Assessing the potential deep-sea biogeochemical hazards to submarine fiber optic and ocean observatory cables

Submarine cables, whether for telecommunications or specifically for seafloor ocean observatories are typically buried from shore stations to a depth of 1500 meters. However, as acoustic and direct imaging technology have increased our insight into morphodynamic and biogeochemical processes in regions not requiring cable burial, the need for greater understanding of the hydro-chemo-geo-hazards to the cable and/or scientific nodes needs to be assessed. In many proposed sites such as the proposed NEPTUNE Stage 1 (Canada), numerous risks include: (A) exposed or near-surface gas hydrates, (B) frequent turbidity currents, debris flows and/or mud flows, (C) abyssal storms with currents exceeding three meters per second, (D) active vent fields with temperatures in excess of 300°Celsius, (E) seismically active regions prone to disruption of the seafloor or in many cases liquefaction, and (F) poorly documented ordinance or hazardous material disposal sites. The risks to cables and observatories are not only limited to the examples listed above but will depend on the specifics of the seabed environments at sites under investigations or routes though which the cable must transit. Cable route surveys today must incorporate a multi-disciplinary approach to identifying potential hydrologic, chemical, anthropogenic and geologic risks and perhaps re-routing or deep-water burial along hazard-prone segments in order to provide the greatest reduction of risk in harsh environments.