Ice shelf retreat decouples Piglet Glacier from the Pine Island catchment and amplifies dynamic mass loss

Piglet Glacier, formed by ~20% area loss of the Pine Island Ice Shelf in 2017-2020, provides a compact analogue for testing how ice‑shelf damage and retreat alters inland glacier dynamics and drainage-basin mass balance. We use Sentinel‑1 feature‑tracking (October 2014~) and CryoSat‑2 (July 2010~) interferometric swath altimetry to monitor change on Piglet Glacier through to May 2025, quantifying both the propagation of ice speedup and the thickness change response. Relative to a 2015-2017 baseline, speed near the grounding line increased by ~40%, with acceleration propagating ~50 km inland with no resolvable lag, indicating efficient transmission of reduced buttressing into grounded ice. Firn‑corrected altimetry reveals a concurrent intensification of dynamic thinning: the basin‑integrated dynamic volume‑loss rate rose from ~2.9 to ~4.5 km³ yr^-1 (a 60% increase). Downstream, post‑calving acceleration was concentrated along pre‑damaged shear margins, and subsequent loss of shear‑margin mélange in 2024-2025 promoted further mechanical decoupling. Sustained shear‑margin attrition and frontal retreat are fragmenting the Pine Island basin system and accelerating mass loss from Piglet Glacier. This example provides a tractable benchmark for improving projections of West Antarctica’s near‑term sea‑level contribution. Future modelling studies should include shear‑margin damage, tributary detachment, and rapid inland transmission of buttressing loss, to improve process‑level constraints.