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Spatiotemporal variability of the low-frequency sound field in a coastal wedge in the presence of an internal Kelvin wave (IKW) is studied both experimentally and theoretically. The experiments were carried out in Lake Kinneret, Israel (also known as the Sea of Galilee) in August 2021, with a wideband sound source deployed near the shore and receiving vertical line arrays located at the lake's center. Parameters of the IKW were obtained earlier from long-term thermistor string measurements combined with conductivity, temperature, and depth data. The IKW initiated range-dependent vertical displacements of the thermocline with a maximum amplitude near the shore and almost zero amplitude in the center of the lake. It corresponded to a thermocline inclination angle of ±0.08° with respect to the horizontal. Temporal variations in depth-averaged acoustic intensity, reaching almost 8 dB, and remarkable changes in the normal mode composition were registered. These effects are explained based on simulations using a parabolic equation and normal mode models. The role of mode coupling in acoustic intensity variations is assessed. [ABSTRACT FROM AUTHOR]

Methane (CH 4 ) is the simplest and most common hydrocarbon in nature. CH 4 gas content is accommodated in discrete bubbles in shallow aquatic sediments. The bubble dynamics there are controlled by a diversity of physical, mechanical and biogeochemical processes that vary spatially and temporally over the aquatic ecosystem. Previous studies explored these controls on gas dynamics in shallow aquatic sediments mostly separately, despite of their coupled nature. In this study, a multiannual (2015-2021) acoustic database on gas content in sediments of Lake Kinneret, Israel is compiled. Gas content is evaluated by acoustic applications based on the sound speed inferred from the reflection coefficient. A multivariate linear regression is fitted and a closed form expression of gas content dependence on the following predictors, which change spatially and temporally over the lake, is obtained: 1) water depth; 2) short-leaving CH 4 production rate peaks fueled by punctuated phytoplankton bloom crashes; and 3) CH 4 bubble dissolution rates. Our comprehensive multidisciplinary analysis indicates that short-leaving CH 4 production peaks act as major controls on sediment gas content in Lake Kinneret, where the hydrodynamic regime and sloping bottom transport the autochthonous organic matter toward the profundal lake zone. In contrast, the water depth predictor has the least significance, which is explained mainly by lack of ebullition in the deepest part of the lake. Our novel process-based correlation analysis enables quantification and prediction of gas content dynamics in sediments of Lake Kinneret under changing spatial and temporal conditions. Our modeling could be extended to other marine and lacustrine ecosystems with different predictors and temporal variability. Predicting CH 4 gas content dynamics is important for accurate evaluation and even reduction of a long-persisting uncertainty related to CH 4 flux from aquatic sediments and for assessment of sediment load-bearing capabilities affected by gas presence., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)