Modeling the Impacts of Aswan High Dam Driven Nile Discharge Reduction on the Mediterranean Sea

Understanding the anthropogenic influence on the ocean is essential for quantifying the human-induced changes in the state of the ocean. The Levantine basin is a key semi-enclosed sub-basin of the Eastern Mediterranean that underwent significant human induced modifications following the construction and operation of Aswan High Dam (AHD) on the Nile River which became operational in 1964. Large river systems play a crucial role in modulating thermohaline properties in the semi-enclosed basins, and river regulation can alter key physical processes including circulation, eddy activity, stratification, and basin-scale salinity budgets.

Here we investigate the oceanic response to the post-AHD reduction in Nile freshwater discharge using a 1/16° mesoscale-resolving configuration of the Mediterranean Sea implemented, with open boundary conditions in the Atlantic Ocean. Simulations are performed using the NEMO v5 modelling framework, forced with ECMWF ERA5 atmospheric fields. The model is initialized in January 1958 and constrained at the open boundaries with monthly fields from the ECMWF ORAS5 ocean reanalysis. Sensitivity tests have been conducted in order to avoid the stochastic behavior of the numerical models and to distinguish between the signal from the numerical noise. Our results provide new insight into the physical impacts of Nile river damming on the Mediterranean thermohaline structure and circulation, contributing to a more quantitative understanding of human-induced modifications in semi-enclosed marine basins.