Airborne Observations of Shoaling and Breaking Internal Waves

Abstract

Internal waves occur at a density interface, and in deep-water may be generated through tidal or wind forcing (Alford, 2001;Baines, 1982;Helfrich & Melville, 2006). Alternatively, they can be locally generated on the continental shelf (e.g., Sandstrom & Elliott, 1984;Shroyer et al., 2010). No matter the generation mechanism or location, internal waves (IW) on the inner-shelf can shoal and break, modulating the transport of sediment, heat, contaminants, and nutrients (e.g., Lamb, 2014;Sinnett et al., 2022). They are crucial for understanding the rates of energy dissipation and mixing (Jones et al., 2020;Moum et al., 2007). One of their most important characteristics is their large vertical velocities (in comparison to typical upwelling indices, Bakun, 1973), which facilitates vertical transport of suspended material, heat and horizontal momentum.Traditional methods for measuring IW include in-situ moorings and towed instruments (Colosi et al., 2018;Moum et al., 2002). By employing ADCPs and temperature sensors on fixed or freely drifting moorings, it is possible to determine velocities and density as a function of depth. The energy dissipation rate can subsequently be determined from these measurements (e.g., Moum et al., 2007). While a mooring yields high resolution temporal information at one location, it does not capture the directionality and scales of the horizontal spatial variability of an internal wave, particularly as it shoals and breaks. Several previous studies have used a spatial array of moorings to try to address this shortcoming (

Strongly Nonlinear Effects on Determining Internal Solitary Wave Parameters From Surface Signatures With Potential for Remote Sensing Applications

“…Compared to image intensity determined by velocity divergence and other oceanic factors, velocity appears to be a more suitable choice, which monotonically changes with η 0 (Figure 3d). Some new technologies for measuring surface currents induced by ISWs have been developed, such as interferometric SAR (Romeiser & Graber, 2015) and airborne PIV (Vrećica et al., 2022). If the maximum velocities of ISWs and D p − p are both taken into account, a new accurate retrieval method can be established.…”