Science aboard Tara provides a 360° perspective. A tool designed to analyze atmospheric particles over oceanic areas has been set up aboard the schooner to study the interactions between ocean and atmosphere. According to Michel Flores – postdoctoral fellow at the Weizmann Institute of Science in Israel and scientist aboard Tara – a multidisciplinary approach is necessary to understand air-water exchanges and better apprehend the laws of Nature on a global scale.
Michel Flores (scientist in charge of aerosol sampling) changing the filters of the particle collecting system. © Maéva Bardy / Fondation Tara Expéditions
Set 12 meters above deck, on the shrouds, two funnels connected to a pump continuously collect atmospheric particles, also called aerosols. These liquid or solid particles can be generated by natural phenomena (volcano, sand storm, pollination, waves, etc.) or anthropogenic sources (combustion of hydrocarbons, chemical industries, etc.). Various instruments set in the rear hold quantify their size (ranging from nanometers to micrometers) and collect aerosols on filters for further chemical, morphological and genomic analysis.
Michel Flores started studying aerosols a few years ago for their optical properties. Depending on their color, aerosols absorb sunlight in different ways. Soot particles (black) from the combustion of hydrocarbons absorb all visible light, thus generating a rise in atmospheric temperature. Conversely, crystals of salt (white) reflect all visible light and cause climatic cooling. Other studies have shown that their presence is essential for the water cycle: without aerosols, water could not condense in the form of clouds. Therefore, these particles influence the climate balance.
Michel Flores has recently identified viruses within these aerosols, whose presence explains the sudden interruption of massive proliferation of phytoplankton, called “plankton bloom”. The extent of this phenomenon is such that it is visible in satellite images. These planktonic viruses are able to survive in the atmosphere and spread more quickly with the winds. Aerosols have been shown to be carried over great distances: for instance, pollution from Mexico City can reach the United States and mineral dusts from the Sahara Desert fertilize soils in the Amazon forest.
Plankton boom © NASA
The Tara Pacific expedition will provide the opportunity to map the diversity of particles and to highlight the influence of islands on the distribution and variety of aerosol samples. Michel Flores is looking for a potential correlation between coral reef ecosystems and the aerosols collected in these regions. The multidisciplinarity of the Tara Pacific scientific project will furnish an overall picture, as Michel explains: “We compartmentalize Nature into various disciplines because of the challenges we face in understanding it, but in reality there are no barriers, everything is connected.”
Maéva BARDY, on board correspondent
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