Determines the path from the 12°C isotherm at 400-m depth, which was obtained daily for 740 days (April 1983-May 1985) from objective analysis maps of the thermocline topography measured by inverted echo sounders (IESs). Smooth transitions from (i) downstream propagating and growing short-period meander modes, to (ii) standing modes at intermediate period, to (iii) upstream propagating long-period modes were revealed. For periods shorter than semiannual, meanders propagate downstream with speeds monotonically increasing. For periods between semiannual and annual, the entire path shifts like a standing mode with no detectable phase lag within the study region, and its envelope accounts for the local minimum ( node ) that has been observed near 70°W. For periods from annual to at least 500 d, fluctuations propagate upstream at about 9 km d - 1 , and their amplitude decreases to the west in the direction of propagation.