Caspian Sea and Black Sea Response to Greenhouse Warming in a High-Resolution Global Climate Model

The Caspian Sea and the Black Sea are the Earth's largest inland seas. How their temperature, circulation, and freshwater balance will respond to greenhouse warming remains unresolved. Previous studies have relied on coarse-resolution coupled or regional uncoupled climate models with limited abilities to resolve regional features. Here, we present results from century-long greenhouse warming simulations conducted with the Community Earth System Model using a global horizontal resolution of 1/10 degrees in the ocean and inland seas and 1/4 degrees in the atmosphere. In response to CO2 doubling surface temperatures in the inland seas increase by about 2.5 degrees C. An overall reduction of wind stress curl causes a spin-down of the main gyre circulations, reaching about -20%/CO2 doubling for the Black Sea Rim Current. Increased future evaporation translates to negative equivalent sea level trends of about -0.1 m/year/CO2 doubling. The robust climate shifts presented here are likely to impact ecosystems, fisheries, and threaten existing coastal infrastructures.