Abstract
Abstract. As glaciers adjust their size in response to climate variations, long-term changes in meltwater production can be expected, affecting the local availability of water resources. We investigate glacier runoff in the period 1955–2016 in the Maipo River basin (4843 km2, 33.0–34.3∘ S, 69.8–70.5∘ W), in the semiarid Andes of Chile. The basin contains more than 800 glaciers, which cover 378 km2 in total (inventoried in 2000). We model the mass balance and runoff contribution of 26 glaciers with the physically oriented and fully distributed TOPKAPI (Topographic Kinematic Approximation and Integration)-ETH glacio-hydrological model and extrapolate the results to the entire basin. TOPKAPI-ETH is run at a daily time step using several glaciological and meteorological datasets, and its results are evaluated against streamflow records, remotely sensed snow cover, and geodetic mass balances for the periods 1955–2000 and 2000–2013. Results show that in 1955–2016 glacier mass balance had a general decreasing trend as a basin average but also had differences between the main sub-catchments. Glacier volume decreased by one-fifth (from 18.6±4.5 to 14.9±2.9 km3). Runoff from the initially glacierized areas was 177±25 mm yr−1 (16±7 % of the total contributions to the basin), but it shows a decreasing sequence of maxima, which can be linked to the interplay between a decrease in precipitation since the 1980s and the reduction of ice melt. Glaciers in the Maipo River basin will continue retreating because they are not in equilibrium with the current climate. In a hypothetical constant climate scenario, glacier volume would reduce to 81±38 % of the year 2000 volume, and glacier runoff would be 78±30 % of the 1955–2016 average. This would considerably decrease the drought mitigation capacity of the basin.
Highlights
Most glaciers on Earth have retreated due to global atmospheric warming during the 20th century (Zemp et al, 2019)
Using the synthetic meteorological time series derived to calculate the committed ice loss, we conduct 10 additional TOPKAPIETH simulations for the Maipo River basin (SIM-2A) and the modeled glaciers (SIM-2B), which are used for extrapolation (SIM-2C)
5.1 Glacier changes and runoff contribution in the period 1955–2016 In Fig. 6, we present the temporal variability of precipitation (Fig. 6a), air temperature (Fig. 6a), the equilibrium line altitude (ELA) (Fig. 6b), and cumulative mass balance (Fig. 6c and d) in the Maipo River basin since 1955
Summary
Most glaciers on Earth have retreated due to global atmospheric warming during the 20th century (Zemp et al, 2019). Global-scale studies indicate a large heterogeneity in the geographical distribution of peak water, while several catchments in the Himalayas and Alaska are expected to increase their glacier runoff due to the enhanced ablation in the decades and reach a maximum at some point of the 21st century, other regions in the world, such as the semiarid Andes, central Europe, and western Canada, have already reached a regional maximum, and glacier runoff will only decrease in the future (Bliss et al, 2014; Huss and Hock, 2018). Catchmentscale studies place glacier runoff in the context of other components of the water cycle and evaluate the impacts of glacier changes on downstream areas
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