Fate of water pumped from underground and contributions to sea-level rise

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1 Fate of water pumped from underground and contributions to sea-level rise Yoshihide Wada, Min-Hui Lo, Pat J.-F. Yeh, John T. Reager, James S. Famiglietti, Ren-Jie Wu, Yu- Heng Tseng Further descriptions about model uncertainty: The NCAR Community Earth System Model (CESM) Large Ensemble (CESM-LE) project is designed to enable the assessment of climate changes with considering the internal climate variability 43. Thus, the CESM-LE simulations can be utilized to help interpret model uncertainties and the associated magnitudes in the NCAR CESM. Table S2 shows the standard deviations of the mean changes (from 1920 to 2005) in water budget components among 30 ensemble members. Over the land, the mean change caused by GWD forcing in the terrestrial water budget (P-E-R) is approximately 238 km 3 yr -1 (Table 1) while the standard deviation of P-E-R among 30 CESE-LE ensemble runs is only 25 km 3 yr -1. (Table S2). This indicates that the magnitude of GWD forcing (238 km 3 yr -1 ) is significantly larger than the natural variability in the CESM-LE, and hence the resulting change in terrestrial water storage is robust. Individual terms are also tabulated in Table S2, indicating that the contributions from each component are all consistently larger than natural variability. In addition, the change over the ocean under GWD forcing run is found to be slightly smaller than the standard deviation of 30 CESM-LE members (238 km 3 yr -1 vs 247 km 3 yr -1, Table S2). This is not surprising because the GWD forcing is placed over the land with no direct impacts on the ocean (only with indirect impacts). The change over the ocean is still within the same order of magnitude (uncertainty) as the internal variations in the CESM-LE, supporting the indirect influence through the ocean-atmosphere interactions. Water budget closures of the land and ocean: In the following equations, the subscripts Land, Ocean and Atmos. are used to denote three coupled storages respectively. (1) For the control (CTR) run (all the variables with units of km 3 yr -1 ) - (S1) ( ) (S2) NATURE CLIMATE CHANGE 1

2 ( ) = (S3) ( ) and the vapor transport from ocean to the land (i.e., atmospheric vapor convergence) is: = = (S4) ( = = ) where the storage change of atmosphere above land ( about ~0 km 3 yr -1, while that above the ocean ( ) is calculated from model output as ) is calculated as ~10 km 3 yr -1. Also, this amount of (+41835) can also be checked to be equal to ), according to the combined land-atmosphere water balance. ( (2) For the GWD run (units of km 3 yr -1 ) - = (S5) ( ) = (S6) ( ) = (S7) ( ) and the vapor transport from ocean to the land (i.e., atmospheric vapor convergence) is: = = (S8) ( = = ) where the storage change of the atmosphere above land ( ) is computed from model output as about ~0 km 3 yr -1, while that above the ocean ( ) is calculated as ~11 km 3 yr -1. Also, this amount of (+41749) can also be checked to ensure that it is equal to + + ( ), according to the combined land-atmosphere water balance. Finally, for both the control (CTR) and GWD runs, they can be checked that the total storage changes combining land, ocean and atmosphere are zero: = 0 (S9) 2 NATURE CLIMATE CHANGE

3 SUPPLEMENTARY INFORMATION For the Control (CTR) run - ( = 0 ) For the GWD run - ( = 0 ) References (continued from the main manuscript) 43 Kay, J. E. et al. The Community Earth System Model (CESM) Large Ensemble Project: A Community Resource for Studying Climate Change in the Presence of Internal Climate Variability. Bull. Am. Meteorol. Soc., 96, , doi: /BAMS-D (2015). Figure S1. Relationship between the annual range of global averaged water storage and corresponding P- E-R (precipitation minus evaporation and runoff) simulated by 19 global climate models (listed in Table S1) participating in the CMIP5 archives. Global annual water storage range derived from GRACE satellite measurements corresponds to -42mm as a reference. NATURE CLIMATE CHANGE 3

4 Figure S2. Normalized Taylor diagram presents a comparison of the GRACE observations with the CMIP5 simulations for the seasonal cycle time series of global land water storage. The diagram shows the correlation and ratio of the standard deviation. 4 NATURE CLIMATE CHANGE

5 SUPPLEMENTARY INFORMATION Table S1. CMIP5 models used in Figure S1 and S2. Model Bcc-csm1-1 BNU-ESM CanESM2 CCSM4 CESM1-BGC CESM1-CAM5 CESM1-FASTCHEM CESM1-WACCM CNRM-CM5 FGOALS-g2 GFDL-CM3 GISS-E2-H GISS-E2-R inmcm4 5 -ESM-CHEM -ESM MPI-ESM-LR MRI-CGCM3 Institution ID BCC BNU CCCma NCAR CNRM-CERFACS LASG-CESS NOAA GFDL NASA-GISS NASA-GISS INM MPI-M MRI Table S2. Standard deviations of the mean changes (from 1920 to 2005) in water budget components among 30 ensemble member runs in the CESM-LE. km 3 yr -1 Precipitation Runoff Evaporation Total storage change GW storage change Precipitation minus evaporation Land Ocean NATURE CLIMATE CHANGE 5