Investigating Climate Variability over the Last Four Glacial Cycles using Surface and Thermocline Dwelling Foraminifera from the Sulu Sea in the Far Western Pacific

• Main Author: Weiss, Thomas L.
• Format: Thesis
• Language: English
• Published: 2022
• Subjects: Paleoclimatology; Foraminifera; Thermoclines (Oceanography); Neogloboquadrina; Calcification; Pacific; Planktonic foraminifera
• Online Access: https://doi.org/10.7916/g9vk-fy83

The geographic location of the Sulu Sea in the far western equatorial Pacific results in the basin’s oceanographic sensitivity to: 1.) the East Asian Monsoon strength, 2.) the Kuroshio Current and open western Pacific conditions, 3.) Indonesian Strait geometry, 4.) past sea level, and 5.) the Indonesian Throughflow (ITF). Due to the sea’s unique bathymetry as a deep basin (~5,000 m maximum depth) surrounded by shallow sills with maximum depths of 440 m, Sulu Sea bottom water is relatively warm with minimum temperature of ~10°C, low dissolved oxygen, high carbonate concentrations, excellent CaCO3 preservation, and low bioturbation which combine to produce a remarkable sedimentological record. Sulu Sea sediments have previously been utilized to generate high-resolution paleoclimate records of past variability of surface ocean conditions using the planktonic foraminifera Globigerinoides ruber. However, past changes in the Sulu Sea subsurface and thermocline have been largely unexplored until now. Here I will show that reconstructing subsurface upper ocean conditions in the Sulu Sea reveals a rich archive of paleoclimatic information relating to past upper ocean dynamics. In this dissertation I seek to understand Indo-Pacific and global glacial-interglacial variability over the last four glacial cycles by generating foraminiferal δ18O, Mg/Ca-based temperature, and seawater δ18O (δ18Ow) records using the thermocline calcifying foraminifera Globorotalia tumida from high-resolution sediment core MD97-2141 from the Sulu Sea. Additionally, I extend existing G. ruber Mg/Ca-based temperature and δ18Ow paleoclimatic results to now span intervals of the last four glacial cycles. Sulu Sea thermocline reconstructions monitor regional paleoclimate on their own while also providing insight into surface variability when the surface and thermocline depth paleoclimatic records are compared.In Chapter 1 of this dissertation, I use Sulu Sea G. tumida reconstructions to investigate the North Equatorial Current (NEC) bifurcation ...