The first global “winter” on Earth fell 34 million years ago (Ma), when a warm, ice-free and humid climate gave way to a cooler and drier one. During this transition now known as the Eocene–Oligocene transition (EOT), cooling at high latitudes resulted in rapid growth of ice sheet on Antarctica, which, according to a recent study published in Nature Communications , has enhanced the drying and cooling at Third Pole at the same time.

 

Photo by Agustin Lautaro on Unsplash 

 

According to Prof. AO Hong, lead author of the study from the Institute of Earth Environment, Chinese Academy of Sciences , major Asian aridification and cooling across the EOT can be attributed to the decline of CO2 density in the atmosphere and the rapid ice sheet increase in Antarctica. The team came to this conclusion using magneto-chronological and astro-chronological analysis on samples they collected from the Northeast Third Pole. They found that following the Antarctic glaciation built-up at ~33.8–33.6 Ma, the Third Pole hydroclimate shifted from eccentricity-dominated cycles to oscillations paced by a combination of eccentricity, obliquity, and precession. The long-term trend in their records also confirms previous inferences of Asian aridification and cooling across the EOT. 

 

Dupont-Nivet , co-author of the study from the Universite de Rennes, CNRS pointed out that the high-resolution records they obtained have revealed that the climatic shifts across the Eocene–Oligocene boundary occurred in multiple stages that can be correlated to the initial temperatures drop stage (EOT-1 cooling event) and the following Antarctic glaciation built up stage (Oi-1 glaciation event) in detail.

 

According to the study, terrestrial orbital response transition coincided with a similar transition in the marine benthic δ18O record for global ice volume and deep-sea temperature variations. The dramatic reorganization of the Asian climate system coincident with Oi-1 was thus a response to coeval atmospheric CO2 decline and continental-scale Antarctic glaciation. 

 

AN Zhisheng, corresponding author of the study from the Institute of Earth Environment, Chinese Academy of Sciences says they hope that reviewing the wealth of evidence of Eocene–Oligocene climate change can shed more light on the mechanisms and sensitivities of Cenozoic climate. “It can also help answer questions relating to the dynamics of global change during greenhouse-icehouse climate switching” added professor AN. 

 

The study sends out a daunting message about our future. Ecosystems might adapt and recover from climate changes. However, even a recovery that is “fast” in the geologic sense would take hundreds of thousands of years. 

 

Editor’s note: The study is supported by STEP, a TPE related science project.