THE VULNERABILITY OF MAJOR US COASTAL CITIES TO STORM SURGE FLOODING IS INCREASING PRIMARILY DUE TO RISING SEA LEVELS AND COSTAL SUBSIDENCE. ALTHOUGH THE MASS GAIN FROM ICE SHEETS WILL DOMINATE A CENTURY FROM NOW AT THE MOMENT DYNAMICAL ADJUSTMENTS OF THE OCEAN TO VARIABLE WINDS AS WELL AS THE CONTRIBUTION OF VERTICAL LAND MOTION (VLM) CAUSE MUCH MORE SIGNIFICANT DEVIATIONS OF REGIONAL RELATIVE SEA LEVEL AWAY FROM THE GLOBAL MEAN. IT HAS ALREADY BEEN DEMONSTRATED IN SEVERAL REGIONS THAT THESE DYNAMICAL CHANGES IN MEAN SEA LEVEL EXCEED GLOBAL MEAN SEA LEVEL RISE BY A FACTOR OF THREE TO FOUR TIMES FOR PERIODS OF TWENTY YEARS OR LONGER. ONE EXAMPLE IS IN THE WESTERN PACIFIC AND STUDIES HAVE INDICATED THIS IS PRIMARILY DUE TO WINDS ASSOCIATED WITH THE PACIFIC DECADAL OSCILLATION (PDO). WITH GROWING EVIDENCE FOR A CHANGE IN THE STATE OF THE PDO THE WEST COAST OF THE UNITED STATES MAY BE IN STORE FOR RAPIDLY RISING SEA LEVEL OVER THE NEXT FIFTEEN TO TWENTY YEARS OR LONGER. IT IS IMPORTANT TO QUANTIFY THE POSSIBLE SIZE. WE PROPOSE TO STUDY BOTH THE DYNAMICAL OCEAN SIGNAL AND THE VERTICAL LAND MOTION IN COMBINATION AS IT IS RELATIVE SEA LEVEL CHANGE THAT IS MOST IMPORTANT TO SOCIETY. VERTICAL LAND MOTION INCLUDES ONGOING GLACIAL ISOSTATIC ADJUSTMENT (FOR WHICH SEVERAL MODELS ARE AVAILABLE) SEDIMENT COMPACTION TECTONIC SIGNALS AS WELL AS ANTHROPOGENIC SOURCES DUE TO GROUNDWATER AND OIL EXTRACTION AND POPULATION GROWTH. THE VLM HAS BEEN LITTLE STUDIED IN TERMS OF THE EFFECT ON REGIONAL SEA LEVEL. THUS WE WILL EVALUATE IT ALONG THE ENTIRE PACIFIC GULF AND ATLANTIC COAST OF NORTH AMERICA USING GPS AND INSAR WITH A FOCUS ON LARGE AND IMPORTANT COASTAL CITIES: SAN FRANCISCO LOS ANGELES SEATTLE NEW YORK CITY HOUSTON/GALVESTON AND MIAMI. THE METHODS WE WILL USE ARE BRIEFLY SUMMARIZED BELOW: 1. WE WILL IDENTIFY THE RELEVANT MECHANISMS FORCING DECADAL- TO MULTI-DECADAL VARIATIONS IN REGIONAL MEAN SEA LEVEL AT SELECT LOCATIONS AROUND THE UNITED STATES BASED ON ANALYSIS OF TIDE GAUGE RECORDS AND A REGIONAL OCEAN MODEL NESTED WITHIN A GLOBAL GENERAL CIRCULATION MODEL. WE WILL QUANTIFY HOW WELL THE REGIONAL MODEL SEA SURFACE HEIGHT (AND/OR BOTTOM PRESSURE) MATCHES THE OBSERVED RECORD FROM TIDE GAUGES QUANTIFY HOW THE VARIATIONS ARE RELATED TO LARGER-SCALE CLIMATE MODES (E.G. PDO EL NI O NORTH ATLANTIC OSCILLATION ATLANTIC MUTIDECADAL VARIABILITY ETC) AND ADJUST THE REGIONAL MODEL TO BETTER MATCH BOTH THE MAGNITUDE AND TIMING OF OBSERVED SEA LEVEL EVENTS. THIS WILL BE DONE VIA A COMBINATION OF REGIONAL SCALING ADJUSTING FORCING PARAMETERS AND/OR ADJUSTING SELECT PARAMETERS IN THE MODEL. ONCE THE REGIONAL MODEL IS VALIDATED WE WILL USE PAST WIND RECORDS REPRESENTING PAST STATES OF THE CLIMATE SYSTEM (I.E. PDO WIND VARIABILITY FROM THE 1950S-1970S ENSO WIND VARIABILITY FROM THE 1980S-1990S) AND FORCE THE MODEL TO MAKE PREDICTIONS OF POSSIBLE SEA LEVEL EXCURSIONS FOR THE NEXT TWENTY TO THIRTY YEARS. 2. WE WILL UTILIZE GPS AND INSAR TO DETERMINE VERTICAL DISPLACEMENTS IN THE COASTAL REGIONS OF THE AFOREMENTIONED CITIES. INSAR PROVIDES DETAILED COMPREHENSIVE BUT LOCALIZED OBSERVATIONS OF DISPLACEMENT IN THE SATELLITE LINE OF SIGHT AT PIXELS A FEW METERS APART. GPS WILL BE USED TO CALIBRATE INSAR REDUCE INSAR ATMOSPHERIC AND BASELINE ERRORS AND DETERMINE INSAR RANGE RELATIVE TO THE (CM) MASS CENTER OF EARTH THE IDENTICAL REFERENCE FRAME THAT SEA LEVEL FROM SATELLITE ALTIMETRY IS DETERMINED IN. INSAR MEASUREMENTS FROM ASCENDING AND DESCENDING PASSES WILL BE FURTHERMORE COMBINED WITH GPS TO DETERMINE TIME SERIES OF DISPLACEMENTS IN THREE DIMENSIONS. THE ACCURACY OF INSAR RELATIVE POSITION ESTIMATES OF SITES SEPARATED BY MORE THAN 50 KM WILL BE EVALUATED WITH GPS PROVIDING AN INDEPENDENT CHECK OF THE ATMOSPHERE DELAY MODELS USED TO REDUCE THE INSAR DATA THE PROPOSAL TEAM INCLUDES EXPERTS ON REGIONAL OCEAN MODELING TIDE GAUGES AND WIND-FORCED INTERANNUAL AND DECADAL-SCALE VARIATIONS IN SEA LEVEL GPS AND INSAR.