Collaborative Research: Magnetic characterization of dust in Greenland Ice

这是拉蒙特-多尔蒂地球天文台和罗格斯大学之间的一项合作计划。 格陵兰冰的磁性测试样品的全新世（间冰期）和末次冰期最大（LGM）年龄。冰的主要抗磁性阻止了有用的磁化率测量，但样品含有足够浓度的氧化铁磁性矿物，可以使用等温回复磁化强度（RESISTANCE）强度进行估计。 为了获得可靠的测量结果，必须解决一些不寻常的问题。格陵兰冰样品的矫顽力谱与占主导地位的磁铁矿载体是一致的。初步磁性数据的一个不寻常的方面是，LGM冰样品往往比间冰期冰样品具有较低的磁化率值，尽管LGM冰通常含有比间冰期冰高得多的风成尘浓度。磁性矿物只占风输送尘埃的一小部分，但可能反映了源区成土作用和其他环境条件的变化，以及可能的源区和/或大气环流和输送的差异。源区被认为是东亚，现在是塔克拉玛干和其他内蒙古和蒙古沙漠，这也是中国黄土高原沉积物的源区。本研究的目的是验证冰磁性测量的方法，通过校准冰磁性数据与直接测量的灰尘提取物，并比较格陵兰岛的冰与可能的源区，如中国黄土和沙漠沉积物的极地灰尘的磁性特性。这些数据将使我们能够评估使用磁特性作为格陵兰岛灰尘的独立来源示踪剂的可行性，并增加我们对冰和黄土沉积物磁特性变化的深刻古气候过程的理解。

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.