Did the central Arctic become a sediment-starved basin in the Quaternary?

The Arctic Coring Expedition (ACEX) remains the only scientific ocean drilling project conducted in the central Arctic Ocean by IODP and its predecessors. Despite its success, substantial uncertainty persists regarding Neogene and Quaternary sea-ice extent. A major challenge to resolving this is the ongoing debate about the age of sediments in the upper 5–15 m below the seafloor. Classical interpretations of apparent paleomagnetic reversals as chron and subchron boundaries result in ultra-low sedimentation rates across the central Arctic. When applied to the ACEX record this yields sedimentation rates of mm/kyr back to at least the Late Miocene – predicting ages that are incompatible with the observed decay of 10 Be and the dinocyst biostratigraphy. It is conceivable that the Quaternary expansion of the perennial sea-ice zone and development of ice shelves may have reduced sedimentation across parts of the Arctic Ocean, but establishing the existence, timing and extent of this transition requires improved resolution on the age of Pleistocene Arctic sediments. Critically, older age constraints from ACEX indicate that cm/kyr sedimentation rates existed through the Neogene, possibly due to a less extensive perennial ice pack. Future efforts are needed to acquire the spatial sampling necessary to constrain the position of the marginal ice zone, which should have exhibited large variability between the end-member states of a seasonally and perennially sea-ice covered ocean.