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3 SMB ~ net accumulation of snow GCMs precipitation increase (21 st c.) ↔ Sea level rise Coast : major precipitation area & major changes 1 – Coastal area SMB & sea level rise July, MOCA 2009 mm w.e. yr
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Estimating the Surface Mass Balanceof the Antarctic coastal areafor climate models validation
1 – Coastal area SMB & sea level rise2 – SMB observation for climate model validation3 – Contribution of remote sensing data4 – Conclusion & Outlook
Cécile AGOSTA, V. Favier, C. Genthon, G. Krinner, H. Gallée, G. Picard, D. Six
Plan
July, 23 2009MOCA 2009
1 – Coastal area SMB & sea level rise
July, 23 2009MOCA 2009
3
SMB ~ net accumulation of snow GCMs precipitation increase (21st c.) ↔ Sea level rise
Coast : major precipitation area & major changes
1 – Coastal area SMB & sea level rise
July, 23 2009MOCA 2009
mm w.e. yr-120015010050200-50
2 – SMB observation for climate model validation
July, 23 2009MOCA 2009
5
200 km
2 – SMB observation for climate model validation
http://www-lgge.obs.ujf-grenoble.fr/ServiceObs
Dome C
42004000380036003400320030002800240022002000180016001400120010008006004002000-10-60
Stake line (from 2004) Annual measurements
emergence + density 91 stakes over 150 km
Prud’homme Cape
Glacioclim-SAMBA French Observatory of the Antarctic SMB
Surface height (m)
July, 23 2009MOCA 2009
6
2 – SMB observation for climate model validation
Glacioclim-SAMBA stake line
July, 23 2009MOCA 2009
SMB
(mm
w.e
. yr-1
)
km along the stake line
7
Glacioclim-SAMBA stake line (average over 10 km)
July, 23 2009MOCA 2009
SMB
(mm
w.e
. yr-1
)
km along the stake line
2 – SMB observation for climate model validation
8
Measurements from IPEV From 1971 to 1991 First 15 km of the stake line
2 – SMB observation for climate model validationComparison with older repports
Stationarity of spatial distributionkm along transect
SMB
(mm
w.e
. yr-
1 )
July, 23 2009MOCA 2009
9
Similar temporal variabilityNo significant trend
Measurements from IPEV From 1971 to 1991 First 15 km of the stake line
July, 23 2009MOCA 2009
YearsSMB
(mm
w.e
. yr-1
)
2 – SMB observation for climate model validationComparison with older repports
10
MAR Regional
Atm. Model40 km
2 – SMB observation for climate model validationFirst assessement of climate models
SMB distribution in coastal area Very different meso-scale distribution
LMDZ4 Atm. GCM
60 km
Courbes
90080070060055050045040035030025020015010070503020100
mm w.e. yr-1
July, 23 2009MOCA 2009
1981-2000
km along stake lineSM
B (m
m w
.e. y
r-1)
11
2 – SMB observation for climate model validation First assessement of climate models
Long term mean
July, 23 2009MOCA 2009
Years
SMB
(mm
w.e
. yr-
1 )
3 – Contribution of remote sensing data
July, 23 2009MOCA 2009
13
Data assimilation
3 – Contribution of remote sensing dataReference climatology : Arthern et al., 2006
1200100070060055050045040035030025020015010070503020100-100
mm w.e. yr-1
Parameters κ,θ,n
n
T
PPeSMB
)( 0
Infrared TMicrowaves P-P0 Background
modelJuly, 23 2009MOCA 2009
Field mesurements
1950 – 1990
14
Strong control of the Background model on Arthern’s final map (in Adelie land)
Background model Arthern’s final map
90080070060055050045040035030025020015010070503020100
mm w.e. yr-1
July, 23 2009MOCA 2009
15
Suspicious lack of variation in coastal area Ability of background model to capture variations ?
3 – Contribution of remote sensing data
July, 23 2009MOCA 2009
90080070060055050045040035030025020015010070503020100
mm w.e. yr-1
Arthern’s climatology km along stake lineSM
B (m
m w
.e. y
r-1)
16
Spatial variability seems too weak in coastal area : Microwave footprint 60 km ?
higher SMB should be modeled Melting ?
low melting above 20 km from the coast
3 – Contribution of remote sensing dataBackground model limitation
July, 23 2009MOCA 2009
17
Reproducing mesoscale variations requires misleading parameters
3 – Contribution of remote sensing data
Background model with adjusted parameters
July, 23 2009MOCA 2009
90080070060055050045040035030025020015010070503020100
mm w.e. yr-1
km along stake lineSM
B (m
m w
.e. y
r-1)
18
Spatial variability seems too weak in coastal area : Microwave footprint 60 km ?
higher SMB should be modeled Melting ?
low melting above 20 km from the coast Orographic precipitation ?
complementary parametrisation in the background model ?
3 – Contribution of remote sensing dataBackground model limitation
July, 23 2009MOCA 2009
Conclusion & Outlook
July, 23 2009MOCA 2009
20
Stake line Stable accumulation pattern Similar IPEV (20 yr) and Glacioclim (5 yr) average
and variability
First evaluation of 2 models in coastal area LMDZ4 seems OK MAR seems too dry / low variability
Lateral variability is required
Conclusion & Outlook
July, 23 2009MOCA 2009
21
Remote sensing in coastal area : Spatial variability seems too weak
Complementary parameterisation is proposed (slope)
Assessing additionnal information on lateral SMB distribution Ground Penetrating Radar + Ice cores
Conclusion & Outlook
July, 23 2009MOCA 2009
www-lgge.ujf-grenoble.fr/ServiceObs/SiteWebAntarc/background.html
References : Arthern et al., 2006Magand et al., 2008
Acknowledgement : ice2sea, IPEV, Charmant
NASA
