Effects of climate changes

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The deep southern subalpine lakes (Maggiore, Lugano, Como, Iseo and Garda) constitute the most important lake district in Italy (Fig. 1). They are located south of the Alps, in one of the most densely populated and highly productive areas of the country, and represent an essential strategic water supply for agriculture, industry, fishing and drinking. Moreover, they are an important resource for recreation and tourism with their attractions of landscape, mild climate and water quality. They have morphometric characteristics in common, with narrow, north-south elongated shapes, and floors lying below sea level. The collection of chemical (and biological, see Aquatic ecology section) data on lake water on a regular basis is of extreme importance in the evaluation of water quality and its temporal change. Furthermore water chemistry is closely related to biological processes taking place in the lake and to mixing and turnover processes. As a consequence, monitoring the main chemical variables with standardised analytical methods and sampling plays an important role in the nutrient budget of the lake and in the interpretation of biological phenomenon. The temporal behaviour of the physical properties of lakes under the impact of climate change is of great relevance in the deep subalpine lakes. The availability of long-term data series enables us to clarify, and subsequently to model, the change in hydrodynamic processes which are fundamental in the mixing processes and the renewal time of the lake water.

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Research

The main objective of our research is to acquire increasing knowledge of the physical and chemical characteristics of the deep subalpine lakes, focusing particularly on Lake Maggiore, and of their changes in time. To achieve this goal, the long-term trends in the main physico-chemical variables are analysed in relation to anthropogenic (eutrophy/oligotrophy, atmospheric deposition of pollutants, land use change) and climatic drivers (Fig. 2a and Fig. 2b). Specifically, the analysis of long-term data aims to clarify whether lake hydrodynamics and the mixing depth reached at the end of the winter overturn are mainly driven by large-scale climatic oscillations or by meteorological features at a local scale. Long-term series of chemical data are also analysed, in order to evaluate the chemical budget of the principal solutes and algal nutrients, and the response of lake chemical properties to different drivers (atmospheric input of nitrogen and other pollutants, nutrient loads from the main inflowing rivers and climate change).