Report
Teaser, summary, work performed and final results
Periodic Reporting for period 1 - Sea2Cloud (Are marine living microorganisms influencing clouds?)
Teaser
Earth, as a whole, can be considered as a living organism emitting gases and particles in its atmosphere, in order to regulate its own temperature (Lovelock, 1988). In particular oceans, which cover 70% of the Earth, may respond to climate change by emitting different species...
Summary
Earth, as a whole, can be considered as a living organism emitting gases and particles in its atmosphere, in order to regulate its own temperature (Lovelock, 1988). In particular oceans, which cover 70% of the Earth, may respond to climate change by emitting different species under different environmental conditions. Temperature regulation can be achieved via cloud coverage, that modulates the amount of incoming solar radiation and outgoing terrestrial radiation. Cloud coverage is dependant on the availability of aerosol particles in the atmosphere. At the global scale, a large fraction of the aerosol number concentration is formed by nucleation of low-volatility gas-phase compounds, a process that is expected to ultimately determine the concentrations of Cloud Condensation Nuclei (CCN). Nucleation occurrence over open oceans is still debated, due to scarce observational data sets and instrumental limitations, although recent findings suggest biologically driven nucleation from seawater emissions and the presence of newly formed particles at high altitude above the sea. Marine aerosol can also be emitted to the atmosphere as sea spray via bubble bursting, among which living microorganisms, such as bacteria, are suspected to act as ice nuclei (IN) and impact clouds precipitation capacities. The main goal of the project Sea2Cloud is to investigate how marine emissions from living microorganisms can influence CCN, IN and ultimately cloud properties. We will investigate the whole process chain of gas-phase emissions, nucleation and growth through the atmospheric column, and impact on the CCN population above oceans. We will also quantify marine primary aerosol emissions, including particles of biological origin, and evaluate how they impact IN and cloud precipitation capabilities. Experiments will be performed in the Southern Hemisphere, especially sensitive to the natural marine aerosol concentration variability.
Work performed
A first ship-based campaign was performed in the subtropical West Pacific where ambiant nanocluster chemical composition and aerosol size distribution was measured simultaneously to the seawater biogeochemical properties, and in particular the phytoplankton abundance. In parallel, sea spray physical and chemical fluxes were measured, as well as their cloud condensation and ice nuclei properties. The data set will help ameliorate sea spray physical fluxes published from a recent ship campaign in the Southern Ocean (Hartery et al. 2020) with the implementation of the role of biological effects of fluxes.
Another ship campaign is being prepared on the R/V Tangaroa East of New Zealand in March 2020 with the goals of:
(1) quantifying the chemical precursors to new particles and the impact of an increasing ozone level of these precursors. The experimental approach will be to use enclosures of seawater and the atmosphere above it, in order to link marine emissions to the biogeochemical properties of natural seawater with little perturbations of its biodiversity.
(2) identifying the impact of temperature changes on the effect of biology-driven sea spray fluxes, using a sea spray generator fed with underway ambiant seawater
These process-based approaches will be complemented with ambient measurements of aerosol properties (size distribution, CCN, IN) and their precursors simultaneously.
Final results
Publications on the biologically-driven sea spray fluxes (Sellegri et al. subitted), biology-dependant chemical fluxes (Freney et al. in prep.), biology-dependant Ice Nuclei fluxes (Trueblood et al. in prep.), and biology-driven nucleation (Peltola et al. in prep.) are in preparation.
New measurment field campaign will provide insights on the impact of the future evolution of the oxidation capacity of the amtosphere on nucleation, and temperature dependance of biological sea spray fluxes.
Website & more info
More info: https://sea2cloud.wordpress.com/.