Paleoceanographic cyclicity in the Plio-Pleistocene Arctic: a case study from the Northwind Ridge, western Arctic Ocean

Abstract:

The role of the orbital cycles that drove global paleoclimatic changes remains unclear in the Arctic, especially prior to the onset of major Northern Hemisphere glaciations ~1 Ma ago. We investigate several paleoceanographic proxies in two sediment cores from the Northwind Ridge, western Arctic, to identify the dominant long-term cyclicities that affected this part of the Earth during the early Pleistocene (ca. 0.8-2.8 Ma). Based on their location within the depth range of the Atlantic Intermediate Water (AIW) and abundant calcareous microfossils, these records are uniquely suited to provide a comparison with global paleoclimatic records. For the first time we recognize long-eccentricity (~400-kyr) cycles in Arctic sediment grain-size, geochemical, and paleobiological proxies. The strongest signal is identified in benthic foraminiferal δ¹³C signal, which appears to be consistent with global paleoceanographic records. We attribute these cycles to pulses of intensified circulation washing the Northwind Ridge during periods of sea level lowstand. Tuning of these δ¹³C cycles to global sea level variability shows a good agreement with an earlier developed strontium-isotope stratigraphy (Dipre et al., 2018). This correspondence suggests that the long-eccentricity signal can be used as a chronostratigraphic tool for the early Pleistocene and potentially older sediments in other Arctic paleoceanographic records.