The seasonal circulation and volume transport on the northwest European continental shelf: A fine‐resolution model study

Abstract

In this paper the circulation of the northwest European continental shelf is investigated using the first year‐long density‐evolving simulation at shelf wide scales and sub‐Rossby Radius resolution (∼1.8 km). A series of numerical experiments are conducted to distinguish between the wind‐, density‐, and oceanic‐driven components of the flow. These demonstrate that, while all components have a role throughout the year, the density‐driven component is particularly important during the summer and autumn months. The time evolution of the density field makes a significant contribution to the seasonal variation of volume transport on shelf wide scales and is persistent in direction; whereas the wind‐driven volume transport acts on much shorter timescales and is more variable in direction. The importance of the oceanic forcing is demonstrated, representing tidal residuals and large‐scale oceanic sea level (pressure) variation; this forcing drives a substantial component of the circulation throughout the year. Twenty six satellite tracked drifters deployed in the summer of 2001 are used for a direct validation of the model currents. The model current speeds are found to be accurate to ∼46% when averaged over ∼40 d, but tend to be too slow. The summer volume fluxes are compared with estimates in the literature showing good agreement, although there is a suggestion that the North Sea inflows are overestimated. Comparisons with the coarser resolution model used for boundary conditions demonstrate the importance of fine‐resolution to the details of the frontal currents with consequences for modeling exchange processes and biological activity in these regions.