Atmospheric CO ₂ Concentrations over the Last Glacial Termination

Abstract

A record of atmospheric carbon dioxide (CO2) concentration during the transition from the Last Glacial Maximum to the Holocene, obtained from the Dome Concordia, Antarctica, ice core, reveals that an increase of 76 parts per million by volume occurred over a period of 6000 years in four clearly distinguishable intervals. The close correlation between CO2 concentration and Antarctic temperature indicates that the Southern Ocean played an important role in causing the CO2 increase. However, the similarity of changes in CO2 concentration and variations of atmospheric methane concentration suggests that processes in the tropics and in the Northern Hemisphere, where the main sources for methane are located, also had substantial effects on atmospheric CO2 concentrations.

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

“…Ice-sheet nucleation may, in addition, depend on chaotic aspects of the weather/climate system; for example, successive winters with heavy snowfall may e almost randomly e cause some locations to receive an initial snow cover with enough volume and albedo feedback to ensure its survival and subsequent growth potential (e.g., Oglesby, 1990). Finally, modelling studies (e.g., Abe-Ouchi et al, 2013) indicate that glacial culminations like the PGM and LGM reflect the outcome of temporal developments in forcings and feedbacks through the preceding glacial cycle that include insolation (e.g., Laskar et al, 2004;Colleoni et al, 2011), CO 2 and CH 4 concentrations (Monnin et al, 2001;Loulergue et al, 2008; Waelbroeck et al, 2002;Rohling et al, 2009Rohling et al, , 2014Elderfield et al, 2012;Grant et al, 2014), and also in state variables such as surface and deep-sea temperature (e.g., Stenni et al, 2010;Elderfield et al, 2012;Parrenin et al, 2013;Rohling et al, 2012Rohling et al, , 2014Martínez-Botí et al, 2015;Snyder, 2016a,b). Climate simulations by Colleoni et al (2014) suggest that orbital and greenhouse-gas changes for the penultimate glacial cycle were more favourable for glacial inception over Eurasia than over North America, relative to the last glacial cycle.…”

“…This probabilistic analysis accounts for (i) chronological and measurement uncertainties for CO 2 (Monnin et al, 2001(Monnin et al, , 2004Schmitt et al, 2012;Schneider et al, 2013;Landais et al, 2013;Ahn and Brook, 2014) and/or CH 4 time series (Loulergue et al, 2008), and (ii) uncertainties associated with conversion of CO 2 and/or CH 4 to DF CO2 , DF CH4 , and DF GHG . Input data for the Monte Carlo routines are the ice-core 'gas ages' with uncertainties of the AICC2012 chronology Bazin et al, 2013) and CO 2 and/or CH 4 data with analytical uncertainties (Monnin et al, 2001(Monnin et al, , 2004Loulergue et al, 2008;Schmitt et al, 2012;Schneider et al, 2013;Landais et al, 2013;Ahn and Brook, 2014). Each data point was separately and randomly sampled n times within its uncertainties and converted to DF values, using the equations of K€ ohler et al…”

“…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.…”

The Global Carbon Cycle During the Last Glacial/Interglacial Transition

“…Further insight into changes in the carbon cycle can be expected from temporally better resolved and (Köhler and Fischer, 2004) (Smith et al, 1999, Monnin et al, 2001 …”

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“…The latter point appears crucial considering that current CO 2 concentrations have taken us out of the Quaternary range, putting us in a new era, the Anthropocene. Monnin et al, 2001;Flückiger et al, 2002) Research on the last 1-2 ka has resulted in several multi-proxy reconstructions of global and hemispheric temperature, and other climatic parameters (e.g., Rutherford et al, 2005;Mann et al, 2006;Luterbacher et al, 2004). Despite this, we still do not sufficiently understand the precise sequence of changes related to regional climate forcings, internal variability, system feedbacks, and the responses of surface climate, land-cover, biosphere and hydrosphere.…”