Method to derive ocean absorption coefficients from remote-sensing reflectance.

Area of Science:

• Ocean optics
• Remote sensing
• In-water biogeochemistry

Background:

• Accurate in-water absorption coefficients are crucial for understanding marine ecosystems and water quality.
• Traditional methods often require in-situ measurements, limiting spatial and temporal coverage.

Purpose of the Study:

• To present and validate an analytical method for deriving in-water absorption coefficients directly from remote-sensing reflectance.
• To assess the method's performance across diverse oceanic conditions.

Main Methods:

• Developed an analytical approach to calculate in-water absorption from total remote-sensing reflectance.
• Collected data in the Gulf of Mexico and Monterey Bay, covering chlorophyll-a concentrations from 0.07 to 50 mg/m³.
• Compared derived absorption coefficients with those obtained using diffuse attenuation coefficients.

Main Results:

• The new method showed high agreement with traditional methods, with differences of 13.0% to 14.5% (r² = 0.96–0.97) at key wavelengths (440, 488, 550 nm).
• The method demonstrated effectiveness across a wide range of oceanic environments, including coastal waters, open ocean, upwelling regions, and the Loop Current.
• Validated for total absorption coefficients ranging from 0.02 to 2.0 m⁻¹.

Conclusions:

• The presented analytical method reliably retrieves in-water absorption coefficients solely from remotely sensed data.
• This technique has significant potential for broad applications in oceanic remote sensing, improving our ability to monitor marine environments.