CO₂ emissions from saline lakes: A global estimate of a surprisingly large flux

The role of saline lakes in CO₂ exchange with the atmosphere was evaluated on the basis of calculated partial pressure (pCO₂) and CO₂ exchange rates with the atmosphere derived from a compilation of published data for 196 saline lakes around the world. The average surface water pCO₂ exceeded atmospheric pCO₂ by a factor of 5-8 times, indicative of a tendency for saline lakes to emit CO₂ to the atmosphere. Chemically enhanced emission, calculated from solute chemistry, pH, and wind speed, increased gas exchange an average of 2.3 times over that of freshwater lakes having equivalent pCO₂. The globally distributed lakes emitted CO₂ at rates in excess of 80 mmol m^-2 d^-1. The Caspian Sea was calculated to support alone a total CO₂ emission of 0.02 to 0.04 Gt Ca^-1, with the total CO₂ emissions to the atmosphere from saline lakes calculated to be 0.11-0.15 Gt C a^-1. Consideration of CO₂ emissions from saline lakes raises the total CO₂ emissions to the atmosphere from all lakes to 028-0.32 Gt CO₂. These results point to a significant role of saline lakes in global C cycling.