Even The Currents in The Ocean's Depths Can't Escape The Effects of Climate Change

We know that global warming affects ocean currents in a variety of ways, but questions remain about exactly how this relationship works. A new study attempts to answer some of those questions.

Scientists pored over data stretching back 66 million years over 293 sites, looking at gaps in sedimentary layers, known as hiatuses, to figure out the varying strength of ocean currents across the millennia and how this relates to temperature changes.

Doing so provided a wealth of extra data beyond the 30 years or so of satellite imagery that researchers traditionally used to look at how ocean current activity changes as the temperature of the globe keeps on rising.

"The satellite data typically used to inform ocean models only cover a few decades, leading to a poor understanding of longer-term ocean variability," says sedimentologist Adriana Dutkiewicz from the University of Sydney in Australia.

"This prompted us to look at the deep-sea geological record to decipher these changes."

The team found that over the last 13 million years, as the Earth has gradually cooled down, the hiatuses in the sediment record became less frequent. That suggests current speed in the deepest parts of the ocean has slowed down overall.

In comparison, in the 'hothouse climate' period that preceded the 13-million-year cooling-off era, deep ocean circulation appeared to be much busier. At this time global temperatures would have been 3-4°C (5.4-7.2°F) warmer than they are today.

You don't have to live on the sea bed to be affected by fluctuations in ocean currents: These deep whirlings have an influence on everything, from major weather patterns to the distribution of marine life.

"A break in sedimentation indicates vigorous deep-sea currents, while continuous sediment accumulation indicates calmer conditions," says geophysicist Dietmar Müller from the University of Sydney.


We know that global warming affects ocean currents in a variety of ways, but questions remain about exactly how this relationship works. A new study attempts to answer some of those questions.