Supplementary material of IODP Site 342-U1410 and COSMOS model

Despite its crucial role in today's climate system, vigorous debate remains as to when deep-water formation in the North Atlantic started. Here, we present datasets from carbonate-rich middle Eocene sediments from the Newfoundland Ridge, revealing a unique archive of paleoceanographic change from the progressively cooling climate of the middle Eocene.

Well-defined lithologic alternations between calcareous ooze and clay-rich intervals occur at the ~41-kyr beat of axial obliquity. Hence, we identify obliquity as the driver of middle Eocene (43.5-46 Ma) Northern Component Water (NCW, the predecessor of modern NADW) variability. High-resolution benthic foraminiferal d18O and d13C suggest that obliquity minima correspond to cold, nutrient-depleted, western North Atlantic deep waters.