Stable carbon isotope ratios of carbon dioxide from EDC and Berkner Island ice cores for 40-50 ka BP, supplement to: Schaefer, Hinrich; Lourantou, Anna; Chappellaz, Jérôme A; Lüthi, Dieter; Bereiter, Bernhard; Barnola, Jean-Marc (2011): On the suitability of partially clathrated ice for analysis of concentration and d13C of palaeo-atmospheric CO2. Earth and Planetary Science Letters, 307(3-4), 334-340

• Main Authors: Schaefer, Hinrich, Lourantou, Anna, Chappellaz, Jérôme A, Lüthi, Dieter, Bereiter, Bernhard, Barnola, Jean-Marc
• Format: Dataset
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2011
• Subjects: Event label; Sample code/label; DEPTH, ice/snow; Gas age; Carbon dioxide; Carbon dioxide, standard deviation; δ13C, carbon dioxide, atmospheric; δ13C, standard deviation; Ice drill; see references; Mass spectrometer Finnigan MAT 252; Dome C; European Project for Ice Coring in Antarctica EPICA; Berkner Island; Schaefer; Antarc*; Antarctica; EPICA
• Online Access: https://dx.doi.org/10.1594/pangaea.809527; https://doi.pangaea.de/10.1594/PANGAEA.809527

The stable carbon isotopic signature of carbon dioxide (d13CO2) measured in the air occlusions of polar ice provides important constraints on the carbon cycle in past climates. In order to exploit this information for previous glacial periods, one must use deep, clathrated ice, where the occluded air is preserved not in bubbles but in the form of air hydrates. Therefore, it must be established whether the original atmospheric d13CO2 signature can be reconstructed from clathrated ice. We present a comparative study using coeval bubbly ice from Berkner Island and ice from the bubble-clathrate transformation zone (BCTZ) of EPICA Dome C (EDC). In the EDC samples the gas is partitioned into clathrates and remaining bubbles as shown by erroneously low and scattered CO2 concentration values, presenting a worst-case test for d13CO2 reconstructions. Even so, the reconstructed atmospheric d13CO2 values show only slightly larger scatter. The difference to data from coeval bubbly ice is statistically significant. However, the 0.16 per mil magnitude of the offset is small for practical purposes, especially in light of uncertainty from non-uniform corrections for diffusion related fractionation that could contribute to the discrepancy. Our results are promising for palaeo-atmospheric studies of d13CO2 using a ball mill dry extraction technique below the BCTZ of ice cores, where gas is not subject to fractionation into microfractures and between clathrate and bubble reservoirs. : The data set contains concentrations and stable isotope ratios (delta13CO2) of carbon dioxide (CO2) from the EPICA Dome C (EDC) and Berkner Island (BIC) ice cores. Gas ages are between 40 and 50 ka BP. CO2 concentrations [CO2] are derived from peak heights of the isotope ratio mass spectrometer m/z = 44 traces. All values for [CO2] and delta13CO2 are averages over multiple runs and corrected for gravitational fractionation using delta15N data for BIC and an empirical relationship between delta15N and deltaD(ice) for EDC. Standard deviations are derived from replicate measurements. delta13CO2 standard deviations for BIC additionally include the standard deviation of the delta15N data used for gravitational correction.Depth, ice/snow = top depth