Verifying Glacial-Interglacial Cycles in the Pleistocene Drillcore Sequence from IODP Site U1532, Amundsen Sea, Antarctica
Abstract
Understanding Antarctic ice sheet behavior and response to climate forcing during past interglacial periods is critical for projecting future rates of change and ice loss. The Amundsen Sea Embayment drains approximately one third of the West Antarctic Ice Sheet (WAIS), and thus marine sedimentary records from this region provide critical insight into the past behavior of the WAIS, which is hypothesized to have undergone retreat during several warm Pleistocene interglacials (~2.6 Ma 11.7 Ka). Existing records, however, are not robustly linked to past oceanographic changes, hindering a deeper understanding of deglacial forcings. International Ocean Discovery Program (IODP) Expedition 379 recovered sediment records at Resolution Drift on the continental rise of the Amundsen Sea. Pleistocene sediments are characterized by biosiliceous-rich mud to biosiliceous ooze and foraminifera-bearing mud, with coherent cyclicity observed in the magnetic susceptibility, bulk density, and x-ray fluorescence (XRF) measurements, such as silicon/aluminum ratios. These cycles may be related to glacial-interglacial (g-ig) cyclicity, but the relationships between climate and sediment processes are nuanced. We present a null hypothesis that planktic foraminifera deposited during different parts of each cycle will not differ in oxygen isotope composition which reflects seawater oxygen isotope composition and can change ~0.5-1.5 between g-ig periods due to mass transfer between the oceans and the ice sheets. This hypothesis is crucial to interpretation of cyclicity in physical properties and XRF data because, if refuted, it suggests a direct relationship between cyclicity and changes in the mass of the ice sheets. The challenge in testing this hypothesis is that foraminifers are not continuously preserved and/or sufficiently abundant in some intervals for stable isotope measurements, in contrast to continuous physical property data sets. We present foraminifer oxygen and carbon stable isotope records, where available, at Site U1532. A successful link between g-ig cycles and the continuous physical properties data will facilitate the use of these records as indicators for climate and oceanographic change to understand the forcings of past WAIS configurations.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMPP52B..06K