Climate change and natural hazards in the Alps

Einhorn, Benjamin; Eckert, Nicolas; Chaix, Christophe; Ravanel, Ludovic; Deline, Philip; Gardent, Marie; Boudières, Vincent; Richard, Didier; Vengeon, Jean-Marc; Giraud, G.; Schoeneich, Philippe

doi:10.4000/rga.2878

Cited by 18 publications

(16 citation statements)

References 37 publications

(21 reference statements)

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“…At the same time, mountains and particularly the Alps are also the most impacted regions with regard to climate change (Beniston et al, 2018;Gobiet et al, 2014) because the rate of warming is amplified with elevation (Pepin et al, 2015). Predicted increases in air temperature will drastically decrease the amount of snow, especially critical at midelevations (Einhorn et al, 2015;Marcolini et al, 2017;Scherrer et al, 2004;Schöner et al, 2009). Decreases in snowfall usually are greatest near the low-elevation margin of the snowpack and cause reductions in surface albedo and increases in absorbed solar radiation, further leading to elevation-dependent amplification of warming (Minder et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Ice Cover and Extreme Events Determine Dissolved Oxygen in a Placid Mountain Lake

Flaim

Andreis

Piccolroaz

et al. 2020

Water Resources Research

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A decrease in hypolimnetic dissolved oxygen (DO) is a commonly seen effect of climate change. However, in oligotrophic Lake Tovel (Italy), a deep mountain lake, annual mean DO (% saturation) has increased from near anoxia to >20% in the bottom layer (35-39 m). We analyzed long-term patterns of DO (1937-2019) using different methods (correlation and trend analysis, identification of extreme events) to link DO to drivers and indices of mixing. While spring mixing remained temporally limited, later ice-in (5.1 days decade −1) and the positive relationship between ice-in and DO the following year evidenced autumn mixing as the main driver for hypolimnetic DO increase. Extreme meteorological events also replenished hypolimnetic DO. Using DO and conductivity (1995-2019), we identified 14 deep mixing events with hypolimnetic DO > 40%. Density-based indices (Schmidt stability, relative thermal resistance, Lake Number, and Wedderburn Number) only partially captured these events that were related to snowmelt, flooding, and cold spells during spring and autumn, with a carryover effect sometimes lasting >1 year. Recently, annual mean DO in the upper layer decreased beyond temperature-dependent solubility. This decrease was not comprehensively confirmed by statistical tests but was possibly linked to atmospheric stilling. We suggest that Lake Tovel's shift from meromixis to dimixis was driven by climate warming (i.e., increasing air temperature 0.6°C decade −1) that delayed ice-in and increased autumn mixing. Our work underlines the vulnerability of mountain lakes and their different response to climate change with respect to more studied lowland lakes. Plain Language Summary Dissolved oxygen is fundamental for aquatic life. Lake Tovel (Brenta Dolomites, Italy) has a long history of limnological studies starting in the 1930s; therefore, we can study oxygen's long-term evolution. Contrary to most temperate lakes, dissolved oxygen is increasing in the deep layers of Lake Tovel since the 1990s. We linked this to later ice-in: as a consequence of climate change, Lake Tovel has lost almost 3 weeks of ice cover since the mid-1980s. This loss (5.1 days decade −1) in ice-in is much steeper than in lowland lakes. Because dissolved oxygen is replenished in lakes by mixing, a longer ice-free period means more time to mix, with oxygen reaching deeper layers. Extreme events such as heavy snowmelt, flooding, and cold spells during spring and autumn also increased mixing with effects often lasting over a year. However, in the last decade, we are beginning to see a decrease in dissolved oxygen at the surface, probably because of less wind. Years with little snow also tend to coincide with lower concentrations of dissolved oxygen in the deep layers. Changes in air temperatures, precipitation, and wind will determine the evolution of dissolved oxygen in Lake Tovel, a sentinel mid-altitude lake for climate change.

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Section: Introductionmentioning

confidence: 99%

Ice Cover and Extreme Events Determine Dissolved Oxygen in a Placid Mountain Lake

Flaim

Andreis

Piccolroaz

et al. 2020

Water Resources Research

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“…Mountains environments are especially sensitive to climatic changes (Pachauri et al, 2014;Kohler et al, 2010;Beniston, 2005). The ongoing changes have already resulted in many impacts on natural hazards in the Alps (Einhorn et al, 2015) including snow conditions and avalanches (Castebrunet et al, 2014;Le Meur et al, 2007), rockfalls (Ravanel and Deline, 2011) or debris flows (Jomelli et al, 2004). Forest fires might also be a major hazard and a threat for many mountain ecosystems and human assets in the next decades.…”

Section: Introductionmentioning

confidence: 99%

Spatio-temporal trends in fire weather in the French Alps

Dupire

Curt²,

Bigot

2017

Science of The Total Environment

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The Alpine area is particularly sensitive to climatic and environmental changes that might impact socio-ecosystems and modify the regime of natural hazards. Among them, wildfire is of major importance as it threatens both ecosystems and human lives and infrastructures. Wildfires result from complex interactions between available vegetation fuels, climate and weather, and humans who decide of the land use and are the main source of fire ignitions. The changes in fire weather during the past decades are rather unknown in the French Alps especially due to their complex topography. Moreover, local institutions and managers wonder if the ongoing climate changes might increase fire risk and affect the environmental quality and the different ecosystem services provided by the mountain forests. In this context, we used the national forest fires database together with daily meteorological observations from 1959 to 2015 to investigate the changes in wildfire danger in the French Alps. We analysed the spatial and temporal variations in terms of intensity, frequency, seasonality and window of opportunity of two fire weather indices: the fine fuel moisture code (FFMC) and the fire weather index (FWI) that measure the daily water content of vegetation and the potential intensity of fires, respectively. Our results showed a major contrast between Southern Alps with a high fire weather danger on average and a significant increase in the past decades, and Northern Alps with low to moderate danger on average that increased only at low elevations. This study contributes to the understanding of the consequences of ongoings climate changes on wildfires in the French Alps. It produced high resolution results that account for the topographic and climatic variability of the area. Finally, the maps of the different fire weather components have practical implications for fire management and modelling and for preventing indirect effects of fires on ecosystems and human assets.

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“…In the Alpine region, an increase in the frequency of intense rainfalls (> 30 mm/day) and permafrost degradation linked to the climatic changes (Einhorn et al 2015) could determine a change in the water regime of soils, promoting an increase of the soil moisture and causing the persistence of saturated or close to saturation conditions all the year round. These conditions are responsible for triggering erosion processes, debris flows and landslides (Collison et al 2000;Lu, Gsodt 2013) and they can represent preparatory factors for flood triggering (jomelli et al 2009).…”

Section: Impact Of Soil Processes Induced By Climatic Changes On Socimentioning

confidence: 99%

“…Moreover, the increase in landslides and flood susceptibility could be responsible for higher risks for the human structures, like blockage and destruction of roads and railways with subsequent isolation of towns and buildings and, as a consequence, for the people living in hazardous areas (Einhorn et al 2015). Thus, better assessment of the soil and environmental conditions will become fundamental that lead to triggering landslides and floods in relation to the forecasted climate change effects, for reducing the hazard and the risk linked to these types of phenomena.…”

Section: Impact Of Soil Processes Induced By Climatic Changes On Socimentioning

confidence: 99%

Climate change impacts on the Alpine ecosystem: an overview with focus on the soil

Chersich¹,

Rejšek²,

Vranová³

et al. 2015

J. For. Sci.

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ABSTRACT:The Alpine ecosystem is very sensitive to climatic changes, which have an influence on glaciers, snow, vegetation and soils. The aim of this review is to illustrate the effects of global change on the Alpine soil ecosystem, which is an optimal marker to record them. The manuscript enhances our understanding of the global change effect on the Alpine environment: on morphology, on ice, on vegetation and points out how the cycles of soil nutrients equilibrium have been changed with a direct effect on soils that support plant species. The changes in cryosphere, glacier reduction and periglacial environment as glaciers retreat, decrease in the snow cover extent and earlier snowmelt, determine an effect on soils (on the structure, organic matter and humus forms, soil processes and soil types) from the top of the Alpine horizon to the bottom. The processes induced by climate change (such as erosion and tree line shifting) have a direct effect on water balance that can be observed on soil profile characters with an effect on upward migration, change in phenology, extensive losses of species. The equilibrium of the biogeochemical cycles has been changed and this has a direct effect on soils that support plant species.

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Climate change and natural hazards in the Alps

Cited by 18 publications

References 37 publications

Ice Cover and Extreme Events Determine Dissolved Oxygen in a Placid Mountain Lake

Ice Cover and Extreme Events Determine Dissolved Oxygen in a Placid Mountain Lake

Spatio-temporal trends in fire weather in the French Alps

Climate change impacts on the Alpine ecosystem: an overview with focus on the soil

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