A sclerochronology defined 600-year baseline of marine dynamics in the North Sea

Arctica islandica is a long-lived marine bivalve mollusc that inhabits the continental shelf seas of the North Atlantic Ocean at subpolar and temperate latitudes. Growth increments formed within A. islandica shells can be analysed to form annually resolved and absolutely dated sclerochronologies that are considered the marine counterpart to dendrochronologies. Here, we present an updated A. islandica chronology from the Fladen Ground (North Sea) that spans between CE 1410 and 2021. The A. islandica chronology significantly (p < 0.05) covaries with observational local sea surface productivity, subsurface seawater temperature and sea surface salinity. These analyses highlight the potential sensitivity of the chronology to the variability in the regional seawater temperature and salinity, and atmospheric circulation patterns (wind stress and the summer North Atlantic Oscillation). The connection between the atmospheric circulation patterns and A. islandica shell growth is likely due to fluctuations in the strength of the Atlantic inflows into the North Sea and local mixing. This highlights the significant potential in using A. islandica records to provide long-term baselines of North Sea marine dynamics. These baselines are critical for understanding the impact future changes in regional oceanic and atmospheric variability may have on North Sea ecosystems and fisheries.This article is part of the theme issue 'Shifting seas: understanding deep-time human impacts on marine ecosystems'.