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Advancements in Monitoring Turbidity Currents
Turbidity currents represent a significant yet often overlooked natural phenomenon. These potent underwater currents play a critical role in shaping submarine canyons, accumulating vast sediment deposits, and posing risks to underwater cables and pipelines. Although this phenomenon has been recognized for roughly a century, measuring its dynamics has remained a challenge due to the extreme forces involved, which can destroy conventional measuring instruments—similar to the destructive power of avalanches in terrestrial environments.
An international research team, spearheaded by the GEOMAR Helmholtz Centre for Ocean Research Kiel in partnership with Durham University in the UK, has recently devised a novel approach to monitor turbidity currents from a safe distance. By utilizing ocean-bottom seismometers—commonly used for earthquake analysis—this study marks the first successful revelation of the internal structure of these formidable currents. The researchers published their findings in the journal Nature Communications Earth and Environment.
Innovative Detection of Sediment Flows
From a distance: Ocean-bottom seismometers detect the longest-runout sediment flows ever recorded on Earth
“Turbidity currents are the primary means by which sediment and organic carbon travel from coastal regions into the deep ocean, paralleling how rivers convey sediment across land,” explains Dr. Pascal Kunath, a seismologist at GEOMAR and the lead author of the study. “However, their complexities render them one of the least understood processes in sediment transport.”
To close this knowledge gap, the research team strategically deployed seismometers in October 2019 within the Congo Canyon and Channel, located off the west coast of Africa. This region is recognized as one of the largest and deepest submarine canyons globally. The instruments were positioned several kilometers away from the central channel axis to remain unaffected by the destructive currents, thereby capturing the seismic signals generated by the turbulence and sediment movement associated with these flows.
The results were groundbreaking; the researchers tracked two turbidity currents traveling at velocities between 5 to 8 meters per second over an astonishing distance of 1,100 kilometers, starting from the Congo River’s mouth and extending through the Congo deep-sea fan and canyon system. These observations represent the longest sediment flows ever documented. Notably, these flows caused damage to several submarine cables during January and March 2020, disrupting internet and data communication in West Africa at a critical time during the early COVID-19 pandemic.
Rethinking Turbidity Current Dynamics
Rethinking turbidity current dynamics
“Our findings reveal that the dense leading edge of these canyon-flushing turbidity currents is not a singular, continuous flow; rather, it is composed of multiple pulses, each enduring between five and thirty minutes,” notes Kunath. Interestingly, the fastest pulses can occur as far as 20 kilometers behind the leading edge. These surges ultimately catch up to the front, contributing additional sediment and maintaining the flow’s momentum over extensive distances.
This insight overturns prior understandings, which posited that peak velocities were found at the flow front. The new evidence implies that turbulent interactions with seawater or other factors significantly affect the behavior of these currents over long stretches.
Expanding Monitoring Techniques
New possibilities for monitoring turbidity currents
This groundbreaking study not only introduces an innovative remote sensing technique for monitoring turbidity currents but also enhances scientific comprehension of how these potent canyon-flushing flows operate. By meticulously analyzing their internal dynamics, researchers can better predict their effects on seafloor infrastructure and refine models concerning sediment and carbon transport in marine environments.
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