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Abstract

Cosmogenic isotope ¹⁰Be is produced in the stratosphere and troposphere by spallation reactions involving interaction between highly energetic galactic cosmic ray and atmospheric isotopes such oxygen and nitrogen. Because the incoming flux of primary galactic cosmic ray is modulated by the strength of geomagnetic field and solar activity, the maximum production of cosmogenic ¹⁰Be appears during geomagnetic dipole lows. Atmospheric ¹⁰Be is eventually removed by aerosols and afterwards deposited on the Earth surface. In the Ocean it is rapidly scavenged by suspended mater and stored within the sedimentary column. In order to use pelagic archives for tracing back cosmogenic ¹⁰Be variations, which are prone to geomagnetic field change, ¹⁰Be is commonly normalized for sediment inhomogenities by stable isotope ⁹Be. Scaling the authigenic ¹⁰Be/⁹Be records, obtained from widely scattered locations, revealed the presence of several environmental components, likely driven by global ocean water masses circulation and regional processes. Detected additive site-dependent ¹⁰Be/⁹Be component is time-invariant over the last 300ka and seems to agree with the pattern of thermohaline circulation. The case study of North Atlantic site revealed the upward long-term and oscillatory trends of ¹⁰Be and ⁹Be records, pointing to the change of regional deep-water masses circulation. Unveiling these trends allows us not only to disentangle environmental and geomagnetic components of ¹⁰Be/⁹Be signal, but also to constrain the main drivers of beryllium isotopes distribution in the ocean.