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 the planet's complex systems. These waves, much like the breaking waves at the beach, create turbulence and mixing, which has long been thought to only matter over long time scales. But a new study challenges this notion, revealing that deep ocean turbulence can influence what happens above the surface, even over the course of a single year. This is a crucial finding because it highlights the importance of considering these small-scale processes in our climate models. The research, published in Nature Communications, uses a clever approach by examining the movement of chlorofluorocarbons (CFCs) in the ocean. CFCs, once used in refrigerants and aerosols, entered the ocean from the atmosphere at a known rate and can be traced to determine how long it takes for deep waters to mix with the surface. This allows scientists to understand how heat, carbon, and nutrients are transferred between the atmosphere and ocean, and how quickly they move around the globe. In just 40 years, CFCs have traveled from Antarctica to the mid-Pacific and north Indian Ocean, demonstrating the rapid movement of deep ocean currents. To further illustrate the impact of these currents, the study used a dye injection experiment in the Rockall Trough, near the United Kingdom. The dye rose towards the surface, climbing as much as 100 meters a day, defying expectations. This experiment highlights the importance of small-scale turbulence in the ocean's mixing processes. The implications of this research are far-reaching. Nutrients like nitrate and phosphate, essential for the marine food web, are at risk if they're not pulled from the deep ocean to the surface. This could lead to the collapse of entire ecosystems and global fisheries, significantly impacting global food security. Additionally, the transfer of heat from the deep ocean to shallower waters affects the melting of Arctic and Antarctic ice, which in turn influences sea level rise, storm intensity, and flooding levels worldwide. However, current 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 parameterisations, some of which date back to the 1990s. This is a problem because these models are crucial for understanding and predicting our climate. To improve our models, we need to update the parameterisations to reflect our enhanced understanding of deep ocean mixing. While observing small-scale mixing is still challenging, significant progress has been made in the past decade through regional and global observation programs and advancements in high-performance computing. However, there are still obstacles to fully understanding the impact of mixing on the climate. As observations of mixing remain rare, we must find ways to overcome this bottleneck and target resources effectively to accelerate progress. In conclusion, the deep ocean's tiny waves have a significant impact on our climate, and it's time to incorporate this knowledge into our models. By doing so, we can better understand our planet's complex systems and make more informed decisions about our future.
