Greenland meltwater storage in firn limited by near-surface ice formation

Approximately half of Greenland's current annual mass loss is attributed to runoff from surface melt. At higher elevations, however, melt does not necessarily equal runoff, because meltwater can refreeze in the porous near-surface snow and firn. Two recent studies suggest that all or most of Greenland's firn pore space is available for meltwater storage, making the firn an important buffer against contribution to sea level rise for decades to come. Here, we employ in situ observations and historical legacy data to demonstrate that surface runoff begins to dominate over meltwater storage well before firn pore space has been completely filled. Our observations frame the recent exceptional melt summers in 2010 and 2012, revealing significant changes in firn structure at different elevations caused by successive intensive melt events. In the upper regions (more than similar to 1,900 m above sea level), firn has undergone substantial densification, while at lower elevations, where melt is most abundant, porous firn has lost most of its capability to retain meltwater. Here, the formation of near-surface ice layers renders deep pore space difficult to access, forcing meltwater to enter an efficient surface discharge system and intensifying ice sheet mass loss earlier than previously suggested.

MacFerrin, MichaelCooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado at Boulder (författare)
van As, DirkGeological Survey of Denmark and Greenland (GEUS) (författare)
Box, Jason E.Geological Survey of Denmark and Greenland (GEUS), København, Denmark (författare)
Charalampidis, Charalampos,1983-Uppsala universitet,Luft-, vatten- och landskapslära,Geological Survey of Denmark and Greenland (GEUS),Ice, Climate and Environment(Swepub:uu)chach903 (författare)
Colgan, WilliamDepartment of Earth and Space Science and Engineering, York University (författare)
Fausto, Robert S.Geological Survey of Denmark and Greenland (GEUS) (författare)
Meijer, Harro A. J.Univ Groningen, Energy & Sustainabil Res Inst Groningen, Ctr Isotope Res CIO, NL-9747 AG Groningen, Netherlands (författare)
Mosley-Thompson, EllenOhio State Univ, Byrd Polar & Climate Res Ctr, Columbus, OH 43210 USA.; Ohio State Univ, Dept Geog, Columbus, OH 43210 USA (författare)
van de Wal, Roderik S. W.Univ Utrecht, Inst Marine & Atmospher Res Utrecht IMAU, NL-3584 CC Utrecht, Netherlands (författare)
Department of Geography, University of ZurichCooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado at Boulder (creator_code:org_t)

Ingår i:Nature Climate Change: Springer Science and Business Media LLC6:4, s. 390-3931758-678X1758-6798

Av författaren/redakt...: Machguth, Horst; MacFerrin, Micha ...; van As, Dirk; Box, Jason E.; Charalampidis, C ...; Colgan, William; visa fler...; Fausto, Robert S ...; Meijer, Harro A. ...; Mosley-Thompson, ...; van de Wal, Rode ...; visa färre...

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