Collaborative Research: Magnetic Characterization of Dust in Greenland Ice

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AbstractKentOPP-01-18470BiscayeOPP-01-18458This is a collaborative proposal between Lamont-Doherty Earth Observatory and Rutgers University. The magnetic properties of Greenland ice were tested in samples of Holocene (interglacial) and Last Glacial Maximum (LGM) age. The dominant diamagnetism of ice prevented useful measurements of magnetic susceptibility, but the samples contain a sufficient concentration of iron oxide magnetic minerals that can be estimated using isothermal remanent magnetization (IRM) intensity. Some unusual problems had to be solved in order to obtain reliable measurements. Coercivity spectra in the Greenland ice samples are consistent with a dominant magnetite carrier. An unusual aspect of the preliminary magnetic data is that the LGM ice samples tend to have lower IRM values than interglacial ice samples, although LGM ice generally contains much higher concentrations of eolian dust than interglacial ice. The magnetic minerals constitute only a small fraction of the wind transported dust, but may reflect variations in pedogenesis and other environmental conditions in the source area(s), as well as differences in the possible source areas and/or atmospheric circulation and transport. The source area is presumed to be eastern Asia, and is presently the Takla Makan and other Inner Mongolian and Mongolian deserts, which were also the source areas for the sediments of the Chinese Loess Plateau. The objectives of this research are to validate a methodology of ice magnetic measurements by calibrating the ice magnetic data with direct measurements of dust extracts, and to compare the magnetic properties of polar dust in Greenland ice with those of possible source area(s), such as Chinese loess and desert sediments. These data will allow us to assess the feasibility of using magnetic properties as an independent provenance tracer of Greenland dust and to increase our understanding of the processes responsible for the profound paleoclimatically-dependent variations in magnetic properties of ice and loess deposits.