Letter

Nature 461, 507-510 (24 September 2009) | doi:10.1038/nature08393; Received 4 May 2009; Accepted 28 July 2009

Stable isotope constraints on Holocene carbon cycle changes from an Antarctic ice core

Joachim Elsig1,2, Jochen Schmitt1,2,3, Daiana Leuenberger1,2, Robert Schneider1,2, Marc Eyer1,2, Markus Leuenberger1,2, Fortunat Joos1,2, Hubertus Fischer1,2,3 & Thomas F. Stocker1,2

  1. Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland
  2. Oeschger Centre for Climate Change Research, University of Bern, Zähringerstrasse 25, CH-3012 Bern, Switzerland
  3. Alfred Wegener Institute for Polar and Marine Research (AWI), Columbusstrasse, D-27568 Bremerhaven, Germany

Correspondence to: Thomas F. Stocker1,2 Correspondence and requests for materials should be addressed to T.F.S. (Email: stocker@climate.unibe.ch).

Reconstructions of atmospheric CO2 concentrations based on Antarctic ice cores1, 2 reveal significant changes during the Holocene epoch, but the processes responsible for these changes in CO2 concentrations have not been unambiguously identified. Distinct characteristics in the carbon isotope signatures of the major carbon reservoirs (ocean, biosphere, sediments and atmosphere) constrain variations in the CO2 fluxes between those reservoirs. Here we present a highly resolved atmospheric delta13C record for the past 11,000 years from measurements on atmospheric CO2 trapped in an Antarctic ice core. From mass-balance inverse model calculations3, 4 performed with a simplified carbon cycle model, we show that the decrease in atmospheric CO2 of about 5 parts per million by volume (p.p.m.v.). The increase in delta13C of about 0.25permil during the early Holocene is most probably the result of a combination of carbon uptake of about 290 gigatonnes of carbon by the land biosphere and carbon release from the ocean in response to carbonate compensation of the terrestrial uptake during the termination of the last ice age. The 20 p.p.m.v. increase of atmospheric CO2 and the small decrease in delta13C of about 0.05permil during the later Holocene can mostly be explained by contributions from carbonate compensation of earlier land-biosphere uptake and coral reef formation, with only a minor contribution from a small decrease of the land-biosphere carbon inventory.