Melting glaciers may have a surprising upside -- but there's a catch

Vast, rapidly melting glaciers pose enormous risks to humans — the water they generate leads to sea level rise, intense flooding, and loss of water sources. But as ice continues to disappear apace, new research suggests there may be two beneficial opportunities amid the loss.

Once-frozen glacier basins could provide humans with both a huge amount of energy — in the form of hydropower — and a reservoir for storing clean water, a new study suggests. The counterintuitive findings were published this week in the journal Nature.

But before you get too excited at the idea of there being a small positive among the devastating effects of climate change, a separate study (published the same day in Environmental Science and Technology) suggests that hydropower — commonly considered to be as green as other renewable energy sources, like wind and solar — emits more greenhouse gases than we thought.

In the first study, the researchers chose to look at one of the major outcomes of climate change from an “unusual angle,” Daniel Farinotti tells Inverse. Farinotti is professor at Eidgenössische Technische Hochschule Zürichone in Switzerland and one of the authors on the study.

"What will happen to those landscapes that are becoming ice free?"

“Typically, the worrying consequences of glacier retreat dominate the discussion - and certainly rightly so,” says Farinotti. “Here, however, we show that some opportunities might arise after all.”

To generate energy and store water in formerly glacial regions would mean installing artificial lakes and dams. Not every post-glacier location would be suitable — but if just a few are, that could lead to big benefits, the researchers say.

The maximum potential power these areas could generate is around 1,400 terrawatt hours per year, which equates to about 7 percent of total global electricity consumption. Not all areas could consistently produce that amount of power, though; so the researchers assigned sustainability scores to different locations.

Storing water in “newly deglacierized areas” at the same time could help mitigate seasonal water scarcity, which threatens water security for millions of people living downstream of these ice-covered mountain ranges.

Farinotti hopes the study provides a nuanced look at future opportunities in glacial basins — some of which will inevitably melt.

“Glacier retreat is one of the most prominent signs of ongoing climatic change,” Farinotti says. “What will happen to those landscapes that are becoming ice free?”

Hydropower has its limits

The future may not all be so rosy in some cases, however. Hydropower can be surprisingly costly to the environment, according to the second study. In that work, the researchers measured greenhouse gas emissions, primarily methane, at different hydropower sites across the globe.

“We realized very quickly that there was this pervasive misconception about the climate impacts of hydropower,” Ilissa Ocko, study lead author and senior climate scientist at the Environmental Defense Fund, tells Inverse.

While hydropower may at times be less harmful to the climate than burning fossil fuels, it’s not guaranteed that it always is, says Ocko. Generating hydropower often involves flooding landscapes to build reservoirs, which in turn releases methane from the decaying organic matter.

Methane is a short-lived climate pollutant, meaning it remains in the atmosphere for a short time compared to carbon dioxide (CO2). But in the time it’s there, it can do much more damage than CO2.

Varying methane emissions across different hydropower sites makes it hard to pinpoint exactly where is best or worst to build hydropower plants, Ocko says. Emissions can “range tremendously” from one facility to the next, or even within a single facility. They also change by season and even through the day and night.

The ratio of surface level consumed by a hydropower plant to its output is a key factor, the study suggests. In other words, deeper reservoirs that take up less land tend to emit less methane.

How warm the surrounding climate is plays a role, too. Above a certain temperature, oxygen doesn’t circulate to lower levels of a reservoir, so any decaying organic matter produces methane instead of CO2. That means that a more shallow reservoir may be better, as it would have lower climate impacts in the short-term.

It’s important to keep the huge variability in mind when stacking hydropower against other energy sources, Ocko says.

Wind and solar are better for the climate than burning fossil fuels; and fossil fuels are always going to be detrimental. Hydropower can go either way — so it may be time to separate it from other renewable energy sources.

“We need to be really mindful about this and not lump them into one category of being low-carbon and good for the environment,” Ocko says. When it comes to hydropower, “one size does not fit all.”

Glaciers, revisited

Hydropower reservoirs in former glacier basins found in mountainous areas may well be deep enough to meet Ocko’s team’s ratio test. Plus, glaciers tend to form in cold regions of the world, possibly enabling more climate-friendly hydropower than would be possible in warmer climes. Any future decisions on what do would need to involve a lot of discussion and attention to nuance, Farinotti says.

Any intervention in former glacier basins will involve tradeoffs: Producing electricity requires messing with the environment even more; managing water resources is costly; and increasing renewable energy hampers “the natural evolution of newly forming environments,” he says.

“We want to provide the basis for discussing the options, and urge these discussions to take factors other than economy into consideration.”

Despite the seemingly opposed findings, both studies can help to inform that discussion. One thing on which the scientists agree is the importance of moving away from fossil fuels to different, cleaner and sustainable energy sources.

“As a society, we are in a strong need of transitioning to non-fossil energies,” Farinotti says.

Abstract:

Climate change is causing widespread glacier retreat and much attention is devoted to negative impacts such as diminishing water resources shifts in runoff seasonality and increases in cryosphere-related hazards. Here we focus on a different aspect, and explore the water-storage and hydropower potential of areas that are expected to become ice-free during the course of this century. For roughly 185,000 sites that are glacierized at present, we predict the potentially emerging reservoir storage volume and hydropower potential. Using a climate-driven glacier-evolution model and topographical analysis we estimate a theoretical maximal total storage and hydropower potential of 875 ± 260 cubic kilometres and 1,355 ± 515 terawatt-hours per year, respectively (95% confidence intervals). A first-order suitability assessment that takes into account environmental, technical and economic factors identifies roughly 40 per cent of this potential (355 ± 105 cubic kilometres and 533 ± 200 terawatt-hours per year) as possibly being suitable for realization. Three quarters of the potential storage volume is expected to become ice-free by 2050, and the storage volume would be enough to retain about half of the annual runoff leaving the investigated sites. Although local impacts would need to be assessed on a case-by-case basis, the results indicate that deglacierizing basins could make important contributions to national energy supplies in several countries, particularly in High Mountain Asia.

Abstract: To stabilize the climate, we must rapidly displace fossil fuels with clean energy technologies. Currently hydropower dominates renewable electricity generation, accounting for twothirds globally, and is expected to grow by at least 45% by 2040. While it is broadly assumed that hydropower facilities emit greenhouse gases on par with wind, there is mounting evidence that emissions can be considerably greater, with some facilities even on par with fossil fuels. However, analyses of climate impacts of hydropower plants have been simplistic, emphasizing the aggregated 100-year impacts from a one-year pulse of emissions. Such analyses mask the near-term impacts of methane emissions central to many current policy regimes, have tended to omit carbon dioxide emissions associated with initial plant development, and have not considered the impact of the accumulation of gases in the atmosphere over time. We utilize an analytic approach that addresses these issues. By analyzing climate impacts of sustained hydropower emissions over time, we find that there are enormous differences in climate impacts among facilities and over time. If minimizing climate impacts are not a priority in the design and construction of new hydropower facilities, it could lead to limited or even no climate benefits.