Irina Gorodetskaya *, Hubert Gallée, Gerhard Krinner Laboratoire de Glaciologie et Géophysique de l’Environnement, Grenoble,France * Now at: Katholieke Universiteit Leuven, Belgium CHARMANT, LGGE 19 October, 2009 Comparison of surface mass balance components simulated by LMDZ and MAR forced with LMDZ

SMB compilations Vaughan et al Giovinetto and Bentley 1985 van den Berg et al. 2006: observations van den Berg et al. 2006: calibrated model 166 mmwe 171 mmwe

Changes in precipitation? Linear trends of annual snowfall accumulation (mm yr -1 decade -1 ) for Monaghan et al 2008

Predicted precipitation change: LMDZ (IPSL) Krinner et al. 2007, 2008 Precipitation change: / SIC changes: ( ) - ( )

Large-scale model (ECMWF or GCM) Mesoscale model (MAR) Nesting: MAR forced with LMDZ output

Atmospheric model: mesoscale hydrostatic primitive equation model (Gallée 1994, 1995)  Terrain following vertical coordinates (normalized pressure)  Turbulence: 1 1/2 closure (Duynkerke 1988)  Bulk cloud microphysics (Kessler 1962 and Lin et al improvements of Meyers et al and Levkov et al. 1992)  Solar and infrared radiative transfer scheme (Morcrette 2002, Ebert and Curry 1992)  Snow fall included into infrared radiation scheme Snow model: conservation of heat and water (solid and liquid), description of snow properties (density, dendricity, sphericity and size of the grains), melting/freezing Blowing snow model (Gallée et al, 2001) FSFS FSFS FLFL T4T4 H Lat H Sen Snow H Melt H Freez H Cond Tsfc Percolati on Liquid water             Blowing snow coupling to sea ice, land ice, vegetation...  Horizontal resolution 40 km  33 vertical levels (lowest ~9m, one level each 10 m below 50 m; top = 10hPa)  Initial and boundary conditions: LMDZ4 Modèle Atmosphérique Régional (MAR)

Relative annual mean precipitation change: Krinner et al LMDZ (IPSL): / MAR (lmdz forced): 2082 / 1982

Surface mass balance, mm w.e MAR (lmdz forced)LMDZ 175 mmwe 42 mmwe

Ratio between simulated SMB in S20 and estimates by Vaughan et al Ratio between LMDZ-simulated SMB and observed SMB in selected locations Krinner et al. 2007

SMB components: LMDZ Snow fallSublimation surface Total melt units: mmwe Effective melt 220 mmwe 17 mmwe 29 mmwe

SMB components: MAR Snow fall minus erosion Sublimation surface Melt Sublimation drifting snow units: mmwe 62 mmwe 14 mmwe 5 mmwe 7 mmwe

Annual snow fall, mmwe Difference: MAR-LMZ LMDZ: 220 mmwe MAR: 62 mmwe MAR-LMDZ: -128 mmwe

MAR : removal by wind erosion Blowing snow flux Snow fall minus erosion

Surface sublimation/deposition MEAN = 14 mmwe/yr MAR, : ECMWF ERA-15, Déry and Yau, 2002 MEAN = 14 mmwe/yr

Sublimation of drifting snow MEAN = 6 mmwe/yr MAR, , Liu et al 1983 parametrization: ECMWF ERA-15, Déry and Yau, 2002 MEAN = 15 mmwe/yr

Ablation areas MAR SMB, mmwe/yr Ablation areas van den Broeke et al, 2006 Blue = Blue ice areas > 10% (Winther et al. 2001) Red diam = meteorite sites AIS

Conclusions LMDZ and MAR : large differences in SMB LMDZ: - large precipitation and large melt = compensate - only two processes: precip and surface sublimation - melt calculated offline MAR: - snow fall is corrected for erosion = impossible to separate - lack of snow fall or too much erosion by wind - additional ablation processes: snow drift sublimation - melt is simulated  large local differences two models especially over the coasts  need more observations to tell which one is right

Surface mass balance from a GCM: Laboratoire de Meteorologie Dynamique general circulation model (LMDZ) Krinner et al mmwe (S20)

SMB components: LMDZ Melt Precip Sublimation/ deposition Krinner et al mmwe

Annual mean precipitation: MAR(lmdz forced) - LMDZ LMDZ: only snow fall (no erosion) MAR: precip-erosion (blowing snow parameterization) mmwe

Gallée and Gorodetskaya, Clim Dyn 2008 Surface air temperature over Dome C, East Antarctica MAR validation : Dome C (ECMWF forcing)

Model validation : South Pole (ECMWF forcing) Power spectrum (units 2 /time) Town, Gorodetskaya, Walden, Warren, in prep

warm events Snow accumulation, mm.w.e Integrated snow, mm.w.e Snow accumulation at South Pole (MAR forced with ERA-40) 1994 PSCs Gorodetskaya, Town, Gallée, in prep 54% 24% 7% 11%4%

MAR forced with LMDZ vs LMDZ itself : MAR - larger amplitude! r=0.6

SMB changes: from 1982 to 2082 Diff: Ratio: 2082/1982 MAR forced with LMDZ mmwe

Relative annual mean precipitation change: Krinner et al LMDZ (IPSL): / MAR (lmdz forced): 2082 / 1982

Annual mean surface temperature change: Precipitation change: 2082/1982 ratio MAR forced with LMDZ

Annual mean sea ice concentration change LMDZ [ ] - [ ] % Krinner et al. 2007