warming we are experiencing now could in fact trigger a mini Ice Age which would affect northern Europe very quickly.

The populous parts of Europe are 10 to 15 degrees further north than those populous parts of Northern America. In fact, Rome lies on the same latitude as Chicago, which experiences very cold winters with Oslo and St Petersburg on the same latitude as Anchorage. The reason for the European climate being mild compared to similar latitudes is due to the Gulf Stream merging with the North Atlantic current then flowing up the Norwegian coast. This in effect keeps Europe about 10 °C warmer in winter than comparable latitudes. The volume of the North Atlantic Current is comparable to that of about 100 Amazon Rivers and the effect on Europe and the rest of the world if it stopped would be devastating in terms of climate change.

The North Atlantic Current, or Conveyor as it is also known, distributes its waters through the southern oceans into the Pacific and then proceeds on its return loop that runs deep under the ocean surface. The return loop is deep under the ocean surface as opposed to travelling at the surface because of temperature changes in the current. Fresh water is at its most dense at 4 °C. However, the fact that oceans are made up of seawater complicates things. Salt water’s increase in density is directly proportional to its salinity, hence the saltier it is, the faster it sinks. The Atlantic Conveyor sinks due to the increase in its salinity as its waters evaporate until they are denser than the surrounding seawater. An example of this is the Mediterranean, which is 10% saltier than the Atlantic Ocean and abruptly sinks as it emerges from the straits of Gibraltar.

One of the effects of the global warming we appear to be experiencing at present is that of increased rainfall (fresh water) into the northern oceans. Greenland’s glaciers are another large source of fresh water, the melting of which could affect the ocean density. Were the glaciers to melt, with the water being trapped in ice dams in the fjords, the eventual breaking of the dams would release vast quantities of fresh water in a short period of time. Evidence of this natural phenomenon was observed in Alaska in the 1980s.

In conclusion, it is becoming accepted amongst some of the scientific community that, as global warming proceeds, the increased fresh water that will end up in the North Atlantic could change the seawater density significantly enough to cause the North Atlantic conveyor to sink before it reaches Northern Europe and thus we would see a winter temperature drop of between 5 and 10 °C, not over a prolonged period but probably within a decade of the Conveyor stopping. This would then plunge Northern Europe into a Climate similar to Alaska.