The Secrets of the Longest-Runout Sediment Flow Unveiled
An international team of researchers, spearheaded by GEOMAR Helmholtz Centre for Ocean Research Kiel and Durham University, has recently achieved a groundbreaking feat by unraveling the internal structure of the longest-runout sediment flow ever observed on Earth.
Utilizing advanced seismic measurements, the team delved deep into the intricate dynamics of these massive turbidity currents, stretching tens to hundreds of kilometers – a longstanding oceanographic puzzle that had eluded direct observation until now.
In a bold expedition, the researchers strategically positioned seismometers in the Congo Canyon and Channel off the coast of West Africa in October 2019. Nestled several kilometers outside the canyon-channel axis, beyond the reach of the powerful currents, these instruments meticulously captured the seismic signals emanating from the turbulent flow and sediment transport.
Tracking two turbidity currents hurtling at speeds of 5 to 8 meters per second over a staggering distance of 1,100 kilometers – from the mouth of the Congo River to the expansive Congo deep-sea fan and canyon system – the team witnessed history in the making. These monumental flows, the longest ever documented, left a trail of disruption in their wake, damaging multiple submarine cables in early 2020 and causing disruptions in internet and data communications in West Africa amidst the tumultuous early days of the COVID-19 pandemic.
Their findings revealed a fascinating revelation – the dense front of these canyon-flushing turbidity currents is not a monolithic entity but a series of pulsating surges, each lasting between five to thirty minutes. Contrary to conventional wisdom, the fastest pulses were found trailing up to 20 kilometers behind the front, propelling sediments and sustaining the flow over vast distances.
This paradigm-shifting insight challenges existing assumptions about the behavior of these powerful currents, indicating that factors like turbulent mixing with seawater and other retarding forces play a pivotal role in shaping their trajectory over extended distances.
By shedding light on the intricate dynamics of these formidable currents, the researchers aim to enhance risk assessments for underwater infrastructure, particularly submarine cables, and refine models for sediment and carbon transport in the ocean.
Their groundbreaking findings have been published in the prestigious journal Nature Communications Earth and Environment, marking a significant milestone in our understanding of these enigmatic oceanic phenomena.