Periodic Reporting for period 4 - Sea2Cloud (Are marine living microorganisms influencing clouds?)
Período documentado: 2023-01-01 hasta 2024-06-30
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. This general goal was divided in three objectives : i) to quantitatively and qualitatively investigate the link between marine particles emissions and the biogeochemical properties of the seawater in the Southern Hemisphere, using a ground-breaking experimental approach, ii) evaluate the dependence of these marine emissions to sea surface temperature and (iii) to evaluate their transport and transformation in the atmospheric column, in view of assessing their potential impact of cloud properties.
The project was organized with processes experiments of sea-air biogenic emissions onboard research vessels in the Southern Hemisphere to generated biogenic emissions, and evaluating these new emission parameterizations using ambient air measurements and 3D chemistry models. In order to address the Sea2Cloud objectives, we organized a ship-borne campaign that took place in March 2020 on board of the R/V Tangaroa East of New-Zealand (Sellegri et al. 2023a). Added to this main interdisciplinary ship campaign, we deployed the same experimental set-up during the POLARCHANGE campaign on board the R/V Hesperides in the Weddell Sea.
Ship-borne process experiments
Gaz-phase emissions and subsequent nucleation were studied in dedicated Air-Sea Interface Tanks (ASIT) filled with different seawaters along the ship tracks, and under different environmental stressors (Ozone, UV). The ASIT experiments provided fluxes of reactive gases (DMS, isoprene, monoterpenes etc.) as a function of the seawater biogeochemistry (Rocco et al. in revision). An original result was the finding that marine microorganisms are releasing aromatics (BTEX) that are usually associated to pollution (Rocco et al. 2021). New parameterizations of nanoparticle fluxes as a function of seawater biology are main output of these experiments (Chamba, PhD Thesis; Chamba et al. 2023),
In parallel, sea spray was artificially continuously generated from the underway seawater system and characterized for its size, chemical composition, as a function of seawater temperature. These provides new parameterizations of the sea spray fluxes as a function of the seawater biogeochemistry (Sellegri et al. 2023b), complementing the previous biological dependance of sea spray fluxes at a fixed moderate temperature (Sellegri et al. 2021), the sea spray chemical composition in relation to seawater biogeochemistry (Freney et al. 2021) and the ice nucleating properties of sea spray as a function of the sea water biogechemical properties of seawater (Trueblood et al. 2021).
The aerosol size distribution, cluster size distribution and chemical composition, and aerosol ice nuclei properties were continuously measured at the GAW station Baring Head (tip of NZ north island) from June 2020 to February 2021. From this data set, we provide a statistical occurrence of New Particle Formation (NPF) events in purely marine air masses and its seasonal dependance which is rarely documented (Peltola et al. 2022), while the chemical precursors to particle nucleation and growth were addressed in a second paper (Peltola et al. 2023). High altitude measurements of the newly formed aerosol clusters were achieved from the Maido station with selected nighttime periods representation of the free troposphere (Salignat et al. 2024). The sea spray emission parameterizations as a function of the seawater biogeochemistry were implemented in WRF-Chem and the impact on cloud formation evaluated (Rose et al. under review). The parameterization of the new nucleation process was implemented and its impact on the aerosol number concentration tested (Salignat et al. submitted). Lastly, the final goal of evaluating the role of ocean biology on cloud properties was tested via another approach, i.e. directly using satellite cloud phase products on one hand and ocean biological products on the other hand (Bazantay et al. 2024).
Ship-borne process experiments
Gaz-phase emissions and subsequent nucleation were studied in dedicated Air-Sea Interface Tanks (ASIT) filled with different seawaters along the ship tracks, and under different environmental stressors (Ozone, UV). The ASIT experiments provided fluxes of reactive gases (DMS, isoprene, monoterpenes etc.) as a function of the seawater biogeochemistry (Rocco et al. in revision). An original result was the finding that marine microorganisms are releasing aromatics (BTEX) that are usually associated to pollution (Rocco et al. 2021). New parameterizations of nanoparticle fluxes as a function of seawater biology are main output of these experiments (Chamba, PhD Thesis; Chamba et al. 2023),
In parallel, sea spray was artificially continuously generated from the underway seawater system and characterized for its size, chemical composition, as a function of seawater temperature. These provides new parameterizations of the sea spray fluxes as a function of the seawater biogeochemistry (Sellegri et al. 2023b), complementing the previous biological dependance of sea spray fluxes at a fixed moderate temperature (Sellegri et al. 2021), the sea spray chemical composition in relation to seawater biogeochemistry (Freney et al. 2021) and the ice nucleating properties of sea spray as a function of the sea water biogechemical properties of seawater (Trueblood et al. 2021).
The aerosol size distribution, cluster size distribution and chemical composition, and aerosol ice nuclei properties were continuously measured at the GAW station Baring Head (tip of NZ north island) from June 2020 to February 2021. From this data set, we provide a statistical occurrence of New Particle Formation (NPF) events in purely marine air masses and its seasonal dependance which is rarely documented (Peltola et al. 2022), while the chemical precursors to particle nucleation and growth were addressed in a second paper (Peltola et al. 2023). High altitude measurements of the newly formed aerosol clusters were achieved from the Maido station with selected nighttime periods representation of the free troposphere (Salignat et al. 2024). The sea spray emission parameterizations as a function of the seawater biogeochemistry were implemented in WRF-Chem and the impact on cloud formation evaluated (Rose et al. under review). The parameterization of the new nucleation process was implemented and its impact on the aerosol number concentration tested (Salignat et al. submitted). Lastly, the final goal of evaluating the role of ocean biology on cloud properties was tested via another approach, i.e. directly using satellite cloud phase products on one hand and ocean biological products on the other hand (Bazantay et al. 2024).
Experimental innovation:
The most novel methodology developed during the Sea2Cloud voyage was the use of 2m3 tanks (ASITs for Air Sea Interface tanks) containing seawater and an headspace on board of the ship, that allow for the quantification and characterization of gaz-phase fluxes and subsequent cluster formation from almost unperturbed seawater along the ship track, in an uncontaminated natural atmosphere. The second innovative experiments are the temperature dependent sea spray generation experiments performed on board of the R/V Tangaroa using the ship’s underway seawater circulation system in a continuous way. It is to our knowledge the first time such experiments were performed.
Scientific innovation:
The impact of nanophytoplankton on sea spray number emission reported in Sellegri et al. (2021) was evaluated at a given moderate seawater temperature from a multiple database with a 10 fold increase at high biology compared to low biology conditions, and is now evaluated in the actual WRF-Chem simulations, showing a significant impact on cloud properties. Previous publications show that the temperature dependence of seas pray fluxes is very strong in cold seawaters, significantly higher in natural seawaters compared to artificial (free of biology) seawaters, but that this temperature dependence was not understood. In sellegri et al. 2023b, we confirmed a larger influence on sea spray number fluxes at low temperature than at moderate temperatures, by up to an additional 4 fold impact, and quantify it as a function of seawater biology for further implementation in mesoscale models. The new ASIT methodology (Sellegri et al. 2023a) allowed to evidence that (1) unforeseen volatile organic compounds, usually classified as anthropogenic VOCs were emitted from phytoplankton at the same level than DMS (Rocco et al. 2021), (2) nucleation occurred from the open ocean phytoplankton emissions (Chamba et al. 2023) and (3) precursors to nucleating clusters are mostly originating from terpenes, also emitted in the ASITs headspace (Chamba et al. 2023).
The most novel methodology developed during the Sea2Cloud voyage was the use of 2m3 tanks (ASITs for Air Sea Interface tanks) containing seawater and an headspace on board of the ship, that allow for the quantification and characterization of gaz-phase fluxes and subsequent cluster formation from almost unperturbed seawater along the ship track, in an uncontaminated natural atmosphere. The second innovative experiments are the temperature dependent sea spray generation experiments performed on board of the R/V Tangaroa using the ship’s underway seawater circulation system in a continuous way. It is to our knowledge the first time such experiments were performed.
Scientific innovation:
The impact of nanophytoplankton on sea spray number emission reported in Sellegri et al. (2021) was evaluated at a given moderate seawater temperature from a multiple database with a 10 fold increase at high biology compared to low biology conditions, and is now evaluated in the actual WRF-Chem simulations, showing a significant impact on cloud properties. Previous publications show that the temperature dependence of seas pray fluxes is very strong in cold seawaters, significantly higher in natural seawaters compared to artificial (free of biology) seawaters, but that this temperature dependence was not understood. In sellegri et al. 2023b, we confirmed a larger influence on sea spray number fluxes at low temperature than at moderate temperatures, by up to an additional 4 fold impact, and quantify it as a function of seawater biology for further implementation in mesoscale models. The new ASIT methodology (Sellegri et al. 2023a) allowed to evidence that (1) unforeseen volatile organic compounds, usually classified as anthropogenic VOCs were emitted from phytoplankton at the same level than DMS (Rocco et al. 2021), (2) nucleation occurred from the open ocean phytoplankton emissions (Chamba et al. 2023) and (3) precursors to nucleating clusters are mostly originating from terpenes, also emitted in the ASITs headspace (Chamba et al. 2023).