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Model Results of change in Land Water Storage and Effects on Sea-Level

Model Results of change in Land Water Storage and Effects on Sea-Level. Katia Laval Université Pierre et Marie Curie. Paris LMD/IPSL. Global Mean Sea Level Variations from Altimetry in mm. Steric effect: thermal expansion of the oceans

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Model Results of change in Land Water Storage and Effects on Sea-Level

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  1. Model Results of change in Land Water Storage and Effects on Sea-Level Katia Laval Université Pierre et Marie Curie. Paris LMD/IPSL

  2. Global Mean Sea Level Variations from Altimetry in mm

  3. Steric effect: thermal expansion of the oceans water mass exchanged with other reservoirs: atmospheric water vapor and land water Causes of sea level variations Sea level variations evaluated by T/P for 1993-98 (Black), steric effect evaluated from Ishii et al, 2003, water vapor contribution from NCEP reanalysis and residual signal.

  4. Outline • Land Surface Models • Seasonal Variations of Global Sea level; Interannual variability (1997/1998) • Seasonal Variations of Regional land water (GRACE) • Trend of sea level height during the last 53 years related to terrestrial water storage.

  5. W Land Surface Models P ET S R Precipitation (rain or snow): prescribed Evapotranspiration (Rad Meteor parameters and vegetation and wetness) Runoff Snow melt Storages W: soil moisture S: Snow depth

  6. Land Surface Models SOIL ET P B B’ I Soil Hydrology R D Irrigation Flood plains Runoff Routine and ground water B’ B (SB) Qin Qout = Q’in Q1out V1 Q2out R V2 fast D Q3out slow V3 Orchidee; Runoff Routine scheme: Jan Polcher ;Tristan D’Orgeval

  7. GSWP1: Evaluation of seasonal variation of land water by LSPISLSCP-I International Satellite Land-Surface Climatology Project, produced the atmospheric forcing over the continents for 1987 and 1988 • Seasonal variations of SLH evaluated by T/P and 3 LSM: LaD (GFDL), ISBA Meteo-France, Orchidee (LMD/IPSL) (Snow+soil water+ground water) • The differences could be due to : • incompatibility of the compared periods • data/model uncertainties

  8. LMD AGCM Simulations (+Orchidee): AMIP Simulation (79-99 SST) • Sharp contrast 1997 /1998 (Willis et al, 2004): • Observations from T/P: 13mm compared to 7mm (10mm/7mm) • The variation between 1998 and 1997 is larger than internal variability Contribution of continental water to sea level variations Precipitations computed by the GCM Ngo-duc, T., K. Laval, J. Polcher and A. Cazenave (JGR, 2005a)

  9. Climate-Model Biases in Seasonality revealed by Satellite Gravimetry (Swenson and Milly, 2005, WRR) Models evaluated in this study and water stores used. “X” indicates presence of term; “0” indicates absence from model.

  10. Global map of amplitude (mm) of annual cycle of land water storage from GRACE and from five climate models. (Swenson and Milly, 2005, WRR)

  11. From GRACE Orchidee without Ground Water reservoir Orchidee with Ground Water reservoir Ngo-duc, et al, 2006, submitted,WRR. . Seasonal Variations (April-May minus November 2002) of land water in mm

  12. Time series of water storage variationas simulated by 2 versions of Orchidee, with and without routine scheme and ground water scheme and evaluated by Grace Mission (o). Ngo-duc, et al, 2006, submitted, WRR.

  13. Construction of NCC data NCEP/NCAR Reanalysis 6h; 1°.875; 1948-present Interpolation to the grid 1°x1°, differences in elevation between the grids were taken into account NCEP CRU (Climate Research Unit)precipitation 0.5°x 0.5°, 1901-2000 NPRE CRU (Climate Research Unit) temperature 0.5°x 0.5°, 1901-2000 NCRU Radiation: SRB (Surface Radiation Budget) NCC (NCEP/NCAR Corrected by CRU) 6-hourly, 1°x1°, 1948-2000 http://dods.lmd.jussieu.fr/cgi-bin/nph-dods/Dods/NCC/ (~40GB) Ngo-duc, T., J. Polcher and K. Laval (JGR, 2005b)

  14. agreement between ORCHIDEE and LaD. • (Land Dynamics LSM of GFDL) Effect of global land water storage on global mean sea level greatest variation is associated with ground water, followed by soil moisture no significant trend was detected strong decadal variability driven by precipitation, strong decrease in the beginning of 1970s Milly, P. C., D., A. Cazenave, and M. C. Gennero (Proc. Natl Acad. Sci, 2003) Ngo-duc T., K. Laval, J. Polcher, A. Lombard and A. Cazenave (GRL, 2005)

  15. Relations between land water and thermosteric sea level fluctuations These results suggest a feedback mechanism: Ocean warmer more evaporation and continental precipitation increases continents are wetter: sea-level height decreases

  16. Conclusions • The LSMs are able to simulate the seasonal variations of global land water storage, and some interannual variability is also captured by LSMs and GCMs • We need more studies to strengthen our results on regional seasonal variations • LSMs models: we must improve the reservoirs representation (lakes, dams, processes) • Grace data for several years

  17. Conclusions • Trends of terrestrial water storage have to be ascertained : • NCC data used by other LSMs • Other data (Qian et al, 2006) • Results on last years with Grace • Influence of anthropogenic changes

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