Abstract
Turbulent mixing processes in deep alpine Lake Garda (I) have not extensively been observed. Knowledge about drivers of turbulent fluxes are important for insights in the transport of matter, nutrients and pollutants, in the lake and in natural water bodies in general. In this paper, the occurrence of internal wave induced turbulent convection, termed 'internally forced convection', is addressed as opposed to the more common shear-induced turbulence in a density stratified environment. Observations are analyzed from a dedicated yearlong mooring holding 100 high-resolution temperature sensors at 1.5 m intervals under a single current meter in the deeper half of the 344 m deep lake-center. Episodically, the weakly density stratified waters in the lower 50 m above the lake-floor show spectral slope and coherence evidence of short-term (15–30 min) convective motions under internal waves that are supported by the stronger stratified waters above. The near-homogeneous conditions are not attributable to frictional Ekman dynamics, but to large-scale internal wave crests.
| Original language | English |
|---|---|
| Pages (from-to) | 305–316 |
| Journal | Environmental Fluid Mechanics |
| Volume | 21 |
| Early online date | 12 Nov 2020 |
| DOIs | |
| Publication status | Published - 2021 |
Funding
We highly appreciated the assistance of the Nautical Rescue Team ‘Vigili del Fuoco-Trento’, S. Piccolroaz and M. van Haren around the deployment and recovery of the mooring. We thank M. Laan for all his temperature sensor efforts. S. Piccolroaz supplied the map of Lake Garda and mooring scheme. This project was funded by the Faculty of Science of Utrecht University through a grant to HD and was supported by the National Marine Facilities (NIOZ).
Keywords
- Convection
- Deep-sea turbulence
- High-resolution moored temperature observations
- Internal waves
- Lake Garda