The unexpectedly large impact of salt precipitation on water temperature: A revised energy and mass budget of the Dead Sea during 1979 - 2019

The Dead Sea has warmed up by more than 2°C since the overturn of 1979. This unusually fast warming rate has attracted little attention in comparison with the man-induced rapid lake level fall that has gone unabated since the 1950s. Here we develop a thermal model of the Dead Sea to investigate the causes of the lake temperature increase. The monthly-resolved model quantifies all major heat fluxes at the air-water interface with generic physical equations, uses an empirically-based scheme to simulate lake stratification, and incorporates for the first time the heat flux related to the precipitation of halite (sodium chloride, NaCl). This results in a very good agreement with monitoring data for the net air-water heat flux and for the temperatures of the upper and deep lake layers. The various contributions to the energy budget can be disentangled by turning them on or off in the simulations. We thus explore the role of heat released by halite precipitation and of seasonal air temperature in controlling the temperature of the lake. We find a major role of the heat released by halite precipitation, which was previously ignored and has major implications on the understanding of the water budget of the lake. This study paves the way for a better understanding of the hydrological crisis faced by hypersaline lakes around the world, and opens new perspectives in the study of the past climates that led to the accumulation of evaporite deposits.