Quantifying tidally-driven benthic oxygen exchange across permeable sediments: An aquatic eddy correlation study
Event details
| Date | 04.11.2014 |
| Hour | 16:15 › 17:15 |
| Speaker | Dr Daniel McGinnis, Institute F.-A. Forel, Faculty of Science, University of Geneva, CH |
| Location | |
| Category | Conferences - Seminars |
Abstract:
Permeable sediments make up vast areas of coastal seas, and represent areas of intense oxygen, carbon and nutrient turnover. However, sediment-water column exchange is difficult to resolve using traditional measurement techniques.In this study, we use a combination of aquatic eddy correlation,in situ microprofiles, and benthic chamberto investigate tidally-driven benthic oxygen dynamics in North Sea permeable sediments. Oscillating bottom current velocities above the sediment led to variations in the benthic oxygenfluxby a factor of 25. The observed tidally-driven oxygen fluxes were reproduced using a simple 1-D model linking the bottom water turbulence to the sediment porewater advection represented as an apparent diffusivity. The 25 timesoxygen flux variability results from deeper sediment oxygen penetration and increasedoxygen storage during high velocities, which is then utilized during low flow periods. The study highlights that the benthic hydrodynamics, sediment permeability and subsequent oscillation of porewater redox conditions are all critical parameters determining the oxygen fluxin permeable sediments. We discuss how these parameters may be affected by changing climate forcing, and possible reasons for increasing instances of low oxygen levels in the North Sea bottom waters.
Short biography:
Dr McGinnis completed his PhDin 2003 in Civil and Environmental Engineering at Virginia Tech (USA), where he studied lakes and reservoirs, particularly management and restoration (and often mitigation). He spent considerable time at Eawag in Kastanienbaum during his PhD, and continued with a postdoc studying benthic boundary mixing and processes at the sediment-water interface and greenhouse gas transport. Slowly, his research took him into oceanography and arctic research at GEOMAR (Kiel, Germany) and University of Southern Denmark (Odense, DK). From May 2013 – July 2014, he received a senior scientist fellowship at IGB in Berlin, Germany where he studied benthic transport, sediment fluxes and carbon turnover in lakes. From September 2014, he will begin as Assistant Professor in physical limnology at the University of Geneva, Institute F.-A. Forel, Faculty of Science.
Permeable sediments make up vast areas of coastal seas, and represent areas of intense oxygen, carbon and nutrient turnover. However, sediment-water column exchange is difficult to resolve using traditional measurement techniques.In this study, we use a combination of aquatic eddy correlation,in situ microprofiles, and benthic chamberto investigate tidally-driven benthic oxygen dynamics in North Sea permeable sediments. Oscillating bottom current velocities above the sediment led to variations in the benthic oxygenfluxby a factor of 25. The observed tidally-driven oxygen fluxes were reproduced using a simple 1-D model linking the bottom water turbulence to the sediment porewater advection represented as an apparent diffusivity. The 25 timesoxygen flux variability results from deeper sediment oxygen penetration and increasedoxygen storage during high velocities, which is then utilized during low flow periods. The study highlights that the benthic hydrodynamics, sediment permeability and subsequent oscillation of porewater redox conditions are all critical parameters determining the oxygen fluxin permeable sediments. We discuss how these parameters may be affected by changing climate forcing, and possible reasons for increasing instances of low oxygen levels in the North Sea bottom waters.
Short biography:
Dr McGinnis completed his PhDin 2003 in Civil and Environmental Engineering at Virginia Tech (USA), where he studied lakes and reservoirs, particularly management and restoration (and often mitigation). He spent considerable time at Eawag in Kastanienbaum during his PhD, and continued with a postdoc studying benthic boundary mixing and processes at the sediment-water interface and greenhouse gas transport. Slowly, his research took him into oceanography and arctic research at GEOMAR (Kiel, Germany) and University of Southern Denmark (Odense, DK). From May 2013 – July 2014, he received a senior scientist fellowship at IGB in Berlin, Germany where he studied benthic transport, sediment fluxes and carbon turnover in lakes. From September 2014, he will begin as Assistant Professor in physical limnology at the University of Geneva, Institute F.-A. Forel, Faculty of Science.
Practical information
- General public
- Free
- This event is internal
Organizer
- EESS - IIE
Contact
- Prof. Alfred Johny Wüest, APHYS-Margaretha Kamprad Chair