J. Famiglietti with contributions from D. Chambers, K. Hilburn, S. Nerem, M. Rodell, T. Syed, S. Swenson, I. Velicogna, J. Wahr and J. Willis 2009 NASA Sea Level Meeting Austin, Texas 2-4 November 2009 Framework for Estimating Land Water Storage Contributions to Global Mean Sea Level Rise

Mass balance methods for estimating land contributions to GMSLR Previous estimates from IPCC What we see from GRACE and other mass-based approaches Summary Overview

 S GLOBAL =  S OCEAN +  S LAND +  S ICE +  S ATM = 0 Mass balance methods for estimating land contributions to GMSLR Observing changes in global water storage using GRACE Ignoring  S ATM, all others are observable using GRACE Can measure land contribution directly  S LAND includes all land contributions implicitly: discharge, glaciers, reservoir storage, etc Previously have known what’s happening with  S OCEAN and  S ICE but not with  S LAND

Mass balance methods for estimating land contributions to GMSLR Estimating the global discharge flux using GRACE EOEO ELEL POPO PLPL QAQA QLQL SOSO SLSL  S O = P O - E O + Q L  S L = P L - E L - Q L

Mass balance methods for estimating land contributions to GMSLR Estimating the global discharge flux using GRACE Main land contributions to GMSLR are through global freshwater discharge Q L To a lesser extent from land use change and water management practices that change E L and thus P O We can now calculate Q l using GRACE and solving the land and ocean mass balances [Syed et al., 2005, 2007, 2008, 2009] Q L includes all freshwater discharge: streamflow from monitored and unmonitored regions, submarine groundwater discharge, glacier melt and ice sheet melt – anything exiting from the continents Q L implicitly includes water management, for example, streamflow and reservoir storage regulation

Previous Estimates from IPCC 2001 Church et al., 2001

Previous Estimates from IPCC 2001 Church et al., 2001

Previous Estimates from IPCC 2007 Bindoff et al., 2007

Previous Estimates from IPCC 2007 Bindoff et al., 2007

Previous Estimates from IPCC 2007 and 2001 Church et al., 2001 Land contribution? “In summary, our assessment of the land hydrology contribution to sea level change has not led to a reduction in the uncertainty compared to the TAR, which estimated the rather wide ranges of – 1.1 mm/yr to +0.4 mm/yr for 1910 to 1990, and –1.9 to +1.0 mm yr–1 for However, indirect evidence from considering other contributions to the sea level budget (see Section 5.5.6) suggests that the land contribution either is small (<0.5 mm yr–1) or is compensated for by unaccounted or underestimated contributions.” Bindoff et al., 2007

Mass balance methods for estimating land contributions to GMSLR Observing changes in global water storage using GRACE, Trends (mm/yr) Ocean = 1.2± 0.3 Land = 0.3 ± 0.5 Greenland = ± 0.1 Antarctica = ± 0.2 Famiglietti et al., submitted

Mass balance methods for estimating land contributions to GMSLR Observing changes in global water storage using GRACE, Annual period removed Famiglietti et al., submitted

Mass balance methods for estimating land contributions to GMSLR Observing changes in global water storage using GRACE, Land filter with alpine glaciers scaled Famiglietti et al., submitted Is increasing natural and anthropogenic land storage compensating for alpine glacial melt in this time period?

Mass balance methods for estimating land contributions to GMSLR Estimating the global discharge flux using GRACE Syed et al., 2009 Ocean drainage basins

Mass balance methods for estimating land contributions to GMSLR Estimating the global discharge flux using GRACE Syed et al., 2009

Mass balance methods for estimating land contributions to GMSLR Estimating the global discharge flux using GRACE Syed et al., 2009

R : Global freshwater discharge ΔM : Global ocean mass change from T/P & Jason-1 mean sea level variations. We compared GRACE ΔM with that computed using ARGO floats, and to Ishii (2006) and Ingleby and Huddleston (2007). Comparisons were favorable so we used both Ishii and IH to compute global discharge E : Global ocean evaporation (from OAFlux, HOAPS, SSM/I) P : Global ocean precipitation (from CMAP and GPCP) Trend:+ 45 km 3 /yr Syed et al., in review Shaded grey is ± 1σ of the ensemble mean. Mass balance methods for estimating land contributions to GMSLR Estimating the global discharge flux using ocean mass balance

trend 64 km 3 /yr trend 20 km 3 /yr trend 45 km 3 /yr Syed et al., in review

Summary Focus on big numbers first (global discharge, global land storage change) Need to resolve alpine glacier issue: when they melt, how much is stored on land through groundwater recharge and reservoir storage, and how much contributes to sea level rise. How about the ice sheets? Is there significant local storage Suggest that we differentiate between potential contributions to sea level rise, and actual ones Getting to point where we have consistency in methods. Now need to carefully compare to same time periods. Let’s face it, they have to match Then can worry about individual water management practices. Extremely important for mitigation. Best strategies may be to manage land water storage

Some misconceptions All alpine glacial melt runs off to the ocean We can apply the storage method by only looking at the storage changes in the major river basins