Discovery of argon in air-hydrate crystals in a deep ice core using scanning electron microscopy and energy-dispersive X-ray spectroscopy

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  • Tsutomu Uchida
  • Wataru Shigeyama
  • Ikumi Oyabu
  • Kumiko Goto-Azuma
  • Fumio Nakazawa
  • Tomoyuki Homma
  • Kenji Kawamura
  • Dahl-Jensen, Dorthe

Tiny samples of ancient atmosphere in air bubbles within ice cores contain argon (Ar), which can be used to reconstruct past temperature changes. At a sufficient depth, the air bubbles are compressed by the overburden pressure under low temperature and transform into air-hydrate crystals. While the oxygen (O2) and nitrogen (N2) molecules have indeed been identified in the air-hydrate crystals with Raman spectroscopy, direct observational knowledge of the distribution of Ar at depth within ice sheet and its enclathration has been lacking. In this study, we applied scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) to five air-hydrate crystals in the Greenland NEEM ice core, finding them to contain Ar and N. Given that Ar cannot be detected by Raman spectroscopy, the method commonly used for O2 and N2, the SEM-EDS measurement method may become increasingly useful for measuring inert gases in deep ice cores.

OriginalsprogEngelsk
TidsskriftJournal of Glaciology
Vol/bind68
Udgave nummer269
Sider (fra-til)547-556
Antal sider10
ISSN0022-1430
DOI
StatusUdgivet - 2022

Bibliografisk note

Funding Information:
We thank all the NEEM project members involved in logistics, drilling, and ice core processing. NEEM is directed and organized by the Centre of Ice and Climate at the Niels Bohr Institute and the United States National Science Foundation, Office of Polar Programs. NEEM is supported by funding agencies and institutions in Belgium (FNRS-CFB and FWO), Canada (NRCan/GSC), China (CAS), Denmark (FIST), France (IPEV, CNRS/ INSU, CEA, and ANR), Germany (AWI), Iceland (RannIs), Japan (NIPR), Korea (KOPRI), The Netherlands (NWO/ALW), Sweden (VR), Switzerland (SNF), the United Kingdom (NERC), and the USA (US NSF, Office of Polar Programs).

Funding Information:
This study was supported by the Environment Research and Technology Development Fund (JPMEERF20202003) of the Environmental Restoration and Conservation Agency of Japan, the Japan Society for the Promotion of Science KAKENHI (Grants JP22221002, JP18H04140, JP20H04327 and JP20H04980), the Arctic Challenge for Sustainability (ArCS) project (JPMXD1300000000), the Arctic Challenge for Sustainability II (ArCS II) project (JPMXD1420318865), a grant for the National Institute of Polar Research, Japan (Project Research KP305 and General Collaboration Project no. 3-6), and the Graduate University for Advanced Studies, SOKENDAI.

Publisher Copyright:
Copyright © The Author(s), 2021. Published by Cambridge University Press.

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