Two centuries of relative sea-level rise in Dublin, Ireland, reconstructed by geological tide gauge

Abstract

We demonstrate the utility and reproducibility of the saltmarsh foraminifera-based ‘geological tide gauge’ (GTG) approach by developing two independent records of relative sea-level (RSL) change for Dublin, Ireland. Our records, recovered from two different saltmarshes, indicate that RSL rose at a century-scale rate of 1.5 ± 0.9 mm yr–1 over the last 200 years. This compares favourably with the shorter, but more precise, mean sea level (MSL) record from the Dublin Port tide gauge, which indicates long-term (1953–2016 CE) rise at a rate of 1.1 ± 0.5 mm yr–1 . When corrected for the influence of glacio-isostatic adjustment our saltmarsh-based reconstruction suggests sea levels in Dublin rose at a rate of 1.6 ± 0.9 mm yr–1 since the start of the 19th century, which is in excellent agreement with the regional value of MSL rise over the same period (1.5 ± 0.2 mm yr–1) calculated from a compilation of tide gauge records around Britain. Whilst our record has decadal-scale temporal resolution (1 sample every 8 years), we are currently unable to resolve multidecadal-scale variations in the rate of sea-level rise which are masked by the size of the vertical uncertainties (± 20 cm) associated with our reconstruction of palaeomarsh-surface elevation. We discuss the challenges of applying the GTG approach in the typically minerogenic saltmarshes of the NE Atlantic margin and outline potential solutions that would facilitate the production of Common Era RSL reconstructions in the region.