25 Nov 2021
25 Nov 2021
Status: this preprint is currently under review for the journal TC.

Exploring the role of snow metamorphism on the isotopic composition of the surface snow at EastGRIP

Romilly Harris Stuart1,4, Anne-Katrine Faber2, Sonja Wahl2, Maria Hörhold3, Sepp Kipfstuhl3, Kristian Vasskog4, Melanie Behrens3, Alexandra Zuhr5,6, and Hans Christian Steen-Larsen2 Romilly Harris Stuart et al.
  • 1Laboratoire des Sciences du Climat et de l’Environnement, UMR8212, CNRS – Gif sur Yvette, France
  • 2Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway
  • 3Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany
  • 4Department of Geography, University of Bergen, and Bjerknes Centre for Climate Research, Bergen, Norway
  • 5Alfred-Wegener-Institut Helmholtz Zentrum für Polar- und Meeresforschung, Research Unit Potsdam, Telegrafenberg A45, 14473 Potsdam, Germany
  • 6University of Potsdam, Institute of Geosciences, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany

Abstract. Stable water isotopes from polar ice cores are invaluable high-resolution climate proxy records. Recent studies have aimed to improve knowledge of how the climate signal is stored in the water isotope record by addressing the influence of post-depositional processes on the surface snow isotopic composition. In this study, the relationship between changes in surface snow microstructure after precipitation/deposition events and water isotopes is explored using measurements of snow specific surface area (SSA). Continuous daily SSA measurements from the East Greenland Ice Core Project site (EastGRIP) situated in the accumulation zone of the Greenland Ice Sheet during the summer seasons of 2017, 2018 and 2019 are used to develop an empirical decay model to describe events of rapid decrease in SSA, driven predominantly by vapour diffusion in the pore space and atmospheric vapour exchange. The SSA decay model is described by the exponential equation SSA(t) = (SSA0 −26.8) e−0.54t + 26.8. The model performance is optimal for daily mean values of surface temperature in the range 0 °C to −25 °C and wind speed < 6 m s−1. The findings from the SSA analysis are used to explore the influence of surface snow metamorphism on altering the isotopic composition of surface snow. It is found that rapid SSA decay events correspond to decreases in d-excess over a 2-day period in 72 % of the samples. Detailed studies using Empirical Orthogonal Function (EOF) analysis revealed a coherence between the dominant mode of variance of SSA and d-excess during periods of low spatial variability of surface snow over the sampling transect, suggesting that processes driving change in SSA also influence d-excess. Our findings highlight the need for future studies to decouple the processes driving surface snow metamorphism in order to quantify the fractionation effect of individual processes on the snow isotopic composition.

Romilly Harris Stuart et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2021-344', Dorothea Elisabeth Moser, 20 Dec 2021
    • AC1: 'Reply on RC1', Romilly Harris Stuart, 21 Feb 2022
  • RC2: 'Review of tc-2021-344', Florent Dominé, 21 Dec 2021
    • AC2: 'Reply on RC2', Romilly Harris Stuart, 21 Feb 2022

Romilly Harris Stuart et al.

Romilly Harris Stuart et al.


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Short summary
This empirical study uses continuous daily measurements from the Greenland Ice Sheet to document changes in surface snow properties. Consistent changes in snow isotopic composition are observed in the absence of deposition due to surface processes, indicating the isotopic signal of deposited precipitation is not always preserved. Our observations have potential implications for the interpretation of water isotopes in ice cores – historically assumed to reflect isotopic composition at deposition.