Investigating glacial weathering fluxes from West Antarctica across the Mid-Pleistocene: Insights from  Os isotopes

Abstract

The Mid-Pleistocene Transition (MPT) is a period marked by significant changes in the LR04 benthic δ18O record. During this interval (ca. 1.25-0.65 Ma), glacial cycles shifted from symmetrical 41-thousand-year (kyr) cyclicity to asymmetrical 100-kyr cycles. This transition was characterized by a number of large-scale ice sheets, including terrestrial-based ice sheets in the northern hemisphere (e.g.,  the Laurentide and Greenland ice sheets) and a marine-based ice sheet in the southern hemisphere (e.g., the West Antarctic Ice Sheet). Since these different ice sheets respond to climate variability in unique ways, the LR04  stack may fail to capture certain aspects of regional cryospheric behavior across the MPT. Specifically, a potential lag in ice-rafted debris (IRD) fluxes, hinting at possible bipolarity in glacial terminations. This study aims to investigate glacial weathering fluxes from West Antarctica across the MPT by constructing an osmium isotope chemostratigraphic record in conjunction with published IRD records from IODP site U1536 in Iceberg Alley, in the Scotia Sea. This record will be compared to a previously published record from the IRD Belt in the North Atlantic. By examining glacial weathering products in regions with high accumulation of glacially-derived debris, these two records will provide a comprehensive comparison of cryospheric behavior in the North and South Atlantic across the MPT. This new dataset will offer a more detailed perspective of global cryospheric behavior during the MPT and may reveal synchronicity between the two hemispheres.