Dr. Hans van Haren, a researcher at the Royal Netherlands Institute for Sea Research, has published new findings on deep-sea turbulence in the Western Mediterranean Sea. His work, titled “Deep Mediterranean turbulence motions under near-homogeneous conditions,” sheds light on the dynamic nature of seemingly ‘quiescent’ deep waters and its implications for marine life and potentially for the energy sector.
The study reveals that the deep Western Mediterranean Sea often experiences near-homogeneous (NH) conditions, where water temperature varies minimally over hundreds of meters, and the buoyancy frequency is less than the local inertial frequency. Contrary to the perception of these waters as stagnant, van Haren’s research shows that they are far from quiescent. Using a 3D mooring array with nearly 3000 high-resolution temperature sensors, he observed regular bursts of turbulent overturns larger than 10 meters, which are crucial for deep-sea life.
NH conditions can persist for up to a fortnight before stratified waters move over the area. These conditions occur about 60% of the time at the study site. The majority of NH periods are dominated by convection turbulence driven by geothermal heating from below. The turbulence dissipation rate, calculated using Ellison scales after precise band-pass filtering, aligns with historic geophysical heat-flux measurements. This convection turbulence leads to buoyancy-driven scaling of spectra, not just for temperature in the turbulence range, but also extending across the internal-wave band into sub-mesoscales. Limited observations also suggest this applies to kinetic energy and waterflow differences. These spectral patterns were uniform over the 124-meter vertical sensor range above the flat seafloor. However, small spectral deviations were noted when very weakly stratified waters were advected sideways or from above, increasing turbulence levels by about 30%.
For the energy sector, understanding deep-sea turbulence and geothermal heating patterns can be valuable. Offshore energy installations, such as oil and gas platforms or subsea cables, operate in these deep waters. Knowledge of turbulence and heat flux can aid in designing more robust and efficient structures, ensuring they can withstand the dynamic conditions of the deep sea. Additionally, insights into geothermal heating could inform the development of deep-sea geothermal energy projects, although this remains a niche area within the broader energy landscape.
The research was published in the journal Nature Scientific Reports.
This article is based on research available at arXiv.