Abstract
Moonglint and sunglint satellite imagery acquired from Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) satellite sensors were used to study the characteristics of internal waves (IWs) and their relationship to tides and stratification in the Sulu–Celebes Sea. Tidally generated IWs propagate northwestward and southeastward into the Sulu and Celebes Seas, showing a spring–neap tidal cycle behavior with larger/smaller IWs occurring under spring/neap tides, respectively. The length of IW crests, their wavelength, and phase speed derived from the sunglint/moonglint image pairs were observed to decrease from spring to neap tides. IWs in the Sulu–Celebes Sea which are correlated with oceanic stratification display seasonal and regional fluctuations. In the Celebes Sea, IWs were less frequently observed but propagated with faster phase speeds and larger scales compared to those in the Sulu Sea. Comparisons of stratification and barotropic tidal transport among the IWs generation sites indicate that the shallowing maximum Brunt–Vaisala frequency and strongest tidal transport around Pearl Bank are major factors contributing to greater IW activity compared to other generation sites. IWs generated near Pangutaran Island and Pearl Bank further merge into one dynamical system, creating longer wave crests of ~200 km that travel at faster phase speed ( $\sim 2.5\,\,\text{m}\cdot \text{s}^{-1}$ ) in the Sulu Sea. This paper demonstrates a new application using a combination of sunglint/moonglint imagery in tracking an important oceanic phenomenon.
Highlights
I NTERNAL waves (IWs) occur globally within the upper several hundred meters of the ocean water column, where stratification and perturbation co-exist [1],[2]
The combined sunglint/moonglint image pairs acquired within one semidiurnal tidal cycle were further used in this study to explore IWs relationship to tides in the Sulu–Celebes Sea
Satellite-derived IW characteristics revealed a spring–neap tidal cycle behavior with larger/smaller IWs occurring under spring/neap tides in the Sulu–Celebes Sea
Summary
I NTERNAL waves (IWs) occur globally within the upper several hundred meters of the ocean water column, where stratification and perturbation co-exist [1],[2]. IWs are most often observed on continental shelves [3]–[5], straits [6], [7], channels [8], and marginal seas, for example, the Andaman Sea [9], South China Sea (SCS) [10]–[12], Celebes Sea, Sulu Sea [13]–[17], White Sea [18], Red Sea [19], Gulf of Oman [20], and Arabian Sea [21].
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