In this and the seven subsequent slides, five annual cycles of upper ocean variability are illustrated by imaging the temperature field and superimposing the vertical coordinate interfaces and the mixed layer base (thick line). Differences in upper-ocean temperature can be large at grid points located in frontal zones and the boundary regions between gyres. Horizontal displacement of these oceanographic features among simulations can lead to substantial T differences. In general, smaller differences are observed at grid points located at gyre interiors. At the NAC grid point, low- frequency/secular variability in the subtropical/subpolar gyre boundary is evident.