Learn why the thickness of this mixed layer in the ocean is a key factor in deciding just how strong and widespread a tropical cyclone (the umbrella term that encompasses hurricanes and typhoons) can get, and how much global warming has the potential to amp up these severe weather events even further.
Tropical cyclones would affected by The Ocean
Tropical cyclones are intense natural events that can wreak havoc on both marine and terrestrial ecosystems. Such storms derive their energy from warm surface waters, and the presence of moisture in the atmosphere that can supply the energy needed.
The depth of the ocean’s mixed layer is a key factor in tropical cyclone formation, according to recent research published in Frontiers in Marine Science. The mixed layer is the topmost ocean layer that undergoes substantial surface turbulence, which in turn separate the cold depths of the ocean from atmospheric exchanges. The temperature of the upper ocean, in particular, affects tropical cyclones; this layer is significant to their formation and ability to produce damage.
Height of the Mixed Layer –> Cyclone Strength
Yalan Zhang and colleagues at the National University of Defense Technology in China ran computer models of western North Pacific tropical cyclones to investigate how different mixed layer depths might influence their behavior. They discovered that the thickness of the mixed layer influences the size and intensity of the storm, as shallower mixed layers produce less impressive cyclones while deeper ones create more powerful events.
In particular, the researchers found a rise of the cooling effect exerted by surface winds upon the upper ocean when the ocean mixed layer depth is less than 15 meters, causing lower sea surface temperature and consequently limiting the cyclone’s development. However, as the mixed layer depth exceeds 15 meters, this cooling effect weakens and surface warming returns to provide more energy for cyclone intensity. For every 5 meters increase in the mixed layer depth, the destructive potential of the tropical cyclone increased by an average of a whopping 325.2%, compared to about a 50% rise when it hit above around 15 meters and less than 15% at deeper depths.
Conclusion
The research underscores how the depth of a mixed layer in the ocean is a tipping point to both enhance and suppress cyclone-driven winds. The ability to fully elucidate how this ocean-atmosphere interaction will play out with extreme events is critical for us to develop strategies that can help limit their impact on human population and ecosystems at a time when global warming is causing sea surface temperatures to creep ever upward. This understanding of how tropical cyclones and SST interact can inform coastal communities living in regions at high-risk for intense storms, contributing to improved response efforts as more powerful tropical phenomena become a reality.
