A carbonate system time series in the Eastern Mediterranean Sea. Two years of high-frequency in-situ observations and remote sensing
The rate of ocean uptake of anthropogenic CO2 has declined over the past decade, so a critical question for science and policy is whether the ocean will continue to act as a sink. Large areas of the ocean remain without observations for carbonate system variables, and oceanic CO2 observations have d...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2024-02-01
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| Series: | Frontiers in Marine Science |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fmars.2024.1348161/full |
| _version_ | 1797302031262679040 |
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| author | C. Frangoulis N. Stamataki N. Stamataki M. Pettas S. Michelinakis A. L. King L. Giannoudi K. Tsiaras S. Christodoulaki J. Seppälä M. Thyssen A.V. Borges E. Krasakopoulou |
| author_facet | C. Frangoulis N. Stamataki N. Stamataki M. Pettas S. Michelinakis A. L. King L. Giannoudi K. Tsiaras S. Christodoulaki J. Seppälä M. Thyssen A.V. Borges E. Krasakopoulou |
| author_sort | C. Frangoulis |
| collection | DOAJ |
| description | The rate of ocean uptake of anthropogenic CO2 has declined over the past decade, so a critical question for science and policy is whether the ocean will continue to act as a sink. Large areas of the ocean remain without observations for carbonate system variables, and oceanic CO2 observations have declined since 2017. The Mediterranean Sea is one such an area, especially its eastern part, where there is a paucity of carbonate system data, with large areas not sampled or only sampled by ship-based discrete measurements as opposed to high frequency, sensor-equipped time-series fixed stations. The aim of this study was to analyze a multi-year time-series of high-frequency (hourly) partial pressure CO2 (pCO2) and pH measurements in the Eastern Mediterranean, along with low-frequency (monthly) measurements of total dissolved inorganic carbon and total alkalinity. The pCO2 time-series was the first obtained in the Eastern Mediterranean. The study was conducted at a fixed platform of the POSEIDON system (Heraklion Coastal Buoy) located near Crete Island. Temperature was the dominant factor controlling the temporal variability of pCO2 and pH, while the remaining non-thermal variability appeared to be related to evaporation, water mixing, and biological remineralization-production. The air-sea CO2 fluxes indicated a transition from a winter-spring sink period to a summer-autumn source period. The annual air-sea CO2 flux was too low (-0.16 ± 0.02 mol m-2 yr-1) and variable to conclusively characterize the area as a net source or sink of CO2, highlighting the need for additional high frequency observation sites. Algorithms were developed using temperature, chlorophyll and salinity data to estimate pCO2 and total alkalinity, in an effort to provide tools for estimates in poorly observed areas/periods from remotely sensed products. The applicability of the algorithms was tested using Surface Ocean CO2 Atlas (SOCAT) data from the Eastern Mediterranean Sea (1999 to 2020) which showed that the algorithm pCO2 estimates were generally within ±20 μatm of the pCO2 values reported by SOCAT. Finally, the integration and analysis of the data provided directions on how to optimize the observing strategy, by readapting sensor location and using estimation algorithms with remote sensing data. |
| first_indexed | 2024-03-07T23:30:01Z |
| format | Article |
| id | doaj.art-cc4d1bdce90c445497d60118a0ebd3ef |
| institution | Directory Open Access Journal |
| issn | 2296-7745 |
| language | English |
| last_indexed | 2024-03-07T23:30:01Z |
| publishDate | 2024-02-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Marine Science |
| spelling | doaj.art-cc4d1bdce90c445497d60118a0ebd3ef2024-02-20T16:43:21ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452024-02-011110.3389/fmars.2024.13481611348161A carbonate system time series in the Eastern Mediterranean Sea. Two years of high-frequency in-situ observations and remote sensingC. Frangoulis0N. Stamataki1N. Stamataki2M. Pettas3S. Michelinakis4A. L. King5L. Giannoudi6K. Tsiaras7S. Christodoulaki8J. Seppälä9M. Thyssen10A.V. Borges11E. Krasakopoulou12Institute of Oceanography, Hellenic Centre for Marine Research, Heraklion, GreeceInstitute of Oceanography, Hellenic Centre for Marine Research, Heraklion, GreeceDepartment of Physics, Section of Environmental Physics and Meteorology, National and Kapodistrian University of Athens, Athens, GreeceInstitute of Oceanography, Hellenic Centre for Marine Research, Heraklion, GreeceInstitute of Oceanography, Hellenic Centre for Marine Research, Heraklion, GreeceDepartment of Oceanography, Norwegian Institute for Water Research, Oslo, NorwayInstitute of Oceanography, Hellenic Centre for Marine Research, Athens, GreeceInstitute of Oceanography, Hellenic Centre for Marine Research, Athens, GreeceInstitute of Oceanography, Hellenic Centre for Marine Research, Heraklion, GreeceResearch Infrastructure, Finnish Environment Institute, Helsinki, FinlandAix Marseille Université, Université de Toulon, Centre National de la Recherche Scientifique, Institut de Recherche et de Développement, Mediterranean Institute of Oceanology, Marseille, FranceChemical Oceanography Unit, Freshwater and OCeanic science Unit of reSearch, Liège, Wallonia, BelgiumDepartment of Marine Sciences, University of the Aegean, Mytilene, GreeceThe rate of ocean uptake of anthropogenic CO2 has declined over the past decade, so a critical question for science and policy is whether the ocean will continue to act as a sink. Large areas of the ocean remain without observations for carbonate system variables, and oceanic CO2 observations have declined since 2017. The Mediterranean Sea is one such an area, especially its eastern part, where there is a paucity of carbonate system data, with large areas not sampled or only sampled by ship-based discrete measurements as opposed to high frequency, sensor-equipped time-series fixed stations. The aim of this study was to analyze a multi-year time-series of high-frequency (hourly) partial pressure CO2 (pCO2) and pH measurements in the Eastern Mediterranean, along with low-frequency (monthly) measurements of total dissolved inorganic carbon and total alkalinity. The pCO2 time-series was the first obtained in the Eastern Mediterranean. The study was conducted at a fixed platform of the POSEIDON system (Heraklion Coastal Buoy) located near Crete Island. Temperature was the dominant factor controlling the temporal variability of pCO2 and pH, while the remaining non-thermal variability appeared to be related to evaporation, water mixing, and biological remineralization-production. The air-sea CO2 fluxes indicated a transition from a winter-spring sink period to a summer-autumn source period. The annual air-sea CO2 flux was too low (-0.16 ± 0.02 mol m-2 yr-1) and variable to conclusively characterize the area as a net source or sink of CO2, highlighting the need for additional high frequency observation sites. Algorithms were developed using temperature, chlorophyll and salinity data to estimate pCO2 and total alkalinity, in an effort to provide tools for estimates in poorly observed areas/periods from remotely sensed products. The applicability of the algorithms was tested using Surface Ocean CO2 Atlas (SOCAT) data from the Eastern Mediterranean Sea (1999 to 2020) which showed that the algorithm pCO2 estimates were generally within ±20 μatm of the pCO2 values reported by SOCAT. Finally, the integration and analysis of the data provided directions on how to optimize the observing strategy, by readapting sensor location and using estimation algorithms with remote sensing data.https://www.frontiersin.org/articles/10.3389/fmars.2024.1348161/fullcarbonate algorithmsCO2 fluxoligotrophicsatellite salinitysource or sink |
| spellingShingle | C. Frangoulis N. Stamataki N. Stamataki M. Pettas S. Michelinakis A. L. King L. Giannoudi K. Tsiaras S. Christodoulaki J. Seppälä M. Thyssen A.V. Borges E. Krasakopoulou A carbonate system time series in the Eastern Mediterranean Sea. Two years of high-frequency in-situ observations and remote sensing Frontiers in Marine Science carbonate algorithms CO2 flux oligotrophic satellite salinity source or sink |
| title | A carbonate system time series in the Eastern Mediterranean Sea. Two years of high-frequency in-situ observations and remote sensing |
| title_full | A carbonate system time series in the Eastern Mediterranean Sea. Two years of high-frequency in-situ observations and remote sensing |
| title_fullStr | A carbonate system time series in the Eastern Mediterranean Sea. Two years of high-frequency in-situ observations and remote sensing |
| title_full_unstemmed | A carbonate system time series in the Eastern Mediterranean Sea. Two years of high-frequency in-situ observations and remote sensing |
| title_short | A carbonate system time series in the Eastern Mediterranean Sea. Two years of high-frequency in-situ observations and remote sensing |
| title_sort | carbonate system time series in the eastern mediterranean sea two years of high frequency in situ observations and remote sensing |
| topic | carbonate algorithms CO2 flux oligotrophic satellite salinity source or sink |
| url | https://www.frontiersin.org/articles/10.3389/fmars.2024.1348161/full |
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