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

Abstract

The role of saline lakes in CO 2 exchange with the atmosphere was evaluated on the basis of calculated partial pressure ( p CO 2 ) and CO 2 exchange rates with the atmosphere derived from a compilation of published data for 196 saline lakes around the world. The average surface water p CO 2 exceeded atmospheric p CO 2 by a factor of 5–8 times, indicative of a tendency for saline lakes to emit CO 2 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 p CO 2 . The globally distributed lakes emitted CO 2 at rates in excess of 80 mmol m −2 d −1 . The Caspian Sea was calculated to support alone a total CO 2 emission of 0.02 to 0.04 Gt C a −1 , with the total CO 2 emissions to the atmosphere from saline lakes calculated to be 0.11–0.15 Gt C a −1 . Consideration of CO 2 emissions from saline lakes raises the total CO 2 emissions to the atmosphere from all lakes to 0.28–0.32 Gt CO 2 . These results point to a significant role of saline lakes in global C cycling.