Abstract
The Minho and Lima estuaries, separated by approximately 20 km, are two important transitional systems from the NW Atlantic Portuguese coast. Considering their contrasting characteristics, the present work aims to investigate climate change impacts in salt intrusion and estuarine plumes interaction, through an integrated hydrological characterization. The three-dimensional numerical model Delft3D was implemented to explore the hydrological response of these two systems taking into account their interaction. The model was applied to investigate two different climate change scenarios (RCP 4.5 and RCP 8.5), where physical variables such as sea level and river outflow were varied following summer and winter conditions. The numerical results revealed typically estuarine hydrological patterns, although some different features were found for each estuary. The head and mouth of the estuaries may be the zones most affected by climate change. In the first zone, the salinity may increase in the future in response to freshwater reduction from the Minho and Lima rivers. Considering the cumulative impact of the sea level rise, the saline intrusion may increase in the future: in the Minho estuary it reaches 14 km for the Present scenario during the dry season, penetrating further under climate change conditions (15 km for the RCP 4.5 scenario, and 17 km for the RCP 8.5 scenario); in the Lima estuary, the salt propagates further inland, reaching 17 km for the Present scenario, 18 km for the RCP 4.5 scenario, and a maximum of 20 km for the RCP 8.5 scenario. In all scenarios, during winter conditions, the estuarine plumes are larger and wider, being predicted that in the future they will reduce their dimensions during the winter period, and remain unchanged during summertime. Concisely, this modelling study provided more expertise about the physical patterns of these two estuaries and their interaction, as well as to anticipate the climate change impacts in their dynamics.
Highlights
Identified changes in the climate state mean and/or in its property variability, persisting for long periods, is designated as climate change [1,2,3,4,5,6]
The main goal of this paper is to use a single three-dimensional baroclinic model application to study the salt intrusion and estuarine plumes dynamics in two adjacent estuaries, researching the modifications induced by climate change
The salt intrusion and estuarine plumes generation in Minho and Lima estuaries, and their modifications induced by climate change, have been evaluated using the Delft3D model, considering different scenarios simulated using a unique modelling application
Summary
Identified changes (applying statistical tests) in the climate state mean and/or in its property variability, persisting for long periods (from decades to centuries), is designated as climate change [1,2,3,4,5,6]. The sea level rise results from an increase in the volume of the water already present in the ocean, since water warms and expands, as well as from an increase in the mass of the water in the ocean due to the melting glaciers [2] This phenome exacerbates extreme events and coastal hazards, and has numerous adverse impacts on marine coastal ecosystems pp. 321–445 in [5], leading to environmental and human life quality risks associated with floods, shoreline erosion, and other coastal problems [18] This situation induced by global warming has increased the frequency and intensity of coastal inundation, with significant impacts on water level, current, and wave propagation in estuaries [19], leading to, besides others, alterations in saltwater intrusion and estuarine plumes spatial and temporal gradients variability [20,21]
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