Abstract
Abstract. The reconstruction of the stable carbon isotope evolution in atmospheric CO2 (δ13Catm), as archived in Antarctic ice cores, bears the potential to disentangle the contributions of the different carbon cycle fluxes causing past CO2 variations. Here we present a new record of δ13Catm before, during and after the Marine Isotope Stage 5.5 (155 000 to 105 000 yr BP). The dataset is archived on the data repository PANGEA® (www.pangea.de) under 10.1594/PANGAEA.817041. The record was derived with a well established sublimation method using ice from the EPICA Dome C (EDC) and the Talos Dome ice cores in East Antarctica. We find a 0.4‰ shift to heavier values between the mean δ13Catm level in the Penultimate (~ 140 000 yr BP) and Last Glacial Maximum (~ 22 000 yr BP), which can be explained by either (i) changes in the isotopic composition or (ii) intensity of the carbon input fluxes to the combined ocean/atmosphere carbon reservoir or (iii) by long-term peat buildup. Our isotopic data suggest that the carbon cycle evolution along Termination II and the subsequent interglacial was controlled by essentially the same processes as during the last 24 000 yr, but with different phasing and magnitudes. Furthermore, a 5000 yr lag in the CO2 decline relative to EDC temperatures is confirmed during the glacial inception at the end of MIS5.5 (120 000 yr BP). Based on our isotopic data this lag can be explained by terrestrial carbon release and carbonate compensation.
Highlights
Various processes are known to influence changes in the carbon distribution and its isotopic signature between the ocean, the atmosphere, terrestrial and marine organic carbon, reactive sediments and the lithosphere
In the case of the CO2 mismatch of 8 ppm around 128 000 yr BP of our measurements derived for Talos Dome and European Project for Ice Coring in Antarctica (EPICA) Dome C (EDC) (Fig. 3), both records were measured with the sublimation technique
Applying an age scale compression of the TALos Dome Ice CorE” (TALDICE)-1 dating between 129 000 and 126 000 yr BP, the broad shape of the early CO2 peak from the Talos Dome matches the timing of the peak reconstructed from the EDC ice core, but can not explain the higher CO2 concentrations
Summary
Various processes are known to influence changes in the carbon distribution and its isotopic signature between the ocean, the atmosphere, terrestrial and marine organic carbon, reactive sediments and the lithosphere. Goodwin et al (2011) point out that the way in which different climate proxies combine is crucial for accurate past carbon cycle reconstructions. An unequivocal interpretation of past variations in the global carbon cycle is difficult, but not impossible, if proxy data provide adequate and sufficient constraints. The stable carbon isotope signal of atmospheric CO2 (δ13Catm) provides a valuable tool to constrain processes affecting the global carbon cycle. Scrutinizing the potential processes and their contributions to the observed CO2 variations, using long-term δ13Catm data sets in conjunction with other proxies like (δ13Cocean) help disentangle the complex simultaneous changes of processes affecting the carbon cycle in the past. Antarctic ice cores allow for such δ13Catm reconstructions, the small changes in δ13Catm demand very high-precision measurements. Due to the slow gas enclosure process, atmospheric changes are low-pass filtered in polar ice and fast changes in CO2 and δ13Catm are damped
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