Optical influence of ship wakes

Area of Science:

• Ocean optics
• Remote sensing
• Bubble dynamics

Background:

• Ship wakes generate numerous air bubbles, forming foam and releasing surfactants.
• These phenomena significantly alter the optical properties of the ocean's surface layer.

Purpose of the Study:

• To experimentally validate theoretical predictions of optical property variations caused by bubble injection in ship wakes.
• To investigate how bubble size distribution and water types influence these optical changes.

Main Methods:

• Field experiments were conducted in diverse oceanic environments (clear Pacific, turbid coastal waters off New Jersey).
• Measurements included remote-sensing reflectance and bubble size distribution within ship wakes.
• Optical and physical properties of three distinct water types were analyzed.

Main Results:

• Injected bubbles consistently increased ocean backscattering and reflectance across visible and infrared bands.
• The spectral characteristics of enhanced reflectance varied with location and water type.
• Ship wakes appeared greener in the open ocean but showed minimal color change in turbid coastal waters.

Conclusions:

• Bubbles alter ocean color by increasing radiance, with effects dependent on background water properties.
• Foam and surfactants further enhance reflectance, influencing remote sensing accuracy.
• Understanding these optical changes is crucial for interpreting satellite and aerial observations of ship wakes.