Constant Holocene Southern-Ocean C-14 reservoir ages and ice-shelf flow rates

• Published in: Earth and Planetary Science Letters
• Main Authors: Hall, B, Henderson, G, Baroni, C, Kellogg, T
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2016
• Subjects: Antarctic; McMurdo Ice Shelf; Ross Sea; Southern Ocean; Antarc*; Ice Shelf; Ice Shelves
• Online Access: https://doi.org/10.1016/j.epsl.2010.04.054; https://ora.ox.ac.uk/objects/uuid:5a7a4c77-a73e-4d42-af0e-7e8536dbff42

Southern Ocean radiocarbon reservoir ages (i.e. non-zero radiocarbon ages in seawater) are the highest in the world's surface ocean. Constraining these reservoir ages at present and in the past is important not only because unknown reservoir ages limit the interpretation of Antarctic radiocarbon chronologies, but also because reservoir ages provide information about ocean circulation (as a recorder of past circulation and as an end member for major deep-water masses in today's ocean). In this study, we use paired U/Th and 14C ages of an unusual set of solitary coral samples trapped by fringing ice shelves in the Ross Sea to provide the first detailed study of Holocene reservoir ages for the Southern Ocean. Our results indicate a relatively constant marine radiocarbon reservoir age of 1144±120years for the past 6000years. These results are consistent with extrapolation of the relationship between 14C and alkalinity seen elsewhere, supporting the use of this empirical relationship in high latitudes. The results also suggest constant deep-ocean circulation and air-sea exchange during the Holocene and provide a good target for tuning ocean models of modern circulation. Combining the new ages for corals with their distance from the modern-day ice-shelf grounding line provides some of the first long-term records of ice-shelf velocities for any region and indicates constant flow of the McMurdo Ice Shelf during the Holocene, at a rate similar to that observed today. © 2010 Elsevier B.V.