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Data and calculations to support the study of the sea-air flux of methane and carbon dioxide on the West Spitsbergen margin in June 2014


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Ruppel, Carolyn, Pohlman, John, and Casso, Michael, 2017, Data and calculations to support the study of the sea-air flux of methane and carbon dioxide on the West Spitsbergen margin in June 2014: U.S. Geological Survey data release,


A critical question for assessing global greenhouse gas budgets is how much of the methane that escapes from seafloor cold seep sites to the overlying water column eventually crosses the sea-air interface and reaches the atmosphere. The issue is particularly important in Arctic Ocean waters since rapid warming there increases the likelihood that gas hydrate--an ice-like form of methane and water stable at particular pressure and temperature conditions within marine sediments--will break down and release its methane to the overlying ocean. Some researchers have even proposed the possibility of an Arctic methane catastrophe characterized by wholesale breakdown of gas hydrates in marine sediments and release of the methane to the atmosphere [...]


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The data were collected at shallow and deepwater seeps and in background (no seep) areas on the West Spitsbergen margin for the purpose of determining the rate of methane and carbon dioxide exchange (flux) across the sea-air interface. Determining sea-air gas fluxes requires combining various datasets in space and time. This analysis uses the ship's navigational parameters, a hull-mounted seawater temperature sensor, and wind speed sensors; an Airmar PB200 weather station to provide a check on the ship's navigational parameters and record air temperature; two Picarro cavity ring-down spectrometers that measure the concentration of methane (CH4) and carbon dioxide (CO2) in (dried) samples of headspace gas obtained from near-surface seawater and in samples of air within the atmospheric marine boundary layer; and a YSI EXO2 sonde that measure physical and chemical parameters for the near-surface seawater pumped into the lab. The dataset also reports on the stable carbon (δ13C) isotopic composition of methane and carbon dioxide in the near-surface waters as measured by one of the Picarro cavity ring-down spectrometers. Such isotopic data can be used to infer the processes that led to the formation of methane and carbon dioxide (for example, microbial processes). The data have been combined, gridded at 30 second intervals and edited to remove periods when the instruments were being calibrated with lab standards or when data streams were disrupted. This results in non-continuous shiptracks and non-continuous times in the file. Once edited, the data were used to calculate a variety of values related to sea-air gas flux, including the saturation anomaly for methane in near-surface waters, sea-air flux of methane and carbon dioxide expressed in a variety of units, and various intermediate constants (Schmidt number, Ostwald coefficient) needed for sea-air flux calculations.

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DOI doi:10.5066/F7M906V0

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