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Guangyu Xu

Research Scientist/Engineer - Senior

Email

guangyux@apl.uw.edu

Phone

206-543-6860

Research Interests

Guangyu Xu's research combines underwater acoustic and numerical modeling techniques to study fluid flows within both the seafloor and the ocean. Xu's scientific questions focus on: dynamics associated with seafloor hydrothermal discharge and its dispersal near a mid-ocean ridge, deep ocean flows and their interconnections with surface processes, sub-seafloor hydrothermal circulation, and acoustic seafloor characterization.

Department Affiliation

Acoustics

Education

B.S. Ocean Technology, Ocean University of China (Qingdao, Shandong Province, China), 2008

M.S. Marine Sciences, University of Georgia, 2010

Ph.D. Marine Sciences, Rutgers University, 2015

Publications

2000-present and while at APL-UW

Subsurface acoustic ducts in the Northern California current system

Xu, G., R.R. Harcourt, D. Tang, B.T. Hefner, E.I. Thorsos, and J.B. Mickett, "Subsurface acoustic ducts in the Northern California current system," J. Acoust. Soc. Am., 155, 1881-1894, doi:10.1121/10.0024146, 2024.

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7 Mar 2024

This study investigates the subsurface sound channel or acoustic duct that appears seasonally along the U.S. Pacific Northwest coast below the surface mixed layer. The duct has a significant impact on sound propagation at mid-frequencies by trapping sound energy and reducing transmission loss within the channel. A survey of the sound-speed profiles obtained from archived mooring and glider observations reveals that the duct is more prevalent in summer to fall than in winter to spring and offshore of the shelf break than over the shelf. The occurrence of the subsurface duct is typically associated with the presence of a strong halocline and a reduced thermocline or temperature inversion. Furthermore, the duct observed over the shelf slope corresponds to a vertically sheared along-slope velocity profile, characterized by equatorward near-surface flow overlaying poleward subsurface flow. Two potential duct formation mechanisms are examined in this study, which are seasonal surface heat exchange and baroclinic advection of distinct water masses. The former mechanism regulates the formation of a downward-refracting sound-speed gradient that caps the duct near the sea surface, while the latter contributes to the formation of an upward-refracting sound-speed gradient that defines the duct's lower boundary.

Dispersion of deep-sea hydrothermal plumes at the Endeavour Segment of the Juan de Fuca Ridge: a multiscale numerical study

Xu, G., C.R. German, "Dispersion of deep-sea hydrothermal plumes at the Endeavour Segment of the Juan de Fuca Ridge: a multiscale numerical study," Front. Mar. Sci., 10, doi:10.3389/fmars.2023.1213470, 2023.

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20 Jul 2023

A multiscale numerical framework has been developed to investigate the dispersion of deep-sea hydrothermal plumes that originate from the Endeavour Segment of the Juan de Fuca Ridge located in the Northeast Pacific. The analysis of simulation outputs presented in this study provides insights into the influences of tidal forcing and the buoyancy flux associated with hydrothermal venting on ocean circulation and plume dispersion in the presence of pronounced seafloor topography. The results indicate that tidal forcing drives anti-cyclonic circulation near the ridge-axis, while hydrothermal venting induces cyclonic circulation around vent fields within the axial rift valley. Tidal forcing has a notable impact on plume dispersion, particularly near the large topographic features to the north of the Endeavour Segment. Furthermore, plume dispersion exhibits notable inter-annual variability, with a northbound trajectory in 2016 and a southbound trajectory in 2021. The study also reveals that both buoyancy fluxes and tidal forcing enhance the mixing of hydrothermal plumes with ambient seawater.

Sonar observations of heat flux of diffuse hydrothermal flows

Jackson, D., K. Bemis, G. Xu, and A. Ivakin, "Sonar observations of heat flux of diffuse hydrothermal flows," Earth Space Sci., 9, doi:10.1029/2021EA001974, 2022.

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1 Oct 2022

Previous work using multibeam sonar to map diffuse hydrothermal flows is extended to estimate the heat output of diffuse flows. In the first step toward inversion, temperature statistics are obtained from sonar data and compared to thermistor data in order to set the value of an empirical constant. Finally, a simple model is used to obtain heat-flux density from sonar-derived temperature statistics. The method is applied to data from the Cabled Observatory Vent Imaging Sonar (COVIS) deployed on the Ocean Observatories Initiative's Regional Cabled Array at the ASHES vent field on Axial Seamount. Inversion results are presented as maps of heat-flux density in MW/m2 and as time series of heat-flux density averaged over COVIS' field of view.

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
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