Turney, Chris S.M.Palmer, Jonathan G.Hogg, Alan G.Fogwill, Christopher J.Jones, RichardBronk Ramsey, ChristopherFenwick, PavlaGrierson, PaulineWilmshurst, JanetO'Donnell, AlisonThomas, ZoëLipson, Mathew2016-02-1520162016-02-152016Turney, C. S. M., Palmer, J. G., Hogg, A. G., Fogwill, C. J., Jones, R., Bronk Ramsey, C., … Lipson, M. (2016). Multi-decadal variations in Southern Hemisphere atmospheric ¹⁴C: Evidence against a Southern Ocean sink at the end of the Little Ice Age CO₂ anomaly. Global Biogeochemical Cycles, online. http://doi.org/10.1002/2015GB005257https://hdl.handle.net/10289/9905Northern Hemisphere-wide cooling during the Little Ice Age (LIA; CE 1650-1775) is associated with a ~5 ppmv decrease in atmospheric carbon dioxide. Changes in terrestrial and ocean carbon reservoirs have been postulated as possible drivers of this relatively large shift in atmospheric CO₂, potentially providing insights into the mechanisms and sensitivity of the global carbon cycle. Here we report decadally-resolved radiocarbon (¹⁴C) levels in a network of tree rings series spanning CE 1700-1950 located along the northern boundary of, and within, the Southern Ocean. We observe regional dilutions in atmospheric radiocarbon (relative to the Northern Hemisphere) associated with upwelling of ¹⁴CO₂–depleted abyssal waters. We find the inter-hemispheric ¹⁴C offset approaches zero during increasing global atmospheric CO₂ at the end of the LIA, with reduced ventilation in the Southern Ocean and a Northern Hemisphere source of old carbon (most probably originating from deep Arctic peat layers). The coincidence of the atmospheric CO₂ increase and reduction in the inter-hemispheric ¹⁴C offset imply a common climate control. Possible mechanisms of synchronous change in the high latitudes of both hemispheres are discussed.application/pdfenThis is an author’s accepted version of an article published in the journal: Global Biogeochemical Cycles. ©2016 American Geophysical Union.Journal Article10.1002/2015GB005257