Reconstruction of short-term storm surge-driven increases in shallow coastal lake salinity using ostracod shell chemistry

• DOI: 10.1007/s11069-022-05459-9
• Publication Date: 2022-07-02T04:02:41Z
• Authors: Lucy R. Roberts; Jonathan A. Holmes; David J. Horne; Melanie J. Leng; Carl D. Sayer; Rhys G. O. Timms; Katy Flowers; Simon P. M. Blockley; Andrea Kelly
• Keywords: Ostracod; Storm Surge

Climate change threatens the current protection provided by coastal defences in low-lying mid-latitude regions and increases the risk to coastal lakes from future frequent and intense storms. Quantifying and understanding the impacts of past storm surges, therefore, has significant implications for the management and conservation of coastal wetlands worldwide. However, short-term (< 10year) increases in salinity driven by storm surges are problematic to reconstruct via the palaeolimnological record due to sampling resolution and smoothing of trends. Here, we propose that the geochemistry (Sr/Ca and ?18O) of calcitic shells of ostracods (small bivalved crustaceans readily preserved in lacustrine sediments) is a potentially sensitive proxy for reconstructing salinity, in some cases quantitatively, in comparison with sedimentary proxies of allochthonous sediment inputs (XRF and grain size) or other biological proxies. The coastal lakes of the Thurne Broads (Norfolk and Suffolk Broads National Park) in East Anglia, UK, have a long history of sea floods associated with storm surge events in the North Sea, providing a test bed to compare ostracod palaeosalinity reconstructions (using a site-specific calibration) with known storm surges in the region. We show that Sr/Cashell values closely match known salinity changes associated with storm surges; archival records of the salinity of Horsey Mere in CE 1940 suggest a maximum salinity of 13.4 PSU with ostracod Sr/Cashell palaeosalinity calibrations giving a maximum value of 18.3 PSU. Ostracod shell chemistry, therefore, has the potential to afford more reliable reconstructions of high intensity short-term increases in salinity in mid-latitude low-lying coastal lakes.