REU: Changes in benthic foraminifera assemblage preservation associated with onset of deep AMOC during the last deglaciation
Abstract
Benthic foraminifera are used to generate the majority of paleo-proxy records reconstructing past ocean changes including variations in the strength of AMOC. To assess the reliability of geochemical proxy records generated using benthic foraminifera, a Foraminifera Preservation Index (FPI) was developed to quantify assemblage-wide changes in visual preservation quality. The qualitative criteria for preservation included in the FPI are supported by stable isotope and trace element datasets. Early application of the FPI on Cibicidoidesassemblages from the deep Pacific Ocean (IODP Sites 846, 1143, 1208) reveal quantifiably better preservation during glacial periods relative to interglacial periods for the last 1 million years. Here, we present results from two summer REU projects tracking such preservation changes in the deep North and South Atlantic Ocean prior to and throughout the last deglaciation ( 0-35 ka). Changes in Cibicidoides FPI from IODP Site 1089 in the deep South Atlantic ( 4600m water depth: primarily bathed by Antarctic Bottom Water - AABW) mirror those in the Pacific with better preservation during the glacial maximum of Marine Isotope Stage (MIS 2) than the Holocene interglacial (MIS 1). Alternatively, Cibicidoides FPI from IODP Site 1059 ( 3000m water depth: bathed by North Atlantic Deep Water [NADW] during interglacials; and by AABW during glacials) reveal better preservation during the Holocene relative to MIS 2. Despite these opposing trends, changes in FPI occur at both sites at 15 ka corresponding to major changes to AMOC documented throughout the deep Atlantic basin. These findings imply that the same processes involved in water mass CO2-carbonate chemistry on glacial-interglacial timescales affect preservation of benthic foraminifera. Furthermore, our results suggest that the FPI can track major changes in deglacial AMOC, potentially providing an inexpensive method to produce preliminary data prior to or in unison with more expensive geochemical analyses.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP21E1457G
- Keywords:
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- 1616 Climate variability;
- GLOBAL CHANGEDE: 1626 Global climate models;
- GLOBAL CHANGEDE: 4901 Abrupt/rapid climate change;
- PALEOCEANOGRAPHYDE: 4912 Biogeochemical cycles;
- processes;
- and modeling;
- PALEOCEANOGRAPHY