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Barry Ma

Senior Oceanographer





Department Affiliation

Ocean Physics


B.S., ROC Naval Academy, Kaohsiung, Taiwan, 1988

M.S. Physical Oceanography, US Naval Postgraduate School, 1998

Ph.D. Oceanography, University of Washington, 2004


2000-present and while at APL-UW

Energetic stratified turbulence generated by Kuroshio–seamount interactions in Tokara Strait

Takahashi, A., R.C. Lien, E. Kunze, B. Ma, H. Nakamura, A. Nishina, E. Tsutsumi, R. Inoue, T. Nagai, and T. Endoh, "Energetic stratified turbulence generated by Kuroshio–seamount interactions in Tokara Strait," J. Phys. Oceanogr., 54, 461-484, doi:10.1175/JPO-D-22-0242.1, 2024.

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1 Feb 2024

Generating mechanisms and parameterizations for enhanced turbulence in the wake of a seamount in the path of the Kuroshio are investigated. Full-depth profiles of finescale temperature, salinity, horizontal velocity, and microscale thermal-variance dissipation rate up- and downstream of the ~10-km-wide seamount were measured with EM-APEX profiling floats and ADCP moorings. Energetic turbulent kinetic energy dissipation rates and diapycnal diffusivities above the seamount flanks extend at least 20 km downstream. This extended turbulent wake length is inconsistent with isotropic turbulence, which is expected to decay in less than 100 m based on turbulence decay time of N-1 ~100 s and the 0.5 m s-1 Kuroshio flow speed. Thus, the turbulent wake must be maintained by continuous replenishment which might arise from (i) nonlinear instability of a marginally unstable vortex wake, (ii) anisotropic stratified turbulence with expected downstream decay scales of 10–100 km, and/or (iii) lee-wave critical-layer trapping at the base of the Kuroshio. Three turbulence parameterizations operating on different scales, (i) finescale, (ii) large-eddy, and (iii) reduced-shear, are tested. Average ε vertical profiles are well reproduced by all three parameterizations. Vertical wavenumber spectra for shear and strain are saturated over 10–100 m vertical wavelengths comparable to water depth with spectral levels independent of ε and spectral slopes of –1, indicating that the wake flows are strongly nonlinear. In contrast, vertical divergence spectral levels increase with ε.

FlowPilot: Shoreside autonomy for profiling floats

Szuts, Z., T. Harrison, T. Curtin, B. Kirby, and B. Ma, "FlowPilot: Shoreside autonomy for profiling floats," Proc., OCEANS, 25-28 September, Biloxi, MS, doi:10.23919/OCEANS52994.2023.10337384 (MTS/IEEE, 2023).

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11 Dec 2023

Over the last twenty years, profiling floats have revolutionized ocean observations with globally distributed Lagrangian arrays performing fixed vertical sampling cycles. Here we investigate adaptive sampling with an array of inter-dependent floats guided by a software package called FlowPilot, which uses all available float measurements to select park depths that provide favorable drifts based on sampling goals. Drift predictions are performed with multiple prediction methods, including methods that use float data (drift velocity, geostrophic velocity calculations) or from external sources like numerical ocean forecast models. A skill-based weight is assigned to each method based on how accurately it predicts recent drifts. With this generalized approach to prediction, disparate methods can be combined numerically to permit multi-method optimization. The emergent skill of FlowPilot is tested and quantified by numerical simulations that minimize dispersion by keeping a grid of floats close to the center of the deployment box.

Seasonal variability of near-inertial/semidiurnal fluctuations and turbulence in the subarctic North Atlantic

Kunze, E., R.-C. Lien, C.B. Whalen, J.B. Girton, B. Ma, and M.C. Buijsman, "Seasonal variability of near-inertial/semidiurnal fluctuations and turbulence in the subarctic North Atlantic," J. Phys. Oceanogr., 53, 2717-2735, doi:10.1175/JPO-D-22-0231.1, 2023.

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1 Dec 2023

Six profiling floats measured water-mass properties (Т, S), horizontal velocities (u, v) and microstructure thermal-variance dissipation rates χT in the upper ~1 km of Iceland and Irminger Basins in the eastern sub-polar North Atlantic from June 2019 to April 2021. The floats drifted into slope boundary currents to travel counterclockwise around the basins. Pairs of velocity profiles half an inertial period apart were collected every 7–14 days. These half-inertial-period pairs are separated into subinertial eddy (sum) and inertial/semidiurnal (difference) motions. Eddy flow speeds are ~O(0.1 m s-1) in the upper 400 m, diminishing to ~O(0.01 m s-1) by ~800-m depth. In late summer through early spring, near-inertial motions are energized in the surface layer and permanent pycnocline to at least 800-m depth almost simultaneously (within the 14-day temporal resolution), suggesting rapid transformation of large-horizontal-scale surface-layer inertial oscillations into near-inertial internal waves with high vertical group velocities through interactions with eddy vorticity-gradients (effective β). During the same period, internal-wave vertical shear variance was 2–5 times canonical midlatitude magnitudes and dominantly clockwise-with-depth (downward energy propagation). In late spring and early summer, shear levels are comparable to canonical midlatitude values and dominantly counterclockwise-with-depth (upward energy propagation), particularly over major topographic ridges. Turbulent diapycnal diffusivities K ~O(10-4 m2 s-1) are an order of magnitude larger than canonical mid-latitude values. Depth-averaged (10–1000 m) diffusivities exhibit factor-of-three month-by-month variability with minima in early August.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center