Model-oriented ocean tomography using higher frequency, bottom-mounted hydrophones

Area of Science:

• Oceanography
• Acoustics
• Data Assimilation

Background:

• Oceanographic models benefit from real-world data assimilation.
• Ocean surface motion introduces variability in acoustic travel times.
• Accurate acoustic travel time measurements are crucial for oceanographic insights.

Purpose of the Study:

• To develop a tomographic scheme for ingesting ocean acoustic measurements into ocean models.
• To address and remove variability caused by ocean surface motion in acoustic travel times.
• To investigate an assimilation technique for correcting oceanographic models using acoustic travel time differences.

Main Methods:

• Utilizing bottom-mounted hydrophones for ocean acoustic measurements.
• Applying techniques to measure and correct acoustic travel times influenced by surface waves.
• Deriving equations relating travel time differences to oceanographic variables.
• Estimating acoustic and ocean model error covariance matrices.

Main Results:

• A single source-receiver pair demonstrated that tomographic data can constrain ocean circulation models but may introduce biases.
• Utilizing prior knowledge of model bias in a second test case significantly improved model predictions without introducing new biases.
• The developed assimilation technique successfully improved model predictions when applied judiciously.

Conclusions:

• Ocean acoustic tomography offers a valuable method for enhancing oceanographic models.
• Careful application of tomographic data, considering model biases, is essential for accurate predictions.
• The developed techniques effectively mitigate surface wave effects and improve ocean circulation modeling.