Antarctica’s Thwaites ‘Doomsday Glacier’ is melting faster than models predicted

A single glacier in West Antarctica has drawn outsized scientific attention because its fate could reshape coastlines around the world. Thwaites Glacier, an ice mass roughly the size of Florida, has earned the grim nickname of the Doomsday Glacier for its potential to drive significant sea-level rise, and recent research indicates it is retreating faster than many models had anticipated. Studies of the glacier’s underside and its surrounding ocean point to processes that could accelerate its decline in the decades and centuries ahead.

Why Thwaites matters so much

Thwaites is enormous, and it sits in a vulnerable position. Much of the glacier rests on bedrock that lies below sea level and slopes downward inland, a configuration that can make retreat self-reinforcing once it begins, because warm ocean water can reach ever deeper beneath the ice. The amount of ice flowing from Thwaites and its neighbors into the sea more than doubled between the 1990s and the 2010s, and the wider Amundsen Sea region it belongs to already accounts for a notable share of the current global rate of sea-level rise. Observations of Antarctic ice are tracked by NASA as part of its monitoring of the planet’s changing climate.

The direct contribution of Thwaites is only part of the concern. The glacier acts as a kind of plug or buttress holding back a much larger volume of ice in the West Antarctic Ice Sheet. If Thwaites were to disintegrate, it could remove that restraint and allow neighboring ice to flow more freely into the ocean, magnifying the eventual effect on sea levels far beyond the glacier itself.

Melting from below

Much of the damage is happening out of sight, where the glacier meets the sea. Relatively warm ocean water is reaching the glacier’s grounding line, the boundary where ice lifts off the bedrock and begins to float, and melting it from underneath. This basal melting thins the floating ice shelf that helps hold the glacier back, weakening its ability to slow the flow of ice from inland. Field research organized through the British Antarctic Survey and its partners has focused on measuring these conditions directly beneath the ice.

Researchers have also identified feedback processes that can intensify the melting. In some findings, cold meltwater from beneath the ice mixes with warmer, saltier ocean water, generating turbulence that draws additional heat toward the ice and melts still more of it. Because such fine-scale interactions are not fully captured in large-scale climate and ice-sheet models, they represent a mechanism by which the real-world retreat could outpace earlier projections.

Findings that point to faster retreat

Assessments compiled by the international research effort studying the glacier conclude that its retreat has accelerated considerably over the past several decades and is set to continue, and potentially speed up, through this century and beyond. The International Thwaites Glacier Collaboration, a large partnership of scientists, has reported that broad disintegration of the West Antarctic Ice Sheet over long timescales cannot be ruled out, even as the precise timing remains uncertain.

Satellite and airborne measurements have added to the picture, documenting thinning ice, a grounding line that has migrated inland and structural weakening in the floating portions of the glacier. Together these observations describe an ice mass under growing stress, with several of the forces acting on it running in the direction of faster, not slower, change.

The stakes for coastlines

The reason the glacier is watched so intently comes down to water. The ice locked in Thwaites, if fully lost, would raise global sea levels meaningfully on its own, and the additional ice it helps hold back would raise them far more if the broader ice sheet followed. Even partial contributions on the way toward such outcomes would add to the flooding risk facing low-lying communities worldwide, though the largest effects would unfold over long periods rather than suddenly.

Uncertainty remains about exactly how quickly the glacier will change and how much sea-level rise will result over given timeframes, and researchers are careful to distinguish plausible long-term scenarios from precise predictions. What the recent work makes clearer is the direction of travel: the mechanisms driving Thwaites’s retreat appear stronger, and its response faster, than earlier models had assumed, which is why the glacier remains a central focus of climate and polar science.

Studying one of the least accessible places on Earth

Learning what is happening at Thwaites has required extraordinary effort, because the critical action occurs beneath hundreds of meters of ice at a location that is among the most remote and hostile on the planet. Research teams have drilled through the ice shelf to lower instruments and even underwater robots into the ocean cavity below, gathering direct measurements of temperature, currents and melting at the grounding line where earlier work could only estimate conditions. Those observations have repeatedly found the situation more dynamic than models assumed, revealing channels and crevasses through which warm water intrudes and hastens the melt.

The difficulty of the work is one reason projections have carried wide uncertainty: for years, the most important region of the glacier was essentially unobserved. As direct measurements accumulate, they tend to sharpen the picture in the direction of faster change, because they capture fine-scale processes that coarse models smooth over. That pattern, of closer observation revealing greater vulnerability, has characterized much of the recent research on the glacier.

A long-term challenge for coastal planning

Because the largest effects of a Thwaites collapse would unfold over decades to centuries, the glacier figures prominently in long-range planning for coastal cities and low-lying nations. Even modest additional contributions to sea level from Antarctica compound the risks from other sources of rise, raising the frequency of coastal flooding and the cost of protective infrastructure. The deep uncertainty about timing complicates that planning, since communities must weigh scenarios that range from gradual to comparatively rapid. What is not in doubt is that the amount of ice at stake is large enough that the glacier’s future is a matter of global consequence, which is why an ice mass in one of the emptiest corners of the world commands such sustained scientific attention.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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