Measuring the flow through the Kerama Gap
Field Program: June 2009 - June 2011
Mark Wimbush, University of Rhode Island
Jae-Hun Park, University of Rhode Island
Funding for this project was supplied by the Office of Naval Research
Hirohiko Nakamura, Kagoshima University
Ayako Nishina, Kagoshima University
- Determine the time-varying structure and transport of the flow between the Pacific Ocean and the ECS through the Kerama Gap on scales from a few hours to more than a year.
Test the following three hypotheses:
- increase in transport through the Kerama Gap is associated with (a) an increase in ECS-Kuroshio transport across the PN-line, north of Okinawa, and (b) a decrease in Ryukyu Current transport east of Okinawa about two months earlier;
- the arrival of anticyclonic (cyclonic) eddies at the eastern side of the Kerama Gap is associated with an increase (decrease) of transport through the Gap;
- variations in wind stress over the local region cause variation in the flow through the Kerama Gap.
Figure 1. Left panel: East China Sea (ECS) region; ETC = East Taiwan Channel, KG = Kerama Gap,
TKS = Tokara Strait; Jason-1 altimetry tracks shown as gray lines; red bar shows position of the deployed array.
Right panel: Enlargement of Kerama Gap region showing the deployed array: red dots are CPIES moorings, blue
dots are CM moorings. The array is along a line across the Kerama Gap, except that one CPIES instrument near
the center of the Gap is about 10 km northwest of this line. Depth contours are at 200, 500, 1000, 2000,
3000 and 4000 m.
Figure 2. Cross-section diagram of the Kerama Gap array. Four CPIESs are shown as solid red dots
(open red squares immediately above represent the current sensors 50 m above the sea floor). Seven CMs
on three moorings are shown as black open squares. Topography is from measurements taken on the June 2009 cruise.
Note: this section across the Kerama Gap is slightly northwest of the sill, hence the maximum depth at the
section is greater than the sill depth (1050 m).
- Na, H., M. Wimbush,
J.-H. Park, H. Nakamura, and A. Nishina.
Observations of flow variability through the Kerama Gap between the East
China Sea and the northwestern Pacific.
J. Geophys. Res., Oceans, in press, 2014.
- Nakamura, H.,
A. Nishina, Z. Liu, F. Tanaka, M. Wimbush, and J.-H. Park.
Intermediate and deep water formation in the Okinawa Trough.
J. Geophys. Res., Oceans, 118(12):6881–6893, 2013.
- Liu, Z., H. Na,
H. Nakamura, A. Nishina, J.-H. Park, K. Tracey, and M. Wimbush.
Kerama Gap 2009-2011 data report.
GSO Technical Report 12-02, University of Rhode Island, 2012.