evidence: The contribution of the Antarctic Ice Sheet to global sea-level rise has been accelerating7,8, enhancing the risk of flooding and other associated hazards to low-lying coastal communities9. Much of this mass loss has been attributed to warm ocean currents weakening the buttressing effects of its ice shelves10,11,12, primarily in West Antarctica and the Wilkes Land coastline of East Antarctica10,11,12, and hence driving an acceleration of ice discharge into the ocean1,2. Therefore, observational records that track the change in ice-shelf thickness over the longest possible time periods are important for explaining how the Antarctic Ice Sheet is changing and hence forecasting future mass loss. Existing records of ice-shelf thickness change derived from satellite altimetry span 30 years and have shown major ice-shelf thinning in some parts of West Antarctica and the western Antarctic Peninsula, thinning in the Wilkes Land sector of East Antarctica and limited change in most other ice shelves3,4,5,12,13,14. However, this satellite-altimetry record remains short relative to the typically multidecadal response times of many Antarctic ice shelves15, and we do not know how widespread ice-shelf thinning was before 1992. [...] Paolo, F. S. et al. Response of Pacific-sector Antarctic ice shelves to the El Niño/Southern Oscillation. Nat. Geosci.11, 121–126 (2018). [...] Fürst, J. J. et al. The safety band of Antarctic ice shelves. Nat. Clim. Change6, 479–482 (2016).