Satellite Radar Altimetry Supporting Coastal Hydrology: Case Studies of Guadalquivir River Estuary and Ebro River Delta (Spain)

Coastal zones close to big river systems are hydrodynamically characterized by inland and open ocean waters. Satellite altimetry data have recently been scientifically exploited in coastal zones. However, more efforts are still needed in terms of using these data in new applications in the coastal strip. Our study analyzes the capability of the European Space Agency CryoSat-2 satellite to measure the sea level elevation associated with bulge-like lens of less salty waters from river discharges, spreading into the adjacent coastal zones. We analyze four events of high river freshwater discharges in two river estuaries in Spain: Guadalquivir and Ebro. We obtain along-track Absolute Dynamic Topography from CryoSat-2 satellite during these events and compare them with periods of low discharge conditions. In three of the events, the bulges increase the sea level between 5 and 10 cm with respect to the sea level observed in low / normal discharge conditions. The extension of the lens is far from the estuary mouth: more than 25 km from the coast in the case of the Guadalquivir River and about 50 km for the Ebro River. The wind regime and the surface circulation explain the lack of a higher sea level in one of the events analyzed.