Submarine canyons are among the most spectacular and fascinating geological formations to be found on our ocean floors, but at an international level scientists have yet to uncover many of their secrets, especially of those located in remote regions of the Earth like the North and South Poles. Now,
an article published in the journal Marine Geology has brought together the most detailed catalogue to date of Antarctic submarine canyons, identifying a total of 332 canyon networks that in some cases reach depths of over 4,000 metres.
The catalogue, which identifies five times as many canyons as previous studies had, was produced by the researchers David Amblàs, of the Consolidated Research Group on Marine Geosciences at the Faculty of Earth Sciences of the University of Barcelona, and Riccardo Arosio, of the Marine Geosciences Research Group at University College Cork. Their article shows that Antarctic submarine canyons may have a more significant impact than previously thought on ocean circulation, ice-shelf thinning and global climate change, especially in vulnerable areas such as the Amundsen Sea and parts of East Antarctica.
Submarine canyons: the differences between East and West Antarctica
The submarine canyons that form valleys carved into the seafloor play a decisive role in ocean dynamics: they transport sediments and nutrients from the coast to deeper areas, they connect shallow and deep waters and they create habitats rich in biodiversity. Scientists have identified some 10,000 submarine canyons worldwide, but because only 27% of the Earth’s seafloor has been mapped in high resolution the real total is likely to be higher. And despite their ecological, oceanographic, and geological value, submarine canyons remain underexplored, especially in polar regions.
“Like those in the Arctic, Antarctic submarine canyons resemble canyons in other parts of the world,” explains David Amblàs. “But they tend to be larger and deeper because of the prolonged action of polar ice and the immense volumes of sediment transported by glaciers to the continental shelf.” Moreover, the Antarctic canyons are mainly formed by turbidity currents, which carry suspended sediments downslope at high speed, eroding the valleys they flow through. In Antarctica, the steep slopes of the submarine terrain combined with the abundance of glacial sediments amplifies the effects of these currents and contributes to the formation of large canyons.
The new study by Amblàs and Arosio is based on Version 2 of the International Bathymetric Chart of the Southern Ocean (IBCSO v2), the most complete and detailed map of the seafloor in this region. It uses new high-resolution bathymetric data and a semi-automated method for identifying and analysing canyons that was developed by the authors. In total, it describes 15 morphometric parameters that reveal striking differences between canyons in East and West Antarctica.
“Some of the submarine canyons we analysed reach depths of over 4,000 metres,” explained David Amblàs, of the Consolidated Research Group on Marine Geosciences at the UB's Faculty of Earth Sciences. “The most spectacular of these are in East Antarctica, which is characterized by complex, branching canyon systems. The systems often begin with multiple canyon heads near the edge of the continental shelf and converge into a single main channel that descends into the deep ocean, crossing the sharp, steep gradients of the continental slope.”
Riccardo Arosio noted that “It was particularly interesting to see the differences between canyons in the two major Antarctic regions, as this hadn’t been described before. East Antarctic canyons are more complex and branched, often forming extensive canyon–channel systems with typical U-shaped cross sections. This suggests prolonged development under sustained glacial activity and a greater influence of both erosional and depositional sedimentary processes. In contrast, West Antarctic canyons are shorter and steeper, characterized by V-shaped cross sections.”
According to David Amblàs, this morphological difference supports the idea that the East Antarctica Ice Sheet originated earlier and has experienced a more prolonged development. “This had been suggested by sedimentary record studies,” Amblàs said, “but it hadn’t yet been described in large-scale seafloor geomorphology.”
About the research, Riccardo Arosio also explained that “Thanks to the high resolution of the new bathymetric database — 500 metres per pixel compared to the 1–2 kilometres per pixel of previous maps — we could apply semi-automated techniques more reliably to identify, profile and analyse submarine canyons. The strength of the study lies in its combination of various techniques that were already used in previous work but that are now integrated into a robust and systematic protocol. We also developed a GIS software script that allows us to calculate a wide range of canyon-specific morphometric parameters in just a few clicks”.
Submarine canyons and climate change
As well as being spectacular geographic accidents, the Antarctic canyons also facilitate water exchange between the deep ocean and the continental shelf, allowing cold, dense water formed near ice shelves to flow into the deep ocean and form what is known as Antarctic Bottom Water, which plays a fundamental role in ocean circulation and global climate.
Additionally, these canyons channel warmer waters such as Circumpolar Deep Water from the open sea toward the coastline. This process is one of the main mechanisms that drives the basal melting and thinning of floating ice shelves, which are themselves critical for maintaining the stability of Antarctica’s interior glaciers. And as Amblàs and Arosio have explained, when the shelves weaken or collapse, continental ice flows more rapidly into the sea and directly contributes to the rise in global sea level.
Amblàs and Arosio’s study also highlights the fact that current ocean circulation models like those used by the Intergovernmental Panel on Climate Change do not accurately reproduce the physical processes that occur at local scales between water masses and complex topographies like canyons. These processes, which include current channelling, vertical mixing and deep-water ventilation, are essential for the formation and transformation of cold, dense water masses like Antarctic Bottom Water. Omitting these local mechanisms limits the ability that models have to predict changes in ocean and climate dynamics.
As the two researchers conclude, “That’s why we must continue to gather high-resolution bathymetric data in unmapped areas that will surely reveal new canyons, collect observational data both in situ and via remote sensors and keep improving our climate models to better represent these processes and increase the reliability of projections on climate change impacts.”