Arctica Islandica – Annually Banded Mollusc Offers High Temporal Resolution Record Into End Of North Sea Little Ice Age

Abstract: Sclerochronology affirms the well-established fact that banded growth increments in marine molluscs accurately record oscillations in climate and environment for the past millennia or more. This study considers how such records can enhance understanding of environmental shifts across the 18th to 20th centuries. Specifically, it investigates whether sclerochronological data are fundamentally associated with stable carbon and oxygen isotope values and if the climate phenomenon of the Little Ice Age impacts the marine radiocarbon reservoir effect. Furthermore, this study compares the North Sea and the Irish Sea to discover whether observed environmental changes are equivocal or not. Three shells of Arctica islandica were retrieved from the Dutch natural history museum "Naturalis" in Leiden, the Netherlands, to construct a chronology dating back to the 18th century from growth increments. Collection dates for the three shells vary between 1882 and 1954 in the North Sea and the Irish Sea. Shells were prepared, photographed and milled for calcium carbonate material. Digital images allowed counting of increments while the milled material was measured for stable carbon and oxygen isotopes and was radiocarbon dated. The ontogenetic bias was removed from sclerochronological data using MATLAB software to produce a purely environmental growth signal. The results agreed with the proposed hypothesis that there is a link between growth increments and the stable isotope data. However, further analysis is required to validate the presence of the Little Ice Age in the radiocarbon reservoir effect. These results indicate that the stable carbon and oxygen isotopes and growth increments are a good indicator of favourable growth conditions for Arctica islandica. Therefore, this study highlights that Arctica islandica is a suitable proxy for the North Sea and Irish Sea palaeoenvironment reconstructions. On this basis, future climate research can accurately depend on sclerochronological data to aid in understanding the patterns of anthropogenic climate change.