Asynchrony between Antarctic temperature and CO$_2$ associated with obliquity over the past 720,000 years

Ryu Uemura (1) , Hideaki Motoyama (2) , Valérie Masson-Delmotte (3, 4) , Jean Jouzel (3, 4) , Kenji Kawamura (2) , Kumiko Goto-Azuma (2) , Shuji Fujita (5, 2) , Takayuki Kuramoto , Motohiro Hirabayashi (2) , Takayuki Miyake , Hiroshi Ohno , Koji Fujita (6) , Ayako Abe-Ouchi (7) , Yoshinori Iizuka (8) , Shinichiro Horikawa (8) , Makoto Igarashi , Keisuke Suzuki (9) , Toshitaka Suzuki (10) , Yoshiyuki Fujii (2)

1 University of the Ryukyus [Okinawa]
2 NiPR - National Institute of Polar Research [Tokyo]
3 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
4 GLACCIOS - Glaces et Continents, Climats et Isotopes Stables
5 SOKENDAI - The Graduate University for Advanced Studies, japan
6 Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
7 CCSR - Center for Climate System Research [Kashiwa]
8 Institute of Low Temperature Science [Sapporo]
9 Shinshu University [Nagano]
10 Graduate School of Science and Engineering [Yamagata]

The δD temperature proxy in Antarctic ice cores varies in parallel with CO$_2$ through glacial cycles. However, these variables display a puzzling asynchrony. Well-dated records of Southern Ocean temperature will provide crucial information because the Southern Ocean is likely key in regulating CO$_2$ variations. Here, we perform multiple isotopic analyses on an Antarctic ice core and estimate temperature variations at this site and in the oceanic moisture source over the past 720,000 years, which extend the longest records by 300,000 years. Antarctic temperature is affected by large variations in local insolation that are induced by obliquity. At the obliquity periodicity, the Antarctic and ocean temperatures lag annual mean insolation. Further, the magnitude of the phase lag is minimal during low eccentricity periods, suggesting that secular changes in the global carbon cycle and the ocean circulation modulate the phase relationship among temperatures, CO$_2$ and insolation in the obliquity frequency band.

Domains: Environmental Sciences; Global Changes

Ryu Uemura, Hideaki Motoyama, Valérie Masson-Delmotte, Jean Jouzel, Kenji Kawamura, et al.. Asynchrony between Antarctic temperature and CO$_2$ associated with obliquity over the past 720,000 years. Nature Communications, 2018, 9, pp.961. ⟨10.1038/s41467-018-03328-3⟩. ⟨cea-01875223⟩