Molybdenum and Osmium isotope evidence for palaeoceanographic changes in the Arctic Ocean over the Paleocene-Eocene Thermal Maximum (PETM)

The Paleocene Eocene Thermal Maximum (PETM) was a period of substantial global warming thought to have been caused by the sudden input of large amounts of carbon to the ocean/atmosphere system. This carbon may have been sourced from the dissociation of methane hydrate reservoirs, although there is some debate over the role of other carbon sources, e.g. from thermogenic combustion of organic rich marine sediments during the emplacement of the North Atlantic Igneous Province. We present the first Molybdenum (Mo) and Osmium (Os) isotope data measured over the PETM interval of IODP 302 (Arctic Ocean) that reflect changes in ocean oxygenation (Mo), and in the balance between the weathering of old terrestrial rocks and younger basaltic material (Os). Both records display downcore variations that reflect the widely-recognised PETM carbon isotope excursion, suggesting clear changes in oxygenation state and weathering inputs over this event. Furthermore, isotope mass-balance constraints and comparison with other published datasets provides evidence that the Arctic Ocean remained connected to the global ocean over the course of the PETM. We will examine the implications of the new datasets for our understanding of climate dynamics during this interval.