PP028-02
1.3 Ma record of export production at the Pacific entrance to the Drake Passage
Friday, 11 December 2020: 04:07
Virtual
Maria H Toyos1,2, Gisela Winckler3, Carina Lange4,5, Helge W Arz6, Lester Lembke-Jene7 and Frank Lamy7, (1)Programa de Postgrado en Oceanografía, Departamento de Oceanografía, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Concepcion, Chile, (2)Centro de Investigación Dinámica de Ecosistemas Marinos de Altas Latitudes (IDEAL), Universidad Austral de Chile, Valdivia, Chile, (3)Columbia University, Department of Earth and Environmental Sciences, New York, NY, United States, (4)Scripps Institution of Oceanography, La Jolla, CA, United States, (5)Universidad de Concepción, Departamento de Oceanografía, Investigador Asociado COPAS Sur-Austral & Centro FONDAP-IDEAL, Concepción, Chile, (6)Leibniz Institute for Baltic Sea Research, Rostock, Germany, (7)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Bremerhaven, Bremerhaven, Germany
Abstract:
The Southern Ocean plays an important role in regulating atmospheric CO
2 changes. Specifically, in the subantarctic zone (SAZ), dust-borne iron-fertilization is thought to increase nutrient utilization and improve the efficiency of the biological carbon pump during glacial periods. We present an assessment of productivity changes at the subantarctic Pacific entrance to the Drake Passage over the past 1.3 Ma. To evaluate export production changes and the role of Fe-fertilization, we use a combination of elemental ratios (Ba/Fe),
230Th-corrected (down to 350 ka) and age-model-based mass accumulation rates of total organic carbon, Ba
exc, biogenic opal, carbonates, and Fe (lithogenic) in marine sediment core PS97/093-2 (57º 29.94' S; 70º 16.48' W; 3781m water depth).
The export production patterns recorded at the site vary from an enhanced opal-rich export production during glacials to an interglacial production regime dominated by carbonates. However, the absence of carbonate during glacials in PS97/093-2 might reflect carbonate dissolution rather than changes in the export production of calcareous plankton. A comparison of our three proxies for total export production (TOC, Baexc, and Ba/Fe) to opal and carbonates MAR shows that opal yields excellent correspondence with TOC, whereas Baexcand Ba/Fe ratios seem to reflect a combination of both opal and carbonate variations.
Higher opal fluxes during glacial periods correspond to higher siliciclastic fluxes. Lithogenic fluxes at PS97/093-2 generally follow the temporal pattern of lithogenic records at open ocean cores in the SAZ and in Antarctic ice cores, interpreted as eolian dust. However, as the fluxes are significantly higher than inferred from these records and dust models, an additional local source of terrigenous material is required. Because of the proximity to the South American continent, we assume glacial discharge from the Patagonia Icefield to the Chilean continental margin to be the most likely source.
