Middle Miocene intensification of the deep western boundary current offshore eastern Greenland

The Deep Western Boundary Current, whose lower limb includes Denmark Strait Overflow Water and Iceland-Scotland Overflow Water, carries deep water formed in the Arctic, Norwegian, and Greenland Seas along the eastern margin of Greenland, where it joins the global ocean conveyor system. Despite its important role in driving ocean circulation, its early evolution is not well known. Rapidly-accumulated contourite drift deposits along the eastern margin of Greenland contain a record of deep-water flow, with patterns in sedimentation rate and composition reflecting changes in flow intensity and pathways. Nearly the entire thickness of a previously un-sampled contourite drift at 61°N on the SE Greenland margin was cored at International Ocean Discovery Program Expedition 395 Site U1602 in 2023, providing the first record of its depositional history. Age constraints from the borehole allow dating of coincident seismic reflectors. Using the age-constrained seismic data, we describe four distinct spatiotemporal stages of drift development beginning ∼15 million years ago downslope of Site U1602. Seismic reflection and drilling data suggest a depocenter that migrated upslope until 7 Ma, reaching Site U1602 ∼9.6 million years ago. We link the drift development and depocenter migration at this site to an intensification of Denmark Strait Overflow Water from 15–7 Ma, and changes in sediment composition at 3.5 Ma to a Pliocene intensification of Iceland-Scotland Overflow Water.