To study potential turbulent water motions near the deepest point on Earth in the Challenger Deep of the Mariana Trench, a 588-m long string equipped with specially designed sensitive temperature sensors was moored for nearly three years in 10.9 km water depth. Detailed analysis of one year of good data distinguishes ubiquitous 100-m tall internal waves and hundreds of meters slanted convection turbulent spurs due to internal waves breaking from above. The spurs can occur on a tidal periodicity. Furthermore, internal tidal wave breaking including 100-m tall turbulent overturns reaching the trench-floor is associated with warm water push from above. Once, such tidal wave breaking at the trench-floor occurred precisely during the passing of a tropical storm, which thus interacts directly with deep-trench motions possibly via barotropic sealevel variations. The different turbulence types prevent the hadal waters from being still, which is an important necessity for deep-trench life.

The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)