Long-term Platforms for Subsea Acoustic Ranging, Geodetic Monitoring and Ocean Circulation: Past and Future Applications

We present multi-disciplinary case studies for multi-year deployments of an autonomous subsea sensor logging node with acoustic communication capability.

Errors associated with single-point observations of tectonic plate motion, seafloor subsidence and geostrophic current circulation are typically on the same order as expected annual rates of those phenomena.

Hardware platforms suffer from settling rates that contaminate signal for the first few months of deployment. These also require platforms to remain in the same 3D position without recovery and re-deployment to achieve a continuous time series.

Sonardyne Fetch systems have a 10-year lifetime and are used as multi-disciplinary platforms for Acoustic-Ranging, GNSS-A, PIES and self-calibrating (Ambient-Zero-Ambient/AZA) pressure logging. Acoustic modems allow regular data offload without hardware recovery.

Here, we present case studies from academia and industry across disciplines and incorporating manned and unmanned data recovery platforms. We also present projects under active investigation to form permanent near-real-time data communication to pre-existing cabled infrastructure. This will expand the footprint and potential for relocation of subsea observatories while minimising logistical and environmental impact.