A new catalogue of Antarctic submarine canyons

From Hydro by Riccardo Arosio, David Amblas

Mapping the Antarctic continental slopes to understand shelf to abyss connectivity

Submarine canyons, carved into continental margins worldwide, play a key role in ocean circulation, sediment transport and marine biodiversity.
Around Antarctica, their influence extends to global thermoregulation and ecosystem functioning, yet detailed knowledge remains limited.
Using the new International Bathymetric Chart of the Southern Ocean v2 and semi-automatic hydrological techniques, a new study (Arosio and Amblas, 2025) delivers the most comprehensive inventory to date: 332 drainage networks and 3,291 canyon streams, revealing striking regional contrasts shaped by differing glacial histories between East and West Antarctica.

Submarine canyons are widespread geomorphic features found along all continental margins.
Typically steep-sided and sinuous, they form narrow, V-shaped valleys with rugged slopes that begin at the continental shelf or slope and extend down to the rise or abyssal plain.
Antarctic canyons resemble those elsewhere but are generally larger and deeper, shaped by prolonged glacial activity and the vast quantities of sediment delivered to the shelf by ice.
Their development is driven primarily by turbidity currents, which transport suspended sediments downslope at high velocity, scouring the valleys they traverse.

In Antarctica, the combination of steep submarine topography and abundant glacial input intensifies these processes, resulting in exceptionally large canyon systems.
These canyons are increasingly recognized as critical to understanding climate impacts, as they enhance mixing and channel focused flows, thereby facilitating exchange between continental shelves and deep ocean basins.
Because of their role in water mass dynamics and the climate system, detailed mapping and characterization are essential.
Without such knowledge, it is difficult to assess how Antarctic oceanography and the global climate will respond to ongoing and future change.

The release of version 2 of the International Bathymetric Chart of the Southern Ocean (IBCSO v2) in June 2022 (Dorschel et al., 2022) provides the most complete and high-resolution regional bathymetry to date, offering an opportunity to update and refine the Antarctic canyon inventory since the work of Harris et al. (2014).
The aim of this study was to identify, map and characterize Antarctic submarine canyons on the continental slope using a tailored semi-automatic approach that enables efficient extraction of submarine drainage networks.

 

 

A protocol for canyon mapping

Isolated or dendritic valley-like features on the continental slope, up to the detail of the resolution of the bathymetry data, were identified, extracting the main and tributary thalwegs.
To achieve this objective, a semi-automatic procedure using ArcGIS Pro was adopted that included the application of filtering and hydrological tools (Figure 1).
Once the thalwegs were extracted, a custom-made Python toolbox – Canyon Metrics – was written to geomorphometrically describe the canyons.
The toolbox creates sets of ten equally spaced perpendicular transects to each thalweg polyline and automatically extracts canyon profiles and depth values.
The script identifies the lowest point in the profile (real thalweg) and searches for the two closest valley shoulders.
Thalweg and shoulders (Figure 2) are then used to calculate the rest of the statistics.
Owing to limitations in the multisource bathymetric dataset, shoulder detection was not always successful, particularly in areas of low resolution or with data artefacts.
A ‘success rate’ was therefore calculated to quantify the proportion of profiles successfully extracted.

 

Figure 1: Visual representation of the methodology applied for stream extraction.
A) Hillshaded bathymetry with Feature-preserve smoothing applied.
B) Result of the D8 Flow direction tool on the bathymetry data.
C) Result of the D8 Flow Accumulation.
D) Result of the Strahler Stream Order tool, which determines the order of the different segments of the drainage network.

Among the other statistics such as depth, width and slope, canyon cross-sectional shapes were also analysed using curve-fitting methods.
These shape metrics are important because they provide quantitative measures of valley form, allowing distinctions to be made between V-shaped, U-shaped and more complex cross sections.
Such information is critical for understanding canyon evolution, sediment transport pathways and the interaction between submarine morphology and hydrodynamic processes.
Quadratic fits describe parabolic forms, where the curvature coefficient indicates whether the canyon is narrow and V-shaped or broad and U-shaped.
The General Power Law method provides an additional, more reliable shape descriptor, with the exponent (b) also defining profile values near one to represent V-shapes, values of two or greater to indicate U-shaped cross sections, and values outside this range to capture convex or box-shaped morphologies.
As these curve-fitting approaches assume smooth profiles and perform poorly in irregular terrains, the V-index was also applied.
This metric compares the observed valley cross-sectional area with that of an ideal V-shape.
A value of zero indicates a perfect V, positive values reflect U-shaped profiles, and negative values correspond to convex valley walls.

The geomorphometry of Antarctic canyons

Despite the expanded database underpinning IBCSO v2, bathymetric coverage across Antarctica remains uneven, constraining regional geomorphic comparisons.
Nonetheless, analysis of submarine drainage networks and canyons along the continental margin reveals marked contrasts between East and West Antarctica (WA).
West Antarctica is characterized by short, simple networks, whereas East Antarctica (EA) hosts dense, dendritic systems (Figure 3).
These differences are not attributable to data gaps: 33.7% of WA is mapped at high resolution compared with only 13.8% in EA.
Instead, they reflect contrasting shelf geometries and glacial histories.
In WA, broad shelves and major drainage basins (e.g. Ross and Weddell Seas) channel convergent ice streams, generating erosive flows that carve deep troughs and deposit large trough-mouth fans at the shelf edge.
These fans promoted slope instability and canyon initiation but were later infilled by subsequent glaciations, limiting canyon growth.

Figure 2: Diagram showing the procedure of transects creation for each canyon profile and the parameters extracted.
The canyon depth is calculated from the height of the lowest shoulder to the thalweg.
The GPL and quadratic fits give the coefficients of the curves fitted in the canyon transects, while the V-index is the deviation from an ideal V-shaped valley.

By contrast, EA’s narrower shelves and smaller basins supported weaker, isolated ice streams, leading to lower sediment flux and allowing canyon systems to persist and evolve into more complex, longer structures.
The Prydz Bay margin is a notable exception, dominated by a large trough-mouth fan and lacking canyons directly downslope.
The persistence of East Antarctic canyon systems likely reflects both this lower sediment burial and the longer-lived East Antarctic Ice Sheet (EAIS), which sustained prolonged erosion and sediment delivery.
The Antarctic Peninsula shows the strongest tectonic imprint, influenced by the South Shetland Trench.
Here, steep gradients produce highly incised, short canyons and numerous simple networks.
Elsewhere, oceanographic processes further shape canyon morphology.

During glacial maxima, turbidity currents were deflected westward by gravity, contour currents and Coriolis forcing, forming sediment drifts alongside canyon systems (e.g.
Bellingshausen region).
In interglacial periods, canyons channel dense shelf water cascades, preventing canyon infill and contributing to downslope levee development, though their erosional role remains unclear.
Unfortunately, current IBCSO v2 resolution is insufficient to fully resolve these oceanographic imprints.
Targeted high-resolution AUV or ROV surveys are required to capture fine-scale seafloor signatures and improve understanding of canyon evolution and sediment dynamics across the Antarctic margin.
Impact on ocean circulation

Antarctic canyons 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, mix with the surrounding water and form what is known as Antarctic Bottom Water (AABW), the coldest and densest water in the world that plays a fundamental role in ocean circulation and global climate.
These canyons can also channel warmer waters from the open sea towards the coastline, such as the Circumpolar Deep Water (CDW).
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.
When the shelves weaken or collapse, continental ice flows more rapidly into the sea and directly contributes to the rise in global sea level.
This study highlights the fact that current ocean circulation models such as those used by the Intergovernmental Panel on Climate Change (IPCC) do not accurately reproduce the physical processes that occur at local scales between water masses and complex topographies such as 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 such as AABW.
Omitting these local mechanisms limits the ability of models to predict changes in ocean and climate dynamics.

Conclusion

This study delivers the most detailed geomorphic characterization of Antarctic submarine canyons to date, highlighting fundamental contrasts between East and West Antarctica.
East Antarctic canyons are longer, dendritic and more depositional in character, reflecting the earlier onset and persistence of the EAIS.
West Antarctic canyons are shorter, steeper and more erosional, shaped by convergent ice streams and broad shelves.
Beyond their morphology, canyons are critical conduits for ocean–ice interactions, influencing CDW inflow, dense water export, basal melt and AABW formation.
The density of EA canyons suggests a stronger role in ice-sheet stability than previously recognized.
Advancing this understanding requires expanded bathymetric coverage in poorly surveyed regions and targeted high-resolution observations to resolve canyon-scale processes with system-wide implications.

Figure 3: Overview of the results of the drainage mapping.

Acknowledgements

The authors would like to thank Marta Bono Garcia for her work on the initial phases of the project and part of the mapping.
Luca Biffi is thanked for his support in developing a version of Pattyn’s GPL script that allows for batch processing.
Riccardo Arosio received funding from the Irish Marine Institute’s research grant PDOC 19/08/03.
David Amblas acknowledges the support from the Spanish government through grant no.
PID2020-114322RBI00 funded by MICIU/AEI/10.13039/501100011033 and from the Catalan Government Excellent Research Groups grant no. 2021-SGR-01195.

IBCSO is a regional mapping project of GEBCO, the General Bathymetric Chart of the Oceans, which is conducted under the International Hydrographic Organization (IHO) and the Intergovernmental Oceanographic Commission (IOC) to produce the authoritative map of the world’s oceans.
It is supported by the Nippon Foundation–GEBCO Seabed 2030 Project, launched in 2017, and is also part of the Antarctic research community and an expert group of the Scientific Committee on Antarctic Research (SCAR).

Links :

Arosio, R. & Amblas, D., 2025.
The geomorphometry of Antarctic submarine canyons, Mar. Geol., 488, 107608, https://doi.org/10.1016/j.margeo.2025.107608.

Dorschel, B., Hehemann, L., Viquerat, S., Warnke, F., Dreutter, S., Schulze Tenberge, Y., et al, 2022.
The International Bathymetric Chart of the Southern Ocean Version 2 (IBCSO v2) [dataset].
PANGAEA, https://doi.org/10.1594/PANGAEA.937574

Harris, P.T., Macmillan-Lawler, M., Rupp, J., Baker, E.K., 2014.
Geomorphology of the oceans, Mar. Geol., 352, pp. 4-24, https://doi-org.sire.ub.edu/10.1016/j.margeo.2014.01.011

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