New research describes a period of rapid global climate change that is currently covered by ice – but 304 million years ago. Over the course of some 300,000 years, the carbon dioxide level in the atmosphere doubled, the oceans became more toxic, and the earth’s ecosystems plummeted.
It was one of the fastest growing events in the history of the Earth, “said Isabel Montañez, a senior professor in the Department of Earth and Planetary Science at the University of California, Davis.
Although some ‘hyperthermal’ or rapid warming events are known in the history of the earth, this is the first to be identified in icehouse Earth, where the planet has layers of ice and glaciers, compared to today. It shows that the icehouse Climate may be more sensitive to changes in atmospheric carbon dioxide than warmer climates, where CO2 levels are already higher. This work was published this week (May 2) in the Proceedings of the National Academy of Sciences.
Montañez Lab has studied between 300 million and 260 million years ago, when the Earth’s climate shifted from freezing to tropical. In 2007, they showed that the weather changed several times during that time.
More recently, Montañez ‘team and others were able to return home to the revolution 304 million years ago, across the Kasimovian-Gzhelian border or the KGB. They used multiple proxies, including carbon isotopes and trace elements from rocks and plant debris, as well as modeling to estimate atmospheric CO2 at that time.
Researchers estimate that about 9000 Gigatons of carbon was released into the atmosphere just before the KG border.
“We don’t have a standard, but it was one of the fastest in the history of the Earth,” Montañez said. That double the atmospheric CO2 from about 350 parts per million, compared to modern pre-industrial levels, to about 700 ppm.
Deep seas
One of the effects of global warming is marine anoxia, or depletion of the oceans. Soluble ice sheets release fresh water into the oceans, creating a barrier to deep water circulation and preventing oxygen supply. Without oxygen, marine life is dying.
Oxygen deprivation leaves its mark on uranium isotopes embedded in rocks that form in the ocean floor. By measuring uranium isotopes in the carbonate rocks of modern China, researchers can find a representative of the amount of oxygen – or its lack – in the ocean when those rocks are laid.
They estimate that about 23 percent of the world’s oceans become dead toxic. That is in line with other studies showing the massive loss of biodiversity at the same time and in the oceans.
The impact of carbon emissions on ocean anoxia was much greater than that observed in other studies of rapid warming during ‘greenhouse’ conditions. That may be because the basic CO2 level in the atmosphere was very high.
“If you increase CO2 by the same amount in the greenhouse world, there is not much impact, but ice houses seem very sensitive to change and marine anoxia,” Montañez said.
Excess carbon emissions may have been caused by volcanic eruptions that ripped through carboniferous coal beds, Montañez said. The explosion would also start fires, and the heat could dissolve the permafrost, leading to the release of additional living carbon.
Source Journal Reference: Jitao Chen, Isabel P. Montañez, Shuang Zhang, Terry T. Isson, Sophia I. Macarewich, Noah J. Planavsky, Feifei Zhang, Sofia Rauzi, Kierstin Daviau, Le Yao, Yu-ping Qi, Yue Wang, Jun-xuan Fan, Christopher J. Poulsen, Ariel D. Anbar, Shu-zhong Shen, Xiang-dong Wang. Marine anoxia linked to abrupt global warming during Earth’s penultimate icehouse. Proceedings of the National Academy of Sciences, 2022; 119 (19) DOI: 10.1073/pnas.2115231119
