1. JAN LENAERTS SNOWDRIFT CLIMATE Snowdrift climate of Greenland and Antarctica Jan Lenaerts Michiel van den Broeke Institute for Marine and Atmospheric Research, Utrecht University, Netherlands

2. JAN LENAERTS SNOWDRIFT CLIMATE Goals SMB = PR - RU - SU s - SU ds - ER ds DECEMBER 8, 20112AGU FALL MEETING 2011 INTRODUCTION surface mass balance Snowdrift sublimation Snowdrift erosion Regional climate model (RACMO2) + Snowdrift routine

3. JAN LENAERTS SNOWDRIFT CLIMATE DOMAIN GREENLANDANTARCTICA HORIZONT AL RESOLUTI ON 11 KM27 KM SIMULATIO N PERIOD 1960-20101979-2010 LATERAL FORCING ERA-40 / ERA- INTERIM ERA-INTERIM Methodology 3AGU FALL MEETING 2011DECEMBER 8, 2011 METHODS

4. JAN LENAERTS SNOWDRIFT CLIMATE Spatial variability DECEMBER 8, 20114AGU FALL MEETING 2011 GrISAIS SU ds (Gt y -1 ) 24171 % of snowfall 36 % of ablation 874 ER ds (Gt y -1 ) 14 R ESULTS I

5. JAN LENAERTS SNOWDRIFT CLIMATE Interannual variability DECEMBER 8, 2011AGU FALL MEETING 20115 GREENLAND RESULTS II

6. JAN LENAERTS SNOWDRIFT CLIMATE Seasonal variability DECEMBER 8, 20116AGU FALL MEETING 2011 ANTARCTICA Summer: SU s and Melt // Winter: only SU ds Annual cycle in SU ds related to wind speed and surface snow conditions RESULTS III

7. JAN LENAERTS SNOWDRIFT CLIMATE Wind climate DECEMBER 8, 2011AGU FALL MEETING 20117 EVALUATION I 115 quality-controlled AWS stations

8. JAN LENAERTS SNOWDRIFT CLIMATE Wind climate (II) DECEMBER 8, 2011AGU FALL MEETING 20118 Entire ice sheet Without “rough” areas Horizontal resolution is crucial Extreme wind speeds are underestimated EVALUATION II

9. JAN LENAERTS SNOWDRIFT CLIMATE Wind climate (III) DECEMBER 8, 20119AGU FALL MEETING 2011 EVALUATION III

10. JAN LENAERTS SNOWDRIFT CLIMATE Snowdrift frequency DECEMBER 8, 2011AGU FALL MEETING 201110 Remote sensing (laser altimetry) In-situ stations EVALUATION IV Neumayer station, DML, East Antarctica

11. JAN LENAERTS SNOWDRIFT CLIMATE Snowdrift frequency (II) DECEMBER 8, 2011AGU FALL MEETING 201111 Palm et al., 2011 Laser altimetry + DEM -> depth of snowdrift layer Only strong events (> 20 m) and non-cloudy conditions EVALUATION V

12. JAN LENAERTS SNOWDRIFT CLIMATE Ablation areas DECEMBER 8, 2011AGU FALL MEETING 201112 EVALUATION VI Snowdrift (partly) explains presence and location of ablation areas

13. JAN LENAERTS SNOWDRIFT CLIMATE First attempt of describing snowdrift climate on large ice sheets Model evaluation focuses on wind speed climate and snowdrift frequency (in-situ and from space) Snowdrift sublimation is a significant contributor to the ice sheet SMB, mainly on Antarctica and in winter Snowdrift erosion is locally important Snowdrift increases near-surface humidity and impacts top snow layer characteristics Conclusions DECEMBER 8, 2011AGU FALL MEETING 201113 CONCLUSIONS