Impact of Climate Change on the Thermohaline Properties in the Ria de Vigo (NW Iberian Peninsula) 

Climate change will have far-reaching consequences on the environment, primary production, the economy, and society as a whole. Changes in hydrodynamic patterns pose a significant threat to low-lying coastal areas that often present high economic and biological value. The Ria de Vigo is part of the Rias Baixas, which are located in the NW of the Iberian Peninsula. This system, as well as the rest of the Galician coast, is an area of high primary production that is vulnerable to changes in hydrodynamics induced by climate change. These changes could have a detrimental effect on the system and the local communities as they strongly depend on the income brought by aquaculture, and therefore this study aims to understand how climate change will affect the thermohaline properties in the Ria de Vigo. To better understand these impacts, a hydrodynamic model of the Rias Baixas was implemented to analyse the effect of climate change on the Ria de Vigo’s thermohaline properties. The methodology followed consisted of the application of the Delft3D three-dimensional numerical model in the Rias Baixas and the adjacent ocean with variables obtained from global and regional climate models, in future scenarios provided by CMIP6. This was done for the summer season and for two scenarios, the present-day and CMIP6’s SSP5-8.5 future scenario. The results show that the water temperature in the Ria will increase in the future due to climate change, and it tended to be higher at the surface and lower at the bottom due to the intrusion of oceanic water from the Eastern North Atlantic Central Water (ENAWC). The salinity is expected to decrease and will be highest in the bottom layer near the connection with the ocean, and lowest in the surface layers and near the river, in the latter case, due to freshwater discharges. The density presented similar patterns, also decreasing in the future, and showing the expected stratification associated with the upwelling season.