0 20 40 60 80 100 120 140 160
High spatial variability of the annual SMB at the kilometer scale
Stationnary since 2004
Stationnary since the 1970’s
Surface mass balance (SMB) observations in coastal Adelie Land
IPEV
French polar institute archives
From the coast to 17 km inland
22 accumulation stakes
Measured annually
(stakes height)
Dec. 1970 → Dec. 1991 : 21 years
GS
GLACIOCLIM-SAMBA stake-line
From the coast to 156 km inland
91 accumulation stakes
Surveyed annually
(height + snow density on each stake)
a) b) GS Stakes Line 180° 4200 3000 138° 139° 140° 68° 67° 2000 1000 0 0 200 -10 -60 67.5° 270° 70° 60° 400 600 800 1000 1200 1400 1600 1800 2000
A 40-year accumulation dataset for Adelie Land, Antarctica
and its application for model validation
Cécile Agosta
(1), Vincent Favier
(1), Christophe Genthon
(1), Hubert Gallée
(1), Gerhard Krinner
(1), Jan T. M. Lenaerts
(2), Michiel R. van den Broeke
(2)(1)
Laboratoire de Glaciologie et Géophysique de l’Environnement,
Université Joseph Fourier / CNRS, Grenoble, France
(2)
Institute for Marine and Atmospheric research Utrecht,
Utrecht University, Utrecht, The Netherlands
Contact :
cecile.agosta@gmail.com
/ Reference :
Climate Dynamics, Vol 38, Numbers 1-2, 75-86, DOI:10.1007/s00382-011-1103-4
a) b) GS Stakes Line 180° 4200 3000 138° 139° 140° 68° 67° 2000 1000 0 0 200 -10 -60 67.5° 270° 70° 60° 400 600 800 1000 1200 1400 1600 1800 2000
Surface elevation in m from Bamber et al. (2009)
Black dots : GS stakes
Coastal Adelie Land
High interannual variability
Unchanged temporal variability
since the 1970’s
Temporally-averaged SMB
Blue lines and light blue band :GS mean and minimum-maximum interval (2004-2008) Red lines and light red band :
IPEV mean and the 80% interval of SMB values (1971-1991)
Horizontal black bars :
Uncertainty associated with the location of the IPEV stakes
Gap-filled GS SMB
temporally-averaged
(2004-2008)
km from the coast
2004 2005 2006 2007 2008 -200200 600 1000 G S SMB (mm w .e . a -1 ) -200200 600 1000 1400 2004 : 50 stakes / 52 km 2005 : 71 stakes / 104 km 2006-2011 : 91 stakes / 156 km -200200 600 1000 -200200 600 1000 -200 200 600 1000 Me a n SMB p e r st a ke (mm w .e . a -1 )
km from the coast
IPEV 1971-1991 GS 2004-2008
IPEV GS
km from the coast
S M B (m m w .e . a -1 ) 0 200 400 600 800 0 40 80 120 160 ±σ
km from the coast
SMB (mm w .e . a -1 ) 20 km average Me a n SMB (mm w .e . a -1 )
Spatially-averaged SMB (0 to 17 km)
Vertical bars :
2-standard deviation intervals
van de Berg et al.
LMDZ4 0 40 80 120 160 ERA-40 ERA-Int RACMO 0 400 800 Arthern et al. MAR SMB (mm w .e. a -1 ) km along transect PMM5 0 400 800 0 400 800 0 400 800 0 40 80 120 160 0 40 80 120 160 0 40 80 120 160 0 40 80 120 160 0 40 80 120 160 0 40 80 120 160 0 40 80 120 160 km along transect SMB (mm w .e. a -1 ) SMB (mm w .e. a -1 ) 0 200 600 800 400 MAR 1970 1980 1990 2000 2010 PMM5 1970 1980 1990 2000 2010 0 200 600 800 400 RACMO 1970 1980 1990 2000 2010 0 200 600 800 400 LMDZ4 1970 1980 1990 2000 2010 0 200 600 800 400 1970 1980 1990 2000 2010 ERA-40 0 200 600 800 400 ERA-Int 1970 1980 1990 2000 2010 0 200 600 800 400
Evaluation of Antarctic SMB climatologies for the end of the 20th c.
Conclusions
No significant accumulation trend over the last 40 years in Coastal Adelie Land GLACIOCLIM-SAMBA stake line, SMB observatory :
Representative of the climatology of coastal Adelie Land from the 1970’s to present
Designed to evaluate and validate climate models at the mesoscale and at interannual time scales : Adequately sample small-scale spatial variability to be properly averaged out
Large spatial extent to fit the scales resolved by the models Annual resolution over a multi-year time span (to be continued)
At the periphery of the ice sheet where present accumulation and predicted change are largest Distributed data : http://www-lgge.ujf-grenoble.fr/ServiceObs/SiteWebAntarc/background.html
SMB climatologies evaluation :
The meso-scale spatial pattern of the annual-mean accumulation is qualitatively reproduced (except MAR) MAR model underestimated significantly the mean SMB : corrected now
Reanalyses and models forced by reanalyses correctly represent the chronological variability (good large-scale circulation)
The magnitude of the SMB interannual variability is underestimated
Observation-based climatologies :
Arthern et al. (2006) and van de Berg et al. (2006)
Re-analyses :
ERA-40 and ERA-Interim
Atmospheric global circulation model :
LMDZ4
Atmospheric regional circulation models :
MAR, PMM5 and RACMO2
Spatial patterns (temporally-averaged SMB)
Colored lines : Model
Black lines : GS stakes SMB averaged on each model grid box (2004-2008)
Interannual variability (spatially-averaged SMB)
Spatial mean over 17 km-IPEV (empty circles) / 156 km-GS (full circles)
Colored lines : Model / Black lines : Observations (IPEV or GS)
Boxes : length = period of computation/measurement, middle dashed line = mean SMB, width = two standard deviation intervals
