Arctic Ocean stratification set by sea level and freshwater inputs since the last ice age ...

• Main Authors: Farmer, Jesse R., Sigman, Daniel M., Granger, Julie, Underwood, Ona M., Fripiat, François, Cronin, Thomas M., Martínez-García, Alfredo, Haug, Gerald H.
• Format: Text
• Language: English
• Published: ETH Zurich 2021
• Subjects: Marine chemistry; Palaeoceanography; Palaeoclimate; Arctic; Arctic Ocean; Bering Strait; Foraminifera*; Sea ice
• Online Access: https://dx.doi.org/10.3929/ethz-b-000501734; http://hdl.handle.net/20.500.11850/501734

Salinity-driven density stratification of the upper Arctic Ocean isolates sea-ice cover and cold, nutrient-poor surface waters from underlying warmer, nutrient-rich waters. Recently, stratification has strengthened in the western Arctic but has weakened in the eastern Arctic; it is unknown if these trends will continue. Here we present foraminifera-bound nitrogen isotopes from Arctic Ocean sediments since 35,000 years ago to reconstruct past changes in nutrient sources and the degree of nutrient consumption in surface waters, the latter reflecting stratification. During the last ice age and early deglaciation, the Arctic was dominated by Atlantic-sourced nitrate and incomplete nitrate consumption, indicating weaker stratification. Starting at 11,000 years ago in the western Arctic, there is a clear isotopic signal of Pacific-sourced nitrate and complete nitrate consumption associated with the flooding of the Bering Strait. These changes reveal that the strong stratification of the western Arctic relies on ... : Nature Geoscience, 14 (9) ...