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Projects > KESS - Kuroshio Extension System Study
Project Summary
The warm, northward-flowing waters of the Kuroshio
western boundary current leave the Japanese coast to flow eastward
into the North Pacific as a free jet—the Kuroshio Extension. The Kuroshio
Extension forms a vigorously meandering boundary between the warm
subtropical and cold northern waters of the Pacific. A recirculation
gyre exists to the south of the Kuroshio Extension. Another may exist
to the north. This is also one of the most intense air–sea heat exchange
regions on the globe, where the warm Kuroshio waters encounter the
cold dry air masses coming from the Asian continent. The Kuroshio
Extension system exhibits variations which strongly affect North American
climate. Among the diverse fields that will benefit from this work
are fisheries and climate research, and understanding storm tracks.
Understanding the processes that govern the variability of and the
interaction between the Kuroshio Extension and the recirculation gyre
is the goal of this study. Processes coupling the baroclinic and barotropic
circulations will be examined by case studies of the local dynamical
balances, particularly during strong meandering events. The mechanisms
by which water masses are exchanged and modified as they cross the
front will be characterized. The objective is to determine the processes
governing the strength and structure of the recirculation gyres in
relation to the meandering jet.
Principal Investigators cooperating
from three US institutions postulate dynamical and thermodynamical
connections from mesoscale eddies to gyre-scale recirculations and
to global climate variations and propose observations designed to
test these hypotheses. They will deploy a state-of-the-art array consisting
of moored-profiler and current-meter moorings and inverted echo sounders
equipped with near-bottom pressure and current sensors. Shipboard
surveys will conduct case studies of the water properties and currents
throughout the water column. Profiling floats will monitor the temperature
and salinity structure in the recirculation gyre south of the Kuroshio
Extension. The proposed approach makes extensive use of satellite
data (surface temperature and sea-surface height). They will also
collaborate closely with Japanese scientists studying the overall
Kuroshio system.
The Kuroshio Extension system is the right place
to test hypotheses formulated from previous observational and modeling
studies because of its distinct stratification, bathymetry, and thermohaline
circulation. The time is right to conduct a study of the Kuroshio
Extension system. Over the last several decades a number of substantial
programs have been undertaken, focused on different parts of these
western boundary currents, mostly in the Atlantic. These include studies
of the Brazil-Malvinas Confluence, the Western Tropical Atlantic Studies,
the Subtropical Atlantic Climate Study, and the North Atlantic Current
Study. The program that is most closely related to this proposal and,
arguably the most ambitious, was the Synoptic Ocean Prediction Experiment.
These studies fundamentally changed the scientific community’s understanding
of the interconnected system of currents, recirculations, eddies,
cross-frontal exchange mechanisms, and processes affecting the upper
ocean heat budget. This improved dynamical understanding enables these
scientists to pose new questions treating the western boundary current
regime as a coupled system, linking eddy and gyre and global scales.
Today’s fundamentally improved remote-sensing, in situ observational,
and computing abilities enable them to address these questions in
a comprehensive manner.
This project is supported by the National Science Foundation.
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