Glacial troughs are flat-bottomed, steep-sided submarine valleys that almost or en-tirely incise the shelf, and significantly alter coastal circulation. When the alongshore flow is in the Kelvin-wave (downwave/downwelling favorable) direction, troughs eject most of the shelf transport offshore to the slope. This offshore ejection diminishes wind-driven alongshore transport downwave of the trough. Conversely, when the alongshore flow isagainst the Kelvin wave direction (upwave/upwelling favorable), the trough moves transport, which had been on the slope, to the shelf, enhancing shelf transport downwave ofthe trough. Troughs enhance offshore ejection by generating relative vorticity, which isdissipated by bottom friction, leading to cross-isobath transport, and by accelerating along-shelf flow, which leads to increased bottom Ekman transport. A barotropic, linear, steady-state model is used to quantify the increased exchange between shelf and slope, as a function of the trough geometry.