Stability of Antarctica is threatened by submarine canyons

In the silent depths beneath the Antarctic Ice Sheet, submarine canyons are silently playing a massive part in the ice sheet’s instability.

A captivating new study casts these underwater formations in the role of critical conduits, channeling relatively warm Circumpolar Deep Water up from yawning abyssal depths to the continental shelf. This warmer water then trails to the base of the ice sheet, contributing to its slow but steady melting.

Submarine canyons and Antarctic glaciers

The extensive research, led by the National Institute of Oceanography and Applied Geophysics (OGS), including experts from the University of Southampton, shines a spotlight on sedimentary bodies within these canyon systems.

These bodies bear the geological traces of persistent bottom currents coursing along these canyons, carrying the ocean’s heat like a silent, creeping courier to the Antarctic landmass.

“The intrusion of relatively warm water onto the continental shelf is widely recognised as a threat to the Antarctic ice sheet,” said study lead author Federica Donda, a marine geologist in the OGS Geophysics Department.

“Our endeavor to constrain the extent and long-term persistence of this phenomenon is crucial in deciphering potential responses of the ice sheet to global warming.”

Totten and Ninnis glaciers

The team’s dedication drew them to Totten and Ninnis glaciers, the gatekeepers to the two most significant subglacial features in East Antarctica: Aurora-Sabrina and Wilkes sub-glacial basins.

A goldmine of discovery awaited the team. Their rigorous analysis unearthed dome-shaped sedimentary bodies (or sediment drifts) spanning several thousand meters wide and measuring 40 to 80 meters thick.

The properties of these bodies strongly suggest they were sculpted by bottom currents streaming towards the continental shelf.

Water through the submarine canyons

Recent data collected from one of the canyons flowing off Totten Glacier reported currents of about 10 cm/s near the seafloor, a startling discovery at a depth of about 3,500 meters.

This current is part of an oceanic circulation characterized by large cyclonic eddies transporting different water masses, including the warm waters of the Circumpolar Deep Water. A portion of these eddies find their way southward through these canyons, paving easy routes to transport these warmer water masses toward the continent.

“This thickness of the sedimentary bodies identified within the canyons is an indirect testament to the continuation of oceanic heat transfer for at least the past one million years,” noted Donda.

Melting of East Antarctic glaciers

“Until a few years ago we thought that the East Antarctic Ice Sheet was stable. But the evidence today doesn’t just reveal that some East Antarctic glaciers are melting,” said Dr. Alessandro Silvano from the University of Southampton.

“We have crucial new insights that there are preferred pathways for warm waters to constantly reach two of the largest glaciers on Earth and melt them from below.”

The East Antarctic ice sheet has recently started piquing the interest of the scientific world, because even a partial melting of this ice giant could drive a significant rise in sea level.

To put this in perspective, the Aurora-Sabrina and Wilkes sub-glacial basins alone bear the equivalent of over 8 meters of global mean sea level rise.

Implications for global sea level rise

The repercussions of these findings stretch far beyond the icy realms of Antarctica. As the warmer water continues its journey beneath the ice, the gradual melting of glaciers poses a looming threat to global sea levels.

Scientists are increasingly concerned that even a moderate increase in melting could displace millions of people in coastal regions worldwide.

Understanding the dynamics of submarine canyons and their influence on ice sheet stability is vital for modeling future sea-level scenarios and preparing for inevitable environmental changes.

Next steps in research

The research team underscores the importance of ongoing exploration of Antarctic submarine canyons, advocating for further studies that will enhance our understanding of the region’s complex interactions between the ocean and the ice sheet.

Implementing advanced technologies, such as autonomous underwater vehicles and high-resolution sonar mapping, will allow researchers to gather more precise data on ocean currents and temperature variations.

By unveiling more about these critical areas, scientists hope to develop strategies to mitigate the impacts of climate change and better predict the future of Earth’s ice-covered regions.

The findings of this research elevate submarine canyons to a key position in understanding the mechanisms tied to the ice sheet’s melting, both in the past and at present. Consequently, this understanding boosts our ability to predict future sea level rise.

The study is published in the journal Nature Communications.

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