The ocean's deep, hidden currents are having a profound impact on our climate, and it's time we pay attention. Tiny waves in the deep ocean, often overlooked, can affect the climate thousands of kilometres away, and this is a game-changer for our understanding of global climate dynamics. These small-scale movements, much like the ripples caused by a pebble dropped in a pond, have far-reaching consequences that are only now being fully appreciated.
For decades, scientists have focused on the long-term effects of deep ocean turbulence, assuming it only mattered over centuries to millennia. But our recent research, published in Nature Communications, reveals a different picture. We found that what happens deep below the ocean's surface can significantly influence the atmosphere above, even within a single year. This is a crucial revelation, as it highlights the importance of studying these tiny, yet powerful, movements.
The study used a clever approach, combining physical and chemical measurements to examine the various scales at which deep ocean turbulence influences the global climate system. We focused on chlorofluorocarbons (CFCs), chemicals once used in refrigerants and aerosols, to track their journey through the ocean. By measuring CFC concentrations at different depths, we could calculate how long it had been since these deep waters last mixed with the surface and how quickly they moved around the globe.
In just 40 years, some deep waters transported CFCs from Antarctica to the mid-Pacific and north Indian Ocean. This discovery is significant because it provides valuable insights into the transfer of heat, carbon, and nutrients between the atmosphere and ocean. It also highlights the rapid movement of these elements, which can have immediate and far-reaching effects.
To further illustrate the impact of these small-scale processes, we conducted experiments using a dye. By injecting the dye into a deep canyon in the Rockall Trough, we observed that it rose towards the ocean surface, climbing as much as 100 meters a day. This experiment demonstrated the power of these tiny movements, as they can significantly affect the distribution of nutrients and heat.
The importance of this small-scale turbulence cannot be overstated. Nutrients like nitrate and phosphate are the foundation of the marine food web, and if they're not pulled from the deep ocean to the surface, the entire ecosystem could collapse. This would have devastating consequences for global fisheries and food security. Additionally, the way heat is transferred from the deep ocean to shallower waters influences the melting of Arctic and Antarctic ice, which in turn affects sea level rise, storm intensity, and flooding levels worldwide.
However, our current global climate models fall short in capturing these small-scale processes. They significantly underestimate the mixing and vertical movement of water, relying on simple approximations called parameterizations. These parameterizations, many dating back to the 1990s, are a missing piece of the puzzle. The way clouds form is another example of tiny physical events with outsized impacts on the climate, and this, too, is a challenge for climate models.
To improve our models, we need to update them with new parameterizations that account for our enhanced understanding of deep ocean mixing. This will make them more accurate and useful for predicting future climate scenarios. While observing small-scale mixing remains challenging, we've made significant progress in the past decade, thanks to regional and global observation programs and advancements in high-performance computing.
Despite these advancements, significant obstacles remain. The rarity of mixing observations means we must find ways to overcome this bottleneck and target resources effectively. By doing so, we can accelerate progress and gain a deeper understanding of how these small-scale processes influence the climate. The ocean's deep currents are a powerful force, and it's time we fully embrace their impact on our planet's future.
