Reconstruction of a high resolution Holocene and late Glacial record of atmospheric carbon dioxide concentration from stable carbon isotopes in peat

Here a new method for reconstructing atmospheric CO{dollar}sb2{dollar} concentrations based on stable carbon isotopes in peat is presented. The CO{dollar}sb2{dollar} record from the Harberton peat core in Patagonia (55{dollar}spcirc{dollar}S 72{dollar}spcirc{dollar}W) has decadal resolution and spans 14,000 radiocarbon years. The late glacial (10-14 ka) is characterized by three large and rapid CO{dollar}sb2{dollar} pulses at approximately 10.2, 11.6, and 12.9 ka. When compared to two high resolution marine core records, Troll 3.1 and RC11-83, and to records of atmospheric {dollar}Deltasp{lcub}14{rcub}{dollar}C, these CO{dollar}sb2{dollar} pulses appear to be controlled by changes in the ocean's thermohaline circulation. Two broad Holocene excursions are identified at approximately 4.2 and 7.7 ka. The driving mechanism behind these excursions appear to be different than those in the late glacial.; Three tests of the accuracy of the peat CO{dollar}sb2{dollar} method are presented. These tests rely on the rapid ({dollar}sim{dollar}1 year) interhemispheric mixing time of CO{dollar}sb2{dollar}. Because of the global signature of CO{dollar}sb2{dollar}, records of CO{dollar}sb2{dollar} from different climatic settings should be identical. In the first test, the Harberton CO{dollar}sb2{dollar} record is compared to two Antarctic ice core CO{dollar}sb2{dollar} records. In the second test, the Harberton late glacial CO{dollar}sb2{dollar} record is duplicated in another peat core from Patagonia. Finally, the anthropogenic CO{dollar}sb2{dollar} increase due to fossil fuel burning and deforestation over the last century is captured in a third peat core. All tests are positive. The latter two tests provide a means for estimating the uncertainty in reconstructed CO{dollar}sb2{dollar} values. The two estimates are consistent and indicate CO{dollar}sb2{dollar} error bars of approximately 11-14 ppm.; The Harberton CO{dollar}sb2{dollar} record indicates that throughout the late glacial as well as the Holocene, the natural carbon cycle has been characterized by instability rather than one or two stable modes. How this instability in CO{dollar}sb2{dollar} is amplified or modified by anthropogenic influences remains an open question.