The Antarctic ice core chronology (AICC2012): an optimized multi-parameter and multi-site dating approach for the last 120 thousand years

Abstract

The deep polar ice cores provide reference records commonly employed in global correlation of past climate events. However, temporal divergences reaching up to several thousand years (ka) exist between ice cores over the last climatic cycle. In this context, we are hereby introducing the Antarctic Ice Core Chronology 2012 (AICC2012), a new and coherent timescale developed for four Antarctic ice cores, namely Vostok, EPICA Dome C (EDC), EPICA Dronning Maud Land (EDML) and Talos Dome (TALDICE), alongside the Greenlandic NGRIP record. The AICC2012 timescale has been constructed using the Bayesian tool Datice (Lemieux-Dudon et al., 2010) that combines glaciological inputs and data constraints, including a wide range of relative and absolute gas and ice stratigraphic markers. We focus here on the last 120 ka, whereas the companion paper by Bazin et al. (2013) focuses on the interval 120–800 ka. <br><br> Compared to previous timescales, AICC2012 presents an improved timing for the last glacial inception, respecting the glaciological constraints of all analyzed records. Moreover, with the addition of numerous new stratigraphic markers and improved calculation of the lock-in depth (LID) based on &delta;¹⁵N data employed as the Datice background scenario, the AICC2012 presents a slightly improved timing for the bipolar sequence of events over Marine Isotope Stage 3 associated with the seesaw mechanism, with maximum differences of about 600 yr with respect to the previous Datice-derived chronology of Lemieux-Dudon et al. (2010), hereafter denoted LD2010. Our improved scenario confirms the regional differences for the millennial scale variability over the last glacial period: while the EDC isotopic record (events of triangular shape) displays peaks roughly at the same time as the NGRIP abrupt isotopic increases, the EDML isotopic record (events characterized by broader peaks or even extended periods of high isotope values) reached the isotopic maximum several centuries before. <br><br> It is expected that the future contribution of both other long ice core records and other types of chronological constraints to the Datice tool will lead to further refinements in the ice core chronologies beyond the AICC2012 chronology. For the time being however, we recommend that AICC2012 be used as the preferred chronology for the Vostok, EDC, EDML and TALDICE ice core records, both over the last glacial cycle (this study), and beyond (following Bazin et al., 2013). The ages for NGRIP in AICC2012 are virtually identical to those of GICC05 for the last 60.2 ka, whereas the ages beyond are independent of those in GICC05modelext (as in the construction of AICC2012, the GICC05modelext was included only via the background scenarios and not as age markers). As such, where issues of phasing between Antarctic records included in AICC2012 and NGRIP are involved, the NGRIP ages in AICC2012 should therefore be taken to avoid introducing false offsets. However for issues involving only Greenland ice cores, there is not yet a strong basis t...

Spatial and temporal variability of snow chemical composition and accumulation rate at Talos Dome site (East Antarctica)

“…These features, together with its position on a geographical dome, are believed to allow reconstruction of the environmental and climatic changes occurring in the Ross SeaWilkes Land coast marine sector for the last 200 kyear and to allow a comparison of such stratigraphies with those obtained from the EPICA-Dome C and Taylor Dome ice cores (Bianchi et al, 2003;Frezzotti et al, 2004;Urbini et al, 2006). TALDICE drilling (2005)(2006)(2007)(2008) reached the depth of 1650 m, covering the last 250 kyear Veres et al, 2013). The TALDICE ice core revealed that the Talos Dome site is very sensitive to the climatic variations occurring at regional-to-global scale over the last climate cycle .…”

Iron Fertilization of the Subantarctic Ocean During the Last Ice Age

“…The high-resolution XRF Fe concentration records from ODP Site 1090 and TN57-06 were used to align the two cores using the software Analyseries (46). The good correlation of the two records after the alignment allows us to directly compare the measurements performed in the two cores with minimal stratigraphic uncertainty ( The age model of our record was generated by graphic correlation of the highresolution 230 Th-normalized Fe flux from ODP Site 1090 to the most recent ice core dust reconstruction from EPICA Dome C (44), using ice core chronology (AICC2012) (47,48) (Fig. S2).…”

“…S1a). This indicates that the 230 Th measurements performed in can be used to reconstruct sedimentary fluxes of different elements and/or organic compounds in both records.For example, in Figure S1c, the high-resolution 230 Th-normalized mass flux (Fig.S1b) was used to calculate iron fluxes both in ODP Site 1090 and TN057-6 ( The age model of our record was generated by graphic correlation of the highresolution 230 Th-normalized Fe flux from ODP Site 1090 to the most recent ice core dust reconstruction from EPICA Dome C (44), using ice core chronology (AICC2012) (47,48) (Fig. S2).…”

Differences between the last two glacial maxima and implications for ice-sheet, δ18O, and sea-level reconstructions

“…For this analysis, we performed Monte-Carlo-style probabilistic assessments (n ¼ 10,000 simulations) based on the uncertainties associated with the various records. For CO 2 , CH 4 , and Antarctic temperature records (Monnin et al, 2001(Monnin et al, , 2004Loulergue et al, 2008;Lourantou et al, 2010;Stenni et al, 2010;Schmitt et al, 2012;Schneider et al, 2013;Landais et al, 2013;Parrenin et al, 2013;Ahn and Brook, 2014), we account for uncertainties associated with chronology (AICC 2012, Veres et al, 2013;Bazin et al, 2013) and proxy measurement in each record to determine the 68% (16 th e84th percentile) and 95% (2.5 th e97.5th percentile) probability intervals, the median (50 th percentile), and the probability maximum (modal value) with its 95% probability interval (e.g., Grant et al, 2012;Rohling et al, 2014;Marino et al, 2015). We probabilistically calculate greenhouse gas (GHG) components of Earth's radiative balance (DF CO2 , DF CH4 , and DF GHG ) from ice-core time series of CO 2 and/or CH 4 , referencing radiative forcing estimates to the values at AD1000 (cf.…”