Articles | Volume 9, issue 3
The Cryosphere, 9, 1089–1103, 2015
The Cryosphere, 9, 1089–1103, 2015

Research article 22 May 2015

Research article | 22 May 2015

Constraints on the δ2H diffusion rate in firn from field measurements at Summit, Greenland

L. G. van der Wel1,*, H. A. Been1, R. S. W. van de Wal2, C. J. P. P. Smeets2, and H. A. J. Meijer1 L. G. van der Wel et al.
  • 1Centre for Isotope Research (CIO), Energy and Sustainability Research Institute Groningen (ESRIG), University of Groningen, 9747AG Groningen, the Netherlands
  • 2Institute for Marine and Atmospheric Research Utrecht (IMAU), University of Utrecht, 3584 CC Utrecht, the Netherlands
  • *present address: Institute of Climate and Environmental Physics, University of Bern, 3012 Bern, Switzerland

Abstract. We performed detailed 2H isotope diffusion measurements in the upper 3 m of firn at Summit, Greenland. Using a small snow gun, a thin snow layer was formed from 2H-enriched water over a 6 × 6 m2 area. We followed the diffusion process, quantified as the increase of the δ2H diffusion length, over a 4-year period, by retrieving the layer once per year by drilling a firn core and slicing it into 1 cm layers and measuring the δ2H signal of these layers.

We compared our experimental findings to calculations based on the model by Johnsen et al. (2000) and found substantial differences. The diffusion length in our experiments increased much less over the years than in the model. We discuss the possible causes for this discrepancy and conclude that several aspects of the diffusion process in firn are still poorly constrained, in particular the tortuosity.

Short summary
We performed 2H isotope diffusion measurements in the upper 3 metres of firn at Summit, Greenland, by following over a 4-year period isotope-enriched snow that we deposited. We found that the diffusion process was much less rapid than in the most commonly used model. We discuss several aspects of the diffusion process that are still poorly constrained and might lead to this discrepancy. Quantitative knowledge of diffusion is necessary for use of the diffusion process itself as a climate proxy.