A new study describes a period of rapid global climate change in an ice-capped world 304 million years ago. In about 300,000 years, atmospheric carbon dioxide levels doubled, oceans became anoxic, and biodiversity dropped on land and at sea.
It was one of the fastest warming events in the history of the planet.
The first identified rapid warming event in an icehouse Earth, when the planet had ice caps and glaciers, is similar to the present day. The icehouse climate may be more sensitive to changes in atmospheric carbon dioxide than warmer conditions. The work is published in a journal.
The lab studied the period from 300 million to 260 million years ago, when the climate went from a glacier to a hot, ice-free greenhouse. They showed that the climate swung back and forth several times.
The team and others have been able to home in on a transition 304 million years ago. They used multiple proxies, including carbon isotopes and trace elements from rocks and plant fossils, and modeling to estimate atmospheric CO 2 at the time.
The researchers estimate that 9000 tons of carbon were released into the atmosphere before the K-G boundary.
It was one of the fastest in Earth's history, but we don't have a rate. It doubled atmospheric CO 2 from 350 parts per million to 700 parts per million.
There are deep ocean dead zones.
A drop in dissolved oxygen in the ocean is a consequence of global warming. A barrier to deep water circulation and cutting off the supply of oxygen can be created by melting ice caps. Without oxygen, marine life dies.
Lack of oxygen leaves a mark on the rocks at the bottom of the ocean. The researchers could get a proxy for the amount of oxygen in the ocean when the carbonate rocks were laid down.
They estimate that about 23 percent of the seafloor worldwide became anoxic dead zones. That is in line with other studies that show big losses in biodiversity on land and at sea at the same time.
The effect of carbon release on ocean anoxia was more pronounced than other studies. The baseline level of atmospheric CO 2 was already higher.
If you raised CO 2 by the same amount in a greenhouse world, there isn't much affect, but icehouses seem to be more sensitive to change.
The volcanic eruptions that tore through the carboniferous coal beds may have triggered the massive carbon release. Warming may have caused the release of more organic carbon, and the eruptions may have started fires.
Montañez is a co-corresponding author on the paper with Jitao Chen, who was a researcher at UC Davis and now works at the Nanjing Institute of Geology and Palaeontology, China.
More information: Marine anoxia linked to abrupt global warming during Earth's penultimate icehouse, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2115231119 Journal information: Proceedings of the National Academy of Sciences Citation: Carbon, climate change and ocean anoxia in an ancient icehouse world (2022, May 2) retrieved 2 May 2022 from https://phys.org/news/2022-05-carbon-climate-ocean-anoxia-ancient.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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