Ancient Ice Sheet Collapse Triggered Strong Climate Change

With climate change already impacting various parts of the world, scientists have started looking into Earth's past in order to better predict how it will affect our future. To add to growing evidence, a new study has found that ice sheet collapse 135 million years ago triggered events of strong global climate change.

The Cretaceous period, 145 to 66 million years ago, was one of the warmest times in Earth's history - though some say it was interrupted with a significant cold snap. During this time, the poles were devoid of ice and average ocean temperatures in the Atlantic reached up to a sweltering 35 degrees Celsius (95 degrees Fahrenheit).

Given these warming temperatures, it's no surprise that during the ice age before last, continental ice sheets started to melt. While that's not groundbreaking in itself, scientists were interested in the fact that these climatic events were surprisingly different to those of the last ice age.

The new findings were published in the journal Nature.

"To our surprise, the sequence of climate events 135,000 years ago looks very different from what happened at the end of the last ice age, about 20,000 to 10,000 years ago," study lead author Dr. Gianluca Marino, of The Australian National University, said in a statement. "Ice-ages may superficially look similar to one another, but there are important differences in the relationships between the melting of continental ice sheets and global climate changes."

"During the major climate warmings ending an ice age, periods of slower change alternated with periods of faster change," he added, "but it was unclear if these alternations were always the same at the end of every ice age."

To find out, the research team used cave records and marine sediments from the Mediterranean region to reconstruct changes in all critical climate parameters over the course of history.

"We have now added a view of the climate changes at the end of another ice age, for comparison, and we found that the patterns were different," said co-author Professor Eelco Rohling, from the University of Southampton.

Researchers found that at the end of the Ice Age, ice melt in the Northern Hemisphere and major climate changes - affecting the ocean and atmosphere, for example - did not occur at the same time.

However, 135 million years ago at the end of the ice age before last, "a rapid collapse of the Northern Hemisphere ice sheets into the North Atlantic Ocean suppressed ocean circulation, and caused global climate impacts," Rohling said.

"The North Atlantic cooled while the Southern Ocean warmed. The latter destabilized Antarctic land ice, causing a continuation of melting that eventually drove sea level rise to several meters above the present," he explained.

These findings help scientists better understand the processes that control Earth's dramatic climate changes at the end of an ice age, which may have important implications for the future.

"Recent studies have shown that Southern Ocean warming linked with human-caused greenhouse effects is driving accelerated melting in Antarctica. The ends of ice ages were different, but we can still use them to learn more about the sensitivity of the massive Antarctic ice sheet to climate change," Marino concluded.

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