Paleoceanographic and climatic teleconnections between the subarctic and subtropical North Atlantic during the last interglacial (MIS 5e)

• Main Author: Zhuravleva, Anastasia
• Format: Thesis
• Language: English
• Published: 2018
• Subjects: Greenland; East Greenland; Labrador Sea; Nordic Seas; North Atlantic; Subarctic
• Online Access: https://oceanrep.geomar.de/id/eprint/44461/; https://oceanrep.geomar.de/id/eprint/44461/1/Zhuravleva_2017_Dissertation.pdf; https://macau.uni-kiel.de/receive/dissertation_diss_00023531

The last interglacial, MIS (Marine Isotope Stage) 5e, lasting from about ~129 to 116 ka, holds important implications for the projected global warming, as this geological interval is believed to have been significantly warmer-than-preindustrial. This thesis refines the current understanding of the MIS 5e paleoceanography in the subarctic and subtropical North Atlantic, providing new insights into ice-sheets dynamics and cross-latitudinal climatic teleconnections. For this purpose, a multi-proxy dataset comprising stable isotope compositions, foraminiferal assemblages and lithic as well as X-ray fluorescence data was produced using marine sediments from the Nordic Seas and the Bahama region. Several lines of evidence from the Nordic Seas suggest a strong sea surface freshening that persisted in the region until mid-MIS 5e (~125 ka). Comparison of published data from the Labrador Sea with the new records from the East Greenland margin provides evidence for a millennial-scale sea surface cooling and reduction in vertical water convection during early MIS 5e (at ~126.5 ka), which appears to follow a meltwater discharge event attributed to the Greenland deglaciation. A multiproxy dataset from the Bahama region further reveals a comparable cooling event as found in the high northern latitudes during early MIS 5e. The cooling was associated with a sudden southward displacement of the Intertropical Convergence Zone, in relation to a temporary reduction in deep-water formation. These observations lead to the inference that the persistent high-latitude freshening and unstable deep-water overturning during early MIS 5e accounted for a particularly sensitive climatic regime, resulting in the abrupt cold-warm switches which could be traced across various oceanic basins.