A History of Futility and The Trajectory for Promise, on the Southern Ocean Radiocarbon Problem

Radiocarbon remains the single best chronologic tool for marine sediments of Late Quaternary age surrounding the Antarctic continent and has proven to be valuable for constraining important events in the development of the Antarctic Ice Sheet, the surrounding ocean, and in associated biogeochemical cycles. Yet immense uncertainty remains in many conclusions derived from radiocarbon chronologies due to the seemingly intractable problem of the reservoir effect. Whereas it has been nearly 50 years since the GEOSECs program first documented the antiquity of the radiocarbon pool in subsurface waters of the Southern Ocean there has been limited advancement on the resolution of temporal and spatial application of an acceptable reservoir correction for sectors of the southern Ocean and Antarctic continental margin. Recovery of continuous time series of marine laminated sediments (ie. Palmer Deep, Adelie Drift) can help to address temporal shifts in the correction factor for complex detrital matrices of organic carbon. Yet these detrital carbon particulates are derived from multiple sources, multiple seasons, and various vital systems which are linked only temporarily to a surface layer at equilibrium with the atmosphere. What are needed are long-lived biogeochemical archives that record fixed ocean chemistry at a variety of depths. Given recent success of using deep sea corals in sub Antarctic settings we discuss the spatial and temporal range of a variety of deep sea coral habitats from the Antarctic continental margin. Further, we provide radiocarbon ages on short time series which demonstrate realistic shifts in reservoir age along the boundary between Circumpolar Deep Water and typical shelf waters. We summarize a plan for systematic sampling and analysis of such deep sea coral communities which promises to improve our understanding of spatial and temporal shifts in the Southern Ocean reservoir correction.