New isotopic constraints on the role of continental weathering in the neodymium cycle of the Nordic Seas over the last 22,000 years

Neodymium isotopic composition (εNd) extracted from authigenic sediment phases has become a widely used proxy to track past changes in water masses and ocean circulation. The Nordic Seas are a key region of rare earth element exchange between seawater and particles, complicating reconstruction of past deep-water variability from εNd. Here, we present authigenic and detrital εNd records from the deep northern Norwegian Sea to assess how glacial fluctuations and shifts in sediment provenance regulate the supply of mineral phases, and how these processes, in turn, shape seawater εNd. Results showed that, homogeneous authigenic εNd values across the Nordic Seas during the LGM and the late Holocene (< 4 kyr BP) were primarily controlled by deep-water mixing rather than local sediment inputs. By contrast, the last deglaciation (18–10 kyr BP) shows large εNd variability linked to Barents-Kara Sea sediments. These labile-rich sediments contain high kaolinite/illite ratios, organic carbon and pyrite. We propose that these labile materials from the Barents-Kara Sea are more efficient at exchanging Nd with seawater than sediments generated by intense physical erosion during glacial periods. Accordingly, deep-water εNd was mainly governed by partially soluble sediments and/or desorption from Barents-Kara Sea deposits. Long-term changes in authigenic εNd were closely linked to the relative inputs from the Barents-Kara Sea, regulated by the retreat of the Svalbard-Barents Sea Ice Sheet (SBIS) and the Fennoscandia Ice Sheet (FIS) during the deglaciation. Thus, fluctuations in the advance and retreat of the SBIS and FIS largely dictated deep-water εNd. This finding underscores the pivotal role of glaciers in regulating Nd cycling and glacially derived nutrients in high-latitude regions.