Sensitivity of Iberian estuaries to changes in sea water temperature, salinity, river flow, mean sea level, and tidal amplitudes

Abstract

This study evaluated how multiyear changes in sea water temperature, salinity, river flow, sea level, and tidal amplitudes influenced the exchange mass flow, tidal energy propagation, water column stratification, and saline intrusion in 93 Iberian estuaries. To do this, trends estimated between 2000 and 2015 in four vulnerability indices that characterize these properties were evaluated. The analysis of the indices suggested that most of the estuaries reduced both exchange mass flow and tidal energy during the analysis period mainly due to the overall decreasing trends in the M2 tidal amplitude from 2000 to 2015, which are more significantly in the southwestern estuaries of the Atlantic façade. The bulk Richardson number for most of the Spanish estuaries, particularly those in Mediterranean waters, decreased due to the strong reduction of river flows in recent years. This fact, along with the increasing trends in mean sea level, produced a saline intrusion increase at all locations, being more pronounced in the Mediterranean and the South Atlantic estuaries of the Iberian Peninsula. With a view to identify the most sensitive estuaries to environmental changes, the four indices were merged into a single net sensitivity index. Overall, the most vulnerable estuaries were those located along the Mediterranean coast, especially Júcar and Segura inlets. In Atlantic waters, the Guadalquivir and Guadiana River estuaries showed the highest relative variations of the four indices. This study indicates that the reduction of river flows is the most influential factor that affects most Spanish Iberian estuaries.