CO-ORDINATING AND PUMP-PRIMING INTERNATIONAL EFFORTS FOR DIRECT MONITORING OF ACTIVE TURBIDITY CURRENTS AT GLOBAL 'TEST SITES'

Lead Research Organisation: Durham University
Department Name: Earth Sciences

Abstract

Turbidity currents are the volumetrically most import process for sediment transport on our planet. A single submarine flow can transport ten times the annual sediment flux from all of the world's rivers, and they form the largest sediment accumulations on Earth (submarine fans). These flows break strategically important seafloor cable networks that carry > 95% of global data traffic, including the internet and financial markets, and threaten expensive seabed infrastructure used to recover oil and gas. Ancient flows form many deepwater subsurface oil and gas reservoirs in locations worldwide. It is sobering to note quite how few direct measurements we have from submarine flows in action, which is a stark contrast to other major sediment transport processes such as rivers. Sediment concentration is the most fundamental parameter for documenting what turbidity currents are, and it has never been measured for flows that reach submarine fans. How then do we know what type of flow to model in flume tanks, or which assumptions to use to formulate numerical or analytical models? There is a compelling need to monitor flows directly if we are to make step changes in understanding. The flows evolve significantly, such that source to sink data is needed, and we need to monitor flows in different settings because their character can vary significantly.

This project will coordinate and pump-prime international efforts to monitor turbidity currents in action. Work will be focussed around key 'test sites' that capture the main types of flows and triggers. The objective is to build up complete source-to-sink information at key sites, rather than producing more incomplete datasets in disparate locations. Test sites are chosen where flows are known to be active - occurring on annual or shorter time scale, where previous work provides a basis for future projects, and where there is access to suitable infrastructure (e.g. vessels). The initial test sites include turbidity current systems fed by rivers, where the river enters marine or freshwater, and where plunging ('hyperpycnal') river floods are common or absent. They also include locations that produce powerful flows that reach the deep ocean and build submarine fans. The project is novel because there has been no comparable network established for monitoring turbidity currents

Numerical and laboratory modelling will also be needed to understand the significance of the field observations, and our aim is also to engage modellers in the design and analysis of monitoring datasets. This work will also help to test the validity of various types of model. We will collect sediment cores and seismic data to study the longer term evolution of systems, and the more infrequent types of flow. Understanding how deposits are linked to flows is important for outcrop and subsurface oil and gas reservoir geologists.

This proposal is timely because of recent efforts to develop novel technology for monitoring flows that hold great promise. This suite of new technology is needed because turbidity currents can be extremely powerful (up to 20 m/s) and destroy sensors placed on traditional moorings on the seafloor. This includes new sensors, new ways of placing those sensors above active flows or in near-bed layers, and new ways of recovering data via autonomous gliders. Key preliminary data are lacking in some test sites, such as detailed bathymetric base-maps or seismic datasets. Our final objective is to fill in key gaps in 'site-survey' data to allow larger-scale monitoring projects to be submitted in the future.

This project will add considerable value to an existing NERC Grant to monitor flows in Monterey Canyon in 2014-2017, and a NERC Industry Fellowship hosted by submarine cable operators. Talling is PI for two NERC Standard Grants, a NERC Industry Fellowship and NERC Research Programme Consortium award. He is also part of a NERC Centre, and thus fulfils all four criteria for the scheme.

Planned Impact

The project will develop and field test sensors, moorings and techniques for recovering data with wide applicability for ocean monitoring. For instance, wave-powered gliders can act as mobile communications hubs, thereby avoiding the need for expensive vessels. Insights gained through this project into how to operate technology will have widespread benefits, including the NERC marine autonomous and robotic systems group.

Networks of sea floor cables have considerable strategic importance because they now carry of 95% of global data traffic, including the internet and financial markets. It is important to understand submarine flow dynamics and triggers because such flows can break multiple cables. This is one of the few ways to seriously disrupt internet connections to large areas, as multiple breaks prevent mitigation by rerouting traffic on adjacent cables. For instance, a submarine flow associated with a major river flood offshore Taiwan in 2009 broke 14 cables, causing major disruption to the internet across a large part of the Far East. Submarine flows can also badly damage pipelines and other sea floor infrastructure used to recover oil and gas reserves in locations worldwide are worth many millions of dollars. Talling will disseminate results through presentations at the annual plenary session of the International Cable Protection Committee that is already funded by his Royal Society Industry Fellowship.

Slope failures on deltas have generated very damaging tsunamis for adjacent (often densely populated) areas. Slope failure in Lake Geneva in AD563 generated a ~11m high tsunami that inundated Geneva. An 8 m tsunami in 1975 inundated Kitimac in Canadian British Columbia, which is about to be a major shipping terminal for liquid natural gas. Project results will be disseminated to local authorities through Project Partners in the Canadian Geological Survey and University of Geneva, as well as through links to tsunami risk managers more generally through a 28 partner EU project on tsunami hazards that involves Talling at NOC.

Submarine flows deposited layers of sandstone that hold strategically important subsurface petroleum reserves, both in the UK North Sea and worldwide. It is essential to understand submarine flows in order to predict the location, shape and extent of the sandstone layers more accurately; in order to recover the oil and gas reserves most effectively. Talling leads the UK Turbidite Architecture and Processes (UK-TAPS) industry consortium that has involved many of the major oil and gas companies since 2002. Project results will be disseminated to this audience through invited presentations and by presentations at the AAPG/SEPM annual conference (which will be paid for by industry through UK-TAPS).

Publications


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