High-resolution climate reconstruction for the Holocene based on growth chronologies of the bivalve Arctica islandica from the North Sea

Abstract

Until now, there has been no published documentation of North Sea year-to-year climate variability during the last 8000 to 10000 years. High-resolution instrumental time series of climatic and environmental data for the North Sea and the adjacent North Atlantic are only available for the last decades or a century at best. Long term paleoclimatic reconstructions in higher latitudes have been predominantly undertaken using land-based annually banded archives, such as trees, varves, glaciers, and speleothems. A suitable long-term environmental archive with annual may be provided by CaCO3-skeletons of long-lived marine invertebrates. This study evaluates whether recent and subfossil shells of the long-lived bivalve Arctica islandica from the North Sea carry feasible information on Holocene climatic and oceanographic conditions. I compared modern shells of Arctica islandica from two very different habitats, a near-coastal shallow site ( German Bight ) and a northerly, more central, deep site ( Fladen Ground ). From the latter, subfossil shells were analysed, also. This study demonstrates that Arctica from both sites provides suitable archives of marine environmental conditions in the form of (i) variations in annual shell growth rates and of (ii) its shell chemistry, both which allow for the reconstruction of local past climate conditions. In summary, this study enhances our understanding of the relationships between environmental conditions and shell properties in Arctica islandica in the North Sea. We could demonstrate suitable proxies for: Winter water temperatures of the southern North Sea (Sr/Ca ratios), bottom water temperatures of the northern North Sea (δ18O) and spring Elbe river discharges of the southern North Sea (Ba/Ca ratios). The application of these proxies allows the reconstruction of past marine environmental conditions for both coastal and offshore sites in the North Sea.