Gulf Stream meanders: Observations on propagation and growth


  • D. Randolph Watts,

  • William E. Johns


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, λ) increase from (4 days, 180 km) to (30 days, 600 km), the phase speed decreases smoothly from 40 to 20 km d−1. 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 κ−1 ∼400 km for (T, λ) ≲ (9 days, 300 km), and a temporal e-folding scale σ−1 ∼ 6 days for (T, λ) ≳ (14 days, 400 km).