Antarctic temperature and CO 2 : near-synchrony yet variable phasing during the last deglaciation

Jai Chowdhry Beeman , Léa Gest (1) , Frédéric Parrenin (1) , Dominique Raynaud (2) , Tyler A Fudge (3) , Christo Buizert (4) , Edward A Brook (4)

1 IGE - Institut des Géosciences de l’Environnement
2 GEMAS - Groupe d'étude des méthodes de l'analyse sociologique
3 University of Washington [Seattle]
4 CEOAS - College of Earth, Ocean and Atmospheric Sciences [Corvallis]

The last deglaciation, which occurred from 18 000 to 11 000 years ago, is the most recent large natural climatic variation of global extent. With accurately dated paleocli-mate records, we can investigate the timings of related variables in the climate system during this major transition. Here, we use an accurate relative chronology to compare temperature proxy data and global atmospheric CO 2 as recorded in Antarctic ice cores. In addition to five regional records, we compare a δ 18 O stack, representing Antarctic climate variations with the high-resolution robustly dated WAIS Divide CO 2 record (West Antarctic Ice Sheet). We assess the CO 2 and Antarctic temperature phase relationship using a stochas-tic method to accurately identify the probable timings of changes in their trends. Four coherent changes are identified for the two series, and synchrony between CO 2 and temperature is within the 95 % uncertainty range for all of the changes except the end of glacial termination 1 (T1). During the onset of the last deglaciation at 18 ka and the deglacia-tion end at 11.5 ka, Antarctic temperature most likely led CO 2 by several centuries (by 570 years, within a range of 127 to 751 years, 68 % probability, at the T1 onset; and by 532 years, within a range of 337 to 629 years, 68 % probability , at the deglaciation end). At 14.4 ka, the onset of the Antarctic Cold Reversal (ACR) period, our results do not show a clear lead or lag (Antarctic temperature leads by 50 years, within a range of −137 to 376 years, 68 % probability). The same is true at the end of the ACR (CO 2 leads by 65 years, within a range of 211 to 117 years, 68 % probability). However, the timings of changes in trends for the individual proxy records show variations from the stack, indicating regional differences in the pattern of temperature change, particularly in the WAIS Divide record at the onset of the deglaciation; the Dome Fuji record at the deglaciation end; and the EDML record after 16 ka (EPICA Dronning Maud Land, where EPICA is the European Project for Ice Coring in Antarctica). In addition, two changes-one at 16 ka in the CO 2 record and one after the ACR onset in three of the isotopic temperature records-do not have high-probability counterparts in the other record. The likely-variable phasing we identify testify to the complex nature of the mechanisms driving the carbon cycle and Antarctic temperature during the deglaciation.

Domaines: Glaciologie; Climatologie

Jai Chowdhry Beeman, Léa Gest, Frédéric Parrenin, Dominique Raynaud, Tyler A Fudge, et al.. Antarctic temperature and CO 2 : near-synchrony yet variable phasing during the last deglaciation. Climate of the Past, 2019, 15 (3), pp.913-926. ⟨10.5194/cp-15-913-2019⟩. ⟨hal-02395942⟩