ENVIRONMENTAL SYSTEMS DO NOT WAIT UNTIL IT IS CONVENIENT FOR HUMANS TO RESPOND TO PERTURBATIONS AND A PRIME EXAMPLE OF THIS IS THE RAPIDLY CHANGING ARCTIC THAT HAS SCIENCE AND POLICY SCRAMBLING TO KEEP UP. THIS HIGHLIGHTS A CRITICAL NEED FOR PROGRAMS SUCH AS NASA S ARCTIC-BOREAL VULNERABILITY EXPERIMENT (ABOVE) AND ARCTIC-COASTAL LAND OCEAN INTERACTIONS (ARCTIC-COLORS) THAT AIM TO CHARACTERIZE THE EXTENT OF CHANGE TO TERRIGENOUS AND COASTAL SYSTEMS IN THE ARCTIC RESPECTIVELY AND THE STRENGTH OF ASSOCIATED FEEDBACKS. HOWEVER IT ALSO HIGHLIGHTS THE ISSUE OF TIMING THAT THESE PROGRAMS NEED TO BE FULLY IMPLEMENTED AS QUICKLY AS POSSIBLE FOR MAXIMUM IMPACT ON FUTURE POLICY DECISIONS. THE PROPOSED RESEARCH OUTLINED HERE SEEKS TO JUMPSTART ARCTIC-COLORS WHILE FILLING MAJOR GAPS IN OUR UNDERSTANDING OF THE LINKAGES BETWEEN AQUATIC OPTICAL AND BIOGEOCHEMICAL PROPERTIES AND OUR KNOWLEDGE ABOUT THE TRANSFORMATION OF INLAND WATER QUALITY CONSTITUENTS FROM THE ABOVE DOMAIN THROUGH ESTUARIES TO THE NEAR COASTAL ENVIRONMENT. OUR OVERARCHING GOAL IS TO USE NEW AND ENHANCED REMOTELY SENSED WATER QUALITY OBSERVATIONS TO BETTER UNDERSTAND BIOGEOCHEMICAL FLUXES AND TRANSFORMATIONS ACROSS TERRESTRIAL-AQUATIC INTERFACES IN THE ARCTIC. SPECIFICALLY WE PROPOSE TO: 1) LAY THE FOUNDATION FOR ARCTIC-COLORS BY ESTABLISHING CURRENT BASELINE WATER QUALITY CONDITIONS FROM THE HEAD OF TIDES TO THE NEAR COASTAL ENVIRONMENT IN TWO LARGER RIVER SYSTEMS (YUKON AND MACKENZIE RIVERS) AND A SMALLER RIVER SYSTEM ON THE NORTH SLOPE OF ALASKA. 2) CHARACTERIZE THE TRANSFORMATION OF RIVERINE MATERIAL THROUGH ESTUARINE GRADIENTS ACROSS DIFFERENT SEASONAL AND HYDROLOGIC CONDITIONS IN ORDER TO MODEL DELIVERY OF MATERIALS TO THE NEAR COASTAL ENVIRONMENT FROM MORE THAN A DECADE OF PAST RIVER MEASUREMENTS FROM THE ARCTIC GREAT RIVERS OBSERVATORY (ARCTIC-GRO) DATASET. 3) REFINE AND DEVELOP ALGORITHMS FOR WATER QUALITY CONCENTRATIONS FROM REMOTE SENSING DATA WHICH CAN THEN BE USED TO HINDCAST COASTAL ARCTIC CONDITIONS BACK TO 2002 AND QUANTIFY THE EXTENT AND RATES OF CHANGE IN DELIVERY OF RIVERINE MATERIALS TO THE NEAR COASTAL ENVIRONMENT. THE VALIDITY OF THESE HINDCAST VALUES WILL BE ASSESSED THROUGH DATA SYNTHESIS EFFORTS OF PAST MEASUREMENTS AND MODELED EXPORTS AS OUTLINED IN ITEM #2. TO LINK OPTICS TO AQUATIC BIOGEOCHEMISTRY ACROSS THE CONTINUUM OF ARCTIC RIVERS ESTUARIES AND THE COASTAL OCEAN WE PLAN INTENSIVE FIELD SAMPLING ON THE YUKON RIVER-DELTA FOR THREE TRANSECTS IN SPRING EARLY AND LATE SUMMER ACQUISITION OF ADDITIONAL TRANSECT SAMPLES DURING SIMILAR FLOW REGIMES THROUGH OUR COLLABORATORS ON THE NORTH SLOPE AND MACKENZIE RIVER AND A PERIOD OF CONTINUOUS MONITORING IN THE YUKON RIVER. THESE STUDY REGIONS ARE PART OF BOTH THE ABOVE AND ARCTIC-COLORS CORE STUDY DOMAINS. IN ADDITION TO THE PROPOSED NEW FIELD OBSERVATIONS WE WILL CONDUCT A SERIES OF CONTROLLED SALINITY MIXING EXPERIMENTS ON SAMPLES FROM ALL THREE SYSTEMS THAT WILL SIMULATE TRANSPORT THROUGH ESTUARINE GRADIENTS DURING SEASONS IN WHICH WE ARE NOT COLLECTING TRANSECTS. THIS IS CRUCIAL FOR UNDERSTANDING THE FATE OF TERRIGENOUS ORGANIC MATTER IN THE ARCTIC OCEAN. FINALLY WE PROPOSE TO SYNTHESIZE EXISTING BIO-OPTICAL HYDROLOGICAL AND BIOGEOCHEMICAL DATASETS IN COASTAL AND INLAND ARCTIC ECOSYSTEMS COLLECTED AS PART OF OUR PRIOR WORK IN THE FRAMEWORK OF ARCTIC-GRO AND ABOVE AND THROUGH OUR PROPOSED COLLABORATIONS. THESE NEW AND EXISTING OBSERVATIONS WILL ALLOW US TO DEVELOP NEW AND REFINED REMOTE SENSING BIO-OPTICAL RETRIEVALS AND ATMOSPHERIC CORRECTIONS THAT WILL ALLOW REGIONAL SCALING AND TEMPORAL HINDCASTING. THROUGH THE PROPOSED INTEGRATION OF FIELD SAMPLING SATELLITE ALGORITHM DEVELOPMENT HINDCASTING AND SYNTHESIS EFFORTS THE PROPOSED STUDY WILL PROVIDE CRITICAL NEW KNOWLEDGE OF BIOGEOCHEMICAL TRANSFORMATIONS ACROSS ARCTIC TERRESTRIAL-AQUATIC INTERFACES AND AN URGENTLY NEEDED LINK BETWEEN THE ABOVE AND ARCTIC-COLORS FIELD PROGRAMS BOTH ON THE SPATIAL AND TEMPORAL DOMAIN.