Seasonality and Trends in East Coast South Florida fCO2 Fluxes

Abstract:

An anthropogenically driven increase in atmospheric CO₂ concentrations is known to drive an increase in the globally integrated ocean carbon sink. However, recent studies suggest that CO₂ uptake rate may be decreasing in some regions. Three decades of sea surface observations collected from the southeast Florida coastal waters reveal behavior over seasonal and interannual timescales for a region important to global carbon storage and transport. The strong temperature dependence of fCO₂ in the region drives the seasonal cycle of air-sea flux. Yearly averaged flux was found to be an unreliable indicator of interannual trends due to the nonuniform distribution of observations. We define a seasonally weighted flux with equal contribution from each season in the calculation of a yearly average. The results indicate that uptake in the region has not changed over time and demonstrate the importance of robust non-seasonally biased data sets in conducting climate studies. Seasonally biased data are not only a problem for polar regions, but also exist in sub-tropical regions. Although not statistically significant, different responses of different seasons over time lead to seasonal amplification and a decoupling of the annual mean and the seasonal means.