Energetics and damping of basin-scale internal waves in a strongly stratified lake

Shimizu Kenji, J├Ârg Imberger

Limnol. Oceanogr., 53(4), 2008, 1574-1588 | DOI: 10.4319/lo.2008.53.4.1574

ABSTRACT: Energetics and damping of basin-scale internal waves and subsequent near-bottom transport processes in Lake Kinneret were investigated using the modal analysis in a layer-stratified irregular basin. The theory was extended to include small linear damping, and energy budgets and damping rates of five dominant internal waves were extracted by fitting numerically calculated internal waves to isotherm displacements measured by six thermistor chains distributed throughout the lake. Energy contained in the dominant internal waves (~3 GJ) resulted from a balance between energy input from diurnal winds and dissipation within a day, both of which were estimated to be 3~4 GJ d-1. Damping was caused primarily by bottom friction, and the damping rates (e-folding time) varied from 1 to 3 d, depending on the velocity structure. Currents induced by the internal waves caused considerable spatial variability of the bottom shear stress and near-bottom transport processes, such as entrainment rate at the top of the benthic boundary layer and mass transfer at the sediment-water interface.

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