Lakes Release Far More Carbon Than Scientists Thought, Study Finds
A major analysis of freshwater CO2 emissions reveals that lakes and reservoirs are inconsistent carbon sources—releasing 25% more or less CO2 year to year. The finding exposes critical gaps in global carbon accounting and could force revisions to climate models and carbon credit frameworks that currently underestimate freshwater contributions to atmospheric warming.
Originaltitel: Diel, seasonal, and inter-annual variation in carbon dioxide effluxes from lakes and reservoirs
<p>Accounting for temporal changes in carbon dioxide (CO<sub>2</sub>) effluxes from freshwaters remains a challenge for global and regional carbon budgets. Here, we synthesize 171 site-months of flux measurements of CO<sub>2</sub> based on the eddy covariance method from 13 lakes and reservoirs in the Northern Hemisphere, and quantify dynamics at multiple temporal scales. We found pronounced sub-annual variability in CO<sub>2</sub> flux at all sites. By accounting for diel variation, only 11% of site-months were net daily sinks of CO<sub>2</sub>. Annual CO<sub>2</sub> emissions had an average of 25% (range 3%-58%) interannual variation. Similar to studies on streams, nighttime emissions regularly exceeded daytime emissions. Biophysical regulations of CO<sub>2</sub> flux variability were delineated through mutual information analysis. Sample analysis of CO<sub>2</sub> fluxes indicate the importance of continuous measurements. Better characterization of short- and long-term variability is necessary to understand and improve detection of temporal changes of CO<sub>2</sub> fluxes in response to natural and anthropogenic drivers. Our results indicate that existing global lake carbon budgets relying primarily on daytime measurements yield underestimates of net emissions.</p>