La variabilité de la circulation océanographique globale au cours du dernier cycle climatique
Duplessy, J.-C. (1989). La variabilité de la circulation océanographique globale au cours du dernier cycle climatique, in: Denis, M. (Ed.) Océanologie: actualité et prospective. pp. 101-116
In: Denis, M. (Ed.) (1989). Océanologie: Actualité et prospective. Centre d' Océanologie: Marseille. ISBN 2-907752-00-6. 387 pp., more
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| Abstract |
During the last climatic cycle, the global deep water circulation experienced major variations, which were linked to geographical changes of the areas where winter convection was active: during interglacial conditions, the Norwegian Sea and the Weddell Sea are the more active deep water sources for the world ocean. During full glacial times, the southern ocean source was dominant. The Norwegian Sea was covered with ice during the whole year and was stratified. Consequent\y, surface water was not dense enough to sink at great depth and deep water sources were located in the North Atlantic. As this cold water was not blocked by topographic sills, the whole deep water mass of the Atlantic Ocean cooled down by about 3-4 °C; this process was responsible for a global cooling of the whole oceanic deep water realm. Increased Intermediate Water circulation between 1 and 2 kilometer water depth resulted in the presence of a water mass more oxygenated than at present. From 115,000 to 65,000 years B.P., during the inception of the glaciation, the global deep water circulation exhibited intermediate trends between modern and full glacial conditions. For instance, this pattem was characterized by Atlantic deep waters cooler than today by 1-2 °C. Carbon-14 analyses of planktonic and benthic Foraminifera show that the ventilation rate of the Pacific deep water was smaller than today, during the last ice age. However, during the deglaciation, the rate of ventilation, and probably of water circulation, dra- matically increased during a few thousand years, facilitating the mixing of the meltwater within the global ocean. |
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