Ocean circulation changes off southern Greenland during the abrupt climate events of mid-to-late MIS3

• Main Author: Griem, Lisa
• Other Authors: orcid:0000-0002-6515-6781
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Bergen 2021
• Subjects: Greenland; Dansgaard-Oeschger events; East Greenland; Greenland ice core; ice core; Ice Sheet; Nordic Seas; North Atlantic; Sea ice
• Online Access: https://hdl.handle.net/11250/2732835

Marine sediment cores from the North Atlantic and ice cores from the Greenland Ice Sheet serve as natural archives of past climate variability. Ice cores have revealed that during the last glacial period the climate comprises both relatively stable intervals such as the Last Glacial Maximum (LGM, ca. 26-19 ka) and unstable climate intervals such as Marine Isotope Stage 3 (MIS3, ca. 59-29 ka). The climate of MIS3 is characterized by abrupt changes from colder stadial to warmer interstadial conditions, well-known as Dansgaard-Oeschger events (DO). Although DO events had repercussions over the climate system outside of the high latitude Northern Hemisphere, they are especially pronounced in records from the North Atlantic region. North Atlantic marine sediments record changes in sea ice cover, surface productivity and iceberg discharge, which are all associated with DO events. Iceberg discharge from the Northern Hemisphere ice sheets, and hence release of fresh water into the North Atlantic was especially pronounced during so-called Heinrich (H) Stadials. H-Stadials occurred approximately every 7 to 10 kyrs and are particularly cold and long stadials within the DO event oscillations. The freshwater discharge further contributed to sea ice formation in the North Atlantic and Nordic Seas. This near-perennial sea ice cover during stadials prevented ocean-atmosphere interaction while during interstadials the Nordic Seas were seasonally ice-free. These interstadial periods allowed moisture to evaporate from the ocean´s surface where after it was transported towards the Northern Hemisphere Ice Sheets, and thereby sustain their growth during MIS3 and the LGM. This thesis aims to give insights into the complex interactions between ice sheets, sea ice and ocean circulation during MIS3 and the LGM. Herein, the main focus lies on changes along the South-East Greenland margin, complemented by thoroughly studied sediment core sites from the Nordic Seas and Greenland ice core records. Paper I investigates environmental ...