Analysis of Low Frequency Current Fluctuations in the North-East Atlantic Ocean

摘要

Eulerian current measurements from 13 positions in the Atlantic between 28 N and 42 N and east of 27 W are analyzed. Most of the time series are from the main thermocline and 200 to 380 days long; for position N1, (33 N, 22 W) the series are 2049 days long. Mean current vectors confirm the mean baroclinic circulation pattern inferred from historical data but show higher velocities. Integral time scales of the fluctuative part of the currents are of the order of 20 to 30 days. Only the east component on position N1 has an extremely long integral time scale (70 days). The level of the fluctuative part of kinetic energy is moderate according to position and depth. In the northern Canary basin it has a maximum in the range 50 to 200 days. Neither in the currents nor in their variances is a seasonal signal detected. The zonal component at N1 shows a very slowly varying signal of 3.5 year period. Barotropic and the first baroclinic mode contain greater than 80 percent of the fluctuative part of the energy.