Unstructured-grid modeling of transport and dispersion in the Lofoten-Vesterålen region

Unstructured-grid modeling of transport and dispersion in the Lofoten-Vesterålen region

The prospect of future oil activity in Lofoten-Vesterålen raises concerns about possible impacts on the marine ecosystem in the region. To assess the risks involved we need a good understanding of 1) ecosystem dynamics, 2) the effects of pollutants on organisms and 3) oceanic transport processes that influence the spatiotemporal distributions of both marine organisms and pollutants. The focus of this project will be on the third and, specifically, on how complex ocean dynamics influences the life cycle of marine species in the region.

In this PhD project, we will study transport and dispersion in the Lofoten-Vesterålen region using new unstructured-grid ocean model technology. This technology allows a variable spatial resolution of the numerical grid, enabling us to optimize computational resources by putting high resolution where it is needed, i.e. in the narrow passages that cut through the Loften archipelago and in the canyons that cut across the continental slope and shelf. The study should thus allow an investigation into what small-scale dynamical processes are actually important as well as an assessment of the combined impact of these processes on the life cycle of marine species, more specifically the arctic cod since Lofoten-Vesterålen is a major spawning ground for this species.

Three specific research questions are raised:

1.       How important is rectified tidal transport in narrow straits that cut through the Lofoten-Vesterålen archipelago for the total transport of biological material between Vestfjorden and the continental shelf outside? At what grid resolution are these processes adequately represented in models?

2.       How important is the cross-slope transport due to many submarine canyons? Are there important interactions between the macro-turbulent field from frontal instability and the flow due to canyons?

3.       What are the typical transport paths for arctic cod larvae from Vestfjorden, through the Lofoten-Vesterålen archipelago and along the continental shelf? What are the most important transport processes that determine these paths and the collocation between cod larvae with its food source C. finmarchius?

Figur 1 Bottom topography (from www.norgeskart.no) showing the characteristics canyons on the continental slope and the straits through the Lofoten archipelago. Red stars show position of historic moored flow observations while the yellow star shows the position of the currently active LoVe marine observatory.