by Rebecca Herrera
The peatlands and tundras of the Arctic perform vital ecosystem services to the earth through their ability to sequester carbon (CO2) and methane (CH4) and function as a carbon sink. The ability of the permafrost in the peatlands and tundra ecosystems of the Arctic to continue to function as a natural reservoir for carbon and methane may be disrupted by rising global temperatures that increase the rate of soil decomposition. Watts et al. (2014) integrate a terrestrial carbon flux (TCF) model to include a newly developed CH4 emissions algorithm. The new TCF model simultaneously assesses CO2 and CH4 fluctuations and the corresponding net ecosystem carbon balance (NECB), which is contingent upon gross primary productivity (GPP) subtracted from ecosystem respiration. The integrated TCF model uses data gathered through satellite remote sensors to assess fluxes in CO2 and CH4.
The researchers examined data from six pan-Arctic peatland and tundra sites in Finland, Sweden, Russia, Greenland, and Alaska that are representative of wet permafrost ecosystems with varied terrain and vegetation. While previous assessments of CO2 and CH4 fluxes have been effective at providing localized measurements, extrapolating the data to larger geographic regions has proved challenging. Efficacy of the integrated model was proven through a comparison of the model to previous data collected through previous NECB measurements.
Although the model estimated CH4 emissions to be small when compared to ecosystem respiration per annum, the model also showed that these CH4 emissions reduced study site NECB by 23%. The model indicates a net carbon sink for five of the six monitored sites; meaning ecosystem respiration exceeded annual GPP. Excluding two mitigating study sites, the model estimates annual CO2 and CH4 fluxes have significant potential to contribute to global warming.
Reduced NECB has global effects on climate change. CO2 and CH4 are greenhouse gasses whose increased concentrations contribute to global surface temperature increases and perpetuate a positive feedback loop of increased GHG concentrations and increased global temperatures as permafrost continues to thaw. Biogeochemical models that monitor CO2 and CH4 ought to continue to be improved and studied as Arctic peatlands and tundras continue to loose their permafrost.
Watts, J. D., Kimball, J. S., Parmentier, F. J. W., Sachs, T. et al. 2014. A satellite data driven biophysical modeling approach for estimating northern peatland and tundra CO2 and CH4 fluxes. Biogeosciences, 11, 1961-1980.