Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Supplemental Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Project Information
• Funding

Location: SUSTAIN wind-wave Tank, University of Miami

See Supplemental files "Experimental Conditions in SUSTAIN wind wave tank" which contain the same experiment numbers as this DiscreteNobleGasData dataset.

Methodology:

The noble gas concentrations (He, Ne, Ar, Kr and Xe) were measured at the Isotope Geochemistry facility at WHOI according to the method of Stanley et al. 2009 but with isotope dilution method for Kr and Xe, as in Jenkins et al. 2019. The copper tube samples were collected at the SUSTAIN tank at the start or end of each experiment and then shipped to WHOI for analysis. Full description of the sample collection and analysis is in Stanley et al., “Gas Fluxes and Steady-State Saturation Anomalies at Very High Wind Speeds" Submitted to JGR-Oceans in Dec. 2021 (Stanley et al., 2022). Temperature was measured by an optode and salinity was interpolated from discrete samples collected by salinity and measured at the University of Miami.

Sampling and analytical procedures:

A full description of the sample collection and analysis is in Stanley et al., “Gas Fluxes and Steady State Saturation Anomalies at Very High Wind Speeds “ Submitted to JGR-Oceans in Dec. 2021. Here is the relevant paragraph about discrete noble gas measurements from that paper:

At the end of every experiment, and at the beginning of approximately half the experiments (the experiments conducted with U_10 = 20, 30, 40 and 50 m s-1 and the invasion/evasion experiments), samples for discrete noble gas analysis were collected in copper tubes (Jenkins et al., 2019; Loose et al., 2016). The samples were drawn from the tank through pre-soaked tygon tubing into 1 m of 5/8” diameter copper tubing, bubbles were removed by rapping, and at least 1 L of water was allowed to flow through the tube. Flow was temporarily stopped by clips and then the ends of the copper tube were cold-welded (Young and Lupton, 1983), producing two gas-tight samples of ~45 g each per time-point, though typically only one sample was analyzed. Samples were shipped to the Isotope Geochemistry Facility at WHOI where the gases were first extracted from the sealed copper tube into 30 mL aluminosilicate glass ampoules using an evacuated noble gas extraction line (Jenkins et al., 2019) and then analyzed for He, Ne, Ar, Kr and Xe on a quadrupole mass spectrometer by first being separated cryogenically and then using ion beam manometry spectrometry for He, Ne and Ar, and isotope dilution for Kr and Xe (given the smaller abundances of Kr and Xe, isotope dilution is required for better precision and accuracy) (Jenkins et al., 2019; Stanley et al., 2009a). Precison of the system, based on measurements of duplicate samples, is 0.1% for He, Ne, Ar, Kr and 0.2% for Xe.

Temperature was interpolated from in situ measurements of temperature made by an Anderra optode located next to the in situ pump that brought water to the copper tubes. Salinity measurements were made at the beginning and end of most experiments and then interpolated to the time of noble gas data collection to obtain an appropriate salinity. The salinity in the SUSTAIN tank changed slowly for the most part since typically it was a closed system and thus evaporation was the only cause for change. However, at certain points within the experiment, new water was added to the tank and at those times, salinity samples were also taken. Thus the salinity data is usually smoothly changing but with some jumps.

William Jenkins at the IGF converted the raw mass spectrometry data to concentrations of gases in the samples by comparing standards and samples. 

BCO-DMO Data Manager Processing Notes:
* File DiscreteNobleGasData.txt imported into the BCO-DMO data system.
* Parameters (column names) renamed to comply with BCO-DMO naming conventions. See https://www.bco-dmo.org/page/bco-dmo-data-processing-conventions
* DateTime (UTC) column added in ISO 8601 format yyyy-mm-ddTHH:MMZ.
* Experimental conditions table attached as a supplemental file to this dataset.

NSF Abstract:

An exact description of gas exchange between the atmosphere and the ocean is not fully developed, yet it is a critical process for understanding climate change and ecosystem dynamics. This is particularly problematic when evaluating the important role of bubbles in air-sea gas exchange, especially in remote ocean locations where high winds and waves make direct measurements extremely difficult. This project seeks to provide needed fundamental, high wind/wave gas-exchange measurements by using a large, state-of-the-art, wind-wave tank. Here the PIs can apply their novel measurements of noble gases (neon, argon, krypton, and xenon) to calculate overall gas fluxes under precisely controlled conditions. This tank setting allows a systematic approach to define the physical and chemical parameters (temperature, salinity, pH, wind speed, turbulence, bubble size distribution, etc.) required to construct more accurate models without the great uncertainties inherent in making similar measurements from a ship in storm conditions. A significant outcome of this study, beyond improved understanding of air-sea gas exchange, could be greatly improved estimates of the critical ecological balance between photosynthesis and respiration. Current methods use carbon dioxide and oxygen dissolved in seawater as an indication of biological activity, but cannot distinguish between biological processes and atmospheric exchange, and estimates are especially inaccurate under high wind and wave conditions with strong bubble injection. This study will improve our ability to separate biological and physical processes in evaluation of dissolved gasses in seawater.

Also, this project will provide 15 female undergraduate students at Wellesley College with an exciting, on-site research experience using a state-of-the-art tank facility at the University of Miami, and results will be incorporated into general and advanced chemistry classes. The production of student-created, short format videos, and other public outreach activities will also be supported to disseminate information on the importance of marine gas exchange.

The study of gas exchange processes between the ocean and the atmosphere has been hindered by the lack of data required to define quantitative relationships that account for bubble processes under a variety of wind, wave, and temperature conditions. Current gas exchange models tend to be highly unreliable in their parameterization of bubble processes. In large part, this is due to the difficulty of making traditional measurements at sea in remote locations within well-defined conditions, especially with high winds and waves. By using the large SUSTAIN wind-wave tank (23 m x 6 m x 2 m), the researchers in this project plan to greatly advance our understanding of the effect of wind, wave, and temperature variability on gas transfer. The use of a recently developed, field-portable equilibrator mass spectrometer that allows nearly continuous measurements of noble gas ratios (Ne, Ar, Kr, and Xe) will result in these SUSTAIN tank experiments providing precisely characterized gas flux data under varying wind speeds from 10 to 40 m/s. In addition, an underwater shadowgraph system will image bubbles, allowing the researchers to quantify bubble size distributions, a key factor missing from bubble models. Current models use a greatly simplified, two size-class representation of bubbles; an approach that this research will re-evaluate in hopes of creating better parameterizations of the role of bubble size on gas flux, and consequently improved air-sea gas exchange models for oceanic and climatic applications.