Sea Level Rise 2006

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

Causes of sea level variationsCauses of sea level variations Steric effect: thermal expansion of the oceans water mass exchanged with other reservoirs:

atmospheric water vapor and land water

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.

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.

Land Surface Models

W

P ET

R

S

Storages

W: soil moisture

S: Snow depth

Precipitation (rain or snow): prescribed

Evapotranspiration (Rad Meteor parameters and vegetation and wetness)

Runoff

Snow melt

SOIL

P

RI

B B’

D

B (SB) B’

R

D

QinQ1

out

Q2out

Q3out

Qout = Q’in

ET

Runoff Routine and ground water

Soil Hydrology

V1

V2

V3

IrrigationFlood plains

Land Surface Models

Orchidee; Runoff Routine scheme: Jan Polcher ;Tristan D’Orgeval

fast

slow

GSWP1: Evaluation of seasonal variation of land water by LSP

ISLSCP-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

LMD AGCM Simulations (+Orchidee): AMIP Simulation (79-99 SST)LMD AGCM Simulations (+Orchidee): AMIP Simulation (79-99 SST)

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)

•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

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.

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

.

Seasonal Variations (April-May minus November 2002) of land water in mm

From GRACE

Orchidee without Ground Water reservoir

Orchidee with Ground Water reservoir

Ngo-duc, et al, 2006, submitted,WRR.

Time series of water storage variation as 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.

Construction of NCC dataNCEP/NCAR NCEP/NCAR ReanalysisReanalysis

6h; 1°.875; 1948-present

NCEP

NPRE

NCRU

NCC

Interpolation to the grid 1°x1°, differences in

elevation between the grids were taken into account

CRU (Climate Research Unit) precipitation

0.5°x 0.5°, 1901-2000

CRU (Climate Research Unit) temperature

0.5°x 0.5°, 1901-2000

Radiation: SRB (Surface Radiation Budget)

(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)

Effect of global land water storage on global mean sea level

agreement between ORCHIDEE and LaD.(Land Dynamics LSM of GFDL)

greatest variation is associated with ground water, followed by soil moistureno 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)

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

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

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