A NEAR REALTIME SYSTEM FOR ESTIMATING LAND-TO-OCEAN RIVER DISCHARGE FLUX ACROSS THE GULF OF MAINE WATERSHED

Climate change is transforming the water cycle, with future increases in precipitation, evaporation, and river discharge---an intensification of the hydrological cycle---likely under several global change scenarios. This paper describes a component of the new UNH Earth Systems Observatory which aims to quantify and evaluate in near real time the land-to-ocean river discharge fluxes through the Gulf of Maine watershed. This work traces its origins to research promoted by S.L. Dingman which links terrestrial ecosystems and the hydrological cycle. Near real time estimates are obtained by linking the hydrological model with meteorological forcings from a mesoscale numerical weather prediction model. By combining--in a GIS framework---the simulated fluxes with observations of river discharge, we obtain a broad survey of the spatial and temporal variability in the river flow regimes which transport constituents through the watershed and impact coastal ecosystems. We show that the hydrological model is strongly sensitive to the climatic forcings used, and that it is able to simulate recent discharge flows well when driven with gridded precipitation data interpolated from observed station records. Against a backdrop of recent historical extremes in precipitation and discharge, the hydrological estimates are used to examine the potential influence of anomalous freshwater discharge and nutrient fluxes on near-shore biological productivity as estimated from optical remote sensing data. By synthesizing components of the regional hydrosphere in a spatial analysis system we obtain an improved predictive capability for monitoring the changing atmosphere-land-ocean system and a better quantification of the water fluxes and stores, a theme emphasized throughout the career of S.L. Dingman.