The purpose of this paper is to investigate whether global warming could affect the thermohaline circulation cycle (THC) significantly enough that it could even shut it down and thus cause a shift in the climate of Europe severe enough to cause another Little Ice Age. To answer the question about whether global warming could cause another ice age, I have divided this paper into segments. The first will explain what the thermohaline circulation cycle is. Next, I will look at the last interglacial period and observe what the conditions were like especially in respect to the THC. I will look at how the last interglacial led to the last great Ice Age, and the sudden demise of that Ice Age, as well as the nearly equally sudden cooling that occurred in the Younger Dryas about 12,000 years ago before the warming resumed in earnest shortly thereafter. In the final part of this paper I will look at two different predictions of what could happen as a result of the melting of the North Atlantic region's ice sheets with respect to the THC and how it could affect the regional climate in Europe.
What is the thermohaline Circulation Cycle?
The thermohaline circulation cycle (THC) delivers heat to the North Atlantic. In the winter the heat from the water is released into the eastward moving air masses like the Gulf Stream, thereby warming much of western and northern Europe. Cooling in the North Atlantic increases the density of the 'upper ocean water' to the point at which it becomes so dense that it sinks to the bottom and flows south towards the Antarctic, forming the 'lower limb' of this conveyor belt of North Atlantic Deep Water (NADW) (1583 Broecker).
Figure 1 (9.8, Principles of Environmental Science, 198 Cunningham)
This 'limb' extends past the tip of southern Africa, joining the 'raceway' which brings deep water from Antarctica north. This 'raceway' is also fed by newly generated deep water that cascades down along the margins of the Antarctic continent. It is dispersed north to the Indian and Pacific Oceans. This particular input of deep water from Antarctica is the main supply for the Indian and Pacific Oceans, for it is too warm in the former, and not saline enough in the latter to generate their deep water (1585 Broecker).
The Last Interglacial
During the last interglacial period (otherwise known as the Eemian Period; look to Table 2.4 for key terms), the volume of heat to Europe increased due to the enhancement of THC, which also produced a steady stream of moisture to feed the growing northern glaciers. The North Atlantic Current (which brings warm air to Europe) was also stronger than today for most of this period.
Heat flux to the Nordic seas was greater and more variable. A strong east/west gradient existed during the early part of the warming cycle between high temperatures in the Norwegian Sea and correspondingly low temperatures in the Icelandic Sea. With the intensification of the warm interval, as...