EGU2020-18201, updated on 12 Jun 2020
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Subducting filaments at fronts in the Alboran Sea: Physical, turbulent and biological evidences.

Francesco Marcello Falcieri1, Mathieu Dever2,3, Mara Freilich2,4, Annalisa Griffa1, Katrin Schroeder1, and Amala Mahadevan2
Francesco Marcello Falcieri et al.
  • 1CNR - ISMAR, Venezia, Italy
  • 2Woods Hole Oceanographic Institution, Woods Hole, MA, United States
  • 3RBR, Ottawa, Canada
  • 4Department of Earth, Atmospheric and Planetary Sciences, MIT, Cambridge, MA, USA

Submesoscale instabilities along oceanic fronts can cause water mass intrusions from the surface mixed layer into the stratified pycnocline. These are important drivers of vertical exchange that have a potentially significant impact on the transfer of physical properties and biological tracers.

The CALYPSO (Coherent Lagrangian Pathways from the Surface Ocean to Interior) ONR research initiative focuses on observing and understanding coherent vertical pathways by which vertical exchange occurs. The Alboran Sea (located in the south-western Mediterranean, east of Gibraltar) is well known for its strong density fronts and eddies. During a research cruise, onboard R/V Pourquoi Pas? in early April 2019, we found that fronts in this area support the generation of subducting filaments. Several types of observations (using CTD, uCTD, microstructure profiles, drifters and floats) were collected along numerous cross-front transects over a period of two weeks.

The analysis of the temperature profiles highlighted the presence of several intruding filaments moving along isopycnal surfaces in the proximity of the frontal area. The intrusion signal was also clearly visible in biophysical properties with elevated Chlorophyll-a concentrations, well below the deep chlorophyll maximum, in conjunction with high dissolved oxygen values. From a microstructure point of view, the upper and lower limits of the subducting filaments exhibited high turbulent dissipation rates, with values of O(10-7) W/m2. These dissipation rates are higher than what is generally observed at such depths and point to enhanced mixing activity at the boundaries of the intrusions even along isopycnal surfaces.

How to cite: Falcieri, F. M., Dever, M., Freilich, M., Griffa, A., Schroeder, K., and Mahadevan, A.: Subducting filaments at fronts in the Alboran Sea: Physical, turbulent and biological evidences., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18201,, 2020

This abstract will not be presented.