OCEANIC VARIABILITY DURING THE MID- TO LATE-PLEISTOCENE: A STATISTICAL APPROACH USING ELEMENTAL (XRF CORE SCANNING) AND PHYSICAL PROPERTIES DATA FROM ODP HOLE 1207A, NORTHWESTERN PACIFIC OCEAN

Current end of century (2100) projections of atmospheric CO₂ concentrations (> 475 ppm) and warming (> 2.0° C) are historically unprecedented. Geologic analogues are necessary if we are to accurately predict future oceanographic changes in detail. Studies of intervals that were warmer than present are particularly pertinent. Several extreme warming events, or super interglacials, have been observed during the Mid- to Late-Pleistocene in Arctic lake sediment records (Lake El’gygytgyn) and coincide with dramatic ice-volume loss of the West Antarctic Ice Sheet. Such coeval warming implies a strong interhemispheric climate coupling that could be related to changes in thermohaline circulation. However, there is a lack of robust records from the North Pacific Ocean to evaluate these interhemispheric teleconnections and the role of the Pacific as an oceanic linkage.

Here we present a ~2 myr record of elemental (XRF core scanning) and physical properties data from a marine sediment core collected at Ocean Drilling Program Hole 1207A. We find that the elemental ratio of Ca/Ti, used as a proxy for biogenic CaCO₃ displays clear glacial/interglacial variability with unique expressions around the super interglacials MIS 9, 11, and 31. We perform Principle Component Analysis (PCA) in conjunction with unsupervised (hierarchical) cluster analysis to display lithologic variations throughout the record. PCA and clustering results display strong agreement with visual core descriptions of lithology, which supports the practicality in applying these techniques to open marine sediments. We also employ time series analysis and identify a 41-kyr periodicity across the entire record, associated with orbital variations in Earth’s axial tilt angle (obliquity). Future work involving foraminiferal assemblages, stable isotopes, and biogenic opal will be performed in order to further delineate details regarding Pleistocene climate change in the northwestern Pacific Ocean.