Collaborative Research: Magnetic characterization of dust in Greenland Ice

AbstractKentOPP-01-18470BiscayeOPP-01-18458This是拉蒙特-多尔蒂地球天文台和罗格斯大学的合作项目。在全新世(间冰期)和末次冰盛期(LGM)样品中测试了格陵兰冰的磁性。冰的主要抗磁性阻碍了磁化率的有用测量，但样品中含有足够浓度的氧化铁磁性矿物，可以用等温剩余磁化强度(IRM)来估计。为了获得可靠的测量结果，必须解决一些不寻常的问题。格陵兰冰样中的矫顽力谱与主要的磁铁矿载体相一致。初步磁性数据的一个不同寻常的方面是，LGM冰样往往比间冰期冰样的IRM值低，尽管LGM冰通常含有比间冰期冰高得多的风尘浓度。磁性矿物只占风输送粉尘的一小部分，但可能反映了源区成壤作用和其他环境条件的变化(S)，以及可能的源区和/或大气环流和运移的差异。推测其源区为东亚，目前为塔克拉玛干等内蒙古和蒙古族沙漠，也是中国黄土高原沉积物的源区。本研究的目的是验证一种冰磁测量方法，将冰磁数据与尘埃提取物的直接测量进行校准，并将格陵兰冰中极地尘埃的磁特性与可能的源区(S)的磁特性进行比较，例如中国的黄土和沙漠沉积物。这些数据将使我们能够评估利用磁性作为格陵兰尘埃的独立来源示踪剂的可行性，并增进我们对导致冰和黄土沉积物磁性随古气候发生深刻变化的过程的理解。

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.