Ok
Did you study the ocean currents a bit during your thesis, I suppose?
Seen on:
http://fr.wikipedia.org/wiki/Gulf_stream
Possibilities of disappearance of the Gulf-stream
For more than a million years, the Earth has known a succession of glaciations and inter-glacial periods, with a periodicity of 100 years. Each of these periods lasts roughly 000 years with transitions of approximately 10 years. It was found, thanks to ice samples in Antarctica, that the CO² rate in the atmosphere varied with temperatures. It oscillated indeed from 000 ppmv during glaciations to 40 ppmv in inter-glacial periods (000 ppmv is one part per million in volume, that is to say 180 cm³ per m³ of air). We have been in an inter-glacial period for 280 years today. Everything suggests that the next glaciation is not far away.
However, with human activities, the level of CO² in the atmosphere reaches 370 ppmv, a level never reached in the last million years. Its growth accelerates and becomes exponential, so that in 2050, it should reach 700 ppmv, and have thus doubled. Without forgetting methane, resulting from the digestion of ruminants and marshes and rice fields, which is also a greenhouse gas, and which is also increasing rapidly. We already know that the temperature has increased by 0,6 ° C in 10 years, on the surface of the globe; and that by expansion of hot water the level of the oceans rises (the melting of continental glaciers cannot induce a quantifiable rise in the oceans).
But on the North Atlantic, another phenomenon, linked to global warming, is lying in wait. The greenhouse effect is melting Arctic glaciers, but also increasing rainfall in the North Atlantic. These two phenomena combined are at the origin of a supply of fresh water to this region. If ever the latter were to be too large, as was the case at the start of the last ice age (around 11 BCE: glaciers are melting in North America, releasing the waters of immense lakes which cool the currents marine and produce a general cooling of the Earth's climate), then the Gulf Stream could disappear. Indeed, a large supply of fresh water would increase the differences in water salinity between the equator and the Norwegian Sea. The place of diving of warm and salt water would be found at the level of the Azores; and the Gulf Stream would fold in on itself, no longer going beyond the Azores.
This climatic upheaval would be very rapid: in less than 10 years, the temperature of all of Western Europe (from Portugal to Finland) would drop by 5 ° C. When we know that average temperatures drop by one degree Celsius every 500 km of latitude, we would find the climate from Oslo to Madrid. But this cooling would be much more marked in winter than in summer, because the ocean jet stream would bring directly to Europe, the climate of Canada. Bordeaux, which is at the same latitude as Montreal, could regularly have temperatures of -25 ° C in the middle of winter. This climate change would be so rapid that it is called "climate surprise". This would be the brutal arrival of a glaciation on Western Europe, with extension of the glaciers. But in reality, it would not be one, since on all the rest of the globe, the greenhouse effect would continue to raise temperatures, melt glaciers, and rise the sea. What would happen on Western Europe would therefore be very localized, but would favor the development of European winter sports. Indeed, in Europe, glaciers would expand, while elsewhere, they would melt! This is why, the sea level would continue to rise, despite this local cold snap. In true glaciation, it would have been 100 meters lower.
However, this theory needs to be verified, hence the use of the conditional. For the moment, this brutal local climate change is envisaged for the second half of the XNUMXst century.
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