Asynchrony between Antarctic temperature and CO2 associated with obliquity over the past 720,000 years

Ryu Uemura,Shinichiro Horikawa,Valérie Masson-Delmotte,Shuji Fujita,Kenji Kawamura,Keisuke Suzuki,Makoto Igarashi,Ayako Abe-Ouchi,Takayuki Kuramoto,Jean Jouzel,Yoshinori Iizuka,Hiroshi Ohno,Kumiko Goto-Azuma,Yoshiyuki Fujii,Hideaki Motoyama,Koji Fujita,Takayuki Miyake,Toshitaka Suzuki,Motohiro Hirabayashi

doi:10.1038/s41467-018-03328-3

Abstract

The δD temperature proxy in Antarctic ice cores varies in parallel with CO2 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 CO2 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, CO2 and insolation in the obliquity frequency band.

Highlights

The δD temperature proxy in Antarctic ice cores varies in parallel with CO2 through glacial cycles
The latitudinal temperature differences between Antarctica and the surrounding ocean may arise from annual mean insolation (AMI) variations because the amplitude of AMI variations is largest in the polar regions and smallest in the mid-latitude regions[12,13,14,15,16]
The new DF2 data were combined with earlier data from the first Dome Fuji core (DF121,22) and were plotted on the AICC2012 time scale[23]

Summary

Introduction

The δD temperature proxy in Antarctic ice cores varies in parallel with CO2 through glacial cycles. A strong 41-kyr cycle that is likely related to the local AMI variations was recognized in the Antarctic temperature record obtained from the Vostok ice core in the 1980s15. Uncertainties in the age models of the ice cores and ocean sediments limit our understanding of the potentially different time lags between Antarctic and Southern Ocean temperatures relative to AMI changes. Well-dated surface temperature records with high temporal resolution from the Southern Ocean provide crucial information In addition to these climatic mechanisms, the validity of δD as a temperature proxy should be considered. After correcting the δD variations for this moisture source effect, the ΔTsite record shows a stronger correlation with CO2 over the past 350 kyr[18], suggesting a potential bias in the use of δD as a temperature proxy

Methods

Results

Conclusion