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Dissolved methane concentrations, diffusive methane flux and EOVs in the German Bight in February 2025 (Sternfahrt 13)

In continuation of the previous cruises (Sternfahrten) we covered a similar area with the RV Heincke. All instruments were set up in the MOSES laboratory container. Standard hydrographic parameters were determined with a pocket ferrybox running with ship's surface water supply. In addition, dissolved methane was determined continuously. We used a degassing unit which was using surface water from the ship's water supply. The gas mixture was subsequently analysed with a Greenhouse Gas Analyzer from LosGatos. Conversion to methane concentration was performed with water samples, from which the methane content was determined with gas chromatography. Atmospheric methane concentrations were obtained from the ICOS-station Helgoland. Wind speed was obtained from the ships meteorological systems. The diffusive flux was calculated as outlined in the additional meta data description.

Dissolved methane concentration variability along freshwater-sea continuum at Heligoland, Southern North Sea, 2021

The dataset is about temporal variability of dissolved methane along the freshwater-sea continuum in northern Germany. Sensors were installed at fixed stations at in total three sites at different water depths. This dataset is from the station in Heligoland (54.1833 N, 7.8667 E) at about 9-12m depth (depending on the tide). The data was obtained between 27 April and 28 October in high frequency measurements (1 min) with a methane sensor from Kongsberg (4H Jena model CONTROS HydroC CH4,). Methane concentrations were calculated according to manufacturer's instructions, based on temperature and salinity values from UW-node Heligoland (Fischer, Philipp; Happel, Lea; Brand, Markus; Eickelmann, Laura; Lienkämper, Miriam; Bussmann, Ingeborg; Anselm, Norbert; Brix, Holger (2022): Hydrographical time series data of Helgoland, Southern North Sea, 2021. PANGAEA, https://doi.org/10.1594/PANGAEA.950173). A gap in the salinity data was replaced with the median value of the observed time span (31.66). For the quality control of the data a local range of 0.1 – 1000 nmol/L was set, a technical range for the pump power 2 – 8. Watt, a spike and gradient value of 1. For a more detailed description see the article cited in References.

Dissolved methane concentration variability along freshwater-sea continuum at Geesthacht, northern Germany, 2021

The dataset is about temporal variability of dissolved methane along the freshwater-sea continuum in northern Germany. Sensors were installed at fixed stations at in total three sites at different water depths. This dataset is from the station in Geesthacht (53.4112 N, 10.4032 E) at about 2 meter depth. The data was obtained between 14 April and 29 September 2021) in high frequency measurements (1 min) with a methane sensor from Kongsberg (4H Jena model CONTROS HydroC CH4,). Methane concentrations were calculated according to manufacturer's instructions. Data on temperature were provided by from Vattenfall, Kernkraftwerk Krümel, a salinity of 0.01 was assumed. Special thanks to the colleagues from Vattenfall for the logistic and technical support. For the quality control of the data a local range of 0.1 – 5000 nmol/L was set, a technical range for the pump power 2 – 8. Watt, a spike and gradient value of 1. For a more detailed description see the article cited in References.

Dissolved methane concentration variability along freshwater-sea continuum at Cuxhaven, northern Germany, 2021

The dataset is about temporal variability of dissolved methane along the freshwater-sea continuum in northern Germany. Sensors were installed at fixed stations at in total three sites at different water depths. This dataset is from the station in Cuxhaven (53.8771 N, 8.7048 E) taken at about 2-7m depth (depending on the tide). The data was obtained between 11 April and 28 August 2021 in high frequency measurements (1 min) with a methane sensor from Kongsberg (4H Jena model CONTROS HydroC CH4). Methane concentrations were calculated according to manufacturer's instructions, based on temperature and salinity values from COSYNA Container Cuxhaven. For the quality control of the data a local range of 0.1 – 1000 nmol/L was set, a technical range for the pump power 2 – 8 Watt, a spike and gradient value of 1. Due to heavy biofouling the external pump of the sensor failed, resulting in data gaps. For a more detailed description see the article cited in References.

Water samples off Cuxhaven, for 48h, from anchored ship

The vessel Ludwig Prandtl was anchored for 48 h off Cuxhaven at Medem Reede. Water samples were taken approx. every 2 hours during daytime, while sensors were recording continuously. Water samples were taken from ferrybox outlet from surface (1 m).

Water samples off Cuxhaven, for 48h, from anchored ship

The vessel Reykjanes was anchored for 48 h off Cuxhaven at Medem Reede. Water samples were taken approx. every 2 hours during daytime, while sensors were recording continuously. Water samples were taken from different sources: ship's water supply, in-situ pump and niskin bottle, from surface (1 m) and bottom water (12 m).

Hydrographic parameters, dissolved CH4, atmospheric CH4 and CO2 along the river Elbe, August 2020

In August 2020 the research vessel Albis investigated the river Elbe from Schmielka towards Geesthacht. Basic hydrographic parameters were measured continuously, with a portable ferryBox. Dissolved methane was continuously determined with a degassing unit and a Greenhouse Gas Analyzer from LosGatosResearch. Atmospheric CH4 and CO2 was determined with a Licor system.

Single water samples from MOSES project's cruise stern_3

During Stern_3 single water samples were taken either from a rosette (vertical) or from on the way systems. For the on the way systems a time off-set was calculated and subtracted from the original time. The aim of the sampling was mainly to counter-check with different sensors. More details can be found in the expedition report (Fahrtbericht Moses Sternfahrten). For methane concentrations, water was transferred to glass bottles (120 ml) and stored cold (4°).

Single water samples from MOSES project's cruise stern_2

During Stern_2 cruise single water samples were taken either from a rosette (vertical) or from on the way systems. For the on the way systems a time off-set was calculated and subtracted from the original time. The aim of the sampling was mainly to counter-check with different sensors. More details can be found in the expedition report (Fahrtbericht Moses Sternfahrten). For methane concentrations, water was transferred to glass bottles (120 ml) and stored cold (4°). In the home laboratory a 20 ml head space was created and analyzed via gas chromatography. Magen et al. (2014).

Single water samples from MOSES project's cruise stern_1

During Stern_1 single water samples were taken either from a rosette (vertical) or from on the way systems. For the on the way systems a time off-set was calculated and subtracted from the original time. The aim of the sampling was mainly to counter-check with different sensors. More details can be found in the expedition report (Fahrtbericht Moses Sternfahrten). For methane concentrations, water was transferred to glass bottles (120 ml) and stored cold (4°). In the home laboratory a 20 ml head space was created and analyzed via gas chromatography. Magen et al. (2014).

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