During the Jurassic, abrupt global warming of between 9 and 18 Fahrenheit (5 and 10 degrees Celsius) was associated with severe environmental change. Many organisms went extinct and the global carbon cycle was thrown off balance. One of the most intriguing effects was that the oxygen content of the oceans became drastically reduced, and this caused many marine species to die off.
These intervals of reduced oxygen content in the oceans are now known as oceanic anoxic events, or OAEs. OAEs are associated with periods of global warming and have occurred a few times in Earth's history. In the recent study, researchers focused specifically on the Toarcian OAE, a well-documented OAE from the early Jurassic.
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By studying organic-rich marine deposits from the Toarcian OAE, the Open University researchers were able to compare the oxygen levels of ancient seawater to the oceans of today. The sedimentary rocks contain molybdenum, whose isotopic composition is altered depending on how oxygenated the seawater was when the sediments formed. By studying how the isotopic composition of molybdenum changed during the Toarcian OAE, scientists have developed a unique way to trace fluctuations in the oxygen content of Earth's oceans.
The Open University team determined that major disruptions in the global carbon cycle during the Jurassic period were intimately linked with the development of anoxic oceans and with global warming. Ultimately, this ties global warming to the demise of numerous life forms on Earth millions of years ago. Additionally, the research is providing insight into how the Earth's oceans and atmosphere evolved over time.
Anyone have the paper? Not that I have a lot of time to read it, but...
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