Abstract
The evidence for global warming can be seen in various forms, such as glacier shrinkage, sea ice retreat, sea level rise and air temperature increases. The magnitude of these changes tends to be critical over pristine and extreme biomes. Chilean Patagonia is one of the most pristine and uninhabited regions in the world, home to some of the most important freshwater reservoirs as well as to evergreen forest, lakes and fiords. Furthermore, this region presents a sparse and weak network of ground stations which must be complemented with satellite information to determine trends on biophysical parameters. The main objective of this work is to present the first assessment on snow cover over the Aysén basin in Patagonia-Chile by using Moderate Resolution Imaging Spectroradiometer (MODIS) data from the period 2000–2016. The MOD10A2 product was processed at 500 × 500 m spatial resolution. The time-series analysis consisted in the application of non-parametric tests such as the Mann–Kendall test and Sen’s slope for annual and seasonal mean of snow covered area (SCA). Data from ground meteorological network and river discharges were also included in this work to show the trends in air temperature, precipitation and stream flow during the last decades. Results indicate that snow cover shows a decreasing non-significant trend in annual mean SCA with a −20.01 km2⋅year−1 slope, and neither seasonal mean shows statistical significance. The comparison with in situ data shows a seasonal decrease in stream flows and precipitation during summer. The hydrological year 2016 was the year with the most negative standardized joint anomalies in the period. However, the lack of in situ snow-monitoring stations in addition to the persistence of cloud cover over the basin can impact trends, creating some uncertainties in the data. Finally, this work provides an initial analysis of the possible impacts of global warming as seen by snow cover in Chilean Patagonia.
Highlights
The warming of the climate system and radiative forcing observed since the 1950s have increased the temperature of the atmosphere and oceans, reduced the amount of snow and ice cover, and raised the sea level (3.2 mm·year−1 ) [1]
Due to the physical properties of snow, it has a high reflectance in the visible spectrum (0.5–0.7 μm) and high absorption in the shortwave infrared (1.0–3.5 μm), which provide the basis of the Normalized Difference Snow Index (NDSI) for differentiating snow from other types of cover
An initial approach is presented for evaluating snow cover variability in the Aysén river basin in Chilean Patagonia
Summary
The warming of the climate system and radiative forcing observed since the 1950s have increased the temperature of the atmosphere and oceans, reduced the amount of snow and ice cover, and raised the sea level (3.2 mm·year−1 ) [1]. Water 2018, 10, 619 yet been carried out on the variability in snow cover, which plays a crucial role in water supply for agriculture and hydroelectric energy production, mainly in the southern area of the Andes [8,9]. Monitoring snow and its properties can be very problematic since conventional methods of measuring at high altitude are limited by rugged topography and adverse weather conditions. For this reason, satellite images are useful because they provide information on snow cover in mountainous areas at regular intervals of time [10]. This reflectivity depends on factors such as the snow grain size and shape, the content of liquid water, the depth of the snowpack and the presence of impurities [10,11]
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