Ice Nuclei properties in seawater, sea ice and brine from the Southern Ocean, Weddell Sea and Antarctic Peninsula: on the potential anti-freezing properties of polar microbiota

Early studies from the 90’s on INPs in the Southern Ocean (SO) have already revealed lower INP concentrations in the SO region than in other marine regions. This feature was confirmed in recent measurements and modeling exercises, with implications on our ability to model the cloud persistence in the Southern Ocean. The INP populations found in these regions were commonly organic and heat-stable, which contradicts the hypothesis of microorganism promoting ice nuclei formation. Here we present results from the POLARCHANGE ship campaign where samples of Southern Ocean seawater were taken and analyzed across a latitudinal gradient down to the vicinity of sea ice formed in the Weddell Sea. In addition, samples of Sea Ice cores were collected and ice nuclei particle (INP) concentrations were analyzed at various depths of the Sea Ice cores, and within brine samples. The comparison between Sea Ice, brine and Seawater INP concentrations latitudinal gradient, in relation with the biogeochemical properties of these different compartments provides insight into processes that could explain the very low INP concentrations in the SO and polar atmosphere.