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  • 1
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    PANGAEA
    In:  Supplement to: Fiedler, Björn; Fietzek, Peer; Vieira, Nuno; Silva, Pericles; Bittig, Henry; Körtzinger, Arne (2013): In Situ CO2 and O2 Measurements on a Profiling Float. Journal of Atmospheric and Oceanic Technology, 30(1), 112-126, https://doi.org/10.1175/JTECH-D-12-00043.1
    Publication Date: 2024-02-01
    Description: In recent years, profiling floats, which form the basis of the successful international Argo observatory, are also being considered as platforms for marine biogeochemical research. This study showcases the utility of floats as a novel tool for combined gas measurements of CO2 partial pressure (pCO2) and O2. These float prototypes were equipped with a small-sized and submersible pCO2 sensor and an optode O2 sensor for highresolution measurements in the surface ocean layer. Four consecutive deployments were carried out during November 2010 and June 2011 near the Cape Verde Ocean Observatory (CVOO) in the eastern tropical North Atlantic. The profiling float performed upcasts every 31 h while measuring pCO2, O2, salinity, temperature, and hydrostatic pressure in the upper 200 m of the water column. To maintain accuracy, regular pCO2 sensor zeroings at depth and surface, as well as optode measurements in air, were performed for each profile. Through the application of data processing procedures (e.g., time-lag correction), accuracies of floatborne pCO2 measurements were greatly improved (10-15 µatm for the water column and 5 µatm for surface measurements). O2 measurements yielded an accuracy of 2 µmol/kg. First results of this pilot study show the possibility of using profiling floats as a platform for detailed and unattended observations of the marine carbon and oxygen cycle dynamics.
    Keywords: Carbon dioxide, partial pressure; CVOO Floater; DATE/TIME; deployment_d4; deployment_d5; deployment_d6; deployment_d7; DEPTH, water; Event label; LATITUDE; LONGITUDE; Nemo float; NFLOAT; off Cape Verde Islands; Oxygen; Pressure, water; Profile; Salinity; SOPRAN; Surface Ocean Processes in the Anthropocene; Temperature, water
    Type: Dataset
    Format: text/tab-separated-values, 509900 data points
    Location Call Number Limitation Availability
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  • 2
    Publication Date: 2019-09-23
    Description: The role of the global surface ocean as a source and sink for atmospheric carbon dioxide and the flux strengths between the ocean and the atmosphere can be quantified by measuring the fugacity of CO2 (ƒCO2) as well as the dissolved inorganic carbon (DIC) concentration and its isotopic composition in surface seawater. In this work, the potential of continuous wave cavity ringdown spectroscopy (cw-CRDS) for autonomous underway measurements of ƒCO2 and the stable carbon isotope ratio of DIC [δ13C(DIC)] is explored. For the first time, by using a conventional air-sea equilibrator setup, both quantities were continuously and simultaneously recorded during a field deployment on two research cruises following meridional transects across the Atlantic Ocean (Bremerhaven, Germany–Punta Arenas, Chile). Data are compared against reference measurements by an established underway CO2 monitoring system and isotope ratio mass spectrometric analysis of individual water samples. Agreement within ΔƒCO2 = 0.35 μatm for atmospheric and ΔƒCO2 = 2.5 μatm and Δδ13C(DIC) =0.33‰ for seawater measurements have been achieved. Whereas “calibration-free” ƒCO2 monitoring is feasible, the measurement of accurate isotope ratios relies on running reference standards on a daily basis. Overall, the installed CRDS/equilibrator system was shown to be capable of reliable online monitoring of ƒCO2, equilibrium δ13C(CO2), δ13C(DIC), and pO2 aboard moving research vessels, thus making possible corresponding measurements with high spatial and temporal resolution.
    Type: Article , PeerReviewed
    Format: text
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  • 3
    Publication Date: 2019-09-23
    Description: The impact of ocean acidification on benthic habitats is a major preoccupation of the scientific community. However, the natural variability of pCO2 and pH in those habitats remains understudied, especially in temperate areas. In this study we investigated temporal variations of the carbonate system in nearshore macrophyte meadows of the western Baltic Sea. These are key benthic ecosystems, providing spawning and nursery areas as well as food to numerous commercially important species. In situ pCO2, pH (total scale), salinity and PAR irradiance were measured with a continuous recording sensor package dropped in a shallow macrophyte meadow (Eckernförde bay, western Baltic Sea) during three different weeks in July (pCO2 and PAR only), August and September 2011.The mean (± SD) pCO2 in July was 383±117 µatm. The mean (± SD) pCO2 and pHtot in August were 239±20 µatm and 8.22±0.1, respectively. The mean (± SD) pCO2 and pHtot in September were 1082±711 µatm and 7.83±0.40, respectively. Daily variations of pCO2 due to photosynthesis and respiration (difference between daily maximum and minimum) were of the same order of magnitude: 281±88 µatm, 219±89 μatm and 1488±574 µatm in July, August and September respectively. The observed variations of pCO2 were explained through a statistical model considering wind direction and speed together with PAR irradiance. At a time scale of days to weeks, local upwelling of elevated pCO2 water masses with offshore winds drives the variation. Within days, primary production is responsible. The results demonstrate the high variability of the carbonate system in nearshore macrophyte meadows depending on meteorology and biological activities. We highlight the need to incorporate these variations in future pCO2 scenarios and experimental designs for nearshore habitats.
    Type: Article , PeerReviewed
    Format: text
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  • 4
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    AMS (American Meteorological Society)
    In:  Journal of Atmospheric and Oceanic Technology, 31 (1). pp. 181-196.
    Publication Date: 2020-08-04
    Description: We present a detailed quality assessment of a novel underwater sensor for the measurement of CO2 partial pressure (pCO2) based on surface water field deployments carried out between 2008 and 2011. The commercially available sensor, which is based on membrane equilibration and NDIR spectrometry is small and can be integrated into mobile platforms. It is calibrated in water against a proven flow-through pCO2 instrument within a custom-built calibration setup. The aspect of highest concern with respect to achievable data quality of the sensor is the compensation for signal drift inevitably connected to absorption measurements. We use three means to correct for drift effects: (i) a filter correlation or dual-beam setup, (ii) regular zero gas measurements realized automatically within the sensor and (iii) a zero-based transformation of two sensor calibrations flanking the time of sensor deployment. Three sensors were tested against an underway pCO2 system during two major research cruises providing an in situ temperature range from 7.4 to 30.1°C and pCO2 values between 289 and 445 μatm. The average difference between sensor and reference pCO2 was found to be -0.6 ± 3 μatm with a RMSE of 3.7 μatm.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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  • 5
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    AMS (American Meteorological Society)
    In:  Journal of Atmospheric and Oceanic Technology, 30 . pp. 112-126.
    Publication Date: 2020-08-04
    Description: In recent years, profiling floats, which form the basis of the successful international Argo observatory, are also being considered as platforms for marine biogeochemical research. This study showcases the utility of floats as a novel tool for combined gas measurements of CO2 partial pressure (pCO2) and O2. These float prototypes were equipped with a small-sized and submersible pCO2 sensor and an optode O2 sensor for high resolution measurements in the surface ocean layer. Four consecutive deployments were carried out during Nov. 2010 and June 2011 near the Cape Verde Ocean Observatory (CVOO) in the eastern tropical North Atlantic. The profiling float performed upcasts every 31 h while measuring pCO2, O2, salinity, temperature and hydrostatic pressure in the upper 200 m of the water column. In order to maintain accuracy, regular pCO2 sensor zeroings at depth and surface, as well as optode measurements in air, were performed for each profile. Through the application of data processing procedures (e.g., time-lag correction) accuracies of float-borne pCO2 measurements were greatly improved (10 – 15 μatm for water column and 5 μatm for surface measurements). O2 measurements yielded an accuracy of 2 μmol kg−1. First results of this pilot study show the possibility of using profiling floats as a platform for detailed and unattended observations of the marine carbon and oxygen cycle dynamics.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
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  • 6
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    American Chemistry Society
    In:  Environmental Science & Technology, 47 (15). pp. 8130-8137.
    Publication Date: 2019-09-24
    Description: Inland waters transport and transform substantial amounts of carbon and account for 18% of global methane emissions. Large reservoirs with higher areal methane release rates than natural waters contribute significantly to freshwater emissions. However, there are millions of small dams worldwide that receive and trap high loads of organic carbon and can therefore potentially emit significant amounts of methane to the atmosphere. We evaluated the effect of damming on methane emissions in a central European impounded river. Direct comparison of riverine and reservoir reaches, where sedimentation in the latter is increased due to trapping by dams, revealed that the reservoir reaches are the major source of methane emissions (0.23 mmol CH4 m–2 d–1 vs 19.7 mmol CH4 m–2 d–1, respectively) and that areal emission rates far exceed previous estimates for temperate reservoirs or rivers. We show that sediment accumulation correlates with methane production and subsequent ebullitive release rates and may therefore be an excellent proxy for estimating methane emissions from small reservoirs. Our results suggest that sedimentation-driven methane emissions from dammed river hot spot sites can potentially increase global freshwater emissions by up to 7%
    Type: Article , PeerReviewed
    Format: text
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  • 7
    Publication Date: 2019-09-23
    Description: The potential of a continuous wave cavity ringdown spectrometer for monitoring the isotope ratio 13CO2/12CO2 and the partial pressure pCO2 of CO2 dissolved in water was thoroughly analyzed by quantitative measurements. Running calibration gas standards under typical operation conditions, a relative accuracy of D(d13C[CO2]) = ±0.1‰ with 120 min averaging time has been demonstrated. Absolute uncertainties were determined to be D(d13C[CO2]) = ±0.2‰ and D(xCO2) = ±0.5 ppmv. No principle problems were encountered when using the instrument in combination with a water-air equilibration setup. By contrast, when performing measurements of CO2 in gas matrices with a composition different from that of ambient air, pressure broadening linewidth effects induced significant errors in both d13C(CO2) and xCO2 values. These effects, which compromise the accessible accuracy in environmental studies, can be quantitatively taken into account by using a spectroscopically based correction procedure. Relying on linewidth analysis, the instrument was shown to be capable of continuous and simultaneous measurement of d13C(CO2), pCO2, as well as water content and O2 supersaturation, and thus holds the potential for online monitoring of these quantities aboard research vessels.
    Type: Article , PeerReviewed
    Format: text
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  • 8
    Publication Date: 2012-07-12
    Description: During SOPRAN I & II, field work activities focused mainly on the Eastern Tropical North Atlantic (ETNA) near the Cape Verde Ocean Observatory (CVOO). Here we report about two major achievements during SOPRAN I & II: (i) A typical ARGO float with a small-sized and novel submersible CO2 partial pressure (pCO2) sensor and an optode O2 sensor for high resolution measurements in the upper ocean was developed and field-deployed successfully. We report on the quality of the data as well as the distribution of the air-sea fluxes of the two gases. (ii) Autonomous measurements have shown extremely low O2 concentrations below the mixed layer (〈 1 µmol/kg) in certain mesoscale features drastically contrasting the otherwise reasonably well oxygenated open North Atlantic Ocean (〉 40 µmol/kg). To our knowledge no such anoxic water parcels have ever been reported before for the open North Atlantic.
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 9
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    In:  [Poster] In: 4. Argo Science Workshop, 27.-29.09.2012, Venice, Italy .
    Publication Date: 2012-10-12
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 10
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    In:  [Talk] In: AquaLife Seminar 2012, 05.-06.06.2012, Kiel, Germany .
    Publication Date: 2012-09-07
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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