In light of the ongoing fifteen-year megadrought in Chile, an international team of researchers, including Francesca Pellicciotti from the Institute of Science and Technology Austria (ISTA), addressed a bold future scenario. Their findings: by the end of the century, the considerably worn-out glaciers will not be able to buffer a similar megadrought. They call for coordinated global climate policies to develop effective water management strategies. The results were published in Communications Earth & Environment.
Could a drought have no end? Fifteen years of severe and persistent drought in Chile have already passed, and the country seems left to bleed dry of its precious water resources. As surprising as this may sound, no one saw this coming. “Climate scientists only realized in 2015 that the unending drought in Chile was really a big thing,” says Francesca Pellicciotti, Professor at the Institute of Science and Technology Austria (ISTA). “The Chilean megadrought was never forecast in any climate model. The existing models even showed absurd likelihoods for such an extreme event. And yet, it has happened and is still ongoing.” In light of this evidence, a question emerges: Are we prepared for future climate disasters?
Now, Pellicciotti, together with Álvaro Ayala and Eduardo Muñoz-Castro, two Chilean Earth scientists now based at the Swiss Federal Institute for Forest, Snow and Landscape Research WSL, sought to address this problem. With a team of international researchers, they modeled an audacious future scenario based on the ongoing Chilean megadrought. At the center of their analysis are glaciers in the Southern Andes, the majestic ‘water towers’ that are currently buffering the ongoing megadrought at the cost of their own survival.
‘Chile 2.0’ megadrought by 2100?
With the Atacama Desert in the north, Chile’s semiarid central region depends on snow for its water security. During droughts, glacier meltwater comes to the rescue. According to Ayala, Chileans were accustomed to recurrent droughts every five to six years, which would typically last for one or two years. “During the first few years of the current megadrought, people in Chile remained hopeful that things would improve the following year, and again the year after,” he says. But disillusionment would follow soon.
Perhaps all it takes to understand megadroughts is a bolder scientific approach. “Álvaro asked an elegant question: ‘What would happen if a similar megadrought struck Chile at the end of the century?’,” says Pellicciotti. “This simple, yet very clever question led to some really cool results.”
Half of today’s summer meltwater resources
In their model, the team focused on the 100 largest glaciers in the southern Andes (Central Chile and Argentina), accounting for seasonal snow and rain. They started by modeling 10 years before the onset of the drought and 10 years of megadrought. “We ensured we had a clear idea about the fate of glaciers, how much they lose mass, and what happens to the water,” says Ayala. “We then projected the model until the end of the 21st century, when the glaciers will be considerably smaller than now, and simulated a similar megadrought under these conditions.”
The scientists demonstrated that, in such a scenario, what will be left of the largest 100 glaciers in the Southern Andes will only be able to contribute half of today’s runoff meltwater during the dry summer months. For the smaller glaciers in the region, which were not included in this work, the situation might be even more dramatic. “The smaller glaciers will likely have disappeared by then, and a future ‘Chile 2.0’ megadrought will very likely be a severe blow for their ecosystems,” explains Ayala.
Megadroughts as the new normal?
Are these results realistic, considering that we did not even foresee the current megadrought in Chile? “There is a consensus that general models underestimate extremes,” says Pellicciotti. A recurrent pattern is that amid the general trend of global warming, episodic droughts occur as discrete severe events on a gradually worsening baseline, accompanied by continuous glacier mass loss. But while droughts are regular, megadroughts are quite unprecedented. “In projections that consider very severe scenarios, we can indeed see megadroughts. However, in more moderate scenarios, the precipitation patterns are more similar to those we are experiencing today,” says Pellicciotti. “So, there must be something else that we don’t see in the models.”
Recently, Pellicciotti was involved in another study that reanalyzed global data collected over 40 years, confirming that multi-year extreme droughts will become more frequent, severe, and extensive. While this might forebode an age of megadroughts, scientists underline that it is still difficult to define them in the first place. Currently, megadroughts are labeled as such through their impact on vegetation. Even more strikingly, it becomes apparent during annual geosciences meetings that scientists still do not know what exactly causes megadroughts, Pellicciotti explains.
While the detailed mechanisms are still under investigation, researchers are increasingly warning that megadroughts have become the new normal and calling on policymakers to act accordingly. However, sometimes, the challenge remains to convince funding bodies of the need to research megadroughts on a global scale. “We started studying megadroughts in Europe because of the Chilean case,” says Pellicciotti. “However, reviewers were not always in favor of our efforts, arguing that there has been no megadrought in Europe since the Middle Ages. But then, a sequence of droughts hit Europe at an increasing frequency.”
Chile and Europe in one boat?
In Chile, the keyword “desertification” has become difficult to bypass. “We see this pattern slowly extending from the north toward the south. So, the deserts in the north likely show us today what central Chile might look like in the future,” says Ayala. “Similarly, in Europe, one can look at the Mediterranean mountains to understand the future of the Alps.”
In light of this, the researchers underline the need for coordinated global climate policies to develop effective water management strategies. While Chile has assigned priorities, Europe must still work with water managers to model scenarios on competing water uses and allocation programs. According to Pellicciotti, such scenarios must also account for megadroughts, meaning a system that is water-deficient from the start.
Thinking of their home country, Ayala and Muñoz-Castro also call for coordinated action. “We must be well prepared for what will come next, as we won’t be able to rely on all the factors that ‘worked’ until now during the current megadrought. We must be flexible enough with our water management plans to handle future situations without counting on the glacier’s contribution,” Ayala concludes.
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The present study was conducted by researchers in Chile (Center for Advanced Studies in Arid Zones CEAZA, La Serena; Department of Civil Engineering, Universidad de Chile; Department of Geography, Universidad de Concepción; Advanced Mining Technology Center AMTC, Universidad de Chile), Switzerland (Swiss Federal Institute for Forest, Snow and Landscape Research WSL; WSL Institute for Snow and Avalanche Research SLF; Climate Change, Extremes and Natural Hazards in Alpine Regions Research Center CERC; Institute for Atmospheric and Climate Science, ETH Zurich; Laboratory of Hydraulics, Hydrology and Glaciology VAW, ETH Zurich), New Zealand (Waterways Centre, University of Canterbury and Lincoln University), and Austria (Institute of Science and Technology Austria ISTA).
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