Seismological Society of America: Environmental Seismology 2025
Date:
Taking the Temperature of the Ocean from Pressure: Using Ocean Bottom Pressure Measurements of Internal Waves in the South China Sea to Track the Annual Cycle of Sea State
Oceans are stratified by density gradients resulting from vertical variations in temperature and salinity, creating a medium for internal gravity waves. Nonlinear internal waves can form and propagate hundreds of kilometers before breaking in shallow water. Their activity is modulated by climate change and plays a critical role in numerous oceanic processes, including vertical thermal mixing, nutrient supply, sediment transport, and acoustic transmission. Despite their importance, nonlinear internal waves remain difficult to detect over large spatial and temporal scales. We perform a 10-year analysis of nonlinear internal waves using satellite imagery complemented by a 1 year record of ocean bottom pressure (OBP). In this study, we (1) generate a decade-long dataset of propagation speeds and back azimuths of nonlinear internal waves generated in the eastern Luzon Strait of the South China Sea — home to some of the world’s largest-amplitude internal waves — using Himawari-8 geostationary satellite data and analyze the periods and amplitudes recorded during wave passages over the OBP deployed offshore of Dongsha Atoll in 2020. From the pressure data, we find that the half-duration of the waves varies seasonally and anti-correlates with amplitude. The data is best explained by variations in local stratification. Ocean bottom pressure can potentially by used to track the gradient of near-surface ocean temperature as it responds to seasonal forcing and climate changes.
For more details, visit my Internal Wave repository.