The importance of nonlinear internal waves in a deep subalpine lake: Lake Iseo, Italy

Abstract

The energy transfer from basin‐scale internal waves to internal nonlinear waves was investigated in a large, deep subalpine lake through a combination of field data and three‐dimensional hydrostatic and nonhydrostatic modeling. The response of the internal wave field induced by two storm events, with distinct characteristics, showed that, for the whole lake, around 15% of the total potential energy contained in the basin‐scale internal waves was transferred to nonlinear internal waves in response to moderate forcing, the large transfer being the direct result of the small surface layer thickness compared with the depth of the lake. Locally, the energy transfer to nonlinear waves was up to 30% for the more severe forcing. To model such energy transfers, a nonhydrostatic three‐dimensional hydrodynamic model was required; this implies that the inclusion of nonhydrostatic effects is essential for accurate modeling of ecological processes in deep large lakes, which is a challenge considering currently available computational resources.