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Filaments are cold surface features often found in eastern boundary current regions. A typical filament originates near the shelf and extends as a narrow (100 km or less) tongue extending hundreds of kilometers offshore. These features represent the main focus of the the Coastal Transition Zone program, which took place in 1987 and 1988 off the northern coast of California. The historical background for the program is discussed, as well as the questions that motivated it. The general approach of the program is described, followed by an overview of the initial findings, representing a summary of our current understanding of these features and their relation with eastern boundary current dynamics.

It is well known that along-isobath flow above a sloping bottom gives rise to cross-isobath Ekman transport and therefore sets up horizontal density gradients if the ocean is stratified. These transports in turn eventually bring the along-isobath bottom velocity, hence bottom stress, to rest (''buoyancy arrest'') simply by means of the thermal wind shear. This problem is revisited here. A modified expression for Ekman transport is rationalized, and general expressions for buoyancy arrest time scales are presented. Theory and numerical calculations are used to define a new formula for boundary layer thickness for the case of downslope Ekman transport, where a thick, weakly stratified arrested boundary layer results. For upslope Ekman transport, where advection leads to enhanced stability, expressions are derived for both the weakly sloping (in the sense of slope Burger number s 5 aN/f, where a is the bottom slope, N is the interior buoyancy frequency, and f is the Coriolis parameter) case where a capped boundary layer evolves and the larger s case where a nearly linearly stratified boundary layer joins smoothly to the interior density profile. Consistent estimates for the buoyancy arrest time scale are found for each case.

An intensive, yearlong deployment of current meter moorings was made over and around Fieberling Guyot (32.5°N, 127.75°W) in the North Pacific. The measurements are used to investigate tidal currents, the mean flow, and subinertial current fluctuations. The K1 and O1 diurnal tides were greatly amplified over the seamount, apparently through dynamics resembling nonlinear seamount‐trapped waves. The diurnal tides interacted nonlinearly to induce constituents at the sum frequency (M2) and difference frequency (fortnightly) above the summit. Diurnal amplification was strongest at about 450 m, and it extended from the seamount center out over the flanks. The S2 semidiurnal tide was not substantially amplified over the seamount. The mean flow was primarily along isobaths and was strongest about 50 m above the seamount rim. It was driven by tidal rectification, so that mean along‐isobath velocity at a given location correlated well with the amplitude of the local fortnightly tide at that location. Accompanying the mean flow was a “cold dome” over the seamount that was presumably maintained by a balance of mean downward advection and eddy (tidal) radial heat transport. Lower frequency current fluctuations were enhanced near the seamount and were apparently driven by fluctuations in the ambient flow.