Near-inertial shear and kinetic energy in the North Atlantic experiment (NISKINe): Moored observations

An 18-month deployment of moored sensors in Iceland Basin allows
characterization of near-inertial (frequencies near the Coriolis frequency
f with periods of ~14 h) internal gravity wave generation and propagation
in a region with an active mesoscale eddy field and strong seasonal wind
and heat forcing. The seasonal cycle in surface forcing deepens the mixed
layer in winter and controls excitation of near-inertial energy. The
mesoscale eddy field modulates near-inertial wave temporal, horizontal,
and vertical scales, as well as propagation out of the surface layer into
the deep permanent pycnocline. Wind-forced near-inertial energy has the
most active downward propagation within anticyclonic eddies. As oceanic
surface and bottom boundaries act to naturally confine the propagation of
internal waves, the vertical distribution of these waves can be decomposed
into a set of “standing” vertical modes that each propagate horizontally
at different speeds. The lowest modes, which propagate quickly away from
their generation sites, are most enhanced when the mixed layer is deep and
are generally directed southward.