Modelling hydrodynamics and carbon in high permeability substrates

Project Rationale:
Coarse substrates (sands and gravels) have open matrices and high permeabilities that allow pore-water flows in their upper layers. These sediment types are spatially significant in the shelf seas and coastal environments around the UK (~35% of North Sea shelf) and also overseas. Their role as efficient bioreactors, rapidly exchanging nutrients and carbon between the bed and water column, has been highlighted in numerous studies (Huettel, 2014 and references there-in). Nevertheless, many ecosystem models used by Cefas (and other organisations), such as ERSEM, Delft3d/Eco, neglect pore water transport within the bed and assume that transport occurs only by molecular diffusion. This assumption affects the modelling of physical, chemical and biological cycles within the seabed and is a serious weakness when undertaking model predictions of seabed state, functioning and potential future changes. Diffusion models may be underestimating water flow and carbon exchanges or respiration by at least an order of magnitude (Middelberg et al., 2004; Ahmerkamp et al., 2017).
This coupled observational and modelling studentship aims to provide underpinning research for modelling permeable substrates that will be incorporated into existing shelf biogeochemical models. This will allow more realistic modelling of biogeochemical processes associated with the full range of sediment types ranging from muds or sands to gravels.

Methodology:
The studentship will combine: new (and existing) observational measures of sediment parameters and variables using experimental flume systems (UoS) to understand and measure physical & chemical processes, and the modelling of these processes at small scale within existing validated packages (COMSOL, OMEXDIA). The implications of these outputs will then be tested in simplified forms in GIS based spatial models and/or larger scale shelf sea models (ERSEM).

Training:
The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at University of Southampton. Specific training (UoS and Cefas) will include the use of laboratory flumes, sampling techniques and modelling using COMSOL and ERSEM.