Abstract for "Observations of the poleward undercurrent along the
eastern boundary of the mid-latitude Pacific"
We examine several recent data sets which improve our view of the subsurface
poleward undercurrent along the continental margin of North America. First,
during the 1995 upwelling season, two studies provided direct evidence of the
appreciable transport [O(1 Sv)] and alongshore continuity [O(1000 km)] of the
A NMFS Pacific whiting survey made ADCP sections across the shelf break from
32-47N at about 20 km N-S spacing. In 65 of the 80 transects, a poleward
undercurrent with speed > 5 cm/s, width > 10 km, and thickness > 100 m at
200 m was evident. In these sections the core velocity ranged from 6-46
cm/s with a mean of 24 cm/s. The data suggest continuity of the undercurrent
over the entire latitudinal range, with a slight poleward weakening and
A nearly simultaneous study in August 1995 focused on the coastal
upwelling region near Cape Blanco, Oregon (43N) and included both ADCP and
high-resolution CTD on Seasoar. This data set allows for a detailed study of
the undercurrent in the vicinity of the Cape, where it meanders offshore and
crosses underneath the equatorward coastal jet.
In addition to evidence of the alongshore extent of the undercurrent, we
also have good evidence of its continuity in time: the Eastern Boundary
Current moored array at 38.5N measured currents for 22 months at 5 cross-shore
locations extending from the inner slope (410 m depth) to the abyssal plane
(3650 m depth) at 14 km spacing. Mean poleward flow was observed at depths
greater than 100 m, with the maximum poleward flow at the innermost mooring
at about 175 m. The poleward flow decreases offshore with an e-folding width
of 24 km.
Move up one level.