Abstract for "Moored Current Measurements over the Continental Slope
in EBC: A First Look"
An array of five current meter moorings was maintained over the continental
slope south of Point Arena between June 1992 and June 1994, as part of the
Eastern Boundary Currents ARI supported by ONR, to study the equatorward
current jets, poleward undercurrent, and mesoscale eddies, and their
interactions. The moorings were deployed in a cross pattern, with 3 moorings
forming a cross-slope transect (ME at 415m, MC at 1975m and MW at 2975m); MC
and the other 2 moorings (MN and MS) forming a three-element transect along the
1975m isobath. The inshore mooring was located near the same isobath as the
CODE C5 mooring. Separations between nearest moorings was approximately 14 km.
This array matched those maintained by T. Chereskin and P. Niiler (SIO) further
For the cross-slope transect, the mean alongshore currents (toward 330T)
were poleward at depths of 100m and greater, and strongest at the 150m
instrument at all 3 moorings. The strength of this poleward undercurrent
decreased with distance from shore, from 11.9 cm/s at ME to 3.4 cm/s at MW.
At ME, mean poleward flow was weakest during the winter of each year, and
strongest during the summer. Summer and fall mean poleward currents at ME were
twice as large as those found at C5 in 1981-82. The mean currents showed an
onshore component at each instrument, relative to the 330T.
Upper-ocean fluctuations of low-passed alongshore currents were well
correlated horizontally over the four offshore moorings in the array;
however, correlations between the inshore and offshore mooring were low.
Fluctuations in deep alongshore currents, measured on MC at depths of 1000m,
1400m and 1800m in 1993-94, were well correlated vertically, and show some
correlation with currents in the upper water column. Upper-ocean slope
currents at MC and MW showed extended episodes of strong on-shore flow (e.g.
10 days in June 1993); currents at the inshore mooring ME were more strongly
polarized alongshore. In April-May 1993, slope currents rotate cyclonically
when satellite imagery shows a coastal filament sweeping offshore across the
array. In mid-January 1994, an anticyclonic eddy (relative vorticity < -f/3
at 150m) passed over the array.
Move up one level.