Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Journal of Geophysical Research: Biogeosciences
Lakes are typically discussed as substantial natural carbon dioxide (CO2) sources to the atmosphere based on findings in small lakes, which dominate in numbers globally. This is because lakes receive large amounts of carbon with the water from their catchments, making the surface water supersaturated with CO2 and resulting in CO2 emissions into the atmosphere. While lakes larger than 100 km2 account for more than half of the total global lake area, their CO2 exchange with the atmosphere has not been extensively studied. These large lakes therefore constitute a blind spot with regards to aquatic CO2 exchange with the atmosphere.
Sandborn and Minor [2024] address this issue by measuring surface water CO2 concentrations over four years of ice-free periods covering large parts of Lake Superior, which has an area of about 82, 100 km2 or 2.5% of the global lake area. These measurements were used to make the first comprehensive seasonal estimates of CO2 fluxes from such a large freshwater lake based on multi-year data.
The results indicate a CO2 uptake by the surface water, in contrast to findings in many smaller lakes, and that Lake Superior acts as a carbon sink similar to oceans during ice-free periods. This leads to the important conclusions that we may have to re-evaluate the CO2 flux across a large fraction of the global lake area and highlights the need to study and better understand the roles of large lakes in the continental carbon cycle.
Citation: Sandborn, D. E., & Minor, E. C. (2024). Underway pCO2 surveys unravel CO2 invasion of Lake Superior from seasonal variability. Journal of Geophysical Research: Biogeosciences, 129, e2023JG007877. https://doi.org/10.1029/2023JG007877
—David Bastviken, Associate Editor, JGR: Biogeosciences