A revised 1000 year atmospheric δ¹³C‐CO₂ record from Law Dome and South Pole, Antarctica

Abstract

[1] We present new measurements of ı 13 C of CO 2 extracted from a high-resolution ice core from Law Dome (East Antarctica), together with firn measurements performed at Law Dome and South Pole, covering the last 150 years. Our analysis is motivated by the need to better understand the role and feedback of the carbon (C) cycle in climate change, by advances in measurement methods, and by apparent anomalies when comparing ice core and firn air ı 13 C records from Law Dome and South Pole. We demonstrate improved consistency between Law Dome ice, South Pole firn, and the Cape Grim (Tasmania) atmospheric ı 13 C data, providing evidence that our new record reliably extends direct atmospheric measurements back in time. We also show a revised version of early ı 13 C measurements covering the last 1000 years, with a mean preindustrial level of -6.50 . Finally, we use a Kalman Filter Double Deconvolution to infer net natural CO 2 fluxes between atmosphere, ocean, and land, which cause small ı 13 C deviations from the predominant anthropogenically induced ı 13 C decrease. The main features found from the previous ı 13 C record are confirmed, including the ocean as the dominant cause for the 1940 A.D. CO 2 leveling. Our new record provides a solid basis for future investigation of the causes of decadal to centennial variations of the preindustrial atmospheric CO 2 concentration. Those causes are of potential significance for predicting future CO 2 levels and when attempting atmospheric verification of recent and future global carbon emission mitigation measures through Coupled Climate Carbon Cycle Models.

On the state dependency of the equilibrium climate sensitivity during the last 5 million years

“…) tained 1723 data points before the year 1750 CE, the beginning of the industrialization, but it was here resampled to the 2 kyr time step of the ice-sheet simulation results by averaging available data points and reducing the sample size to n = 394. The stack contains data from the ice cores at Law Dome (Rubino et al, 2013;MacFarling-Meure et al, 2006; 0-2 kyr BP), EPICA Dome C (Monnin et al, 2001(Monnin et al, , 2004Schneider et al, 2013;Siegenthaler et al, 2005;Bereiter et al, 2015;2-11 c. CO 2 data from the Foster lab (Foster, 2008;Martínez-Botí et al, 2015) are available for the last 3.3 Myr (n = 105), obtained via δ 11 B from ODP site 999 in the Caribbean Sea. CO 2 purely based on G. ruber δ 11 B was reconstructed for the last glacial cycle (Foster, 2008) and for about 0.8 Myr during the Plio-Pleistocene transition (Martínez-Botí et al, 2015).…”

Compiled records of carbon isotopes in atmospheric CO<sub>2</sub> for historical simulations in CMIP6

“…Records of atmospheric 14 C and δ 13 C have been extended into the past using measurements of tree rings and of CO 2 in air from ice sheets (ice cores and firn), respectively; recent examples include Reimer et al (2013) and Rubino et al (2013). Ice cores are generally not used to construct atmospheric 14 C records due to in situ 14 C production, and tree rings are generally not used to construct atmospheric δ 13 C records due to climatic and physiological influences on 13 C discrimination.…”

“…For that purpose we direct modellers to the original atmospheric observations used to produce the forcing datasets, available through data repositories listed in Table 1. The firn and ice core data, updated from Rubino et al (2013), are available in Table S2.…”

Holocene peatland and ice-core data constraints on the timing and magnitude of CO 2 emissions from past land use

“…Atmospheric CO 2 concentration exhibits a marked decline between 1500 CE and 1650 CE in several ice cores (40,41) and inferred terrestrial C storage increased by 27 ± 4 PgC (17). These changes occur at the time of the European arrival in the Americas and during the subsequent collapse of the native population by around 90% (42).…”