Sea2Cloud: From Biogenic Emission Fluxes to Cloud Properties in the Southwest Pacific
Karine Sellegri, Mike Harvey, Maija Peltola, Alexia Saint‐Macary, Theresa Barthelmeß, Manon Rocco, Kathryn A. Moore, Antonia Cristi, Frédéric Peyrin, Neill Barr, Laurent C.‐Labonnote, Andrew Marriner, John L. McGregor, Karl Safi, Stacy Deppeler, Stephen Archer, Erin Dunne, James Harnwell, Julien Delanoe͏̈, Evelyn Freney, Clémence Rose, Clément Bazantay, Céline Planche, Alfonso Saiz‐Lopez, Jesús López, Rosa Lebrón‐Aguilar, Matteo Rinaldi, Sandra Banson, Romain Joseph, Aurelia Lupaşcu, Olivier Jourdan, Guillaume Mioche, Aurélie Colomb, Gus Olivares, Richard Querel, Adrian McDonald, Graeme Plank, Beata Bukosa, Wayne Dillon, Jacques Pelon, Jean‐Luc Baray, Frédéric Tridon, Franck Donnadieu, Frédéric Szczap, Anja Engel, Paul J. DeMott, Cliff S. Law
Abstract
Abstract The goal of the Sea2Cloud project is to study the interplay between surface ocean biogeochemical and physical properties, fluxes to the atmosphere, and ultimately their impact on cloud formation under minimal direct anthropogenic influence. Here we present an interdisciplinary approach, combining atmospheric physics and chemistry with marine biogeochemistry, during a voyage between 41° and 47°S in March 2020. In parallel to ambient measurements of atmospheric composition and seawater biogeochemical properties, we describe semicontrolled experiments to characterize nascent sea spray properties and nucleation from gas-phase biogenic emissions. The experimental framework for studying the impact of the predicted evolution of ozone concentration in the Southern Hemisphere is also detailed. After describing the experimental strategy, we present the oceanic and meteorological context including provisional results on atmospheric thermodynamics, composition, and flux measurements. In situ measurements and flux studies were carried out on different biological communities by sampling surface seawater from subantarctic, subtropical, and frontal water masses. Air–Sea-Interface Tanks (ASIT) were used to quantify biogenic emissions of trace gases under realistic environmental conditions, with nucleation observed in association with biogenic seawater emissions. Sea spray continuously generated produced sea spray fluxes of 34% of organic matter by mass, of which 4% particles had fluorescent properties, and which size distribution resembled the one found in clean sectors of the Southern Ocean. The goal of Sea2Cloud is to generate realistic parameterizations of emission flux dependences of trace gases and nucleation precursors, sea spray, cloud condensation nuclei, and ice nuclei using seawater biogeochemistry, for implementation in regional atmospheric models.