Atmospheric Aerosol Emissions Related to the Mediterranean Seawater Biogeochemistry
Karine Sellegri1, Allison Schwier1, Clemence Rose1, Frédéric Pierre-Henri Gazeau2, Cecile Guieu2, Barbara D'anna3, Alina Marie Ebling4, Jorge Pey5, Nicolas Marchand5, Bruno Charriere6, Richard Sempéré7 and Sébastien Mas8, (1)Laboratoire de Météorologie Physique Observatoire de Physique du Globe de Clermont-Ferrand, Aubiere Cedex, France, (2)Laboratoire d'Oceanographie, Villefranche-Sur-Mer, France, (3)IRCELyon Institut de recherches sur la catalyse et l'environnement de Lyon, Université de Lyon, Lyon, F-69626, France; Université Lyon 1, Lyon, F-69626, France; CNRS, UMR5256, Villeurbanne, France, (4)Florida State University, Earth Ocean and Atmospheric Science, Tallahassee, FL, United States, (5)Aix-Marseille Université, LCE FRE 3416, Marseille, France, (6)Aix Marseille Université, CNRS/INSU,IRD, Mediterranean Institute of Oceanography (MIO), UM 110, 13288, Marseille, France, (7)Aix-Marseille Univ., Université de Toulon, CNRS, IRD, Mediterranean Institute of Oceanography (MIO) UMR 7294, Marseille, France, (8)MEDIMEER, Mediterranean Center for Marine Ecosystem Experimental Research, UMS 3301 (Université Montpellier 2, CNRS), Sète, France
Abstract:
Marine aerosols contribute significantly to the global aerosol load and consequently has an important impact on the Earth's climate. Different factors influence the way they are produced at the air/seawater interface. The sea state (whitecap coverage, temperature, etc. ) influence the size and concentration of primarily produced particles but also biogeochemical characteristics of the seawater influence both the physical and chemical primary fluxes to the atmosphere. An additional aerosol source of marine aerosol to the atmosphere is the formation of new particles by gaz-to-particle conversion, i.e. nucleation. How the seawater and surface microlayer biogeochemical compositions influences the aerosol emissions is still a large debate. In order to study marine emissions, one approach is to use semi-controlled environments such as mesocosms.
Within the MedSea and SAM projects, we characterize the primary Sea Spray Aerosol (SSA) during mesocosms experiments performed during different seasons in the Mediteranean Sea. Mesocosms were either left unchanged as control or enriched by addition of nutriments in order to create different levels of phytoplanctonic activities. The mesocosms waters were daily analyzed for their chemical and biological composition (DOC, CDOM, TEP, Chl-a, virus, bacteria, phytoplankton and zooplankton concentrations). SSA production by bubble bursting was daily simulated in a dedicated set-up. The size segregated SSA number fluxes, cloud condensation nuclei (CCN) properties, and chemical composition were determined as a function of the seawater characteristics. We show that the SSA organic content was clearly correlated to the seawater Chl-a level, provided that the mesocosm was not enriched to create an artificial phytoplanctonic bloom. In our experiments, the enrichment of the seawater with natural surface microlayer did not impact the SSA organic content nor its CCN properties. At last, nucleation of secondary particles were observed to occur in the mesocosm headspace, without any connection to DMS emissions. The occurrence of nucleation of new particles in the open ocean atmosphere is still debated and these findings will be discussed in regard to observations performed in the ambient Mediterranean atmosphere during the MISTRAL/Charmex project.
