P. Vanmeurs, INTERACTIONS BETWEEN NEAR-INERTIAL MIXED-LAYER CURRENTS AND THE MESOSCALE - THE IMPORTANCE OF SPATIAL VARIABILITIES IN THE VORTICITY FIELD, Journal of physical oceanography, 28(7), 1998, pp. 1363-1388
Satellite-tracked mixed-layer drifter data from the 1987 Ocean Storms
Experiment in the northeast Pacific are used to study the temporal and
spatial variability in the near-inertial currents of the surface mixe
d layer. The data suggest that the near-inertial currents interact wit
h the mesoscale vorticity. To explore the exact nature of this relatio
nship, an asymptotic analysis is extended to include the mesoscale and
it is shown that not only gradients in the planetary vorticity (beta)
but also the gradients in the mesoscale vorticity affect the generati
on and evolution of near-inertial mixed layer currents. While the beta
effect is relevant for the large-scale evolution of the near-inertial
currents, the vorticity gradients of the mesoscale field determine th
e local behavior of near-inertial currents. Using a three-dimensional
model it is shown that areas of large gradients in the mesoscale vorti
city coincide with areas of low near-inertial energy. The smaller spat
ial scales in the near-inertial energy, generated by the vorticity hel
d, result in faster decay of near-inertial currents. The findings that
the near-inertial currents interact with the mesoscale are in apparen
t contradiction with previous research in the same area.