Department of Earth Sciences

Submarine Canyons as Critical Land-to-Ocean Pathways

Submarine canyons form the main conduits transferring sediment, nutrients, pollutants, and organic carbon from continents to the deep ocean. These underwater valleys shape continental margins, regulate deep-marine ecosystems, and play a significant role in long-term biogeochemical and carbon cycles. Through turbidity currents and other sediment transport processes, submarine canyons facilitate the burial of terrestrial organic carbon and influence the efficiency of carbon sequestration in marine basins.

Why Do Submarine Canyons Form?

This project investigates the large-scale controls on submarine canyon occurrence using global geomorphometric datasets and spatial statistical modelling. Analysis of more than 2,000 submarine canyons demonstrates that canyon occurrence is primarily controlled by continental slope inclination. Regions with steeper continental slopes consistently exhibit higher canyon densities, supporting models in which canyon initiation is driven by slope instability, mass wasting, and retrogressive erosion rather than by direct terrestrial sediment supply alone. The findings indicate that tectonic and thermal processes, which govern the morphology of continental margins, indirectly regulate the global distribution of submarine canyons and therefore the pathways through which sediment, nutrients, and carbon reach the deep ocean.

From Canyon Formation to Shore Connectivity

While continental slope morphology explains where submarine canyons are likely to occur, a second question concerns whether canyon heads remain connected to terrestrial sediment sources during sea-level rise. Direct connections between rivers, coastlines, and canyon heads create highly efficient sediment-routing systems that transport sediment and organic carbon from land to the deep sea. However, such connections are uncommon in the modern ocean and are strongly influenced by changes in sea level and continental shelf morphology.

Controls on Shore-Connected Canyons

Using global topographic analyses and Bayesian statistical modelling, this project evaluates the factors that allow submarine canyon heads to remain connected to the shoreline during post-glacial sea-level rise. Results show that shore-connected canyons preferentially occur along narrow and steep continental shelves, particularly on tectonically active margins. Connectivity is further promoted by resistant bedrock and high river discharge, which supply coarse sediment capable of sustaining canyon-head erosion and landward migration. Although nearly 800 canyon heads were positioned close to the Last Glacial Maximum shoreline, only about 183 remain connected to the modern coast, highlighting the rarity of these highly effective land-to-ocean sediment pathways.

Implications for Sediment Transfer and Carbon Burial

Together, these studies demonstrate that submarine canyon evolution is controlled by a hierarchy of interacting processes operating across multiple spatial and temporal scales. Tectonic and thermal controls determine continental margin morphology and therefore canyon occurrence, whereas shelf morphology, river discharge, and sediment characteristics determine whether canyon heads remain connected to terrestrial sediment sources. By regulating both canyon distribution and canyon connectivity, these processes ultimately influence the efficiency of deep-sea sediment transport, organic carbon burial, and long-term climate regulation.