One of the largest and most persistent features in the Alboran Sea is the Western Alboran Gyre (WAG), an
anticyclonic recirculation bounded by the Atlantic Jet (AJ) to the north and the Moroccan coast to the south. Eulerian
budgets from several months of a high-resolution model run are used to examine the exchange of water across the Eulerian
WAG’s boundary and the processes affecting the salinity, temperature, and vorticity of the WAG. The volume transport
across the sides of theWAGis found to be related to vertical isopycnal movement at the base of the gyre. Advection is found
to drive a decay in the salinity minimum and anticyclonic vorticity of the Eulerian WAG. Given the large contributions of
advection, a Lagrangian analysis is performed, revealing geometric aspects of the exchange that are hidden in an Eulerian
view. In particular, stable and unstable manifolds identify a stirring region around the outer reaches of the gyre where water
is exchanged with the WAG on a time scale of weeks. Its complement is an inner core that expands with depth and
exchanges water with its surroundings on much longer time scales. The 3D evolution of one parcel, or lobe, of water as it
enters the WAG is also described, identifying a general Lagrangian subduction pathway.
