Spatial structure of the sea level seasonal cycle within the Gulf of Cadiz

摘要

Sea level anomaly maps from altimeter (AVISO) were retrieved for the Gulf of Cadiz (GoC) for the period 1997-2008, along with maps of Dynamic Atmospheric Correction (DAC), atmospheric pressure at sea level and satellite Sea Surface Temperature (SST). Data were averaged in time to obtain maps of monthly mean time series in order to analyze the seasonal variability of sea level and its main forcing agents along the GoC. Moreover, a very high resolution climatology for the region was combined with the SST maps to explore the steric contribution with enough spatial resolution near the coast. The AVISO sea level anomaly monthly maps were initially de-corrected using the DAC product and then corrected using the inverted barometer method. Atmospheric pressure explained more than 55% of the sea level variance offshore and between 35-45% within the continental shelf. The amplitude of the pressure-adjusted sea level semiannual signal was considerably reduced, confirming its meteorological origin. The steric contribution on the pressure-adjusted sea level was addressed by considering local, open ocean, basin-wide and continental shelf steric effects. The open ocean contribution explained the highest percentage of variance all over the basin with the exception of the western shelf, where the best results were obtained with the local contribution. After correcting for the best steric contribution, the amplitude of the remaining offshore annual signal was negligible (0.5-1.0 ± 1 cm). As for the continental shelves, 2-3 cm (± 0.5-1 cm) of the annual signal remained unexplained, probably due to local effects related with the shelves dynamics.