Lessons learned from the monitoring of turbidity currents and guidance for future platform designs

Abstract

Turbidity currents transport globally significant volumes of sediment and organic carbon into the deep-sea and pose a hazard to critical infrastructure. Despite advances in technology, their powerful nature often damages expensive instruments placed in their path. These challenges mean that turbidity currents have only been measured in a few locations worldwide, in relatively shallow water depths (<<2 km). Here, we share lessons from recent field deployments about how to design the platforms on which instruments are deployed. First, we show how monitoring platforms have been affected by turbidity currents including instability, displacement, tumbling and damage. Second, we relate these issues to specifics of the platform design, such as exposure of large surface area instruments within a flow and inadequate anchoring or seafloor support. Third, we provide recommended improvements to improve design by simplifying mooring configurations, minimising surface area, and enhancing seafloor stability. Finally we highlight novel multi-point moorings that avoid interaction between the instruments and the flow, and flow-resilient seafloor platforms with innovative engineering design features, such as ejectable feet and ballast. Our experience will provide guidance for future deployments, so that more detailed insights can be provided into turbidity current behaviour, and in a wider range of settings.

Quantifying the three‐dimensional stratigraphic expression of cyclic steps by integrating seafloor and deep‐water outcrop observations

“…Observations from modern environments are typically a primary source of information about sedimentary processes, which commonly inform interpretations in the rock record. However, modern deep-water environments are notoriously difficult to study due to their location at substantial water depths and distances from the shore, as well as the unpredictable and destructive nature of turbidity currents (Mutti & Normark, 1987;Paull et al, 2003;Sumner & Paull, 2014;Clare et al, 2020). As a result, the understanding of fundamental deep-water sedimentary processes has been limited compared to other depositional environments that are more easily accessed and readily observed on the Earth's surface.…”

Deep-sea water displacement from a turbidity current induced by the Super Typhoon Hagibis

“…The Edokko Mark 1 (Type HSG) is an all-in-one, free-fall, stand-alone deep-sea monitoring system (Miwa et al, 2016;Japan Agency for Marine-Earth Science and Technology, 2017), provided by Okamoto Glass Co. Ltd. (https://ogc-jp.com/en/). The Edokko Mark 1 and other similar systems (Gallo et al, 2020;Clare et al, 2020) increase our capability for the observation of deep-sea turbidity currents when typhoons, earthquakes, or tsunamis impact marginal seas.…”

Flood and tides trigger longest measured sediment flow that accelerates for thousand kilometers into deep-sea

“…Turbidity currents are also important geohazards 21 . In particular, they break seabed telecommunications cable networks that now carry over 99% of intercontinental data tra c 22 , which underpin the global internet and many other aspects of our daily lives worldwide 23 .…”