Local Sources for the "Megadust" Events at the WAIS Divide Ice Core

Thursday, 18 December 2014
Alejandra Borunda, Columbia University of New York, Palisades, NY, United States, Gisela Winckler, Lamont -Doherty Earth Observatory, Palisades, NY, United States, Steven L Goldstein, Columbia University, Sparkill, NY, United States, Michael R Kaplan, Lamont-DohertyEarthObservatory, Palisades, NY, United States, Joseph R McConnell, Desert Res Inst, Reno, NV, United States and Nelia W Dunbar, New Mexico Institute of Mining and Technology, Socorro, NM, United States
Mineral dust transported through the atmosphere affects the radiative balance of the planet, and can also affect climate on glacial-interglacial timescales by stimulating carbon export from the surface ocean. Tracking changes in dust fluxes and sources in paleoarchives, such as polar ice cores, allows us to reconstruct past atmospheric circulation patterns, dust transport pathways, and atmospheric aerosol loadings. The geographic source of mineral dust particles can be identified using geochemical tools, such as trace element chemistry and radiogenic isotope signatures. We extracted mineral particles and analyzed the Sr, Nd, and Pb isotopic signatures from eight particle-rich “Megadust” layers in the WAIS Divide ice core in order to determine their sources. We also analyzed tephras from three local West Antarctic volcanoes: Mts. Takahe, Mt. Waesche, and Mt. Berlin.

The “Megadust” events occurred between ~60-27ky and deposited mm-cm thick layers of mineral material in the WAIS Divide ice core. Previous hypotheses about the source of the Megadust particles suggested a distal continental source, but our chemical and isotopic analyses, as well as mineralogy, indicate that West Antarctic volcanoes are the dominant source of particles during these events. This further suggests that the active local volcanoes may have contributed to the West Antarctic dust load in discrete events, and that they may be a background source over longer time scales. In addition, these volcanic events may also be useful as stratigraphic markers in other West Antarctic climate archives.