Publication Date:
2022-05-26
Description:
Also published as: Journal of Marine
Research, Volume 36, 3, 1978, pp. 295-310
Description:
Eddy or low frequency (periods greater than a day) kinetic energy per unit mass (KB) in the
western North Atlantic is observed to increase approaching the Gulf Stream system along 55W
longitude from the interior of the subtropical gyre, by a factor of 30 in the thermocline and
by over two orders of magnitude at 4000 m depth. KE at 4000 m depth decreases moving up
the Continental Rise from the Gulf Stream. The relative vertical distribution of KE is found to
be less depth dependent near the Gulf Stream (with increasing KE?) than in the interior of the
gyre. The vertical structure in the MODE-I region is an intermediate case.
The shape of the frequency spectrum for KE varies with depth and with geographical position;
spectral estimates in the thermocline from the MODE-I area (28N, 70W) are dominated
by longer time scales, but at a site near the Gulf Stream (37.5N, 55W), where spectral
shape does not vary strongly in the vertical, the thermocline spectrum is more weighted toward
the temporal mesoscale (~50-100 days) that dominates at 4000 m depth in the MODE-I area.
Spectral estimates at depth appear to be weighted toward shorter time scales moving from the
Gulf Stream up the Continental Rise, Slope, and Shelf. If the frequency spectrum for KB is
divided into two pieces with periods less than 100 days in one and greater than 100 days in the
second, then: (1) The relative vertical KB distribution near the Gulf Stream does not differ
significantly from band to band, whereas in the MODE-I region the lower frequencies are
much more depth dependent than the higher. (2) The relative vertical KE distribution for
periods less than 100 days is not appreciably dissimilar at the two locations, although KE level
and total vertical structure are distinct. (3) The relative vertical KE distribution at the lower
frequencies in the MODE-I region does not differ significantly from the vertical distribution of
total KB at a site farther into the interior of the gyre.
Time averaged currents at all depths where data are available show a relatively narrow
(~200 km) and comparatively depth-independent return flow for the Gulf Stream system along
55W; transporting roughly 70 X 106 m3 s-1 westward, with about 25 X 106 m3 s-1 relative to
the bottom and approximately 45 X 106 m3 s-1 associated with the "bottom transport."
Description:
Prepared for the Office of Naval Research
under Contracts N00014-74-C-0262; NR 083-004
and N00014-76-C-0197; NR 083-400 and for the
International Decade of Ocean Exploration
of the National Science Foundation under Grant
OCE 75-03962.
Keywords:
Heat
Repository Name:
Woods Hole Open Access Server
Type:
Technical Report
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