1. Estimating the Surface Mass Balance of the Antarctic coastal area for climate models validation 1 – Coastal area SMB & sea level rise 2 – SMB observation for climate model validation 3 – Contribution of remote sensing data 4 – Conclusion & Outlook Cécile AGOSTA, V. Favier, C. Genthon, G. Krinner, H. Gallée, G. Picard, D. Six Plan July, 23 2009MOCA 2009

2. 1 – Coastal area SMB & sea level rise July, 23 2009MOCA 2009

3. 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, 23 2009MOCA 2009 mm w.e. yr -1 200 150 100 50 20 0 -50

4. 2 – SMB observation for climate model validation July, 23 2009MOCA 2009

5. 5 200 km 2 – SMB observation for climate model validation http://www-lgge.obs.ujf-grenoble.fr/ServiceObs Dome C 4200 4000 3800 3600 3400 3200 3000 2800 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400 200 0 -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. 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. 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. 8  Measurements from IPEV  From 1971 to 1991  First 15 km of the stake line 2 – SMB observation for climate model validation Comparison with older repports  Stationarity of spatial distribution km along transect SMB (mm w.e. yr -1 ) July, 23 2009MOCA 2009

9. 9  Similar temporal variability  No significant trend  Measurements from IPEV  From 1971 to 1991  First 15 km of the stake line July, 23 2009MOCA 2009 Years SMB (mm w.e. yr -1 ) 2 – SMB observation for climate model validation Comparison with older repports

10. 10 MAR Regional Atm. Model 40 km 2 – SMB observation for climate model validation First assessement of climate models  SMB distribution in coastal area  Very different meso-scale distribution LMDZ4 Atm. GCM 60 km Courbes 900 800 700 600 550 500 450 400 350 300 250 200 150 100 70 50 30 20 10 0 mm w.e. yr -1 July, 23 2009MOCA 2009 1981-2000 km along stake line SMB (mm w.e. yr -1 )

11. 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 )

12. 3 – Contribution of remote sensing data July, 23 2009MOCA 2009

13. 13 Data assimilation 3 – Contribution of remote sensing data Reference climatology : Arthern et al., 2006 1200 1000 700 600 550 500 450 400 350 300 250 200 150 100 70 50 30 20 10 0 -100 mm w.e. yr -1 Parameters κ,θ,n Infrared T Microwaves P-P 0 Background model July, 23 2009MOCA 2009 Field mesurements 1950 – 1990

14. 14 Strong control of the Background model on Arthern’s final map (in Adelie land) Background model Arthern’s final map 900 800 700 600 550 500 450 400 350 300 250 200 150 100 70 50 30 20 10 0 mm w.e. yr -1 July, 23 2009MOCA 2009

15. 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 900 800 700 600 550 500 450 400 350 300 250 200 150 100 70 50 30 20 10 0 mm w.e. yr -1 Arthern’s climatology km along stake line SMB (mm w.e. yr -1 )

16. 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 data Background model limitation July, 23 2009MOCA 2009

17. 17  Reproducing mesoscale variations requires misleading parameters 3 – Contribution of remote sensing data Background model with adjusted parameters July, 23 2009MOCA 2009 900 800 700 600 550 500 450 400 350 300 250 200 150 100 70 50 30 20 10 0 mm w.e. yr -1 km along stake line SMB (mm w.e. yr -1 )

18. 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 data Background model limitation July, 23 2009MOCA 2009

19. Conclusion & Outlook July, 23 2009MOCA 2009

20. 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. 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

22. www-lgge.ujf-grenoble.fr/ServiceObs/ SiteWebAntarc/background.html References : Arthern et al., 2006 Magand et al., 2008 Acknowledgement : ice2sea, IPEV, Charmant NASA