Constraint of the CO₂ rise by new atmospheric carbon isotopic measurements during the last deglaciation

Abstract

[1] The causes of the ∼80 ppmv increase of atmospheric carbon dioxide (CO 2 ) during the last glacial-interglacial climatic transition remain debated. We analyzed the parallel evolution of CO 2 and its stable carbon isotopic ratio (d 13 CO 2 ) in the European Project for Ice Coring in Antarctica (EPICA) Dome C ice core to bring additional constraints. Agreeing well but largely improving the Taylor Dome ice core record of lower resolution, our d 13 CO 2 record is characterized by a W shape, with two negative d 13 CO 2 excursions of 0.5‰ during Heinrich 1 and Younger Dryas events, bracketing a positive d 13 CO 2 peak during the Bølling/Allerød warm period. The comparison with marine records and the outputs of two C cycle box models suggest that changes in Southern Ocean ventilation drove most of the CO 2 increase, with additional contributions from marine productivity changes on the initial CO 2 rise and d 13 CO 2 decline and from rapid vegetation buildup during the CO 2 plateau of the Bølling/Allerød.

Climate warming and vegetation response after Heinrich event 1 (16 700–16 000 cal yr BP) in Europe south of the Alps

“…This suggests that in the warmest areas of northern Italy temperatures never fell significantly below 10 • C during the summers of the LGM, since July air temperatures below 10 • C usually limit tree and forest growth (Lang, 1994). According to the Origlio record (Tinner et al, 1999), deglaciation in the southern Alpine foreland had started significantly before ∼ 18 000 cal yr BP, in line with increasing Northern Hemisphere summer insolation (Berger and Loutre, 1991) and increasing atmospheric CO 2 concentrations (Smith et al, 1999;Lourantou et al, 2010) (Fig. 6).…”

“…However, a chronologically poorly constrained, though characteristic expansion of Betula nana, evidenced both by pollen and macrofossils, occurred at many sites north of the Alps prior to the Bølling-Allerød interstadial. This dwarf birch phase has been attributed either to pedogenesis or to an increase in summer temperatures (Ammann and Tobolski, 1983;Gaillard, 1985), but has also been interpreted as the result of increasing atmospheric CO 2 concentrations that started rising between ∼ 17 000 and ∼ 16 500 cal yr BP (Lourantou et al, 2010). On the basis of the available dates (some on terrestrial macrofossils) the expansion of the dwarf birch tundra has been dated to ∼ 17 500-15 000 cal yr BP (Welten, 1982;Ammann and Lotter, 1989).…”

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

“…Studies where discrepancies have been found between the expected and measured values when using BFI for extraction tests [Leuenberger et al, 1992;Lourantou et al, 2010] should consider the possibility that the BFI used may actually contain trace amounts of the gas being measured. [133] Although the CSIRO BFI ice performed best for CO 2 and ı 13 C of the BFIs used here, we still consider possible that a very small amount of gas is trapped in it.…”

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.…”