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Rotasi Bumi Gerakkan Air Danau Garda Di Italia

Rotasi planet Bumi secara signifikan mengubah pergerakan air dan mempengaruhi pencampuran air kedalaman (deep water mixing) di Danau Garda, Italia. Pergerakan dan percampuran air ini sangat penting dan bermanfaat bagi ekosistem Danau Garda di Trentino, Italia. Begitu hasil riset kolaborasi selama 2 (dua) tahun dari ilmuwan asal Department of Civil, Environmental and Mechanical Engineering, University of Trento (UniTrento) di Italia dan ilmuwan asal The Institute for Marine and Atmospheric research, Utrecht University di Belanda, yang dipimpin oleh Henk Dijkstra (Sebastiano Piccolroaz et al, 2019).

Riset kolaborasi itu melibatkan sejumlah ilmuwan yaitu Sebastiano Piccolroaz asal  Institute for Marine and Atmospheric research Utrecht, Department of Physics, Utrecht University, Utrecht, 3584 CC, Belanda; Mariana Amadori asal Department of Civil, Environmental, and Mechanical Engineering, University of Trento, Trento, I-38123 di Italia; Marco Toffolon asal  Department of Civil, Environmental, and Mechanical Engineering, University of Trento, Trento, I-38123 di Italia; dan Henk A. Dijkstra asal Institute for Marine and Atmospheric research Utrecht, Department of Physics, Utrecht University, Utrecht, 3584 CC di Belanda (Sebastiano Piccolroaz, Mariana Amadori, Marco Toffolon & Henk A. Dijkstra, “Importance of planetary rotation for ventilation processes in deep elongated lakes: Evidence from Lake Garda (Italy),” Scientific Reports 9, Article number: 8290 (2019)).

 “We achieved these results - Sebastiano Piccolroaz (UU) and Marina Amadori (UniTrento), who authored this work together with Toffolon and Dijkstra, say - thanks to an intense field campaign, supported by the results of numerical simulations of Lake Garda hydrodynamics, that kept our researchers busy in Trento and Utrecht for two years, from 2017 to 2018,” ungkap Marina Amadori, insinyur lingkungan dan peneliti pada University of Trento, Italia, dalam siaran pers awal Juni 2019 (Universitàs di Trento, 5/6/2019).

Ventilasi dan percampuran air sangat penting bagi ekosistem Danau Garda selama ini. Tim ahli asal Belanda dan Italia itu melakukan riset kolaborasi model-model hidro-dinamika. Simulasi-simulai gerakan air di Danau Garda menyingkap interaksi khusus antara pola-pola angin setempat di danau itu dan kekuatan-kekuatan rotasi planet.

“According to our study, when the wind blows along Lake Garda's main axis, the Earth's rotation causes a secondary circulation which displaces the water laterally, from one coast to the other. This creates a difference in water temperature between the eastern (Veneto) and western (Lombardia) shore and, highly relevant for the lake's ecology, contributes to the transport of oxygen, nutrients and other substances from the surface to the deep layers and vice versa,” papar Marina Amadori dalam rilis pers awal Juni 2019 (Universitàs di Trento, 5/6/2019).

Pada musim semi dan awal musim panas, ketika es mencair dan tenggelam ke dasar danau itu, dan ketika lapisan atas danau hangat lebih cepat, danau-danau mengalami stratifikasi termal yang mencegah pemerataan oksigen dan nutrisi. Maka angin dan gelombang-gelombang air mencampur bahan bakar (fuel-mixing), yang membantu distribusi nutrisi dan oksigen pendukung rantai makanan air tawar (freshwater food chains).

“In detail, in the case of Foehn winds, cold water surfaces along the eastern side of the lake (upwelling) and warmer water moves down along the western side (downwelling). Between February and April in particular, when the lake water temperature is at its lowest, the vertical movement can reach even the bottom of the lake, that is at a depth of 350m. We did not expect to observe in Lake Garda an event that is typical of the coastal areas of oceans and large lakes,” papar Sebastiano Piccolroaz, peneliti pada Utrecht University di Belanda (Universitàs di Trento, 5/6/2019). 

Oleh: Servas Pandur