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Isotopic Fractionation During Sublimation of Low Porosity Ice
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  • Anthony W Bellagamba,
  • Max Berkelhamer,
  • Hans Christian Steen-Larsen,
  • Yasmeen Hamed,
  • Kristen Pearce
Anthony W Bellagamba
University of Illinois at Chicago

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Max Berkelhamer
University of Illinois at Chicago
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Hans Christian Steen-Larsen
University of Bergen
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Yasmeen Hamed
University of Illinois at Chicago
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Kristen Pearce
University of Illinois at Chicago
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Abstract

The isotopic effects of sublimating ice is poorly understood and disagreement from diverging results from studies spans decades. The core question is whether sublimation occurs layer-by-layer with no fractionation or whether diffusion within the ice and vapor-ice exchange generate fractionation. Here, small ice spheres were suspended in an unsaturated atmosphere and a Rayleigh distillation model was used to estimate fractionation of the spheres. A small, yet statistically significant and repeatable, fractionation (103lna18O of ~ -0.6‰ (ɑ = 0.999) and 103lna2H -3 to -6‰ (ɑ = 0.994 to 0.997 ) was observed, smaller than predicted for equilibrium fractionation at this temperature and humidity. Assuming a modest porosity of 0.0005%, porosity could sufficiently increase diffusivity to explain the observed fractionation. The results help reconcile how sublimation varies between experimental and observational studies where uncontrolled porosity varies substantially across a continuum from porous firn layers to low porosity ice deep in glaciers.
27 Jan 2024Submitted to ESS Open Archive
02 Feb 2024Published in ESS Open Archive