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Published in

American Geophysical Union, Geophysical Research Letters, 8(28), p. 1639-1642, 2001

DOI: 10.1029/2000gl012594

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Isothermal remanent magnetization of Greenland ice: Preliminary results

Journal article published in 2001 by Luca Lanci, Dennis V. Kent ORCID, Pierre E. Biscaye, Aloys Bory
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Data provided by SHERPA/RoMEO

Abstract

The magnetic mineral content of wind-transported dust should reflect atmospheric transport dynamics and conditions in its source areas, and could thus be used as an environmental proxy. To test the feasibility of determining the magnetic mineral content in polar ice, natural remanent magnetization (NRM) and isothermal remanent magnetization (IRM) were measured on a small suite of Greenland ice samples of Holocene (interglacial) and Last Glacial Maximum (LGM) age. All samples contained an easily measurable concentration of magnetic minerals that can be estimated using IRM intensity. However, special precautions were needed to obtain reliable data. We speculate that special measurement problems peculiar to ice arise from electromagnetically induced energy in the magnetic particles causing melting of the immediately surrounding ice matrix, which can allow physical unblocking of the magnetic particles. This severely limits many kinds of standard rock magnetic experiments directly on ice, e.g., alternating field (AF) demagnetization, whereas the extremely low dust concentrations limit weak field (susceptibility) measurements. Nevertheless, acquisition and measurement of IRM at liquid nitrogen temperatures allows us to obtain reproducible estimates of its magnitude and coercivity which are consistent with that expected from varying concentrations of magnetite or maghemite in the Greenland ice samples. Interestingly, the Holocene samples tend to have higher magnetic concentrations, despite having much lower total polar dust contents, than the few LGM samples tested thus far.