MOORING · Monitoring Of Oceanic inteRnal tIdes usiNG fibre optic telecommunication cables

Monitoring Of Oceanic inteRnal tIdes usiNG fibre optic telecommunication cables

Ocean mixing plays a crucial role in the Earth’s climate as it balances the ocean circulation that buffers global warming. Quantifying mixing is challenging because energy enters the ocean at basin-scale but it dissipates at cm-scale over the vast ocean. One common element in the cascade of energy towards small scales is the transfer of energy to internal waves, which ultimately drive ocean mixing. Energy transfers to the internal wave field are largely enhanced through flow interactions with topography, but observations of wave-topographic interactions are scarce. To fill the observational gap in ocean mixing, this project explores wave-topographic interactions using a revolutionary technology in seismology (Distributed Acoustic Sensing, DAS) that allows continuous sampling at high spatio-temporal resolution. The overall objective of the project is to validate DAS for oceanographic studies of bottom tides using conventional measurements combined with numerical advanced modelling. To this end, a proof-of-concept experiment was conducted on the continental slope east of Gran Canaria. The observations collected during the project and the model output generated show the capability of DAS to characterize bottom internal tides over an unprecedented range of scales from meters to kilometers and from seconds to months, opening a new door for oceanographic studies. Moreover, this project has shown the potential of DAS to identify ocean-mixing hotspots for carrying out detailed oceanographic field campaigns and to feed mixing parameterizations that infer energy dissipation rates in the ocean. In contrast to current coastal observatories, the proposed approach allows continuous sampling at low cost by making use of fibre-optic telecommunication cables already in place. As a result, it could be eventually implemented at regional/global scale with a twofold benefit to monitor climate change. First, DAS could record the effects of global warming at the ocean floor across decades. And second, DAS could reduce the uncertainty in the quantification of energy dissipation in the ocean, a process occurring within seconds with the aim to improve mixing parameterizations in climate change models for more accurate climate predictions. Both targets would translate into better mitigation and adaptation strategies.

Data: CORDIS, © European Union