Measuring the flow through the Kerama Gap

Field Program: June 2009 - June 2011

Principal Investigators:

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

Japanese Collaborators:

Hirohiko Nakamura, Kagoshima University

Ayako Nishina, Kagoshima University

Goal:

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:
1. 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;
2. 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;
3. 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).

Publications/Presentations:

Annual Reports of ONR Sponsored Research

Wimbush, M., and J.-H.Park, "Measuring the flow through the Kerama Gap" (2009, 2010 2011 2012)

Published Papers

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, 119(2):689–703, 2014. (doi:10.1002/2013JC008899)
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. (doi:10.1002/2013JC009326)

Technical Reports

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. (PDF)