Estimation of temperature change and of gas age-ice age difference, 108 kyr B.P., at Vostok, Antarctica

• Published in: Journal of Geophysical Research: Atmospheres
• Main Authors: Caillon, N., Severinghaus, J., Barnola, J.-M., Chappellaz, J., Jouzel, J., Parrenin, F.
• Other Authors: Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA))
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2001
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Antarc*; Antarctic; Antarctica; ice core
• Online Access: https://hal.science/hal-03110137; https://hal.science/hal-03110137/document; https://hal.science/hal-03110137/file/2001JD900145.pdf; https://doi.org/10.1029/2001JD900145

International audience Air trapped in ice core bubbles provides our primary source of information about past atmospheres. Air isotopic composition (lSN/•4N and 4øAr/3•Ar) permits an estimate of the temperature shifts associated with abrupt climate changes because of isotope fractionation occurring in response to temperature gradients in the snow layer on top of polar ice sheets. A rapid surface temperature change modifies temporarily the firn temperature gradient, which causes a detectable anomaly in the isotopic composition of nitrogen and argon. The location of this anomaly in depth characterizes the gas age-ice age difference (Aage) during an abrupt event by correlation with the fid (or 15•80) anomaly in the ice. We focus this study on the marine isotope stage 5d/5c transition (108 kyr B.P.), a climate warming which was one of the most abrupt events in the Vostok (Antarctica) ice isotopic record [Petit et al., 1999]. A steplike decrease in 15•SN and •54øAr/4 froin 0.49 to 0.47 %0 (possibly a gravitational signal due to a change in firn thickness) is preceded by a small but detectable 15•SN peak (possibly a thermal diffusion signal). We obtain an estimate of 5350 + 300 yr for Aage, close to the model estimate of 5000 years obtained using the Vostok glaciological timescale. Our results also suggest that the use of the present-day spatial isotope-temperature relationship slightly underestimates (but by no more than 20 + 15%) the Vostok temperature change from present day at that time, which is in contrast to the temperature estimate based on borehole temperature measurements in Vostok which suggests that Antarctic temperature changes are underestimated by up to 50% [Salamatin et al., 1998].