Water Science and Technology; Earth-Surface Processes
Abstract :
[en] Atmospheric warming over the Greenland Ice Sheet during the last 2 decades has increased the amount of surface meltwater production, resulting in the migration of melt and percolation regimes to higher altitudes and an increase in the amount of ice content from refrozen meltwater found in the firn above the superimposed ice zone. Here we present field and airborne radar observations of buried ice layers within the near-surface (0-20 m) firn in western Greenland, obtained from campaigns between 1998 and 2014. We find a sharp increase in firn-ice content in the form of thick widespread layers in the percolation zone, which decreases the capacity of the firn to store meltwater. The estimated total annual ice content retained in the near-surface firn in areas with positive surface mass balance west of the ice divide in Greenland reached a maximum of 74 ± 25 Gt in 2012, compared to the 1958-1999 average of 13 ± 2 Gt, while the percolation zone area more than doubled between 2003 and 2012. Increased melt and column densification resulted in surface lowering averaging -0.80 ± 0.39 m yr-1 between 1800 and 2800 m in the accumulation zone of western Greenland. Since 2007, modeled annual melt and refreezing rates in the percolation zone at elevations below 2100 m surpass the annual snowfall from the previous year, implying that mass gain in the region is retained after melt in the form of refrozen meltwater. If current melt trends over high elevation regions continue, subsequent changes in firn structure will have implications for the hydrology of the ice sheet and related abrupt seasonal densification could become increasingly significant for altimetry-derived ice sheet mass balance estimates.
Disciplines :
Earth sciences & physical geography
Author, co-author :
De La Peña, S.; Byrd Polar and Climate Center, Ohio State University, Scott Hall, Columbus, United States
Howat, I.M.; School of Earth Sciences, Ohio State University, 125 South Oval Mall, Columbus, United States
Nienow, P.W.; School of GeoSciences, University of Edinburgh, Edinburgh, United Kingdom
Van Den Broeke, M.R. ; Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University, Utrecht, Netherlands
Mosley-Thompson, E. ; Byrd Polar and Climate Center, Ohio State University, Scott Hall, Columbus, United States
Price, S.F. ; Fluid Dynamics Group, Los Alamos National Laboratory, Los Alamos, United States
Mair, D.; College of Physical Sciences, University of Aberdeen, King's College, Aberdeen, United Kingdom
Noël, Brice ; Université de Liège - ULiège > Département de géographie > Climatologie et Topoclimatologie ; Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University, Utrecht, Netherlands
Sole, A.J. ; Department of Geography, University of Sheffield, Sheffield, United Kingdom
Language :
English
Title :
Changes in the firn structure of the western Greenland Ice Sheet caused by recent warming
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