The ASUKA project is a collaboration between scientists in Japan and
the United States to enhance our understanding of the structure and
dynamics of the Kuroshio off the coast of southwest Japan.
In this project, nine inverted echo sounders and nine current-meter
moorings were deployed for two years along a line extending 1000 km from
Shikoku Island near a TOPEX/POSEIDON altimeter groundtrack.
Numerous hydrographic profiles along this section were used to convert
inverted echo sounder measurements to dynamic height time series
and to determine the regional gravest empirical modes (GEM)
which relate temperature
and specific-volume anomaly to vertical acoustic echo time.
These GEM's were used in conjunction with the inverted-echo-sounder
data to calculate two-year time series of entire sections of relative
geostrophic velocity and temperature. Current-meter data provided
absolute-velocity references for the geostrophic-velocity sections.
In addition, a time series of Kuroshio position was determined from
the GEM temperature sections. These time series show three
big (> 80 km displacement) and three lesser offshore meanders of the
Kuroshio, occurring in February, May/June, and October of both years.
These meanders may be caused by mesoscale eddies arriving at the Ryukyus
from the east. The observed meanders were preceded by low Kuroshio volume
transport and followed by high Kuroshio volume transport.
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