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

Abstract

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 C a−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 0.28–0.32 Gt CO2. These results point to a significant role of saline lakes in global C cycling.