New international research into how fast-moving waterfalls under the sea control the shape and behaviour of submarine channels has been supported by the University of Hull.
Submarine channels can extend for tens to thousands of kilometres offshore, providing an important conduit for the transfer of sediment, nutrients and pollutants, such as microplastics, to the deep-sea.
Avalanches of sediment that flow down these channels, comparable to rivers but in the deep sea, also pose a hazard to networks of seafloor cables that underpin global communications, including the internet.
New research, led by the National Oceanography Centre and supported by the University, has analysed time-lapse footage from the Bute Inlet, British Columbia, over a nine-year period.
The footage revealed a dramatic series of up to 30m-tall, steep cliffs known as ‘knickpoints,’ which resemble waterfalls in rivers.
While similar features migrate at a rate of less than one metre per year in rivers, the team observed much faster migration rates in the submarine channel - up to 450 metres per year.
Prof. Dan Parsons, Director at the University of Hull’s Energy & Environment Institute, said: “These findings reveal how quickly knickpoints migrate in these submarine channel systems, which has a range of significant implications for how they evolve over time, how stable they are and how they are ultimately recorded into the geological rock record.
“This is important as we use such deposits to infer Earth’s climate and geological history.
“These results suggest that we may need to re-think some of our interpretations of ancient submarine channels which will tell us new things about land-sea interactions and the potential impacts of changing climate.”
A team of experts from the University of Hull, comprising of Prof. Parsons, post-doctoral researcher Dr Steve Simmons and PhD student Ye Chen, supported the international research.
It found almost three quarters of erosion in the channel resulted from fast-moving knickpoints, leading the study’s authors to conclude that knickpoints are far more important for the evolution of submarine channels than other previously-suggested controls, such as the growth of meander bends.
An abundance of repeated aerial photographs and satellite data has revealed how rivers change over time; however, the challenges of surveying deep underwater, has meant that such a wealth of time-lapse surveying does not exist for submarine channels.
Instead, most of our understanding has been based on scaled-down laboratory models or from one-off seafloor surveys that only capture a snapshot in time.
NOC researcher Maarten Heijnen, lead author of the new study which has been published in the journal Nature Communications, said: “We previously knew that knickpoints existed in submarine channels, but had no idea they could move so fast.
“The rate at which they migrate is hundreds of times faster than similar features move in rivers. It surprised us that such large features can be so dynamic and is a stark reminder that there is still much to discover in the deep sea.”
Dr Mike Clare, also of NOC, said: “Our study of deep-sea environments such as submarine channels has been hampered by a lack of long-term monitoring.
“This study, and other exciting technological advances, are providing important and much-needed step-changes into understanding how these globally-important systems behave.”
You can read the full publication, titled ‘Rapidly-migrating and internally-generated knickpoints can control submarine channel evolution,’ here.