Marine reservoir age variability over the last deglaciation: implications for marine carbon cycling and prospects for regional radiocarbon calibrations

• Main Authors: Skinner, Luke, Muschitiello, Francesco, Scrivner, Adam
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2019
• Subjects: 37 Earth Sciences; 3708 Oceanography; 3709 Physical Geography and Environmental Geoscience; 3705 Geology; 14 Life Below Water; 13 Climate Action; Southern Ocean; North Atlantic; Sea ice
• Online Access: https://www.repository.cam.ac.uk/handle/1810/299863; https://doi.org/10.17863/CAM.46937

Marine radiocarbon dates, corrected for ocean-atmosphere reservoir age offsets (R-ages) are widely used to constrain marine chronologies. R-ages also represent the surface boundary condition that links the ocean interior radiocarbon distribution (i.e. ‘radiocarbon ventilation ages’) to the ocean’s large-scale overturning circulation. Understanding how R-ages have varied over time is therefore essential both for accurate dating and for investigations into past ocean circulation/carbon cycle interactions. A number or recent studies have shed light on surface reservoir age changes over the last deglaciation; however a clear picture of global/regional spatiotemporal patterns of variability has yet to emerge. Here we combine new and existing reservoir age estimates to show coherent but distinct regional reservoir age trends in the sub-polar North Atlantic and Southern Ocean. It can be further shown that similar, but lower amplitude changes occurred at mid-latitudes in each hemisphere. An apparent link between regional patterns of reservoir age variability and the ‘thermal bipolar seesaw’ suggests a causal link with changes in ocean circulation, mixed layer depth, and/or sea ice dynamics. A further link to atmospheric CO2 is also apparent, and underlines a potentially dominant role for changes in the ocean’s ‘disequilibrium carbon’ pool, rather than changes in ocean transport. The existence of significant R-age variability over the last deglaciation poses a problem for marine radiocarbon age calibrations. However, its apparent regional consistency also raises the prospect of developing region-specific marine calibration curves for radiocarbon-dating purposes.