The flux of CO₂ and CH₄ from lakes and rivers in arctic Alaska

Abstract

Partial pressures of CO₂ and CH₄ were measured directly or calculated from pH and alkalinity or DIC measurements for 25 lakes and 4 rivers on the North Slope of Alaska. Nearly all waters were supersaturated with respect to atmospheric pressures of CO₂ and CH₄. Gas fluxes to the atmosphere ranged from -6.5 to 59.8 mmol m ^{- 2} d ^{- 1} for CO₂ and from 0.08 to 1.02 mmol m ^{- 2} d ^{- 1} for CH₄, and were uncorrelated with latitude or lake morphology. Seasonal trends include a buildup of CO2 and CH4 under ice during winter, and often an increased CO₂ flux rate in August due to partial lake turnover. Nutrient fertilization experiments resulted in decreased CO₂ release from a lake due to photosynthetic uptake, but no change in CO₂ release from a river due to the much faster water renewal time. In lakes and rivers the groundwater input of dissolved CO₂ and CH₄ is supplemented by in-lake respiration of dissolved and particulate carbon washed in from land. The release of carbon from aquatic systems to the atmosphere averaged 24 g C m ^{- 2} Y ^{- 1}, and in coastal areas where up to 50 % of the surface area is water, this loss equals 1/5 to 1/2 of the net carbon accumulation rates estimated for tundra.