BARIUM-ISOTOPIC PROXIES IN PALEOCEANOGRAPHY: PROGRESS, POTENTIAL, AND PITFALLS (Invited Presentation)

Reliable reconstructions of ocean chemistry require an understanding of the variables that control a given proxy. The effects of these variables are often understood in terms of calibration studies conducted in modern environments. However, such calibrations can be problematic in seawater since many unrelated parameters can exhibit correlations simply because of the large gradients encountered in the ocean. For example, Ba (barium) has been variously exploited as a proxy for deep ocean nutrients, ocean circulation, alkalinity, carbon export, surface runoff, and historical upwelling intensity. Does this remarkable breadth reflect the unparalleled utility of Ba-based proxies to inform on all aspects of paleoceanography? Or does it instead reflect the difficulty in isolating the control variable? Since isotopic approaches are commonly exploited to tease apart multiple confounding processes, the recent development of Ba-isotopic measurements may similarly enable identification of the controls on marine Ba distributions. In this presentation, I will review new and published Ba-isotopic results for seawater, marine particles, and sediments. This synthesis will highlight recent progress towards identifying the controls on marine Ba distributions and attendant potential for reliable reconstructions of past ocean chemistry using Ba-based proxies.