Is ocean mixing upside down? How mixing processes drive upwelling in a deep-ocean basin

Since the seminal work of Walter Munk in the 1960s, oceanographers have believed that the upwelling of cold, abyssal waters that regulates the deep ocean's ability to sequester heat and carbon for decades to millennia is driven by centimetre-scale turbulent mixing associated with breaking waves in the ocean interior. Measurements of deep-ocean turbulence over the last two decades, however, starkly contest this scenario, and instead suggest that mixing by breaking waves drives *downwelling* of abyssal waters. Inspired by this conundrum, recent theoretical investigations have developed a tantalising alternative view of the role of mixing in sustaining deep-ocean upwelling. In this new view (known as the ‘upside-down ocean mixing hypothesis’), upwelling is driven by highly localised turbulence within thin (typically tens of metres thick) layers near the seafloor, known collectively as the bottom boundary layer. 

This project will assess the validity of this new paradigm, and figure out how it works, by analysing the first set of concurrent, systematic measurements of (1) large-scale mixing and upwelling, (2) their interior and bottom boundary layer contributions, and (3) the processes underpinning these contributions, in a representative deep-ocean basin: the Rockall Trough, in the Northeast Atlantic.

For full project details visit the Inspire project page.