Investigating Geochemical Variability and Timing of Holocene Climatic Changes in Productivity and Terrigenous Input on the East Antarctic Margin

Trustees Of Boston University, Boston

Investigators

Abstract

0126110 Murray This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, provides funds for a paleoceanographic and paleoclimate study of recently acquired marine sediment cores from the continental shelf of East Antarctica. The goal of this work is to develop a better understanding of Holocene climate change on the East Antarctic Margin (EAM) via geochemical studies of ultra-high resolution sedimentary sequences recovered during the Coring Holocene Antarctic Ocean Sediments (CHAOS) program conducted in early 2001. A diverse suite of geochemical analyses will be carried out that will provide indicators of nutrient utilization, surface and export production, terrigenous flux, and terrigenous provenance by developing an integrated database of d15N, d13C, opal, TOC, and a diverse suite of 17 major and trace elements. This project has two mutually reinforcing components: inorganic proxy work at Boston University, and complementary isotopic studies at Stanford University. The work will target important hypotheses and questions relating to East Antarctic Margin (EAM) climate variability over decadal-, centennial-, and millennial-scale time scales, as well as assess the impact of global climatic events such as the Little Ice Age, Holocene climatic optimum, Medieval Warm Period, and Younger Dryas. This work will compare and contrast records from the EAM (a terrestrial ice sheet) to the Palmer Deep record off the West Antarctic Peninsula (a predominantly marine-based ice sheet). It will examine relative timing of events between the EAM, Palmer, and Northern Hemisphere Holocene records, and compare the relative timings of climatic change in both the biologic (nutrients and export) and physical (terrigenous) systems acting along the Antarctic continental margin. Integrating biological and physical studies allows for a comprehensive assessment of the combined marine-terrestrial Antarctic system. Documenting changes in export production through inorganic chemical means will be an important independent approach from that taken by researchers focusing on the paleontological record (e.g. diatom assemblages), and will provide quantitative information regarding the frequency of change in the sequestering of atmospheric CO2. In addition, variations in nitrogen isotope ratios can either reflect differences in relative utilization of nitrate in the photic zone or can be used to track the exchange of nutrients between deep and surface waters. Carbon isotope records track bloom events, which reflect productivity in the surface waters. Each of the isotope proxies (d15N, d13C, TOC, biogenic opal, major/trace elements, etc.) responds to different aspects of the biogeochemical cycle, and only by synthesizing them can a more complete picture of the region's systematics be achieved. Changes in the terrigenous flux and chemical provenance may indicate variations in the weathering patterns of bedrock and soil on the EAM, delivery of ice-rafted debris, the strength of ocean currents, or behavior of different glacial regimes on the margin. Interpreting these results within the context of other studies will allow an assessment of the response of local glaciers to changes in climate and precipitation on the margin. These issues have been targeted with similar methodologies and integration of data sets with great success in the Palmer Deep, West Antarctic Peninsula. The sediments from the East Antarctic Margin are of comparable resolution and integrity to allow for future comparisons of the response of both the East Antarctic Ice Sheet and West Antarctic Ice Sheet to climate change.