Gulf Stream Meanders' Observations on Propagation and Growth

We present a new method for continuously tracking the location of the Gulf Stream using a moored array of inverted echo sounders. Time series of lateral displacements of the front, shown accurate to -+8 km, have been collected along three sections spaced 100, 150, and 200 km downstream (NE) of Cape Hatteras, North Carolina, for a period of 12 months. These records are highly coherent at all periodicities longer than 4 days. From the observed phase lags, a dispersion relationship is presented for the meanders' As the period and wavelength (T, h) increase from (4 days, 180 km) to (30 days, 600 km), the phase speed decreases moothly from 40 to 20 km d-•. The meanders exhibited rapid growth at periods longer than 4 days, doubling in variance in each 50-km step downstream. This downstream growth is most appropriately described by a spatial e-folding scale K -• -• 400 km for (T, X) <• (9 days, 300 km), and a temporal e-folding scale tr -• -• 6 days for (T, X) •> (14 days, 400 km).