EarthScope-Oceans: A hydroacoustic and seismic monitoring network for the deep ocean environment, above and below the seafloor

We present recent technological and scientific advances of U.N. Ocean Decade project #171 “EarthScope-Oceans: 300 MERMAIDS”. This unique platform of deep profiling floats carrying hydrophones to 1000-4000 m depth was originally developed to observe seismic signals (earthquakes) where land stations are missing – and has since expanded into the realms of ocean acoustics, oceanography, and marine environmental sciences. Our long-term objective is to achieve global coverage of the world oceans with a fleet of hundreds to thousands of MERMAIDS. The detection and monitoring of oceanic earthquakes, volcanoes, tsunamis, and their impacts on the marine environment, on marine ecosystems and on society could thus be brought to a standard comparable to on-land observations, whereas presently these events are often not even detected. Around 100 MERMAIDS have been deployed so far, and many have been operating continuously for over six years in the remote South Pacific. Recent successes include the network-wide recording of the 2022 Hunga Tonga eruption, the successful relocation of earthquakes in the remote Tonga subduction zone, and the successful modelling of MERMAID waveform recordings. The floats are becoming more modular and versatile through ongoing work on software and hardware capabilities.  Its MeLa software allows the MERMAIDS to be adapted for recording bathymetry, ocean chemistry, and magnetic field variations, for example. Scientific applications in progress concern the year-round location and tracking of marine mammals and of ship traffic, the quantification of rain and wind on the ocean surface and the joint acoustic and biogeochemical characterization of submarine volcanoes. https://oceandecade.org/actions/earthscope-oceans-300-mermaids