The « PlanetSolar DeepWater » expedition was conducted during the summer of 2013 by the University of Geneva, using the unique characteristics of the Swiss solar-powered ship “Tûranor Planet Solar”, the largest vessel of its kind in the world. The primary objectives of the expedition were to undertake measurements at the ocean-atmosphere interface in the vicinity of the Gulf Stream, in order to better understand the complex interactions between the ocean and the atmosphere that have relevance for climatic processes. The Atlantic crossing enabled incursions into cold and warm water masses on the margins of the Gulf Stream, and into ocean vortices exhibiting sharp gradients in temperature and salinity. Atmospheric aerosols were analyzed in real time using a new device especially developed for the campaign, which measures the aerodynamic size and the full fluorescence spectrum (350-650 nm in 32 channels) of individual aerosols particles. The recorded spectra are subsequently categorized into clusters, which can be tentatively identified by comparison with reference spectra of relevant species and organisms (HULIS, proteins, vitamins, phytoplankton, bacteria, algae, etc..), recorded with the same device. Size measurements were backed up by a tropicalized Grimm Aerosol Spectrometer. The oceanic water was investigated using CTD soundings down to 300 m depth, additionally recording dissolved oxygen, salinity and chlorophyll fluorescence. A ferrybox analyzed in real time the water masses at the surface. Meteorological data, as well as ship speed, GPS position, and satellite data completed the data set. Figure 1 shows a typical example of acquired data along the expedition, i.e. number of fluorescing aerosol particles, together with ocean surface temperature and wind direction and speed. Extensive statistical analyses of the data have been carried out and clear correlations are identified between the abundance and type (clusters of fluorescence spectra) of aerosol particles on the one hand, and the properties of the water masses in which the vessel has sailed or distance to the nearest coasts on the other hand.

Aerosol emissions at the ocean-atmosphere interface: The PlanetSolar Deep Water Expedition

251st National Meeting (2016)

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