Automatic Detection of Optical Signatures within and around Floating Tonga-Fiji Pumice Rafts Using MODIS, VIIRS, and OLCI Satellite Sensors

An underwater volcanic eruption off the Vava’u island group in Tonga on 7 August 2019 resulted creation of floating pumice ocean’s surface extending over an area 150 km2. The pumice’s far-reaching effects from its origin region to Fiji and methods automatic detection using satellite imagery are described, making it possible track westward drift raft 43 days. Level 2 Moderate Resolution Imaging Spectroradiometer (MODIS), Visible Infrared Radiometer Suite (VIIRS), Sentinel-3 Ocean Land Color Instrument (OLCI), Sea Surface Temperature (SLSTR) sea temperature, chlorophyll-a concentration, quasi-surface (i.e., Rayleigh-corrected) reflectance, remote sensing reflectance were used distinguish consolidated fragmented rafts as well discolored mesotrophic waters. detected by a 1 3.5 °C enhancement MODIS-derived “sea temperature” due emissivity difference material. Large plumes waters, characterized higher reflectance/backscattering particles blue than surrounding waters (and corresponding either submersed or associated white minerals), with rafts. had relatively lower but this was artificial, resulting blue/red ratio caused reflective particles. Mesotrophic scarce rafts, presumably absence phytoplanktonic response silicium-rich environment these tropical oligotrophic environments. As beach accumulations around Pacific islands surrounded coral shoals recurrent phenomenon that finds far east ocean along Tongan trench, monitoring events space, demonstrated for eruption, might help mitigate their potential economic impacts.