An international team of scientists led by the University of Cambridge, Oxford, and the University of California San Diego, partially supported by the Natural Environment Research Council (NERC), which is part of UK Research and Innovation (UKRI), has determined the scale of underwater turbulence in the Atlantic Ocean. It turns out that their significance is not accurately reflected by the models used to determine climate policy.
Underwater waves
According to the latest research, waves beneath the surface of the ocean play a critical role in storing heat and carbon within the water. This process is dependent on the turbulence within the water body, which pushes heat and carbon deeper into the ocean or closer to the surface. Although the phenomenon of underwater turbulence has been known for a long time, its significance in the transport of the heat and carbon mixture has not been fully examined. The conclusion of the research published in the AGU Advances journal is that the role of underwater turbulence in this process is certainly greater than previously thought.
The oceanic circulation system transports warm water from the tropics into the northern Atlantic, where it cools down, sinks, and returns southward in the deep ocean. The entire process operates like a massive conveyor belt. The Atlantic branch of this circulation pattern is known as the Atlantic Meridional Overturning Circulation (AMOC), which redistributes heat to the polar regions, causing ice to melt, and transfers carbon to the deep ocean, where it can remain stored for thousands of years.
Unique features of the Atlantic
The Atlantic Ocean has a strong pole-to-pole circulation, from the surface to the deep ocean, making it unique in terms of its impact on the global climate. Water moves faster on the surface and slower at greater depths.
Over the last few decades, scientists have investigated whether the Atlantic Meridional Overturning Circulation (AMOC) could be responsible for the loss of a large polar cap in the Arctic while some Antarctic polar caps were growing. One potential explanation for this phenomenon was that the heat absorbed by the ocean in the northern Atlantic required several hundred years to reach the Antarctic. Now, using a combination of remote sensing, ship measurements, and data from autonomous floats, scientists have discovered that heat from the northern Atlantic can reach the Antarctic much faster than originally believed.
The ocean consists of different layers, with colder, denser water at the bottom and hotter, lighter water at the top. Most heat and carbon transport in the ocean occurs in a specific layer, but both heat and carbon can also move between layers of different densities. This way, elements that are hidden in the deep can return to the surface. The movement of heat and carbon between ocean layers is facilitated by turbulence. This important scientific discovery is not yet fully represented in climate models.
Various estimates have shown that turbulence mainly affects the density layers associated with the deep water core moving south from the northern Atlantic to the Southern Ocean. This means that heat and carbon moved by these waters are very likely to cross different density floors.
Scientific precision
In climate models, turbulence is primarily considered in the context of its impact on oceanic circulation. However, in light of the latest discoveries, turbulence has become an essential phenomenon in itself, as it influences the capture of carbon and heat by the ocean. Turbulence controls the amount of anthropogenic heat reaching the polar cap of the Antarctic and helps predict the time scale of this phenomenon.
Research indicates an urgent need to install turbulence sensors on global observation platforms and represent them with greater precision on a small scale in climate models. This will help scientists make more accurate predictions of the consequences of climate change.
