Long Term Ecological Research Paper

Outgassing of carbon dioxide (CO2) from inland waters has been estimated to offset approximately 20% of net uptake of carbon into the terrestrial biosphere. However, this calculation is based on estimates of source strength at the air-water interface that is highly uncertain [Ciais et al., 2013]. One of the largest unknowns is the accuracy and precision of freshwater partial pressure of CO2 (pCO2) estimates. To better understand observational uncertainty in CO2 flux from inland waters, here we conduct an analysis of historical observations and take new field observations at the North Temperate Lake Long Term Ecological Research (NTL LTER) site to quantify random errors in freshwater carbon system. We further estimate errors contribution to the precision of pCO2 derived from multiple carbonate equilibria and identify other sources of uncertainty in pCO2 calculations.
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We perform random error analysis using paired field observations taken under identical conditions from 16 to 26 year records in the North Temperate Lakes Long-Term Ecological Research (NTL LTER) dataset to quantify and characterize the random error in carbon system parameters. We propagate parameter errors onto three carbonate equilibria using a Monte Carlo approach in order to investigate the effect of those uncertainties on calculated pCO2 in four lake groups across a broad gradient of alkalinity and dissolved organic carbon concentrations. We also determine which carbonate equilibrium and alkalinity group is least sensitive to variation in input parameters and gives the most precise estimates of pCO2. We also compare calculated pCO2 with direct pCO2 observations to investigate if random error magnitudes among the two are comparable. Finally, we determine if random errors are the major source of uncertainty in pCO2