Past and future climate change effects on thermal regime and oxygen solubility of four peri-alpine lakes

Abstract

International audienceClimate change modifies the thermal regime and oxygen solubility in lakes globally, resulting in the alteration of lake habitats. The use of 1D lake models has become the standard in lake research to evaluate the effects of climate change. However, the required global scale forcing parameters have several limitations, such as the need of downscaling. Here, we evaluate the possibility to force mechanistic models by following the long-term evolution of shortwave radiation and air temperature while providing realistic seasonal trends for other meteorological parameters. The performance of 1D hydrodynamic lake models was assessed for long-term variations based on 70 years of limnological data collected by the French Observatory of LAkes (OLA). Further the effects of climate change on the thermal regime and oxygen solubility were analyzed in the four-largest French peri-Alpine lakes. Our results show that 1D models forced by air temperature and short-wave radiation accurately predict variations in lake thermal regime, with RMSE of 1.14°C. According to model simulations in the epilimnion and hypolimnion respectively, during the last three decades, water temperatures have increased by 0.46°C/decades (±0.02°C) and 0.33°C/decades (±0.06°C). Accordingly, O2 solubility decreased by -0.104mg/L/decades (±0.005 mg/L) and -0.096mg/L/decades (±0.011 mg/L) due to thermal change. Based on the ssp370 socio-economic pathway of the IPCC, perialpine lakes will face an increase of 3.80°C(±0.20°C) in the future until 2100. These results suggest important degradation in lake thermal and oxygen conditions as well as habitat loss for endemic species