Deglacial sea-level records from NE Ireland between 21 and 11 cal. ka bp record marine transgressions and sensitive lithospheric responses to ice loading. The sawtooth sea-level curve contains four intervals characterized by: (1) strong net uplift, subaerial channelling and a global meltwater pulse (21–19 cal. ka bp); (2) ice loading, isostatic depression and high relative sea level (19–17.5 cal. ka bp); (3) ice loading, renewed isostatic depression and high relative sea level for >1000 years (17–14.5 cal. ka bp); (4) catastrophic ice wastage, rapid uplift and lowstand (14.5–13 cal. ka bp). Geophysical models do not capture these fluctuations.