Polar fossil study raises climate change questions
Global temperatures during the time of the dinosaurs, thought to have been much higher than now, were punctuated by sudden drops in temperature that ask new questions about how we measure and predict climate change.
A team led by the University of Plymouth studied fossils in the area round Svalbard, inside the Arctic Circle in Norway and found evidence of a plunge in average temperatures of up to 9C around 137 million years ago.
At the time, during the Cretaceous Period, the climate was hotter and wetter than it is now, with the now icy Svalbard region home to numerous species of dinosaur and typically characterised by warm, shallow seas and swamps.
The findings, have been published in the journal Geology and featured as a highlight in Nature Geoscience, will further contribute to the debate over climate change as they appear to contradict the common model which links high levels of Carbon Dioxide (CO2) – as recorded in the Cretaceous era – with reduced polar ice caps.
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Dr Gregory Price of the University of Plymouth, led the expedition.
He said: "At certain times in the geological past, the world has been dominated by greenhouse conditions with elevated CO2 levels and warm Polar regions, and hence, these are seen as analogues of future global climate.
"But this research suggests that for short periods of time the Earth plunged back to colder temperatures, which not only poses interesting questions in terms of how the dinosaurs might have coped, but also over the nature of climate change itself."
The research team found evidence in fossils and carbonate materials, preserved in marine rocks in the region, of a transient shift to cooler glacial conditions around 137 million years ago.
Dr Price, along with Dr Elizabeth Nunn, of Johannes Gutenburg Universitat in Mainz, Germany, first visited the Svalbard area in 2005 to collect fossils and samples, in an area famed for a number of paleontological discoveries, including giant marine reptiles such as pliosaurs and icthyosaurs.
The cretaceous period, which ended with the infamous extinction of the dinosaurs around 65 million years ago, is a period widely known for high sea levels and temperatures, with the oceans and the land full of now-extinct dinosaurs as well as early mammals.
The samples were analysed back in Plymouth and prompted return trips to the area to gather more evidence. "
The flourishing of the dinosaurs and a range of other data indicates that the Cretaceous period was considerably warmer and boasted a high degree of CO2 in the atmosphere," said Dr Price.
"But over a period of a few hundred or a few thousand years, ocean temperatures fell from an average of 13C (55F) to between 8C (46F) and 4C (39F).
"Although a short episode of cool polar conditions is potentially at odds with a high CO2 world, our data demonstrates the variability of climate over long timescales."