The Cenozoic palaeoenvironment of the Arctic Ocean

The Cenozoic history (0 to 65 million years, Myr, ago) of the Arctic Ocean is largely unknown from direct evidence. Here we present the first Cenozoic palaeoceanographic record constructed from > 400 m of core from a recent drilling expedition to the Lomonosov Ridge. Our record shows a palaeoenvironmental transition from a warm greenhouse world, of the latest Palaeocene and early Eocene, to an icehouse world influenced by sea ice and icebergs from the middle Eocene to the present. We show: 1-2 cm per thousand years (ka) sedimentation rates occurred from the middle Miocene - Holocene (~18-0 Myr) in stark contrast to rates proposed in earlier studies; the first occurrence of ice-rafted debris (IRD) is in the middle Eocene (~45 Myr), ~35 Myr earlier than previously thought; prior to the IRD, fresh surface waters were present at ~49 Myr; and warm surface waters, ~10° warmer than previous estimates, occurred during the Palaeocene Eocene Thermal Maximum (PETM). The revised timing of Arctic cooling events coincides with those from Antarctica, supporting arguments for bi-polar symmetry in climate change.