Theory 11/Thresholds & Tipping/Ice sheets
Marine Ice Sheets Have a Cliff
The claim
Marine-based ice sheets become unstable above a threshold in bed slope and grounding-line depth, so retreat accelerates without any warming change.
01Mechanism
Retreat exposes thicker ice, which increases discharge, which drives further retreat: a positive feedback once the bed slopes toward the interior.
02Prediction
Retreat rate should accelerate once the grounding line passes a depth threshold.
03Refutation
Retreat tracking warming alone would remove the geometry-driven instability.