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Phase relations between changes in the late quaternary ocean surface and deep water processes in the north atlantic


Natural rapid Late Quaternary temperature variations in the North Atlantic region punctuated the last glacial period and are linked to changes in the North Atlantic thermohaline circulation (THC). Recent evidence suggest that these fluctuations are related to variations in iceberg discharge and the input of melt water to the ocean. Temperature fluctuations have occurred also, but at a lower amplitude, during the Holocene, and will most likely occur in the future. However, the basic forcing mechanisms behind these events are strongly debated. Tracing these triggers is the main objective of the proposed work. For this purpose it is necessary to construct a high resolution record Late Quaternary phase relationships between variations in the surface water conditions and deep water formation, which are the two major components of the North Atlantic's THC. Which changes occurred first and which components contributed to a shift in the strength of the THC? Three major factors have to be taken into account
(i) sea surface temperature variations
(ii) changes in the iceberg discharge and
(iii) variations in the deep water mass intensity. These fluctuations will be reconstructed using an innovative multi-proxy approach, a combination of independent "lithic" and "biogenic" proxies. This combination is a powerful approach and new results show that such an approach is a pre-requisite for obtaining reliable paleoclimatic information. The study areas cover a long distance of the NADW pathway. The time span ranges from c.150 kyr BP to the present with a focus on the Holocene, Eemian, Termination II/I, and, more generally, on time intervals with strong insolation (July 60°N) changes. Apart from the paleoclimate emphasis, new insights in the use of different proxy types can be expected which should be important for future paleoclimatic studies.


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