Posted by Bo Qiu on November 13, 2000 at 21:04:49 (UTC):
Susana,
I read your poster with great interest. I am particularly intrigued
by your 3 time series, indicating that when the KE's 1st crest
moves northward, the KE's volume transport decreases and its bifurcation
latitude shifts eastward.
Lack of subsurface in-situ measurements, I assume that this conclusion
of yours is based on the T/P data analysis. Although the double frontal
structure of the KE is discernible in some T(y,z) observations downstream
of the Shatsky Rise, my experience with the T/P (and the Geosat ERM) data
is that this double-front structure is very difficult to detect in the
SSH measurements. (In your response to Randy's comment, you seem to
agree with this point.) Given this, I wonder how you have determined the
the time series for the northern branch and the bifurcation latitude?
Both Randy and Bruce raised the issue on whether the Oyashio variability
can affect the KE path signals. My thought on this is close to yours, namely,
at least in the region between 140E and the Shatsky Rise (~160E), the KE's
inertia and the nearly right-angled coastal geometry of Japan cause a
"buffer" zone (the so-called Mixed Water Region) in between the eastward
flowing KE and Oyashio. As such, the upstream KE path variability is
dictated more likely by the Kuroshio state south of Japan (via inflow
condition), its interaction with the Izu Ridge, and the presence of the
recirculation gyre (through nonlinearity).
With regard to the transport values, I am a little surprised that the
numbers shown in your map are so small (e.g., 35Sv for the KE just east
of Japan). A recent WOCE survey with CTD, LADCP, and ship-board ADCP
showed that the eastward KE transport at this location reaches 130Sv
(see Fig.6 of Wijffels et al., JGR, 1998, 12,985-). The inflated
eastward transport of the KE is due to the presence of the southern
recirculation gyre. Interestingly, the survey by Wijjfels et al. shows
that the recirculation has a transport of ~80 Sv, rendering the net
eastward transport of the KE to 50 Sv, a value very close to the
interior Sverdrup transport.
My final comment is that because the KE and its recirculation gyre
have very different vertical structures, the 1.5-layer approach may be
difficult to distinguish the volume transport changes due to the KE
itself or its recirculation gyre.
Cheers, Bo