Moored observations of turbulent mixing events in deep Lake Garda, Italy

Mixing events in deep Lake Garda

Abstract

Deep water circulation and mixing processes are responsible for the transport of matter, nutrients and pollutants in deep lakes. Nevertheless, detailed continuous observations are rarely available. To overcome some of these deficiencies and with the aim of improving our understanding of deep mixing processes, a dedicated yearlong mooring comprising 100 high-resolution temperature sensors and a single current meter were located in the deeper half of the 344 m deepest point of the subalpine Lake Garda, Italy. The observations show peaks and calms of turbulent exchange, besides ubiquitous internal wave activity. In late winter, northerly winds activate episodic deep convective overturning, the dense water being subsequently advected along the lake-floor. Besides deep convection, such winds also set-up seiches and inertial waves that are associated with about 100 times larger turbulence dissipation rates than that by semidiurnal internal wave breaking observed in summer. In the lower 60 m above the lake-floor, however, the average turbulence dissipation rate is approximately constant in value year-around, being about 10 times larger than open-ocean values, except during deep convection episodes.

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Author Biographies

Sebastiano Piccolroaz, Institute for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University, Utrecht

Present address: École Polytechnique Fédérale de Lausanne, Physics of Aquatic Systems Laboratory, Margaretha Kamprad Chair, APHYS GR A2 412, 1015 Lausanne, Switzerland

Marina Amadori, Department of Civil, Environmental, and Mechanical Engineering, University of Trento

Present address: Institute for electromagnetic sensing of the environment (IREA), National Research Council, Milan, Italy

Published
2020-11-03
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Issue
Section
Original Articles
Edited By
Aldo Marchetto, CNR-IRSA Verbania, Italy
Keywords:
Yearlong high-resolution moored temperature observations, deep Lake Garda, internal waves, turbulent overturning, convective cooling
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How to Cite
1.
van Haren H, Piccolroaz S, Amadori M, Toffolon M, Dijkstra HA. Moored observations of turbulent mixing events in deep Lake Garda, Italy: Mixing events in deep Lake Garda. J Limnol [Internet]. 2020Nov.3 [cited 2020Nov.27];(AOP). Available from: https://jlimnol.it/index.php/jlimnol/article/view/jlimnol.2020.1983