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

• Main Authors: Vandecrux, Baptiste, Fausto, Robert R.S., Van As, Dirk, Colgan, William, Langen, Peter P.L., Haubner, Konstanze, Ingeman-Nielsen, Thomas, Heilig, Achim, Stevens, Max C.M., Macferrin, Michael, Niwano, Masashi, Steffen, Konrad, Box, Jason J.E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2020
• Subjects: Géologie et minéralogie; Accumulation area; Greenland ice sheet; Meltwater retention; Polar firn; Snow and firn processes; Surface energy balance; Surface mass balance; Surface melt; Greenland; Ice Sheet; Journal of Glaciology
• Online Access: http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/307462; https://dipot.ulb.ac.be/dspace/bitstream/2013/307462/1/doi_291106.pdf

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. SCOPUS: ar.j info:eu-repo/semantics/published