Diel variability of methane emissions from lakes

Area of Science:

• Environmental Science
• Geochemistry
• Atmospheric Science

Background:

• Lakes are a major natural source of atmospheric methane (CH4).
• Current CH4 emission estimates from lakes are uncertain and often neglect diel (daily) variability.
• Diel variations in CH4 flux can significantly impact global CH4 budget calculations.

Purpose of the Study:

• To investigate the diel variability of CH4 flux from lakes.
• To quantify the difference in CH4 emissions between daytime and nighttime.
• To assess the impact of diel variability on overall lake CH4 emission estimates.

Main Methods:

• High-resolution CH4 flux measurements using an automated, sensor-based approach.
• Collected a total of 4,580 measurements across several lakes.
• Analyzed flux patterns during stratification and mixing periods.

Main Results:

• A consistent diel pattern in lake CH4 flux was observed, with peak emissions between 10:00 and 16:00.
• CH4 fluxes were, on average, 2.4 times higher during the day compared to nighttime.
• Daytime measurements alone likely overestimate CH4 emissions, as higher fluxes occurred on nearly 80% of days.

Conclusions:

• Diel variability in lake CH4 emissions is significant and must be considered for accurate global CH4 budget assessments.
• A diel variability correction factor is proposed for daytime-only measurements.
• Accounting for diel cycles is critical for refining estimates of lake CH4 contributions to the atmosphere.