Deep below the ocean’s surface, turbulent swirls of water – invisible to the naked eye and no bigger than a coin – are driving some of the most consequential forces in our climate system; and they are doing so far faster than science previously understood.
A new study, published in the journal Nature Communications and involving scientists from UC San Diego’s Scripps Institution of Oceanography and the University of Cambridge, has found that deep ocean turbulence – the process by which heat, nutrients and carbon are distributed between the ocean’s surface and the seafloor – affects human life not on the timescale of thousands of years, as was previously thought, but within the span of a single human lifetime.
The climate models used to predict these effects and inform policy, the researchers found, do not adequately capture this turbulence or the speed at which it operates.
The implications are wide-ranging. If deep-ocean turbulence is not pulling nutrients to the surface at the rate models assume, marine food chains could break down and fisheries could collapse. The way heat moves between deep and shallow waters affects how Arctic and Antarctic ice melts – and therefore how fast sea levels rise, how intense storms become, and how severe flooding events are. How much carbon dioxide the ocean absorbs from the atmosphere – one of the primary mechanisms keeping climate change in check – is also shaped by the behaviour of these microscopic underwater movements.
“The community is increasingly recognising the role of ocean mixing and turbulence on many scales,” said Matthew Alford, a physical oceanographer at Scripps and co-author of the study.
To test the accuracy of current climate models, the researchers used chlorofluorocarbon – CFC – concentrations as a tracer. CFCs were released into the atmosphere in large quantities before being banned under the Montreal Protocol in the 1980s due to the damage they caused to the ozone layer. By measuring how far and how fast CFCs have travelled through the deep ocean over the past six decades, the team was able to track the movement of deep water masses with unusual precision.
