A hyperthermal warming event that was recorded in Earth's past 300,000 years ago caused global changes in that period of geological history. This happened when carbon dioxide levels rose more than oxygen making oceans anoxic, killing marine and land fauna and flora. The most notable is the fast rise of global warming quickly ended the ice age.
Climate Change Is Deadly
Isabel Montañez, who specializes in Earth and Planetary Sciences at California University, called in the fastest period of increasing global warming recorded so far, reported Phys Org.
There have been more fast warming occurrences in the world's history, the first identified in an icehouse Earth when the entire planet had ice caps and glaciers equivalent to today.
It demonstrates that an icehouse climate may be more sensitive to changes in atmospheric carbon dioxide than warmer conditions with elevated Co2 levels, cited in Science Daily.
Montañez's lab examines samples dating from 300 million to 260 million years ago, when the Earth's temperature shifted from a glacial icehouse to a hot, ice-free greenhouse. The study suggests in 2007 that it shifted from hot to cold several times during the epoch.
Due to a hyperthermal warming event, researchers discovered the shift about 304 million years ago, called the Kasimovian-Gzhelian boundary or KGB. To estimate atmospheric CO2 at the time, scientists used multiple proxies, including carbon isotopes and trace elements from rocks and plant fossils, and modeled in the Earth's past 300,000-years-ago, noted EurekAlert.
Researchers think 9000 gigatons of carbon were discharged into the air shortly before the K-G border. It increased atmospheric CO2 levels by around 350 parts per million (ppm), which is equivalent to modern pre-industrial levels, at about 700 ppm.
An Oxygen-Less Ocean
Marine anoxia, or a decline in dissolved oxygen in the water, is a consequence of global warming. Melting ice caps release freshwater onto the ocean surface, impeding deep-sea movement and reducing oxygen availability. If there is oxygen in the sea, aquatic life perishes.
The absence of oxygen is indicated in uranium isotopes absorbed into rocks occurring at the ocean's bottom. The scientists were able to get a proxy for the amount of oxygen or lack thereof in the ocean when those rocks were put down by analyzing uranium elements in carbonate rocks in present-day China.
They speculate that 23 percent of seafloors had no oxygen, which matched the extinction of animals on land and sea simultaneously.
The concentration of carbon release on ocean anoxia is significantly greater than that seen in other studies of rapid warming during 'greenhouse' conditions.
Montañez remarked the increase in carbon dioxide with the same amount released in a heated climate is not much. But the presence of frozen areas makes it more delicate to a shift like in marine anoxia.
One source of carbon on a large scale will be the volcanic activity that affected the Carboniferous coal beds. Eruptions caused fires that melted permafrost, leading to an increased release of organic carbon.
The study concludes that the hyperthermal warming event changed the Earth's past 300,000-years-ago in terms of its climate, causing less oxygen in the ancient sea.
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