Reconstruction of the spatial and temporal variability of the surface to subsurface ocean dynamics of the North West Pacific during the Pliocene and Pleistocene

• Main Author: Jacobi, Lara
• Format: Thesis
• Language: English
• Published: 2023
• Subjects: Hess; Pacific; Subarctic
• Online Access: https://oceanrep.geomar.de/id/eprint/59712/; https://oceanrep.geomar.de/id/eprint/59712/1/Dissertation_Lara_Jacobi.pdf; https://macau.uni-kiel.de/receive/macau_mods_00004275

The North Pacific (NP) is an essential component of the global climate system as it acts as a significant natural carbon sink and neutralizes a part of the anthropogenic release of CO2. The efficiency of the NP carbon sink depends on a range of variable factors, including gyre circulation, the wind system, influences from tropical and subpolar regions, and internal reorganizations like stratification changes. Thus, a detailed investigation of the NP ocean-climate system of the past is crucial to understand how the ongoing climate change influences this region and will affect future global climate. This thesis, presents proxy records approximating (sub)-surface temperature (foraminiferal Mg/Ca), salinity (combined Mg/Ca and δ18), biological productivity (XRF based element ratios, CaCO3 content and alkenone concentrations) and terrigenous input via wind (XRF-based Fe) from a unique set of six sediment cores from a meridional transect from Hess Rise to the subarctic NP retrieved during R/V SONNE expeditions 202 and 264. The records reveal significantly different upper ocean conditions and a different productivity pattern in the western NP during the Pliocene than during the Pleistocene. This is associate with the intensification of Northern Hemisphere Glaciation, the onset of a permanent halocline and increased seasonality. Further, a different productivity and carbonate deposition/dissolution pattern of records south of 40°N compared to northern cores is linked to different nutrient regimes of the subtropical and subpolar gyre. Moreover, abrupt and pronounced changes in SST at site SO264-45 (e.g. at 480 ka and 280 ka) indicate shifts of the Subarctic Front induced by changes in the strength of the Kuroshio Extension, e.g., caused by sustained La Niña-like conditions in the tropical Pacific.