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Impurity Analysis and Microstructure Along the Climatic Transition From MIS 6 Into 5e in the EDML Ice Core Using Cryo-Raman Microscopy

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Eichler Jan, Weikusat Christian, Wegner Anna, Twarloh Birthe, Behrens Melanie, Fischer Hubertus, Hörhold Maria, Jansen Daniela, Kipfstuhl Sepp, Ruth Urs, Wilhelms Frank, Weikusat Ilka,
Project iCEP - Climate and Environmental Physics: Innovation in ice core science
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Original article (peer-reviewed)

Journal Frontiers in Earth Science
Volume (Issue) 7(20)
Page(s) 1 - 16
Title of proceedings Frontiers in Earth Science
DOI 10.3389/feart.2019.00020

Open Access

URL http://doi.org/10.3389/feart.2019.00020
Type of Open Access Publisher (Gold Open Access)

Abstract

Impurities in polar ice cores have been studied so far mainly for the purpose of reconstructions of past atmospheric aerosol concentrations. However, impurities also critically influence physical properties of the ice matrix itself. To improve the data basis regarding the in-situ form of incorporation and spatial distribution of impurities in ice we used micro-cryo-Raman spectroscopy to identify the location, phase and composition of micrometer-sized inclusions in natural ice samples around the transition from marine isotope stage (MIS) 6 into 5e in the EDML ice core. The combination of Raman results with ice-microsctructure measurements and complementary impurity data provided by the standard analytical methods (IC, CFA, and DEP) allows for a more interdisciplinary approach interconnecting ice core chemistry and ice core physics. While the interglacial samples were dominated by sulfate salts—mainly gypsum, sodium sulfate (possibly thenardite) and iron–potassium sulfate (likely jarosite)—the glacial ice contained high numbers ofmineral dust particles—in particular quartz,mica, feldspar, anatase, hematite and carbonaceous particles (black carbon). We cannot confirm cumulation of impurities in the grain boundary network as reported by other studies, neither micro-particles being dragged by migrating grain boundaries nor in form of liquid veins in triple junctions. We argue thatmixing of impurities onmillimeter scale and chemical reactions are facilitated by the deforming ice matrix. We review possible effects of impurities on physical properties of ice, however the ultimate identification of the deformation agent and the mechanism behind remains challenging.
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