TY - JOUR
T1 - Firn data compilation reveals widespread decrease of firn air content in western Greenland
AU - Vandecrux, Baptiste
AU - MacFerrin, Michael
AU - Machguth, Horst
AU - Colgan, William T.
AU - van As, Dirk
AU - Heilig, Achim
AU - Stevens, C. Max
AU - Charalampidis, Charalampos
AU - Fausto, Robert S.
AU - Morris, Elizabeth M.
AU - Mosley-Thompson, Ellen
AU - Koenig, Lora
AU - Montgomery, Lynn N.
AU - Miège, Clément
AU - Simonsen, Sebastian B.
AU - Ingeman-Nielsen, Thomas
AU - Box, Jason E.
N1 - Funding Information:
Acknowledgements. This work is part of the Retain project funded by Danmarks Frie Forskningsfond (grant no. 4002-00234) and the Programme for Monitoring of the Greenland ice sheet (http://PROMICE.dk, last access: 25 February 2019). The field campaigns were funded by the NASA grant NNX15AC62G in collaboration with the Greenland Analogue Project (GAP). Achim Heilig was supported by DFG grant HE 7501/1-1. We thank Hubertus Fischer from the Department of Climate and Environmental Physics at the University of Bern (Switzerland), for providing low-resolution density data from firn cores collected during the EGIG expeditions of 1990 and 1992. We are grateful to Peter Langen from the Danish Meteorological Institute, Stefan Ligtenberg from the Institute for Marine and Atmospheric Research at Utrecht University (IMAU) and Xavier Fettweis from the Laboratory of Climatology, Department of Geography, University of Liège, for providing the regional climate model output. We thank Sergey Marchenko and an anonymous reviewer for their suggestions, which greatly improved the manuscript.
Publisher Copyright:
© 2019 Author(s).
PY - 2019/3/11
Y1 - 2019/3/11
N2 - A porous layer of multi-year snow known as firn covers the Greenland-ice-sheet interior. The firn layer buffers the ice-sheet contribution to sea-level rise by retaining a fraction of summer melt as liquid water and refrozen ice. In this study we quantify the Greenland ice-sheet firn air content (FAC), an indicator of meltwater retention capacity, based on 360 point observations. We quantify FAC in both the uppermost 10m and the entire firn column before interpolating FAC over the entire ice-sheet firn area as an empirical function of long-term mean air temperature (Ta) and net snow accumulation ( P c/. We estimate a total ice-sheet-wide FAC of 26800±1840 km
3, of which 6500±450 km
3 resides within the uppermost 10m of firn, for the 2010-2017 period. In the dry snow area (Ta ≤-19 °C), FAC has not changed significantly since 1953. In the low-accumulation percolation area (Ta >-19 °C and c ≤ 600 mmw.e. yr
-1/, FAC has decreased by 23±16% between 1998-2008 and 2010-2017. This reflects a loss of firn retention capacity of between 150±100 Gt and 540±440 Gt, respectively, from the top 10m and entire firn column. The top 10m FACs simulated by three regional climate models (HIRHAM5, RACMO2.3p2, and MARv3.9) agree within 12% with observations. However, model biases in the total FAC and marked regional differences highlight the need for caution when using models to quantify the current and future FAC and firn retention capacity.
AB - A porous layer of multi-year snow known as firn covers the Greenland-ice-sheet interior. The firn layer buffers the ice-sheet contribution to sea-level rise by retaining a fraction of summer melt as liquid water and refrozen ice. In this study we quantify the Greenland ice-sheet firn air content (FAC), an indicator of meltwater retention capacity, based on 360 point observations. We quantify FAC in both the uppermost 10m and the entire firn column before interpolating FAC over the entire ice-sheet firn area as an empirical function of long-term mean air temperature (Ta) and net snow accumulation ( P c/. We estimate a total ice-sheet-wide FAC of 26800±1840 km
3, of which 6500±450 km
3 resides within the uppermost 10m of firn, for the 2010-2017 period. In the dry snow area (Ta ≤-19 °C), FAC has not changed significantly since 1953. In the low-accumulation percolation area (Ta >-19 °C and c ≤ 600 mmw.e. yr
-1/, FAC has decreased by 23±16% between 1998-2008 and 2010-2017. This reflects a loss of firn retention capacity of between 150±100 Gt and 540±440 Gt, respectively, from the top 10m and entire firn column. The top 10m FACs simulated by three regional climate models (HIRHAM5, RACMO2.3p2, and MARv3.9) agree within 12% with observations. However, model biases in the total FAC and marked regional differences highlight the need for caution when using models to quantify the current and future FAC and firn retention capacity.
UR - http://www.scopus.com/inward/record.url?scp=85062775000&partnerID=8YFLogxK
U2 - 10.5194/tc-13-845-2019
DO - 10.5194/tc-13-845-2019
M3 - Article
SN - 1994-0416
VL - 13
SP - 845
EP - 859
JO - Cryosphere
JF - Cryosphere
IS - 3
ER -
