Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
• Data Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Deployments
• Project Information
• Program Information
• Funding

A tracer release experiment was conducted in the coastal Baltic Sea during cruise AL510 aboard the research vessel FS Alkor. On June 4th, 2018, we injected 3He and SF6 into the surface ocean (~5 m depth). After the injection, near the center of the SF6 patch, depth profiles of temperature and salinity were measured using a conductivity, temperature, and depth (CTD) sonde and water samples were collected in Niskin bottles.

Discrete SF6 samples (and replicates) were drawn from the Niskin bottles using 550 ml glass bottles with ground-glass stoppers. For discrete 3He samples, ~40 milliliters of seawater were collected in copper tubes mounted in aluminum channels and sealed at the ends with stainless steel clamps.

SF6 samples were taken at the same stations and measured on board the FS Alkor. Concentration of SF6 was measured using a purge-and-trap SF6 analysis system designed following Law et al. (1994). In this system, SF6 was separated from other gases and measured with a gas chromatography electron capture detector (GC-ECD).

3He samples were measured at the Lamont-Doherty Earth Observatory (LDEO) Noble Gas Laboratory.  In the laboratory, 3He samples were extracted from the copper tubes using a vacuum extraction system (Ludin et al., 1998) and measured on a VG-5400 He isotope mass spectrometer. Precision is about 0.5 to 1% in δ3He for samples with high δ3He values (100% < δ3He < 1000%), and 0.2 to 0.5% for samples with lower δ3He values (-1.7% < δ3He < 100%). 

We calculated 3He excess from the measured 3He/4He ratio and 4He concentration.
3He excess is 3He in excess of solubility equilibrium calculated using the following equation: 

[3He]exc = [4He]s (Rs − Ra) + [4He]eqRa(1 − a), 

where: 

• [3He]exc is 3He in excess of solubility equilibrium
• [4He]s is the measured 4He concentration of the sample;
• [4He]eq is the atmospheric equilibrium concentration of 4He (Weiss, 1971);
• Rs is the measured 3He/4He ratio (ratio of sample);
• Ra is the 3He/4He ratio in the atmosphere (1.386 × 10^^-6 (Clarke et al. 1976));
• From (1 - a), a is the solubility isotope effect  (0.983 (Benson and Krause, 1980)).

* Imported data from source file "Baltic_Gas_Ex_1_20231113_with_SF6.txt" into the BCO-DMO data system.
* Modified parameter (column) names to conform with BCO-DMO naming conventions.
* Converted datetime to ISO8601 format yyyy-mm-ddThh:mm:ssZ
* Added column for station based on latitudes and longitudes

NSF Abstract:

Gas exchange, the movement of gases between the atmosphere and the surface ocean (in both directions), is an important process to understand in global biogeochemistry. A particular area of interest is the rate of exchange of gases such as carbon dioxide and dimethyl sulfide, which play important roles in Earth's climate. Understanding and modeling air-sea exchange on a global scale requires understanding of how gas exchange rates vary in response to a number of factors such as temperature, wind speed, and the presence of surface chemical films (known as surfactants) in the ocean. Over the past 25 years, major advances have been made in understanding air-sea gas exchange in the open ocean, mainly due to improvements in methodology and a number of successful process studies. However, some important questions remain, such as what happens near coastal areas (including inland seas), and how surfactants affect gas exchange. The Baltic Sea Gas Exchange Experiment (Baltic GasEx) is a collaboration between scientists from the US and Germany designed to address these questions. Participants in Baltic GasEx will measure the air-sea gas exchange rates with different techniques in the Baltic Sea before and after the spring bloom, when concentrations and compositions of surfactants will be different. The expeditions will be conducted on a German ship (Alkor), with the ultimate goal of quantifying the relationship between wind speed and gas exchange in an inland sea, and understanding the impact of surfactants on air-sea gas exchange. The project will involve significant international collaboration, public education and outreach through both participating U.S. institutions, and substantial student training in partnership with the international collaborators.

NSF funding will support helium-3 and sulfur hexafluoride measurements during Baltic GasEx to determine the gas exchange rate. German colleagues are independently funded to quantify surfactants with AC voltammetry, surface tension, and sum frequency generation; to determine chemical characteristics of the micro layer; and to estimate the gas exchange rate using eddy covariance flux measurements of CO2 and DMS. The proposed experiment is designed to address the question of whether open ocean wind speed/gas exchange parameterizations can be applied to inland seas like the Baltic. Also, the effect of surfactants on gas exchange has been studied extensively in the laboratory, but there is little direct field evidence for the effect of surfactants on gas exchange. The proposed experiment, with expeditions at times with both high and low surfactant concentrations, should shed new light on the effect of natural surfactants on gas exchange. Finally, some wind speed/gas exchange parameterizations proposed for the Baltic Sea appear to be higher than typical open ocean parameterizations. These are typically based on eddy covariance flux measurements of CO2. However, in open ocean experiments where both the helium-3/sulfur hexafluoride approach and eddy covariance of CO2 have been deployed, there seems to be a discrepancy between gas transfer velocities measured with the two techniques. This experiment should show whether a similar difference in gas transfer velocities measured via these two techniques also exists in the Baltic Sea.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

The Surface Ocean Lower Atmosphere Study (SOLAS) program is designed to enable researchers from different disciplines to interact and investigate the multitude of processes and interactions between the coupled ocean and atmosphere.

Oceanographers and atmospheric scientists are working together to improve understanding of the fate, transport, and feedbacks of climate relevant compounds, and also weather and hazards that are affected by processes at the surface ocean.

Oceanographers and atmospheric scientists are working together to improve understanding of the fate, transport, and feedbacks of climate relevant compounds.

Physical, chemical, and biological research near the ocean-atmosphere interface must be performed in synergy to extend our current knowledge to adequately understand and forecast changes on short and long time frames and over local and global spatial scales.

The findings obtained from SOLAS are used to improve knowledge at process scale that will lead to better quantification of fluxes of climate relevant compounds such as CO2, sulfur and nitrogen compounds, hydrocarbons and halocarbons, as well as dust, energy and momentum. This activity facilitates a fundamental understanding to assist the societal needs for climate change, environmental health, weather prediction, and national security.

The US SOLAS program is a component of the International SOLAS program where collaborations are forged with investigators around the world to examine SOLAS issues ubiquitous to the world's oceans and atmosphere.

» International SOLAS Web site

Science Implementation Strategy Reports

US-SOLAS (4 MB PDF file)
Other SOLAS reports are available for download from the US SOLAS Web site

The Ocean Carbon and Biogeochemistry (OCB) program focuses on the ocean's role as a component of the global Earth system, bringing together research in geochemistry, ocean physics, and ecology that inform on and advance our understanding of ocean biogeochemistry. The overall program goals are to promote, plan, and coordinate collaborative, multidisciplinary research opportunities within the U.S. research community and with international partners. Important OCB-related activities currently include: the Ocean Carbon and Climate Change (OCCC) and the North American Carbon Program (NACP); U.S. contributions to IMBER, SOLAS, CARBOOCEAN; and numerous U.S. single-investigator and medium-size research projects funded by U.S. federal agencies including NASA, NOAA, and NSF.

The scientific mission of OCB is to study the evolving role of the ocean in the global carbon cycle, in the face of environmental variability and change through studies of marine biogeochemical cycles and associated ecosystems.

The overarching OCB science themes include improved understanding and prediction of: 1) oceanic uptake and release of atmospheric CO2 and other greenhouse gases and 2) environmental sensitivities of biogeochemical cycles, marine ecosystems, and interactions between the two.

The OCB Research Priorities (updated January 2012) include: ocean acidification; terrestrial/coastal carbon fluxes and exchanges; climate sensitivities of and change in ecosystem structure and associated impacts on biogeochemical cycles; mesopelagic ecological and biogeochemical interactions; benthic-pelagic feedbacks on biogeochemical cycles; ocean carbon uptake and storage; and expanding low-oxygen conditions in the coastal and open oceans.