Oceanography The Official Magazine of
The Oceanography Society
Volume 32 Issue 04

View Issue TOC
Volume 32, No. 4
Pages 10 - 21


INTRODUCTION TO THE SPECIAL ISSUE • FLEAT: A Multiscale Observational and Modeling Program to Understand How Topography Affects Flows in the Western North Pacific

By T.M. Shaun Johnston , Martha C. Schönau, Terri Paluszkiewicz, Jennifer A. MacKinnon, Brian K. Arbic, Patrick L. Colin, Matthew H. Alford, Magdalena Andres, Luca Centurioni, Hans C. Graber, Karl R. Helfrich, Verena Hormann, Pierre F.J. Lermusiaux, Ruth C. Musgrave, Brian S. Powell, Bo Qiu, Daniel L. Rudnick, Harper L. Simmons, Louis St. Laurent, Eric J. Terrill, David S. Trossman, Gunnar Voet, Hemantha W. Wijesekera, and Kristin L. Zeiden 
Jump to
Article Abstract Citation References Copyright & Usage
Article Abstract

Using a combination of models and observations, the US Office of Naval Research Flow Encountering Abrupt Topography (FLEAT) initiative examines how island chains and submerged ridges affect open ocean current systems, from the hundreds of kilometer scale of large current features to the millimeter scale of turbulence. FLEAT focuses on the western Pacific, mainly on equatorial currents that encounter steep topography near the island nation of Palau. Wake eddies and lee waves as small as 1 km were observed to form as these currents flowed around or over the steep topography. The direction and vertical structure of the incident flow varied over tidal, inertial, seasonal, and interannual timescales, with implications for downstream flow. Models incorporated tides and had grids with resolutions of hundreds of meters to enable predictions of flow transformations as waters encountered and passed around Palau’s islands. In addition to making scientific advances, FLEAT had a positive impact on the local Palauan community by bringing new technology to explore local waters, expanding the country’s scientific infrastructure, maintaining collaborations with Palauan partners, and conducting outreach activities aimed at elementary and high school students, US embassy personnel, and Palauan government officials.


Johnston, T.M.S., M.C. Schönau, T. Paluszkiewicz, J.A. MacKinnon, B.K. Arbic, P.L. Colin, M.H. Alford, M. Andres, L. Centurioni, H.C. Graber, K.R. Helfrich, V. Hormann, P.F.J. Lermusiaux, R.C. Musgrave, B.S. Powell, B. Qiu, D.L. Rudnick, H.L. Simmons, L. St. Laurent, E.J. Terrill, D.S. Trossman, G. Voet, H.W. Wijesekera, and K.L. Zeiden. 2019. Flow Encountering Abrupt Topography (FLEAT): A multiscale observational and modeling program to understand how topography affects flows in the western North Pacific. Oceanography 32(4):10–21, https://doi.org/10.5670/oceanog.2019.407.


Baines, P.G. 1995. Topographic Effects in Stratified Flows. Cambridge Press.

Chang, M.-H., S. Jan, C.-L. Liu, Y.-H. Cheng, and V. Mensah. 2019. Observations of island wakes at high Rossby numbers: Evolution of submesoscale vortices and free shear layers. Journal of Physical Oceanography 49(11):2,997–3,016, https://doi.org/​10.1175/JPO-D-19-0035.1.

Cimino, M.A., M. Anderson, T. Schramek, S. Merrifield, and E.J. Terrill 2019. Towards a fishing pressure prediction system for a western Pacific EEZ. Scientific Reports 9(1):461, https://doi.org/10.1038/s41598-018-36915-x.

Colin, P.L. 2018. Ocean warming and the reefs of Palau. Oceanography 31(2):126–135, https://doi.org/​10.5670/oceanog.2018.214.

Dong, C., J.C. McWilliams, and A.F. Shchepetkin. 2007. Island wakes in deep water. Journal of Physical Oceanography 37:962–981, https://doi.org/​​10.1175/JPO3047.1.

Garrett, C., and E. Kunze. 2007. Internal tide generation in the deep ocean. Annual Review of Fluid Mechanics 39:57–87, https://doi.org/10.1146/annurev.fluid.39.050905.110227.

Lermusiaux, P.F.J., P.J. Haley Jr., S. Jana, A. Gupta, C.S. Kulkarni, C. Mirabito, W.H. Ali, D.N. Subramani, A. Dutt, J. Lin, and others. 2017. Optimal planning and sampling predictions for autonomous and Lagrangian platforms and sensors in the northern Arabian Sea. Oceanography 30(2):172–185, https://doi.org/10.5670/oceanog.2017.242.

MacKinnon, J.A., M.H. Alford, G. Voet, K. Zeiden, T.M.S. Johnston, M. Siegelman, S. Merrifield, and M. Merrifield. 2019. Eddy wake generation from broadband currents near Palau. Journal of Geophysical Research 124(7):4,891–4,903, https://doi.org/10.1029/2019JC014945.

Magaldi, M., T. Özgökmen, A. Griffa, E. Chassignet, M. Iskandarani, and H. Peters. 2008. Turbulent flow regimes behind a coastal cape in a stratified and rotating environment. Ocean Modelling 25(1):65–82, https://doi.org/10.1016/​j.ocemod.2008.06.006.

Mayer, F.T., and O.B. Fringer. 2017. An unambiguous definition of the Froude number for lee waves in the deep ocean Journal of Fluid Mechanics 831:R3, https://doi.org/10.1017/jfm.2017.701.

Musgrave, R.C., G. Flierl, and T. Peacock. 2018. The generation of Rossby waves and wake eddies by small islands. Journal of Marine Research 76:63–91, https://doi.org/10.1357/​002224018824845929.

Qiu, B., D.L. Rudnick, S. Chen, and Y. Kashino. 2013. Quasi-stationary North Equatorial Undercurrent jets across the tropical North Pacific Ocean. Geophysical Research Letters 40(10):2,183–2,187, https://doi.org/10.1002/grl.50394.

Qiu, B., D.L. Rudnick, I. Cerovecki, S. Chen, M.C. Schönau, J.L. McClean, and G. Gopalakrishnan. 2015. The Pacific North Equatorial Current: New insights from the origins of the Kuroshio and Mindanao Currents (OKMC) Project. Oceanography 28(4):24–33, https://doi.org/​10.5670/​oceanog.2015.78.

Schönau, M.C., and D.L. Rudnick. 2015. Glider observations of the North Equatorial Current in the western tropical Pacific. Journal of Geophysical Research 120:3,586–3,605, https://doi.org/​10.1002/2014JC010595.

Schramek, T.A., P.L. Colin, M.A. Merrifield, and E.J. Terrill. 2018. Depth-dependent thermal stress around corals in the tropical Pacific Ocean. Geophysical Research Letters 45:9,739–9,747, https://doi.org/10.1029/2018GL078782.

Signell, R.P., and W.R. Geyer. 1991. Transient eddy formation around headlands. Journal of Geophysical Research 96(C2):2,561–2,575, https://doi.org/​10.1029/90JC02029.

Trossman, D.S., B.K. Arbic, J.G. Richman, S.T. Garner, S.R. Jayne, and A.J. Wallcraft. 2016. Impact of topographic internal lee wave drag on an eddying global ocean model. Ocean Modelling 97:109–128, https://doi.org/10.1016/j.ocemod.2015.10.013.

Warner, S.J., and P. MacCready. 2009. Dissecting the pressure field in tidal flow past a headland: When is form drag “real”? Journal of Physical Oceanography 39:2,971–2,984, https://doi.org/​10.1175/2009JPO4173.1.

White, B.L., and K.R. Helfrich. 2013. Rapid gravitational adjustment of horizontal shear flows. Journal of Fluid Mechanics 721:86–117, https://doi.org/10.1017/jfm.2013.41.

White, W. 1971. A Rossby wake due to an island in an eastward current. Journal of Physical Oceanography 1:161–168.

Wunsch, C. 1972. Temperature microstructure on the Bermuda slope with application to the mean flow. Tellus 24(4):350–367.

Zeiden, K.L., D.L. Rudnick, and J.A. MacKinnon. 2019. Glider observations of a mesoscale oceanic island wake. Journal of Physical Oceanography 49(9):2,217–2,235, https://doi.org/​10.1175/JPO-D-18-0233.1.

Copyright & Usage

This is an open access article made available under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution, and reproduction in any medium or format as long as users cite the materials appropriately, provide a link to the Creative Commons license, and indicate the changes that were made to the original content. Images, animations, videos, or other third-party material used in articles are included in the Creative Commons license unless indicated otherwise in a credit line to the material. If the material is not included in the article’s Creative Commons license, users will need to obtain permission directly from the license holder to reproduce the material.