Small Mountainous Rivers Generate High-Frequency Internal Waves in Coastal Ocean

Area of Science:

• Oceanography
• Fluid Dynamics
• Remote Sensing

Background:

• High-frequency internal waves are frequently observed in satellite imagery of small river plumes globally.
• The generation mechanism for these waves in small, rapid river inflows to the sea is not fully understood.

Purpose of the Study:

• To describe the mechanism of high-frequency internal wave generation by small river discharges.
• To analyze the impact of these waves on river plume dynamics and coastal processes.

Main Methods:

• Analysis of in situ and satellite data.
• Observation of hydraulic jump formation due to friction between river runoff and ambient sea.
• Estimation of internal wave parameters (wavelengths, phase speeds, frequencies).

Main Results:

• A hydraulic jump mechanism was identified as the cause of internal wave generation.
• These waves propagate offshore within the stratified layer between river plume and ambient sea.
• Estimated wave parameters for plumes off the northeastern Black Sea coast.

Conclusions:

• Riverine hydraulic jumps are a key mechanism for generating high-frequency internal waves in small river plumes.
• These waves significantly influence turbulence, mixing, and coastal processes in affected areas.
• The phenomenon is common in mountainous coastal regions worldwide, especially during high discharge periods.