|
Barry Ma Senior Oceanographer binbing@uw.edu Phone 206-221-4720 |
Education
B.S., ROC Naval Academy, Kaohsiung, Taiwan, 1988
M.S. Physical Oceanography, US Naval Postgraduate School, 1998
Ph.D. Oceanography, University of Washington, 2004
|
Publications |
2000-present and while at APL-UW |
 |
Residence time of Lagrangian profiling floats: Observational assessment and numerical simulation of station keeping ability Ma, B.B., Z.B. Szuts, T.B. Curtin, "Residence time of Lagrangian profiling floats: Observational assessment and numerical simulation of station keeping ability," Earth Space Sci., 13, doi:10.1029/2026EA005018, 2026. |
More Info |
11 Oct 2026
|
 |
|||||
|
Autonomous profiling floats have revolutionized global ocean observation, yet their passive drift limits their ability to remain within desired regions. Using observations and simulations with numerical ocean models, we quantify observed and potential residence time (RT) of profiling floats and explore station-keeping strategies. Analysis of Argo float trajectories, performing fixed Argo-style sampling, reveals strong spatial variability in RT, from <20 days in western boundary currents to >100 days in subtropical gyre interiors and marginal seas. To quantify RT for alternate sampling behaviors, trajectories are calculated using velocity fields from an assimilative ocean reanalysis model in the dynamically complex western Pacific. A simple selection criterion of choosing to park at the depth of minimum horizontal velocity increases the mean RT by tens to several hundreds of percent, compared with fixed parking at 1,000 m. More sophisticated selection strategies lengthen RT further — such as accounting for flow direction or changing the park depth multiple times during one dive. These control methods provide upper limits on the RT by assuming perfect knowledge of the ocean's velocity profile. These results demonstrate the potential of adaptive park-depth selection for mission-specific profiling floats and regional observing applications where enhanced RT is a primary objective. Such strategies are not intended for the core Argo array, for which consistent parking-depth sampling is important for maintaining the long-term middepth velocity record. |
|||||||||
|
Finescale measurements of Kelvin-Helmholtz instabilities at a Kuroshio seamount Vladoiu, A., R.-C. Lien, E. Kunze, B. Ma, S. Essink, Y.J. Yang, M.H. Chang, S. Jen, J.L. Chen, K.C. Yang, Y.Y. Yeh, "Finescale measurements of Kelvin-Helmholtz instabilities at a Kuroshio seamount," J. Phys. Oceanogr., 55, 2097-2117, doi:10.1175/JPO-D-24-0235.1, 2025. |
More Info |
1 Nov 2025
|
|
|||||
|
Finescale properties of Kelvin-Helmholtz (KH)-like shear instabilities on the trailing edge of a nonlinear lee wave generated by the Kuroshio impinging on a seamount were measured using a towed CTD chain, shipboard ADCP, and echosounder. Lee-wave vertical velocity amplitudes vary in phase with the upstream semidiurnal along-stream current. The instabilities are analogous to atmospheric billows induced by a recirculation on the trailing edge of mountain lee waves. A total of 135 KH billows were identified in a 4-day-long time series roughly 300 m downstream of the center of the lee wave. The KH billows have heights H = 52 ±11 m, widths L = 162 ± 72 m, and aspect ratios H/L = 0.39 ± 0.18. Positive reduced shear squared S2 – 4N2 (where S is the vertical shear magnitude and N is the buoyancy frequency) in the shear-stratified billows suggests actively growing instabilities, with comparable contributions from across- and along-flow vertical shear. Billow cores are convectively unstable (N2 < 0). Large turbulent kinetic energy dissipation rates similar to O(10-5)Wkg-1 are inferred from density overturns. Density, shear, and inferred turbulence properties vary with billow aspect ratios. As H/L increases, density gradients smear out. For 122 billows with H/L < 0.6, dissipation rates increase by one order of magnitude with increasing H/L. These observations of similar to 1-m vertical and similar to 5-m horizontal resolution billow structures and density overturn dissipation rates can provide a reference for future high-Reynolds-number direct numerical simulations. |
|||||||||
|
Validation of surface wave spectral measurements from velocity profiling floats Stadler, J., J. Girton, and B. Ma, "Validation of surface wave spectral measurements from velocity profiling floats," J. Atmos. Ocean. Technol., 42, 449-462, doi:10.1175/JTECH-D-24-0023.1, 2025. |
More Info |
1 May 2025
|
|
|||||
|
EM-APEX floats have primarily been used to measure subsurface ocean velocities for the purpose of studying ocean dynamics and the vertical structure and shear of currents. However, the motionally-induced voltage sensed by the EM-APEX also contains signals from surface wave orbital velocities, and the time taken to pass through the top ~100 m of the water column is sufficient to estimate a spectrum of surface wave amplitudes with periods from 5–20 seconds (i.e., including both wind seas and long swell) with each profile. Following procedures developed by Hsu (2021) and D'Asaro (2015) we analyzed the performance of EM-APEX float measurements of surface-wave spectra, as well as bulk wave parameters such as significant wave height and energy period, against other in-situ wave-measuring platforms during a 2017 field study off the coast of California (ONR's Langmuir Circulation Department Research Initiative, or LC-DRI). We discuss the limitations and uncertainties inherent in the EM-APEX wave measurements, and determine the uncertainty on each individual 1Hz velocity measurement to be on the order of 1.6 cm/s, resulting in a minimal detectable significant wave height of Hs = 0.6 m. Results indicate that the EM-APEX surface wave spectral measurements are in good agreement with the other in-situ wave measurements, with correlation coefficients of R2 = 0.76 for significant wave height, and R2 = 0.65 for energy period. This work demonstrates the potential for these floats to be used as a useful tool in future direct measurements of surface-wave driven mixing processes, Langmuir turbulence, and the interactions between surface waves and ocean currents. |
|||||||||
