As a sequel to Schmitz and Hogg (1978), nine-month moored observations of current and
temperature from the Charlie Gibbs Fracture Zone are further described, and then interpreted
in terms of low frequency quasigeostrophic motions. Large vertical and horizontal changes are
observed in the variance of both mean and fluctuating components. It is demonstrated that
these changes could be associated with the (complex) nature of the topography.
With regard to the mean flow, it is shown through an advective model that the topography
is sufficiently steep to force this motion to closely follow isobaths. Time-dependent motions for
periods from 2 to 96 days are described using the technique of empirical orthogonal functions.
The most energetic mode is always bottom trapped, with flow oriented along isobaths at lower
frequencies and approaching equipartition of along- and cross-isobath motions at higher frequencies.
At the lowest frequencies a second mode which increases upward in energy is also
judged significant, while for periods shorter than 3.6 days the second mode is again highly
bottom trapped. We interpret these motions using linear wave theory. There is relatively close
correspondence between theory and observation when the effects of both large- and small-scale
topographic features are included in the model calculations. In addition to the usual topographic
wave, the abrupt slope changes on the north wall allow for a baroclinic fringe mode with a
ncar bottom node at low frequencies and small-scale bottom corrugations force highly bottom
trapped waves above the smooth slope cut-off frequency.