Deep Ocean Study Yields Climate Clues

Deep Ocean Study Yields Climate Clues

NEW BRUNSWICK, N.J. – Scientists from The Australian National University and Rutgers University have created the first continuous deep ocean temperature record for the last 3.2 million years, shedding new light on the nature of Earth’s past ice ages.

Yair Rosenthal
Yair Rosenthal, professor of marine science

The researchers, Yair Rosenthal of Rutgers University and Sindia Sosdian of The Australian National University, used fossil shells extracted from the deep ocean floor to construct the climate record. Their research is published in the most recent issue of Science. The research is part of Sosdian’s doctoral thesis in collaboration with Rosenthal, her PhD. advisor.

Their study highlights the role of both greenhouse gases and the dynamics of ice sheets in earth’s climate history and suggests that to predict and mitigate future climate change, scientists need to look closely at how ice sheets change in addition to greenhouse gases.

“Our study looked at changes in past climate before modern observations,” said Sosdian. “Over the last 3.2 million years, cyclic ice ages developed in the northern hemisphere. Around 0.9 million years ago, the cycles of ice ages grew longer and more intense. Our study looked at changes in the temperature of the deep ocean and sea level to shed light on the cause of these past changes in ice ages.”

benthic foram
A benthic foram fossil shell of the type used by Rosenthal and Sosdian to establish a deep ocean temperature record going back 3.2 million years.

“Scientists used to argue about whether those transitional enhancements were associated with major cooling, and if so why, and before you had a temperature record you couldn’t actually tell,” Rosenthal said. “We know now that each of these transitions is associated with a potential cooling of the planet.”

The researchers found a cooling of ~3° Celsius in the deep Atlantic Ocean across the last 3.2 million years that occurs along with the development and the change in intensity of ice ages.

Sindia Sosdian
Sindia Sosdian, post-doctoral scholar at The Australian National University

“The paleoclimate evidence also supports the idea that a reduction in the amount of greenhouse gases initiated ice ages in the northern hemisphere around 2.7 million years ago, and that the way ice sheets grew in North America played a role in the change in intensity of ice ages, around 0.9 million years ago,” said Sosdian.

The findings mean that climate scientists will be able to more accurately predict the likely effects of future climate change.

“The study presents a new view of the last 3.2 million years of climate change. Scientists in the climate community can use this temperature and sea level record to reinterpret the reason for shifts in Earth’s climate. These new observations give us a better understanding of the sensitivity of Earth’s climate to changes in greenhouse gases and northern hemisphere ice sheets, which aren’t easily understood from climate models solely,” said Sosdian.

Media Contact: Ken Branson
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