[A-OS13] Exploring Variability and Changes in Ocean Biogeochemical Cycles

[AOS13-09] Particle Size Distribution and sinking velocity of Large Marine Particles in the Global Ocean With In Situ Optical
Observations and Supervised Learning for the all global ocean

*Gian Giacomo Navarra¹, Curtis Deutsch¹, Yohei Takano², Redouanne Lguensat³ (1.Princeton University, 2.British Antarctic Survey, 3.Institut Pierre-Simon Laplace)

The abundance and size distribution of marine particles control a range of biogeochemical and ecological processes in the ocean, including carbon sequestration. These quantities are the result of complex physical-biological interactions that are difficult to observe, and their spatial and temporal patterns remain uncertain. Here, we present a novel analysis of particle size distributions (PSDs) from a global compilation of in situ Underwater Vision Profiler 5 (UVP5) optical measurements. Using a machine learning algorithm,we extrapolate sparse UVP5 observations to the global ocean from well-sampled oceanographic variables.We reconstruct global maps of PSD parameters (biovolume [BV] and slope) for particles for the all water column. These reconstructions reveal consistent global patterns, with high chlorophyll regions generally characterized by high particle BV and flatter PSD slope, that is, a high relative abundance of large versus small particles. The resulting negative correlations between particle BV and slope further suggests synergistic effects on size-dependent processes such as sinking particle fluxes. Our approach and estimates provide a baseline for an improved understanding of particle cycles in the ocean, and pave the way to global, three-dimensional reconstructions of PSD and sinking particle fluxes from the growing body of UVP5 observations.