Simulation of acoustic reflection and backscatter from arctic sea-ice.

The rapidly warming Arctic ocean demands new ways to monitor and characterize changes in sea-ice distribution, thickness, and mechanical properties. Upward-looking sonars mounted on autonomous underwater vehicles offer possibilities for doing so. Numerical simulations were made of the signal received by an upward-looking sonar under a smooth ice sheet using a wavenumber integration code.

Acoustic propagation in gassy intertidal marine sediments: An experimental study.

The need to predict acoustic propagation through marine sediments that contain gas bubbles has become increasingly important for civil engineering and climate studies. There are relatively few in situ acoustic wave propagation studies of muddy intertidal sediments, in which bubbles of biogenic gas (generally methane, a potent greenhouse gas) are commonly found. We used a single experimental rig to conduct two in situ intertidal acoustical experiments to improve understanding of acoustic remote sensing of gassy sediments, eventually including gas bubble size distributions.

Geophysical early warning of salt precipitation during geological carbon sequestration.

Sequestration of industrial carbon dioxide (CO) in deep geological saline aquifers is needed to mitigate global greenhouse gas emissions; monitoring the mechanical integrity of reservoir formations is essential for effective and safe operations. Clogging of fluid transport pathways in rocks from CO-induced salt precipitation reduces injectivity and potentially compromises the reservoir storage integrity through pore fluid pressure build-up. Here, we show that early warning of salt precipitation can be achieved through geophysical remote sensing.

Absolute calibration of hydrophones immersed in sandy sediment.

An absolute calibration method has been developed based on the method of three-transducer spherical-wave reciprocity for the calibration of hydrophones when immersed in sandy sediment. The method enables the determination of the magnitude of the free-field voltage receive sensitivity of the hydrophone. Adoption of a co-linear configuration allows the acoustic attenuation within the sediment to be eliminated from the sensitivity calculation.