Author(s): A. Fenocchi; S. Sibilla; C. Dresti; M. Rogora

Linked Author(s): Andrea Fenocchi

Keywords: Lake Maggiore; Climate change; Mixing regime; Hydrodynamic simulations; GHG emissions

Abstract: The evolution in the mixing regime of Lake Maggiore with climate change is forecast through 1-D hydrodynamic simulations. Future enduring lack of mixing could be avoided only if global GHG emissions were reduced starting from the next few years. The water temperatures of most lakes worldwide are increasing due to the air temperature rise triggered by ongoing climate change. The latter is caused by the combination of natural atmospheric phenomena and anthropogenic greenhouse-gases (GHG) emissions. For deep temperate lakes, this is determining an intensification of the vertical temperature gradient between surface and bottom waters, as the epilimnion is warming at almost the same velocity of air, whereas the hypolimnion at a much lower rate. A decrease in the frequency of full turnover and an increase of stability are thus being observed, causing deep-water oxygenation and surface nutrient replenishment from the hypolimnion to drop. This is affecting the ecosystems of lakes in addition to the direct implications of water warming. Here, we studied through numerical simulations the 2016-2085 evolution under climate change of the thermal structure of Lake Maggiore (Northern Italy/Southern Switzerland), the westernmost of the large deep oligomictic lakes in the subalpine district (the others are Lakes Lugano, Como, Iseo and Garda). Due to the common climate and hydrodynamic features, the obtained results can be qualitatively extended to the other lakes in the region, in addition to other deep oligomictic basins in temperate zones with similar expected air temperature rise. The main research purposes were: (1) to assess if a transition towards persistent thermal stratification would necessarily occur for Lake Maggiore and the neighbouring basins and how it would develop; (2) to determine if and how a reduction of GHG emissions would otherwise be able to revert the process.

DOI: https://doi.org/10.3850/978-981-11-2731-1_039-cd

Year: 2018