The ocean's deep, dark secrets are about to get a lot brighter. We've long known that tiny waves in the deep ocean can have a big impact on the climate, but new research reveals just how profound these effects can be. It turns out that what happens thousands of metres below the surface can change what happens above it, even over the course of a single year. This is a game-changer for our understanding of the climate system, and it highlights the importance of studying small-scale turbulence in the ocean. Personally, I think this discovery is a wake-up call for climate scientists and policymakers alike. It's time to re-evaluate our models and incorporate the effects of these tiny, crucial movements. What makes this particularly fascinating is that it challenges our traditional understanding of ocean dynamics. For a long time, scientists have assumed that deep ocean turbulence only mattered over long time scales, such as centuries to millennia. But this new research shows that these tiny waves can have immediate and significant impacts on the climate. One thing that immediately stands out is the role of chlorofluorocarbons (CFCs) in this process. These chemicals, once used in refrigerants and aerosols, entered the ocean from the atmosphere at a known time and rate. By measuring CFC concentrations at depth today, we can calculate how much time has elapsed since these deep waters last mixed with the surface, and how quickly they moved around the globe. This gives us a better understanding of how heat, carbon, and nutrients are transferred between the atmosphere and ocean, and how they are transported. In just 40 years, some deep waters have transported CFCs from Antarctica to the mid-Pacific and north Indian Ocean. This is a powerful reminder of the interconnectedness of our planet's systems. What many people don't realize is that the impact of these tiny waves extends far beyond the ocean itself. Nutrients such as nitrate and phosphate underpin the marine food web, and if they're not getting pulled from the deep ocean to the surface, that web could collapse. This would devastate entire ecosystems, as well as global fisheries, and have a significant impact on global food security. The way that heat is transferred from the deep ocean to shallower waters and back also affects how Arctic and Antarctic ice melts, and that in turn affects sea level rise, storm intensity, and flooding levels around the world. This raises a deeper question: how can we better capture these small-scale processes in our climate models? Currently, global climate models do a poor job of accounting for these effects, significantly underestimating the mixing and vertical movement of water. This is because they must estimate the effects of small-scale processes using relatively simple approximations, a method scientists call parameterizations. Many of these parameterizations date back to the 1990s. This is a critical issue, as the way clouds form is another process where tiny physical events have outsized impacts on the climate. If we don't improve our models, we risk making decisions about the future based on incomplete or inaccurate information. So, what can we do to improve our models? Observing small-scale mixing, or the microphysics of the ocean, is still challenging. But we have made significant progress over the past decade, thanks to regional and global observation programs, and advances in high-performance computing. However, significant obstacles remain in the way of fully unraveling how it impacts the climate. As mixing observations are still very rare, we need to find ways to overcome this observational bottleneck and target resources to where they can accelerate progress fastest. In my opinion, this research is a call to action for the scientific community. We need to invest in new technologies and observation programs to better understand the microphysics of the ocean and its impact on the climate. Only then can we build more accurate and reliable climate models, and make informed decisions about the future. From my perspective, this is a crucial step towards a more sustainable and resilient future for our planet.
