Precise dating of deglacial Laptev Sea sediments via ¹⁴ C and authigenic ¹⁰ Be∕ ⁹ Be – assessing local ¹⁴ C reservoir ages

Abstract. Establishing accurate chronological frameworks is imperative for reliably identifying lead–lag dynamics within the climate system and enabling meaningful intercomparisons across diverse paleoclimate proxy records over long time periods. Robust age models provide a solid temporal foundation for establishing correlations between paleoclimate records. One of the primary challenges in constructing reliable radiocarbon-based chronologies in the marine environment is to determine the regional marine radiocarbon reservoir age correction. Calculations of the local marine reservoir effect (ΔR) can be acquired using independent 14C dating methods, such as synchronization with other well-dated archives. The cosmogenic radionuclide 10Be offers such a synchronization tool. Its atmospheric production rate is controlled by the global changes in the cosmic ray influx, caused by variations in solar activity and geomagnetic field strength. The resulting fluctuations in the meteoric deposition of 10Be are preserved in sediments and ice cores and can thus be utilized for their synchronization. In this study, for the first time, we use the authigenic 10Be/9Be record of a Laptev Sea sediment core for the period 8–14 kyr BP and synchronize it with the 10Be records from absolutely dated ice cores. Based on the resulting absolute chronology, a benthic ΔR value of +345 ± 60 14C years was estimated for the Laptev Sea, which corresponds to a marine reservoir age of 848 ± 90 14C years. The ΔR value was used to refine the age–depth model for core PS2458-4, establishing it as a potential reference chronology for the Laptev Sea. We also compare the calculated ΔR value with modern estimates from the literature and discuss its implications for the age–depth model.