Mapping Tipping Risks from Antarctic Ice Basins under Global Warming
- Jul 8
- 4 min read
A 2026 study maps tipping thresholds for all 18 Antarctic drainage basins, finding West Antarctic collapse may be triggered at 1–2°C and East Antarctic basins at risk from 2–5°C.
The Antarctic Ice Sheet has long been treated as a single tipping element in the climate system — a monolith that might, beyond some critical threshold, irreversibly collapse and flood the world's coastlines. That framing, while capturing something real about the ice sheet's capacity for self-amplifying retreat, obscures a more complex and more actionable picture.
Winkelmann, Garbe, Donges, and Albrecht (2026) disaggregate the picture, using the Parallel Ice Sheet Model to run long-term quasi-static warming simulations across all 18 individual drainage basins of Antarctica and map, basin by basin, whether ice loss unfolds gradually or tips abruptly — and at exactly what temperature thresholds. What emerges is not one tipping element but a network of several, each with its own critical temperature, sea-level commitment, and risk profile.
Key Findings
Gradual Decline versus Tipping Dynamics: Two Distinct Modes of Ice Loss
Across the 18 basins, the study identifies two qualitatively different modes of response to warming. In some basins — including Abbot/Venable, the West Antarctic Peninsula (George VI), and Ronne — ice volume declines roughly linearly with warming, losing mass incrementally without a clear threshold. In others, small changes occur across a wide warming range, followed by abrupt, near-complete disintegration once a critical temperature is crossed: classic tipping dynamics. Prominent examples of the latter include Dronning Maud Land, Enderby Land, Amery, West/Denman, Totten/Moscow, and Filchner in East Antarctica, as well as the Thwaites/Pine Island basin in West Antarctica. Several basins show a combination of both behaviors, or exhibit two distinct thresholds at different warming levels.
The physical mechanism differs between modes: basins showing gradual decline lose ice primarily through incremental ocean-driven melting, while basins exhibiting sharp tipping dynamics are dominated by marine ice sheet instability (MISI) or the melt–elevation feedback, where ice loss lowers the surface into warmer air, accelerating further melt in a self-amplifying loop.
West Antarctica: Thresholds Already Within Reach
The most alarming results concern West Antarctica, where several basins have the lowest critical temperature thresholds of any region in the analysis. The Thwaites/Pine Island and Ross West (Siple Coast) basins show significant ice loss beginning below +1°C of global warming above pre-industrial levels — a threshold that current warming of approximately 1.3°C has already exceeded. Upon crossing this threshold, the Thwaites/Pine Island basin is committed to losing roughly 70% of its initial sea-level relevant ice volume, translating into approximately 0.9 m of long-term sea-level rise. This loss is driven primarily by MISI, with grounding-line retreat proceeding across retrograde-sloping bed portions before eventually stabilizing as the bed slope reverses — though glacial isostatic rebound provides some dampening.
The Ronne basin similarly shows a critical threshold below +1°C for modest losses and a second threshold around 6–7°C triggering larger-scale disintegration. In total, approximately 40% of the present West Antarctic Ice Sheet's sea-level relevant volume — roughly 2.1 metres sea-level equivalent — is committed to long-term loss at current warming levels.
East Antarctica: Lower Urgency, but Major Stakes at 2–5°C
East Antarctic basins generally have higher critical temperature thresholds, but several with large sea-level potential become vulnerable well within the range of plausible 21st-century warming. The Cook/Ninnis/Mertz basin (Wilkes Subglacial Basin), representing approximately 1.2 m of sea-level potential, reaches a tipping threshold between 2–3°C — a level exceeded by the end of this century in all but the most optimistic IPCC scenario. The mechanism involves destabilization of small outlet glaciers functioning as an "ice plug," triggering self-amplified interior retreat. A second threshold between 6–7°C adds approximately 0.9 m further.
The Totten/Moscow basin, with around 3.3 m of sea-level potential, tips in the 5–7°C range, driven by the Aurora Subglacial Basin geometry. Marine-based sectors across East Antarctica representing roughly 5 m of combined sea-level rise potential are at risk of losing stability between 2–5°C — temperatures reachable under high-emission pathways by 2100 or shortly after.
For global warming above 6°C, threshold behavior emerges across almost all remaining East Antarctic basins, with a combined committed sea-level contribution exceeding 26 m.
A Risk Map, Not a Sea-Level Projection
Combining critical threshold temperature and committed sea-level impact into a combined risk metric, the study identifies the highest-risk basins as Totten/Moscow, Filchner, and Ross East (Byrd) — primarily because of their large sea-level commitments — and Thwaites/Pine Island, Ross West, and Cook/Ninnis/Mertz — because of their low critical thresholds. The authors are explicit that this analysis is a stability assessment, not a sea-level projection: it identifies long-term equilibrium states that the ice sheet is committed to under sustained warming, not the timing or rate at which those states would be approached. Actual sea-level rise from these basins would unfold over centuries to millennia; what the analysis quantifies is the eventual commitment triggered by crossing each threshold.
Antarctica as a Network of Tipping Systems
The broader implication of this basin-by-basin approach is a reconceptualization of Antarctic risk. The ice sheet is not a single switch waiting to be thrown, but a set of dynamically coupled subsystems, each responding to warming on its own terms and at its own threshold temperature. Some are already past their critical points. Others remain stable through the Paris Agreement targets but become vulnerable at 2–3°C. Still others are largely inert until extreme warming levels are reached. Understanding which basins cluster together — responding coherently to the same temperature forcing — and how the destabilization of one may propagate to neighboring systems through shared ocean circulation, grounding-line dynamics, or ice-shelf buttressing, is identified as a priority for future research.
As the authors note, identifying the right scale of aggregation for Antarctic tipping dynamics is essential for the detection of early-warning signals — and for understanding just how much of the ice sheet humanity has already committed to losing.
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