Improved Visualization of Hydroacoustic Plumes Using the Split-Beam Aperture Coherence.

Area of Science:

• Oceanography
• Environmental Science
• Acoustics

Background:

• Natural methane seepage and anthropogenic gas leaks impact the global carbon cycle and ocean environments.
• Accurate detection of these gas releases is vital for environmental and economic reasons.
• Split beam echo sounders (SBES) are used to detect gas plumes, but can struggle in challenging conditions like deep water and high noise.

Purpose of the Study:

• To evaluate the effectiveness of the coherence factor (CF) as a method to improve gas seep detection using SBES data.
• To demonstrate the utility of CF processing for clearer visualization and identification of hydroacoustic plumes.

Main Methods:

• Utilized data acquired from a Simrad EK80 SBES in the Hudson Canyon.
• Calculated the spatial coherence of the wavefield across split beam sectors to derive the coherence factor (CF).
• Compared CF imagery with traditional acoustic backscatter imagery for gas plume visualization.

Main Results:

• Hydroacoustic plumes associated with gas seepage were more clearly defined in the CF imagery.
• The coherence factor (CF) facilitated easier detection of gas plumes compared to acoustic backscatter images alone.
• CF processing offers a complementary approach to acoustic imagery for identifying bubbles in the water column.

Conclusions:

• The coherence factor (CF) is a valuable and computationally simple metric for enhancing the detection of gas seepage plumes.
• CF processing improves the clarity of hydroacoustic plumes, aiding in both visual and automated detection.
• This method shows promise for more effective monitoring of methane release in marine environments.