Firn cold content evolution at nine sites on the Greenland ice sheet between 1998 and 2017

B. Vandecrux*, R. S. Fausto, D. Van As, W. Colgan, P. L. Langen, K. Haubner, Thomas Ingeman-Nielsen, A. Heilig, C. M. Stevens, M. Macferrin, M. Niwano, K. Steffen, J. E. Box

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Current sea-level rise partly stems from increased surface melting and meltwater runoff from the Greenland ice sheet. Multi-year snow, also known as firn, covers about 80% of the ice sheet and retains part of the surface meltwater. Since the firn cold content integrates its physical and thermal characteristics, it is a valuable tool for determining the meltwater-retention potential of firn. We use gap-filled climatological data from nine automatic weather stations in the ice-sheet accumulation area to drive a surface-energy-budget and firn model, validated against firn density and temperature observations, over the 1998-2017 period. Our results show a stable top 20 m firn cold content (CC20) at most sites. Only at the lower-elevation Dye-2 site did CC20 decrease, by 24% in 2012, before recovering to its original value by 2017. Heat conduction towards the surface is the main process feeding CC20 at all nine sites, while CC20 reduction occurs through low-cold-content fresh-snow addition at the surface during snowfall and latent-heat release when meltwater refreezes. Our simulations suggest that firn densification, while reducing pore space for meltwater retention, increases the firn cold content, enhances near-surface meltwater refreezing and potentially sets favourable conditions for ice-slab formation.
Original languageEnglish
JournalJournal of Glaciology
Volume66
Issue number258
Pages (from-to)591-602
ISSN0022-1430
DOIs
Publication statusPublished - 2020

Keywords

  • Greenland ice sheet
  • Accumulation area
  • Surface energy balance
  • Polar firn
  • Surface melt
  • Meltwater retention
  • Surface mass balance
  • Snow and firn processes

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