Spatiotemporal variability in the diffuse attenuation coefficient of sea ice

Area of Science:

• Oceanography
• Remote Sensing
• Climate Science

Background:

• The diffuse attenuation coefficient (Kd) is crucial for understanding light transmittance in sea ice, impacting ocean energy balance and biological processes.
• Measuring Kd in solid sea ice presents challenges for conventional instruments.

Purpose of the Study:

• To develop and utilize a high spectral resolution instrument for measuring sea ice irradiance profiles.
• To investigate the spatio-temporal variability of Kd in sea ice and identify its driving mechanisms.

Main Methods:

• Conducted in-situ experiments in Liaodong Bay and laboratory experiments to measure irradiance profiles.
• Performed experiments focusing on sea ice microstructure, specifically air bubble content.
• Analyzed the relationship between Kd, depth, time, and physical microstructure characteristics.

Main Results:

• Kd values varied significantly with depth (up to 2x difference between layers) and showed temporal variations (1.38x difference in surface layer Kd in 2022).
• Spatio-temporal variability in Kd was strongly correlated with changes in air bubble content (R² = 0.52).
• Air bubbles, due to their intense scattering properties, were identified as the primary factor influencing Kd changes.

Conclusions:

• Air bubble content is the main driver of Kd variability in sea ice.
• Climate-induced changes in bubble volume can alter sea ice scattering properties, consequently affecting Kd and upper ocean light conditions.