Oxygen in the Iberian margin: A modeling study

Highly productive eastern boundary coastal upwelling areas provide interesting environments to study the physical–biological interactions that govern dissolved oxygen ( O 2 ) dynamics. The Iberian Upwelling System is located in the northern limit of the North East Atlantic upwelling region, along the Iberian margin off Portugal and Spain. It presents a marked seasonality in the hydrodynamics and it is under the influence of water masses of different origin. Here, we describe the seasonal variability and spatial patterns of O 2 in this system taking advantage of the 3-dimensional (3D) ocean model Regional Ocean Modeling System (ROMS). The model has been satisfactorily validated and has allowed a sound 3D description of the O 2 dynamics of the coast and adjacent ocean, showing a strong seasonality in the O 2 concentration of the upper water column. This seasonality is mainly caused by the deepening and shoaling of the seasonal mixed layer from winter to summer. O 2 concentration is high during winter and reaches maximum values in spring due to the seasonal phytoplankton bloom. Minimum O 2 values are obtained in summer and autumn. Additionally, the regional circulation of Eastern North Atlantic Central Water (ENACW) noticeably influences the O 2 distribution. Over the shelf and slope, more variability is introduced by the intense hydrodynamics of the upwelling season (spring/summer), the slope poleward flow (autumn/winter) and continental runoff.