Table of Contents

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

This dataset describes the operating conditions for the high-capacity generator that produced primary marine aerosol from western North Atlantic seawater during cruise EN589 on RV/Endeavor during September and October 2016.

The marine aerosol generator was operated by William Keene (wck@virginia.edu) and John Maben. Please direct any related questions to William Keene.

Description and Operation of the Marine Aerosol Generator: Model primary marine aerosol (mPMA) was produced in a high-capacity generator fabricated from Pyrex and Teflon.  See Keene et al. [2007] for a description and schematic of the original configuration of the device and Long et al. [2014] for an explanation of modifications implemented for deployment on ships at sea during the 2010 California Nexis (CalNex) campaign in the eastern North Pacific Ocean and the 2012 Western Atlantic Climate Study (WACS) in the western North Atlantic Ocean.  During all previous deployments, bubble plumes were produced using sintered-glass frits and/or plunging seawater jets.  During the Endeavor cruise, frits were replaced with force-air Venturis as described below. 

Briefly, the 20-cm-diameter generator consisted of a 122-cm-deep seawater reservoir underlying a 97-cm-deep atmosphere. During most periods, fresh seawater drawn from approximately 5-m depth through the ship’s clean seawater line flowed into the base of the seawater reservoir (typically at 4 L min-1) and drained evenly to exhaust over the top annular rim thereby continuously replacing the seawater surface and minimizing formation of standing bubble rafts.  During two periods, feed seawater flowing through the generator was transferred from carboys containing seawater that had been collected at a depth of 2500 m, stored in 20 L Teflon lined carboys, and warmed to room temperature.  Bubble plumes were generated by two mechanisms. (1) Ultra-pure air and seawater (drawn from the base of the generator’s seawater reservoir) were pumped at adjustable rates of 1 to 5 L min-1 each through one of two force-air Venturi nozzles that were fabricated from Teflon and positioned at depths of 42 (shallow) and 72 cm (deep), respectively, below the air-seawater interface.  (2) Bubble plumes were also produced by a seawater jet at flow rates of 1 to 3 L min-1 that impinged on the air-seawater interface.  The jet nozzle was 0.32-cm ID and positioned at 50 cm above the interface.

mPMA was emitted to the headspace when bubbles rose to and burst at the air-seawater interface. Ultra-pure sweep air flowed through the headspace above the seawater reservoir at 70 L min-1. During most sampling periods, sweep air was hydrated to a relative humidity (RH) of ~80%. mPMA was sampled for chemical and physical characterization through isokinetic ports at the top of the generator.

The generator was blank tested by measuring mPMA number concentrations in the headspace at typical flow rates of bubble and sweep air but with no seawater in the reservoir. All blank tests yielded undetectable particle number concentrations (less than 2 cm-3) indicating that all particles measured during routine operation originated from seawater.

Bubble-plume void fractions were quantified over ranges of conditions by filling the generator, turning off the flow of feed seawater, incrementally increasing the flow of air through the Venturi, and measuring the volume of displaced water.

Refer to the elated papers below for additional details regarding the design and operation of the marine aerosol generator and associated analytical methods.

BCO-DMO Processing:
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
- re-formatted date from d-Mon-yy to yyyy-mm-dd
- replaced blank cells with nd  (no data)

The oceans hold a massive quantity of organic carbon that is greater than all terrestrial organic carbon biomass combined. Nearly all marine organic carbon is dissolved and more than 95% is refractory, and cycled through the oceans several times before complete removal. Refractory dissolved organic carbon (RDOC) concentrations are uniform with depth in the water column and represent the "background" carbon present throughout the oceans. However, very little is known regarding RDOC production and removal processes. One potential removal pathway is through adsorption of RDOC onto surfaces of rising bubbles produced by breaking waves and ejection via bubble bursting into the atmosphere. Building on prior research, the investigators will evaluate the importance of ocean- atmosphere processing in recycling marine RDOC during a research cruise in the northwestern Atlantic Ocean. Results of the research will provide important insights regarding the coupled ocean-atmosphere loss of RDOC, thereby improving understanding of and ability to predict the role of RDOC in oceanic and atmospheric biogeochemistry, the global carbon cycle, and Earth's climate. The research will involve three early career faculty, and will provide training for undergraduate and graduate researchers.

Recent results based on a limited set of observations indicate that the organic matter (OM) associated with primary marine aerosol (PMA) produced by bursting bubbles from breaking waves at the sea surface is comprised partly to wholly of RDOC rather than OM of recent biological origin as has been widely assumed. The injection of RDOC into the atmosphere in association with PMA and its subsequent photochemical oxidation is a potentially important and hitherto unrecognized sink for RDOC in the oceans of sufficient magnitude to close the marine carbon budget and help resolve a long-standing conundrum regarding removal mechanisms for marine RDOC. This project will involve a shipboard investigation and modeling study to (1) quantify the relative contributions of marine refractory dissolved organic carbon (RDOC) to primary marine aerosol organic matter (PMA OM) produced from near-surface seawater in biologically productive and oligotrophic regions and from North Atlantic Deep Water, and to (2) determine the importance of atmospheric photochemical processing as a recycling pathway for RDOC. To test these hypotheses, a high-capacity aerosol generator will be deployed at four hydrographic stations in the NW Atlantic Ocean to characterize (1) the natural abundance of 14C in PMA and in surface and deep seawater; (2) the surface tension and physical properties of bubble plumes; (3) size-resolved production fluxes, chemical composition, organic carbon enrichments, spectral absorbance, and photochemical evolution of PMA; and (4) the carbon content, optical properties, and physical properties of seawater. The importance of RDOC recycling via PMA production and photochemical evolution will be interpreted with model calculations.

EN589 Cruise Track

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