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

Abstract

Abstract. Long-term effects of climate change on lakes globally will include a substantial modification in the thermal regime and the oxygen solubility of lakes, resulting in the alteration of ecosystem processes, habitats, and concentrations of critical substances. Recent efforts have led to the development of long-term model projections of climate change effects on lake thermal regimes and oxygen solubility. However, such projections are hardly ever confronted with observations extending over multiple decades. Furthermore, global-scale forcing parameters in lake models present several limitations, such as the need of significant downscaling. In this study, the effects of climate change on thermal regime and oxygen solubility were analyzed in the four largest French peri-alpine lakes over 1850–2100. We tested several one-dimensional (1D) lake models' robustness for long-term variations based on up to 63 years of limnological data collected by the French Observatory of LAkes (OLA). Here, we evaluate the possibility of forcing mechanistic models by following the long-term evolution of shortwave radiation and air temperature while providing realistic seasonal trends for the other variables for which local-scale downscaling often lacks accuracy. Based on this approach, MyLake, forced by air temperatures and shortwave radiations, predicted accurately the variations in the lake thermal regime over the last 4 to 6 decades, with RMSE < 1.95 ∘C. Over the previous 3 decades, water temperatures have increased by 0.46 ∘C per decade (±0.02 ∘C) in the epilimnion and 0.33 ∘C per decade (±0.06 ∘C) in the hypolimnion. Concomitantly and due to thermal change, O2 solubility has decreased by −0.104 mg L−1 per decade (±0.005 mg L−1) and −0.096 mg L−1 per decade (±0.011 mg L−1) in the epilimnion and hypolimnion, respectively. Based on the shared socio-economic pathway SSP370 of the Intergovernmental Panel on Climate Change (IPCC), peri-alpine lakes could face an increase of 3.80 ∘C (±0.20 ∘C) in the next 70 years, accompanied by a decline of 1.0 mg L−1 (±0.1 mg L−1) of O2 solubility. Together, these results highlight a critical alteration in lake thermal and oxygen conditions in the coming decades, and a need for a better integration of long-term lake observatories data and lake models to anticipate climate effects on lake thermal regimes and habitats.

Waterborne Virus Transport and Risk Assessment in Lake Geneva Under Climate Change

“…The simulated results are comparable to the climate change simulations performed by Desgué‐itier et al. (2023), who also found that an increase of around 2°C for surface water temperature in Lake Geneva can be anticipated for year 2060 under RCP8.5 climate conditions. This scenario assumed that the current greenhouse emission situation will remain and no significant measures are taken to alleviate climate change, which has been a typical scenario to consider for the simulations till the middle of the 21st century.…”

A crisis of lake hypoxia in the Anthropocene: The long-term effects of climate and nutrients

“…In addition, since the 1950s, it has experienced a history of anthropogenic eutrophication followed by re-oligotrophication similar to that of several other lakes over about the same time period 11 . And like other lakes, Lake Geneva faces the ongoing effects of climate change with signi cant warming trends and strengthening thermal strati cation 25 .…”

“…Given the projected worldwide increase in strati cation intensity and duration of deep lakes as a response to climate warming [24][25][26] , prolonged isolation of the hypolimnion from the atmosphere is expected. As a result, lakes will be increasingly susceptible to hypoxia because of less frequent mixing with more severe consequences expected for the systems with a eutrophic past.…”

“…Climatic data including air temperature at 2 m above the lake surface, wind speed at 10 m, and surface solar radiation were downloaded from a statistically bias-adjusted and downscaled climate model from the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP3b 12 ). The data were previously veri ed against measurements from a local meteorological station located at Thonon-les-Bains (1987-2019 and 1971-2019 for air temperature and shortwave radiation, respectively, monitoring data from the INRAE CLIMATIK platform) and a scaling factor was implemented to correct the altitude bias 25 . Projections used historical climate from 1850 to 2014 and three future scenarios from 2015 to 2100: SSP1-RCP2.6, SSP3-RCP7.0, and SSP5-RCP8.5.…”

“…The other meteorological variables for which local downscaling often lacks accuracy (relative humidity, cloud cover, and rainfall) were extracted from meteorological observations 31 located at Nyon/Changins from 2000 to 2011 (MétéoSuisse Data Warehouse), from which daily means were calculated and replicated every year from 1850 to 2100 as we currently lack clear expectation for their fate under future scenarios. This approach of reducing model input variables to only those with a high con dence level was previously applied to Lake Geneva 20 and was found to be well-adapted to long-term simulations by overcoming limitations on their scaling and by their negligible effects on the hydrodynamic processes 25 .…”