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Rekonstruktion der Atlantischen Zirkulation innerhalb des letzten Glazialen Zyklus

Böhm, Evelyn

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The climate of the last 150 kyr is mainly driven by orbital forcing leading to long-lasting glacial conditions framed by the short warm periods Eemian and Holocene. To understand this climate variability it is crucial to investigate the response of the Atlantic Meridional Overturning Circulation (AMOC) on the insolation and the consequent effect it has on the climate by redistributing heat and CO2. However, the mechanisms that determine changes of the AMOC are poorly understood within the investigated time period. In this study the strength and direction of the AMOC is examined by temporal high-resolution measurements of the two proxies 231Pa/230Th and eNd from the marine sediment core ODP 1063 which is situated in the North West Atlantic. Despite the short half life of 231Pa, significant 231Pa/230Th ratios were obtained until 134 kyr which extends the so far released scope by 9 kyr. During Dansgaard-Oeschger warm events variations in the northern deep water formation and circulation dynamics are found. Further, rarely detected Heinrich cold events from the early glacial (H7, H9 and H10) are identified. It is demonstrated that the Termination II lacks a Younger Dryas-like cold event due to differences in the summer insolation. Instead to the widely perceped view of a generally shallow and weak AMOC during full glacial conditions, a reduced circulation strength associated with northern sourced water in the deep Atlantic during MIS 4 and the early MIS 3 are found. Due to the significant difference of this pattern to the so far described circulation modes, the new `intermediate mode' is defined.

Item Type: Dissertation
Supervisor: Mangini, Prof. Dr. Augusto
Date of thesis defense: 27 February 2014
Date Deposited: 20 Mar 2014 12:04
Date: 2014
Faculties / Institutes: The Faculty of Physics and Astronomy > Institute of Environmental Physics
Subjects: 500 Natural sciences and mathematics
550 Earth sciences
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