A century of sea-level change in Ireland (1925–2024)

Understanding long-term sea-level change is crucial for assessing coastal vulnerability and guiding adaptation planning, particularly by identifying regions most at risk. Central to this understanding is the availability of long-term sea-level data. In Ireland, digitized records longer than 40 years are rare and mostly confined to the northeast; however, data archaeology – including the digitization of historical marigrams – can fill spatial and temporal gaps where undigitized records exist. Previous studies have focused primarily on individual sites in the north and east. Here we show that integrating previously undocumented records from the southwest with well-documented datasets provides a comprehensive assessment of relative mean sea-level (RSL) change across the country. Modelled RSL rates were obtained from the rate field of the hierarchical Bayesian reconstruction. Mean modelled RSL rates over 1925–2024 ranged from 0.73 mm yr ⁻¹ at Belfast to 1.43 mm yr ⁻¹ at Tarbert in southwest Ireland, reflecting the combined influence of the shared regional signal, site-specific linear Glacial Isostatic Adjustment (GIA)-related contributions, and local effects. The network-mean modelled RSL rate for Ireland was 1.21 mm yr ⁻¹ (95 % CI: 0.90–1.55) over 1925–2024, increasing from 0.59 mm yr ⁻¹ (95 % CI: 0.19–1.02) during 1925–2000 to 3.13 mm yr ⁻¹ (95 % CI: 2.45–3.81) during 2000–2024, indicating a substantial acceleration in recent decades. These historical records provide a robust basis for reconstructing regional RSL rise and contextualising future coastal risk.