Understanding Current and Projected Sea Level Change with Multi-Satellite Observations

THIS PROPOSAL AIMS TO CONTRIBUTE TO THE NASA SEA-LEVEL CHANGE TEAM (N-SLCT) THROUGH AN INTERDISCIPLINARY INVESTIGATION THAT ADDRESSES THE MULTI-FACETED PROBLEM OF CURRENT AND FUTURE SEA LEVEL RISE. ALL FOUR MAIN OBJECTIVES IN THE N-SLCT SOLICITATION ARE ADDRESSED AS FOLLOWS. THE PROPOSAL GOALS ARE: 1) CHARACTERIZE CURRENT CHANGES IN SEA ICL-EL AND REVISIT THE INDIVIDUAL COMPONENTS OF THE SEA LEVEL BALANCE WITH MULTI-SATELLITE OBSERVATIONS; 2) CHARACTERIZE UNDERLYING PROCESSES BY EMPLOYING THE CLIMATE SIMULATION REANALYSIS AND FORECAST CAPABILITIES OF GODDARD EARTH OBSERVING SYSTEM GEOS-S WHICH INCLUDES ATMOSPHERE OCEAN ICE AND LAND HYDROLOGY COMPONENTS; 3) IMPROVE KNOWLEDGE OF ICE MASS CHANGE BY A RECONSTRUCTION OF CURRENT ICE SHEETS AS CONSTRAINED BY ALTIMETRY AND GRACE OBSERV1TTIONS AND RELATE THESE CHANGES TO SURFACE MASS BALANCE VARIABILITY AND ITS ASSOCIATED CLIMATE MECHANISMS AND 4) PROJECT THE "COMMITTED" SEA LEVEL CONTRIBUTION FROM THE ICE SHEETS AND EXPLORE ONE ASPECT OF THIS FUTURE SEA LEVEL RISE IMPACT ON COASTAL CITIES. THE PROPOSED WORK INTEGRATES THREE EXISTING AND INDEPENDENTLY FUNDED EFFORTS WITHIN OUR GROUP: MULTI-MISSION SATELLITE ALTIMETRY FROM NASA'S MEASURES OCEAN ALTIMETRY PROGRAM; SATELLITE GRAVIMETRY FROM A COMPLEMENTARY MEASURES SURFACE-MASS VARIABILITY PROGRAM; AND THE GEOS-5 SYSTEM WHICH IS HOUSED WITHIN GSFC'S GLOBAL MODELING AND ASSIMILATION OFFICE. OUR ULTIMATE GOAL IS TO DETERMINE THE GLOBAL AND REGIONAL FUTURE SEA LEVEL CHANGE TO WHICH MANKIND IS ALREADY COMMITTED BECAUSE OF PAST AND CURRENT GLOBAL WARMING. THIS WARMING HAS ALREADY LOCKED IN A COMMITTED SEA LEVEL RISE DUE TO THE DELAYED RESPONSE FROM ICE SHEETS WHICH WE PROPOSE TO EXPLICITLY MODEL. THIS "COMMITTED TO" PROJECTION WILL COMPLEMENT OTHER TYPES OF PROJECTIONS BASED ON DIFFERENT FUTURE WARMING SCENARIOS WHICH OTHER GROUPS INCLUDING POTENTIALLY SOME WITHIN THE N-SLCT ARE PRODUCING. THE KEY TO OUR NUMERICAL ICE SIMULATIONS WILL BE SUCCESSFUL SIMULATION OF CONTEMPORARY ICE SHEET CHANGES THAT CAN REPRODUCE CURRENT OBSERVATIONS. BUT EVEN DATA-CONSTRAINED MODELS THAT REPRODUCE CONTEMPORARY OBSERVATIONS CONTAIN SIGNIFICANT UNCERTAINTIES SO WE SHALL PRODUCE AN ENVELOPE OF FUTURE "COMMITTED TO" PROJECTIONS BY RE-PLAYING SIMULATIONS TO ACCOUNT FOR UNCERTAINTY OF BOTH PRESENT-DAY OBSERVATIONAL CONSTRAINTS AND MODEL DYNAMICS.