The Effect of Turbulence and Underwater Waves on the Ocean's Heat and Carbon Storage

Sunday - May 7 2023, 22:56 UTC - 1 year ago

A new research has revealed an important role of underwater waves and other forms of turbulence in the Atlantic Ocean in the ocean's heat and carbon storage. The results, reported in the journal AGU Advances, show that turbulence in the interior of oceans is more important for the transport of carbon and heat on a global scale than had been previously imagined.

New research has revealed that underwater waves, some towering as high as 500 meters, located deep below the ocean surface, play a crucial role in the ocean’s heat and carbon storage.

A team of international researchers, headed by the University of Cambridge, University of Oxford, and University of California San Diego, have quantified the impact of underwater waves and other forms of turbulence in the Atlantic Ocean. They discovered that current climate models, which inform government policy, fail to accurately reflect the significance of these underwater phenomena.

Most of the heat and carbon emitted by human activity is absorbed by the ocean, but how much it can absorb is dependent on turbulence in the ocean’s interior, as heat and carbon are either pushed deep into the ocean or pulled toward the surface.

While these underwater waves are already well-known, their importance in heat and carbon transport is not fully understood.

The results, reported in the journal AGU Advances, show that turbulence in the interior of oceans is more important for the transport of carbon and heat on a global scale than had been previously imagined.

Ocean circulation carries warm waters from the tropics to the North Atlantic, where they cool, sink, and return southwards in the deep ocean, like a giant conveyer belt. The Atlantic branch of this circulation pattern called the Atlantic Meridional Overturning Circulation (AMOC), plays a key role in regulating global heat and carbon budgets. Ocean circulation redistributes heat to the polar regions, where it melts ice, and carbon to the deep ocean, where it can be stored for thousands of years.

"If you were to take a picture of the ocean interior, you would see a lot of complex dynamics at work," said first author Dr. Laura Cimoli from Cambridge’s Department of Applied Mathematics and Theoretical Physics. "Beneath the surface of the water, there are jets, currents, and waves – in the deep ocean, these waves can be up to 500 meters high, but they break just like a wave on a beach." .

"The Atlantic Ocean is special in how it affects the global climate," said co-author Dr. Ali Mashayek from Cambridge’s Department of Earth Sciences. "It has a strong pole-to-pole circulation from its upper reaches to the deep ocean. The water also moves faster at the surface than it does in the deep ocean." .

Over the past several decades, researchers have been investigating whether the AMOC may be a factor in why the Arctic has lost so much ice cover, while some Antarctic ice sheets are growing. One possible explanation for this phenomenon is that heat absorbed by the ocean in the North Atlantic takes several hundred years to reach the Antarctic.

Now, using a combination of remote sensing, ship-based measurements, and data from autonomous floats, the Cambridge-led researchers have found that heat from the North Atlantic can reach the Antarctic much faster than previously thought. In addition, turbulence within the ocean – in particular large underwater waves – plays an important role in the climate.

Like a giant cake, the ocean is made up of different layers, with colder, denser water at the bottom, and warmer, lighter water at the top. Most heat and carbon transport within the ocean happens within a particular layer, but heat and carbon can also move betweeen layers. The researchers found that underwater waves can carry a significant amount of heat and carbon from the surface to the deep ocean.