Heavy Guadalquivir River discharge detection with satellite altimetry: The case of the eastern continental shelf of the Gulf of Cadiz (Iberian Peninsula)

In situ water levels in the Guadalquivir River estuary mouth show the effect of strong river freshwater discharges on the monthly means of the sea level on a yearly basis. Accurate altimeter products oriented toward coastal zones are increasing the number of potential applications at different spatiotemporal scales. The present work is focused on the analysis of the sea-level variability in the eastern shelf of the Gulf of Cadiz (between North Africa and the southwestern side of the Iberian Peninsula), adjacent to the Guadalquivir River estuary. Sixteen years (1994-2009) of along-track and standard AVISO maps of sea-level anomalies (SLAs) have been used to generate a new high-resolution product with increased spatiotemporal resolution. The use of a bathymetry constraint and smaller correlation scales in the methodology developed to generate high-resolution altimeter products improves the characterization of the mesoscale signals in the coastal strip adjacent to the estuary due to strong river freshwater discharges. This has been confirmed by the analysis of along-track SLA data in the vicinity of the estuary. The daily evolution (2 weeks) of the sea level obtained in the event of December 2009 might be related to the river plume extension observed by optical Moderate Resolution Imaging Spectrometer (MODIS) images. The spatiotemporal distribution of the altimeter tracks available in the study area might compromise the mapping capabilities to capture coastal and fine-scale features.