VARIABILITY OF LARGE OUTFLOW OF FRESH WATER INTO THE OPEN OCEAN

Rivers discharge freshwater and continental borne nutrients and organic matter on the neighboring ocean. The runoff magnitude and the local dynamics determine the scale of the impact of these buoyant waters on the marine ecosystem. We analyze the regional patterns of sea surface salinity (SSS) as determined from satellite remote sensors to study the impact of continental runoff on the neighboring ocean during a three year period. We focus on large runoff rivers, where the SSS signal is strong and extend over large enough areas to be captured by these sensors. Globally, the regions of largest SSS variability are associated with the outflows of freshwater from the Amazon, Congo, Yangtze and Río de la Plata rivers. The Amazon and Congo rivers show well-defined seasonal cycles comprising 70 and 65 % of the regional SSS variability, respectively. The oceanic impact of the Río de la Plata presents significant seasonality, explaining over 50% of the regional SSS variability, while the region under the Yangtze River influence presents a SSS increase throughout this 3-year period, and large seasonal oscillations. Using a new processing technique that improves time and space resolution and reduces the impact of land contamination, we analyze the dynamics of the cross shelf exchange of each of these large rivers based on Aquarius SSS data.