Using satellite data to estimate partial pressure of CO2 in the Baltic Sea

Abstract

AbstractIn this study we focused on estimating the pressure partial of CO2 (pCO2) in the entire Baltic Sea which can be considered a coastal area in its entirety. We used the self‐organizing multiple linear output (SOMLO) method to estimate the ocean surface pCO2 in the Baltic Sea from the remotely sensed sea surface temperature, chlorophyll a, colored dissolved organic matter, net primary production, and mixed‐layer depth. Uncertainties in the estimates include sparsity of in situ data used to train the algorithms, in particular, for some sectors and seasons. For this application we divided the Baltic Sea in four basins. When comparing the results obtained with this division to those obtained in previous studies, we notice a decrease in the root‐mean‐square error (<40 μatm) between the reconstruction of the pCO2 and their corresponding in situ measurements, as well as an increase of the correlation coefficient (> 0.96) between them. The outputs of this research have a horizontal resolution of 4 km and cover the 1998–2011 period. For the first time, a climatological mean distribution of surface water pCO2 over the Baltic Sea was calculated based on the SOMLO method with a mean pCO2 of 368.3 ± 100 μatm, and a range of 234–514 μatm. The seasonal variability is similar throughout the Baltic Sea, being high in winter and low in summer.