Long-term temperature evolution in a deep sub-alpine lake, Lake Bourget, France: how a one-dimensional model improves its trend assessment

Brigitte Vinçon-Leite (1) , Bruno J. Lemaire (1) , Viet Tran Khac (1) , Bruno Tassin (1)

1 LEESU - laboratoire Eau Environnement et Systèmes Urbains

Water temperature and the alternation of stratification and mixing count amongst key drivers of lake ecology. Reliable long time-series of water temperature are rare. Here, we investigated how a numerical model can fill the gaps in heterogeneous time-series and make it possible to identify a significant trend in the lake thermal regime. We computed the mean water temperature and the Schmidt stability, an indicator of the stratification strength, in a deep and well-stratified lake (Lake Bourget, France), between 1976 and 2008. We first used temperature measurements and then a one-dimensional vertical model, which we describe here. The model performs as well as the best existing models. During the 1976-2008 periods, whereas no statistically significant trend came out of the measurements, we found in the simulation results an increase of 0.12 °C per decade in the water temperature and of 5.9 days per decade in the stratification duration. This shows that the temperature history of a lake can be reconstructed and a reliable long-term trend computed when weather data and a calibrated temperature model are available. Our results also suggest that different local climatic influences cause a slower warming in this lake of the south-western Alps than in other sub-alpine lakes.

Mots clés: One-dimensional vertical model; Lake temperature; Climate variability; South-western Alps

Domaines: Sciences de l'environnement; Milieux et Changements globaux

Brigitte Vinçon-Leite, Bruno J. Lemaire, Viet Tran Khac, Bruno Tassin. Long-term temperature evolution in a deep sub-alpine lake, Lake Bourget, France: how a one-dimensional model improves its trend assessment. Hydrobiologia, 2014, European Large Lakes III. Large lakes under changing environmental conditions, 731 (1), pp.49-64. ⟨10.1007/s10750-014-1818-4⟩. ⟨hal-00967616⟩