Search

Reconstructions of palaeo‐sea level are vital for predicting future sea level change and constraining palaeo‐ice sheet reconstructions, as well as being useful for a wide array of applications across Quaternary Science. Previous reconstructions of the palaeo‐sea level of Britain and Ireland relied on a circular tuning of glacio‐isostatic models: input ice sheet thicknesses and extents were iteratively altered to fit relative sea level data. Here we break that circularity by utilizing new data from the BRITICE‐CHRONO project, which constrains the position of the British–Irish ice sheet margin through time, and we compare derived glacio‐isostatic modelling to the rich relative sea level record. We test a combination of plausible ice thickness scenarios which account for the uncertainty of ice margin position over the North Sea, demonstrating the region where regional sea level data could distinguish between different glaciation scenarios. Our optimal reconstruction is then combined with several global‐scale reconstructions. As the signal of the British–Irish Ice Sheet is constrained, we demonstrate how the relative sea level record of Britain and Ireland can be used to test reconstructions of far‐field ice sheets (e.g. Antarctica, Eurasia and the Laurentide). The derived palaeo‐topography data are likely to be useful for multiple disciplines. Finally, our improved method of sea level reconstruction impacts predictions of contemporary vertical land motion. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: A mathematical wave-erosion model is used to simulate postglacial shoreline profiles along the rocky, high energy coast of the north of Ireland. The wave erosion model is driven by a suite of relative sea-level (RSL) curves for the last 16,000years produced from four glacial rebound models. Multiple runs are performed with different initial shore profiles and rock resistances to investigate shoreline evolution and the significance of inherited morphology on the resultant profile shape. The simulated profiles are then compared with mapped profiles from three areas of the north of Ireland with different lithological and hydrographic properties. Modelled profiles generally replicate the overall mean shoreline gradients observed across the region when rock resistance is relatively high and erosion rates correspondingly low. In these profiles, breaks in mean slope are observed at depths comparable to the RSL minima in several of the RSL scenarios (at c. −10m, −15m and −20m for North Antrim, Derry and Donegal respectively). At Portrush and Portballintrae (Derry), profiles may be influenced by structural controls relating to the underlying basalt surface and the removal of overlying glaciogenic sediments. All RSL scenarios replicate the observed eastward increase in cliff–platform junction height, reflecting the differential glacioisostatic rebound experienced along the coast. However, the precise elevation at which the simulated cliff base occurs is sensitive to the choice of RSL scenario, suggesting that this parameter may prove useful in evaluating glacial rebound model performance. Several of the RSL scenarios generate raised shore platforms or terraces in North Antrim and Derry at heights comparable to raised shoreline features reported in the literature. However, no single curve or combination of parameters is capable of generating the range of platform and terrace features observed in the bathymetric and topographic data. These misfits are consistent with the idea that many rock platform or terrace features are inherited from an earlier phase or phases of RSL. [Copyright &y& Elsevier]