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Antarctic ice cliffs collapse faster than predicted, then stabilize

Antarctic ice cliffs collapse faster than predicted, then stabilize

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Satellite survey of 15,330 ice cliffs challenges the runaway-collapse hypothesis, as a separate Thwaites model doubles projected sea-level contribution

October 27th, 2026: Thwaites model doubles projected sea-level contribution

Overview

Updated Oct 17

A survey of 15,330 ice cliffs in Antarctica and Greenland found that tall cliffs break apart faster than ice-sheet models assume, then stop retreating. MIT and Woods Hole Oceanographic Institution researchers published the results in Science on October 15, 2026.

The finding undercuts a feared runaway process called marine ice cliff instability, which assumed cliffs over about 100 meters would crumble under their own weight. Height alone does not decide stability; water depth, ice thickness and thinning rates matter more. Separately, a late-October model from the University of California, Irvine and NASA projected that Thwaites Glacier alone could add up to 30 millimeters of sea level rise by 2100, twice earlier estimates.

Why it matters

Runaway cliff collapse looks unlikely, but a doubled Thwaites projection shows Antarctic sea-level estimates still carry large uncertainty for coastal planners.

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Key Indicators

15,330
ice cliffs surveyed
Satellite laser altimetry measured 15,330 ice cliffs across Earth's ice sheet margins from 2019 to 2023.
30 mm
Thwaites contribution by 2100
A late-October 2026 UC Irvine and NASA JPL model projects Thwaites Glacier could add up to 30 millimeters of sea level rise by 2100, twice earlier estimates.

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People Involved

Caroline Needell
Caroline Needell
Lead author; doctoral student in the MIT-WHOI Joint Program
Studying at MIT and the Woods Hole Oceanographic Institution
MM
Mathieu Morlighem
Professor of Earth sciences at Dartmouth College; led a 2024 modeling study of Thwaites Glacier
Active at Dartmouth College

Organizations Involved

Massachusetts Institute of Technology (MIT)
Massachusetts Institute of Technology (MIT)
Research university
Co-led the ice-cliff study

Research university in Cambridge, Massachusetts that co-led the satellite analysis of Antarctic ice cliffs.
Woods Hole Oceanographic Institution
Woods Hole Oceanographic Institution
Nonprofit marine research institution
Co-led the ice-cliff study

Nonprofit marine research institution in Woods Hole, Massachusetts that co-led the study.
Dartmouth College
Dartmouth College
University
Hosted the companion modeling study

University in Hanover, New Hampshire that hosts Mathieu Morlighem's ice-sheet modeling group.
Science Magazine
Science Magazine
Scientific journal and news outlet
Published the ice-cliff study

One of the world's leading peer-reviewed research journals, published by the American Association for the Advancement of Science.

Timeline

March 2016 October 2026

4 events Latest: October 27th, 2026 · 2 weeks ago
Tap a bar to jump to that date

  1. Thwaites model doubles projected sea-level contribution

    Latest Modeling study

    A University of California, Irvine and NASA Jet Propulsion Laboratory model that accounts for Thwaites Glacier's grounding zone projects up to 30 millimeters of sea level rise by 2100, twice earlier estimates.

  2. Satellite survey finds fast collapse, then stabilization

    Study

    A Science study tracking 15,330 ice cliffs across Earth's ice sheet margins from 2019 to 2023 finds tall cliffs collapse fast but retreat quickly stabilizes.

  3. Thwaites modeling study resists runaway retreat

    Modeling study

    A Dartmouth-led Science Advances study simulating Thwaites Glacier finds realistic cliff-failure rates do not produce collapse.

  4. Marine ice cliff instability proposed

    Scientific hypothesis

    DeConto and Pollard propose in Nature that ice cliffs above a critical height would collapse in a runaway cascade.

Scenarios

1

Worst-case sea-level projections drop marine ice cliff instability

Likely Resolves by End of 2029

Discussed by: IPCC assessment cycle and the ice-sheet modeling community

Ice-sheet modelers fold the new calving rates and stabilization drivers into their simulations. If bed topography and ice-thinning rates are accounted for across the continent, the next major assessment projects a lower upper bound for Antarctic sea-level rise than current worst cases, which assume runaway cliffs.

2

Researchers identify Antarctic glaciers still vulnerable to rapid cliff retreat

Possible Resolves by Oct 16, 2028

Discussed by: MIT-WHOI team and glaciologists studying Thwaites and Pine Island

The study shows stabilization depends on local conditions — bedrock bumps, water depth, and ice-thinning rates. Follow-up work will map which West Antarctic glaciers sit over deep, flat beds where sustained rapid retreat might still occur. Those regions could still contribute fast sea-level rise.

3

Debate persists; MICI keeps its place in high-end projections

Uncertain Resolves by End of 2029

Discussed by: Climate modelers who defend the original DeConto-Pollard mechanism

Some modelers argue four years of data and a handful of tall cliffs are too thin a record to retire the hypothesis. They keep marine ice cliff instability in high-end scenarios, and the next IPCC report may retain it alongside the new observational constraints.

Historical Context

3 moments from history that rhyme with this story — and how they unfolded.

February–March 2002

Larsen B ice shelf collapse (2002)

About 3,250 square kilometers of the Larsen B ice shelf on the Antarctic Peninsula shattered into icebergs within roughly a month, ending years of gradual retreat.

Then

Glaciers that had been held back by the shelf accelerated two to six times after it disappeared.

Now

The collapse showed how quickly Antarctica can lose ice and helped seed the concern that exposed cliffs could retreat in cascades.

Why this matters now

The new study directly tests that concern: it found cliffs do fall fast, but the retreat stops rather than cascading across the ice sheet.

January 1978

Mercer's West Antarctic collapse warning (1978)

Glaciologist John Mercer warned in Nature that rising carbon dioxide could destabilize the West Antarctic Ice Sheet and drive rapid sea-level rise.

Then

The warning drew sharp debate and launched decades of research into the sheet's stability.

Now

Five decades on, studies repeatedly show the collapse is slower and more contingent on local conditions than the first warning implied.

Why this matters now

The new ice-cliff survey continues that pattern, finding the most feared mechanism is blunted by bedrock shape and ice thinning.

2018–2023

International Thwaites Glacier Collaboration field work (2018–2023)

A US-UK program drilled and surveyed Thwaites Glacier, known as the 'Doomsday Glacier,' to learn whether its undercut ice could collapse quickly.

Then

Researchers found warm water is melting the glacier's shelf from below, but the bed is not as flat as feared.

Now

Companion modeling found Thwaites resists runaway collapse even after its ice shelf is removed.

Why this matters now

This study, published in 2024, is the direct predecessor to the new Science finding and pointed to the same conclusion about ice cliff stability.

Sources

(9)
+3
Human Progress Science MIT News Woods Hole Oceanographic Institution New Scientist Nature Climate Change DSTLD News ScienceDaily Science Advances