Earth + warming = speedier ocean

Sixty-six million years of geological data suggests heating makes ocean currents stronger.

Ocean currents play a big role in floods, droughts, and other large-scale weather patterns. They’re notoriously complicated and there’s debate among researchers about how to untangle conflicting sources of information.

Satellite data seems to suggest that ocean currents are, on average, becoming more intense. But satellite data only stretches back about 30 years – so it’s hard to be conclusive.

Now those findings have been backed up by several million more years of data, thanks to researchers at the University of Sydney – and some rocks.

“If we think of the long-term evolution of the Earth, either in the past or into the future, then three decades is not a lot,” says Dr Adriana Dutkiewicz, geologist at the University of Sydney.

Dutkiewicz, along with colleague Professor Dietmar Müller, went to geological records taken from deep-sea scientific drilling programs, and looked for this longer-term behaviour.

In Geology, they examine the gaps, or “hiatuses”, in these geological records. If there are more hiatuses, then there are likely some more vigorous deepocean currents causing them.

The researchers examined hiatuses from records at 293 global sites. With data stretching back 66 million years, they found an unexpected pattern.

“There were less and less and less hiatuses through time, as the world descended into a more severe ice age over the course of the last 13 million years,” Müller says. “Our results, that happen to be consistent with the results from the satellite data over the last few decades […], suggest that ocean mixing will become more vigorous.”

The ocean absorbs much anthropogenic CO2 and heat, so it’s likely that this speeding up will have multiple effects.