Paleoceanography of the Bering Sea across the Mid- to late Pleistocene

• Main Author: Detlef, Henrieka
• Format: Thesis
• Language: English
• Published: 2018
• Subjects: Arctic; Arctic Ocean; Bering Sea; Pacific; Climate change; Foraminifera*; Sea ice
• Online Access: https://orca.cardiff.ac.uk/id/eprint/120363/; https://orca.cardiff.ac.uk/id/eprint/120363/1/PhD_Thesis_HD_January_2019_no_data_tables.pdf; https://orca.cardiff.ac.uk/id/eprint/120363/2/theses_publication_form.pdf

The Bering Sea represents the gateway between the Pacific and the Arctic Ocean. It is characterized by a seasonal sea ice cycle, which together with upwelling along the continental margin provides nutrients for primary producers. The resulting high sedimentation rates along the margin allow to study Quaternary climate change at an orbital to sub-orbital resolution, ideal to examine the evolution of continental ice volume across the Mid-Pleistocene transition (MPT, 1.2-0.7 Ma), the shift in glacial/interglacial (G/IG) frequency from 41-ka to 100-ka. Additionally, the Bering Sea provides a unique opportunity to study sea ice-ocean/land ice interactions. In the North Pacific, sea ice not only plays a significant role in climatic feedbacks, but also influences the ventilation of mid-depth waters via brine rejection. This thesis focuses on MPT climate change in the eastern Bering Sea, with particular emphasis on bottom water temperature (BWT), seawater oxygen isotopes (δ18Ow), sedimentary redox conditions, and sea ice dynamics. The MPT findings are reinforced by examining the same parameters across the last G/IG cycle. Further, the chemical composition of contamination phases in benthic foraminifera in eastern Bering Sea slope sediments is analysed. Foraminiferal contaminants are primarily composed of authigenic carbonates enriched in Mg, U, Mn, Fe, and Sr with consequences for geochemical proxies, such as Mg/Ca for BWT. Nevertheless, this study also demonstrates the opportunities accompanying authigenic carbonates, such as authigenic U/Mn for sedimentary redox chemistry.