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).
