Last Interglacial paleoceanography of the Nordic Seas based on dinoflagellate cyst assemblages

• Main Author: Van Nieuwenhove, Nicolas
• Format: Thesis
• Language: English
• Published: 2008
• Subjects: Norwegian Sea; Vøring Plateau; Nordic Seas; Sea ice
• Online Access: https://oceanrep.geomar.de/id/eprint/7207/; https://oceanrep.geomar.de/id/eprint/7207/1/2008_Van_Nieuwenhove_Diss.pdf; https://macau.uni-kiel.de/receive/diss_mods_00003116

Understanding the dynamics of a warm climate is essential in order to assess possible scenarios for future climate evolution. The last interglacial, Marine Isotopic Stage (MIS) 5e, is generally believed to have been warmer than the Holocene, under a comparable orbital configuration, and is thus a good candidate to get more insight in those dynamics. Climate is steered by the rate of overturning of warm surface waters into cool deepwaters. One of these overturning cells is located in the Nordic seas, and the area is thus a key region in terms of climate regulation. Marine sediments from three locations in the Nordic seas have been studied for their dinoflagellate cyst (dinocyst) content in order to reconstruct sea surface conditions (temperature, salinity, sea ice) during MIS 5e. In combination with stable oxygen isotope, ice rafted detritus (IRD) and planktic foraminiferal assemblage data, the variations in the dinocyst assemblage composition reflect a stepwise transition from the final phase of deglaciation (Termination II) into typical interglacial conditions, and the subsequent cooling during glacial inception towards MIS 5d. The marked presence of the neritic, warm-temperate dinocyst Lingulodinium machaerophorum towards the end of Termination II tells us that quite particular water masses entered the southern Nordic seas during the latest deglacial phases of MIS 6. A shift towards the inflow of “more Atlantic” waters and a drastic decrease in both IRD input and stable oxygen isotope values mark the start of MIS 5e. The northward heat flow remained relatively weak during the first ~4-5 kyr of MIS 5e, and at no time an east to west sea surface temperature gradient, as pronounced as at present, appears to have prevailed during that period. Quantitative and qualitative analyses of the dinocyst data from the Vøring Plateau in the eastern Norwegian Sea and comparison with core-top and published data substantiate the existence of distinctly different hydrological surface conditions during MIS 5e with respect to the ...