@inproceedings{macovei_an_instrument_2021, 
author={Macovei, V. and Voynova, Y. and Becker, M. and Triest, J. and Petersen, W.},
title={An instrument intercomparison exercise in the Skagerrak allows extending the FerryBox pCO2 observational coverage across the Central and Southern North Sea},
year={2021},
booktitle = {Advances in operational oceanography : expanding Europe's ocean observing and forecasting capacity : Proceedings of the 9th EuroGOOS International Conference},
editor = {Fernández, V.; Lara-López, A.;  Eparkhina, D.; Cocquempot, L.; Lochet, C.; Lips, I.},
pages = {30 - 33},
publisher = {EuroGOOS},
doi = {10.13155/83160},
abstract = {The  partial  pressure  of  carbon  dioxide  (pCO2)  in  surface  seawater  is  an  important  
biogeochemical variable, influencing the direction of air–sea carbon dioxide exchange. 
Large-scale observations of pCO2 are facilitated by Ships-of-Opportunity (SOOP-CO2) 
equipped with underway measuring instruments that are becoming more autonomous. 
Here we performed a comparison between a FerryBox-integrated membrane-based 
sensor and a showerhead equilibration sensor installed on two SOOP-CO2 between 
2013 and 2018. We identified time- and space-adequate crossovers in the Skagerrak 
Strait, where the two ship routes often crossed. We found a mean total difference of 
1.5 ± 10.6 μatm and a root mean square error of 11 μatm. The pCO2 values recorded 
by the two instruments showed a strong linear correlation with a coefficient of 0.91 
and a slope of 1.07 (± 0.14), despite the dynamic nature of the environment and 
the difficulty of comparing measurements from two different vessels. We showed 
the strength of having a sensor-based network with a high spatial coverage that can 
be  cross-checked  against  conventional  SOOP-CO2  methods.  Validating  membrane-based sensors and using the expanded coverage and higher frequency measurements 
they provide can enable a thorough characterization of pCO2 variability in both open 
oceans and dynamic coastal seas.},
note = {Online available at: \url{https://dx.doi.org/10.13155/83160} (DOI). Macovei, V.; Voynova, Y.; Becker, M.; Triest, J.; Petersen, W.: An instrument intercomparison exercise in the Skagerrak allows extending the FerryBox pCO2 observational coverage across the Central and Southern North Sea. In: Fernández, V.; Lara-López, A.;  Eparkhina, D.; Cocquempot, L.; Lochet, C.; Lips, I. (Eds.): Advances in operational oceanography : expanding Europe's ocean observing and forecasting capacity : Proceedings of the 9th EuroGOOS International Conference. Brussels: EuroGOOS, 2021. 30 - 33. (DOI:  /10.13155/83160)}}