Circulation in a Short, Microtidal Submarine Canyon in the Alboran Sea

This study analyzes the circulation of a short, microtidal submarine canyon. The Jolúcar submarine canyon is located near Carchuna beach (Granada, southern Spain) in the northern continental shelf of the Alborán Sea. The canyon is 5-km long and 3-km wide oriented N-S and ending seaward at a water depth of about 600 m. It has two main tributaries that cut the continental shelf, which is aligned with a semi-arid mountain range (Contraviesa). Field data were analyzed from three field surveys in the last ten years, which included long-term moorings and cruises.

Observations showed two layers flowing in opposite directions: down-canyon in the bottom layer and up-canyon in the upper layer. This suggests that the canyon might flush out dense materials from the nearshore. In contrast to observations in other submarine canyons, no turbidity currents were observed. The canyon’s circulation was mainly driven by tidal and, more significantly, by atmospheric forcing. On the one hand, the circulation in the deepest parts was explained by wind stress (35%), local atmospheric pressure gradients (30%), and tides (10%). It is particularly remarkable that 1/3 of the circulation variability at the canyon is induced by local atmospheric pressure gradients. This driving force is mainly balanced by friction, advection, and rotation. On the other hand, observations over the shallow parts, near the tributaries, showed positive vorticity at the pycnocline depth. Although its origin is still debatable, results suggest that the generation mechanism is the propagation of topographically generated internal waves at the pycnocline. Further discussion centers on the implications of these results in understanding hydrodynamics processes in submarine canyons in semi-arid basins.