Regional conditions determine thresholds of accelerated Antarctic basal melt in climate projection
- Hakan Sener
- Jun 25
- 3 min read
A 2025 study finds Antarctic basal melt may surge as hidden ocean thresholds are crossed, with Filchner–Ronne ice shelf near a tipping point.
A new study published by Pengyang Song and colleagues at the Alfred Wegener Institute uses a next-generation Earth system model to reveal how regional ocean and ice-shelf conditions govern thresholds for accelerated Antarctic ice loss. This work marks a major advance by explicitly simulating sub-ice-shelf cavities—regions under Antarctic ice shelves where ocean waters interact with the ice from below.
By comparing two of Antarctica’s largest ice shelves—the Filchner–Ronne (FRIS) and Ross (RIS)—across multiple future emissions scenarios, the team shows that these cavities respond in fundamentally different ways to global warming. While the Ross Ice Shelf exhibits gradual melt acceleration, FRIS reveals a tipping point where warm deep water floods the cavity, causing basal melt rates to surge tenfold within just a decade.
Key Findings: The Hidden Dynamics Under the Ice
Basal Melt Acceleration Is Not Uniform
Under the high-emission SSP585 scenario, Antarctic-wide basal melt rates increase nearly 3-fold by 2100 and 6.5-fold by 2200, compared to pre-industrial levels.
FRIS sees basal melt surge from 179 Gt/yr to over 5,000 Gt/yr; RIS increases from 181 Gt/yr to nearly 1,900 Gt/yr.
A Tipping Point for the Filchner–Ronne Ice Shelf
In warm scenarios, FRIS crosses a critical threshold, shifting from a stable, cold cavity to a connected warm mode.
This shift allows modified warm deep water (mWDW) to flood the cavity, drastically increasing melt and releasing vast freshwater volumes into the Southern Ocean.
Ross Ice Shelf Reacts Differently
RIS shows a more gradual increase in basal melt, influenced by its geometry and stronger connectivity with open-ocean waters.
Unlike FRIS, RIS does not cross a sharp tipping point, due to its stratified water column and shallower topography.
Topography, Geometry, and Stratification Matter
The FRIS cavity is thicker, more isolated, and slopes downward, favoring rapid mWDW intrusion once stratification collapses.
The RIS cavity is thinner and flatter, leading to slower response and better buffering against abrupt change.
Implications for Sea-Level Rise and Climate Modeling
This study underscores the critical role of sub-ice-shelf dynamics in determining the future of the Antarctic Ice Sheet. Ignoring the geometry and circulation of these hidden cavities can lead to significant over- or underestimation of ice loss.
Importantly, the researchers find that most previous models likely overestimated melt by not accounting for the time lag in warming signals traveling from open oceans to the grounding lines. By explicitly simulating these processes, the new model shows that Antarctic meltwater contributions to sea-level rise—and the timing of that contribution—may be more nuanced and delayed than previously thought.
Additionally, changes in basal melting feed back into global ocean circulation, with possible implications for deep water formation and carbon storage, particularly in the Southern Ocean.
Complexity Under the Ice Sheet
By simulating realistic cavity dynamics, this study improves our understanding of one of the greatest uncertainties in sea-level rise projections. It highlights how different regions of Antarctica will respond differently to warming, and why more accurate Earth system models must integrate ice-shelf cavities.
As global emissions determine future warming, the stability of the West Antarctic Ice Sheet—and future coastlines—may hinge on how warm waters interact with these hidden ice–ocean interfaces.
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