A torpedo-shaped underwater robot that spent eight months drifting beneath Antarctica’s vast Thwaites Glacier has detected concentrated flows of warm ocean water eroding the glacier from below a development scientists have long warned could accelerate global sea-level rise.
The autonomous submersible, known as Icefin, was deployed through a narrow borehole drilled deep into the ice in West Antarctica. Operating without GPS beneath hundreds of metres of ice, it mapped water temperatures, salinity and melt rates in areas previously unreachable by humans or satellites.
After 240 days under the glacier, data transmitted back to researchers revealed pulses of unusually warm, salty water pushing inland beneath the ice shelf. Rather than melting uniformly, the water appears to be carving focused vertical channels described by scientists as “chimneys” in critical grounding zones where the glacier rests on the seabed.
Why the findings matter
Thwaites, often dubbed the “Doomsday Glacier,” holds back enough ice to raise global sea levels by more than half a metre if it were to collapse entirely. More importantly, it acts as a keystone for neighbouring glaciers in West Antarctica. If destabilised, it could trigger a broader retreat of the regional ice sheet.
Scientists have long suspected that relatively warm ocean currents were slipping beneath the glacier, weakening it from below. Satellite imagery has shown surface cracking and accelerating ice flow, but could not directly observe the under-ice processes. Icefin’s measurements provide some of the clearest evidence yet that warm water is reaching deeper and further inland than some models had projected.
The concern centres on a process known as marine ice sheet instability. Thwaites sits on bedrock that slopes downward inland. As the glacier retreats into deeper water, thicker ice becomes exposed to ocean heat, potentially creating a feedback loop that accelerates melting and retreat.
No sudden collapse but rising risks
Researchers stress that the new data does not signal an immediate, dramatic sea-level jump. Glacial systems evolve over decades and centuries. However, the patterns detected particularly intensified melting at key anchoring points suggest that the glacier may be edging closer to thresholds that could speed up long-term ice loss.
Even modest increases in sea level can significantly worsen coastal flooding, amplify storm surges and strain infrastructure in low-lying cities worldwide.
Implications for planning and policy
The latest findings are already feeding into updated sea-level projections used by coastal planners and climate modellers. More precise under-ice data helps refine estimates of how quickly Thwaites and neighbouring glaciers could contribute to ocean rise under different emissions scenarios.
For policymakers, the results reinforce the urgency of both emissions reduction and long-term adaptation strategies, including coastal defences, zoning reforms and, in some regions, managed retreat.
As data from beneath Antarctica’s ice continues to emerge, scientists say the focus is shifting from whether melting is occurring to how fast it may accelerate — and what that means for communities far beyond the frozen continent.