High in the Himalayan mountains of rural Bhutan, Thorthormi Lake is hemmed in by a rock dam. Every year, the water within gradually rises, inch by inch, as the glacier feeding it melts. Snow-peaked crags rise above while far below, villages dot the landscape and rivers braid over a flat floodplain where the glacier once extended.
This remote area is one that glaciologist Rachel Carr studies as part of her work on glacial lake outburst floods (GLOFs), events that occur when a rock dam holding back meltwater fails and floods the valley below. Thorthormi Lake is one of four glacial lakes in the Lunana area, which is among the highest-risk sites of its kind in the world.
“It’s a bit of a microcosm,” says Carr, who visited the site in September as part of her research at Newcastle University in the United Kingdom. “But I think it’s a very good example of what we’re all facing, to some extent.”
Scientists estimate that 15 million people are vulnerable to sudden flooding from glacial lakes, one of various consequences of melting ice throughout our climate-disrupted world. The floods are increasingly likely as glaciers melt—and they can prove disastrous for the communities below. When the dam failed near another Lunana-area lake in 1994, a torrent of water flowed into the valley below, killing 21 people. To prevent another disaster like this, Bhutan recently announced that it would relocate nearly 80 families from high-risk areas below Thorthormi Lake.
Extreme adaptation measures like these are typically a last resort. But many communities face complex decisions as thawing accelerates and impacts environments around the globe.
Researchers are learning to predict where certain changes will occur. For some areas, melting ice will compromise drinking water resources. For others, it will impact agriculture or aquaculture. Coastal areas will continue to be significantly inundated by rising seas. And for the millions of people who live in permafrost zones, costs to repair crumbling infrastructure will pile up.
“We are surprised by the rate at which climate change is impacting the icy parts of the world. But I’m not going to say that it doesn’t make sense,” says Doug MacAyeal, a professor emeritus at the University of Chicago who studied glaciers for four decades. “Sadly, it is fully understandable.”
The mountains: From landslides and floods to droughts
From the Himalayas to the Andes to East Africa, many alpine glaciers are melting at unprecedented rates. This effect is particularly pronounced in the high mountain ranges of the tropics. Unlike peaks at the midlatitudes—say, those in the Sierra Nevadas, where heavy winter snowfalls can cause glaciers to gain mass after a summer melting period—tropical glaciers don’t experience the same extreme seasonal temperature changes. As a result, they’re shrinking rapidly.
The effects trickle down to communities in many ways. In India, areas exposed to receding glaciers resulted in a devastating landslide and flood in 2021 that killed approximately 200 people. The debris took out two hydroelectric dams and led authorities to evacuate numerous villages downstream.
“It all started sometime around 10 in the morning. We heard a bang, which shook our village,” Dinesh Negi, a resident of Raini village, told the Associated Press at the time. “We knew something wrong had happened….We could see the fury of the river.” Researchers later determined that an ice and rock avalanche caused the disaster, demonstrating the increasing risk from warming and development.
In the Andes, where scientists have documented unprecedented glacier retreat, the impacts are being felt in Cordillera Blanca, a mountain range in Peru. There, local farmers who traditionally grew corn, wheat, and potatoes are contending with hotter, drier conditions. To adapt, they’re experimenting with different crops, such as sugar snap peas, and relying on the increased meltwater collecting in glacial lakes. But this shift has created tensions with others seeking to profit from the lake surpluses, including large-scale irrigation projects and power companies.
“One of the things we’ve been looking at is who gets to manage that water and who has the rights,” says Mark Carey, a professor of environmental studies and geography at the University of Oregon, who has studied the region’s increased glacier hazards and resulting water troubles. “We see a lot of communities who are really struggling to ensure that they have a water supply as the climate changes.”
Even as a severe drought grips much of South America, hydroelectric companies are capitalizing on the influx of water from melting glaciers. One company, Ardian, acquired six hydroelectric plants in Peru just last year.
NRDC’s global managing director Amanda Maxwell, who has worked on water access rights and other environmental issues in Latin America for more than a decade, has observed a troubling pattern of exploitation of local waterways by corporations like Ardian. “Local communities who depend on that ecosystem for their livelihood, they’re the ones who will feel the change in that ecosystem most acutely,” Maxwell says. “If that’s fishing or tourism or farming, any change to a nearby river can have ripple effects throughout those very immediate economies that depend on that river. These companies often come with promises of jobs and economic benefits, but we’ve seen enough now where those promises fall flat and aren’t actually delivered.”
The poles: From sea level rise to shellfish decline
As global average temperatures tick up, the sea ice that covers the Arctic Ocean forms later in the fall and melts earlier in the spring. That ice reflects sunlight back into the atmosphere. When it melts, the darker water surfaces below absorb more sunlight and heat—leading to further warming and more melting.
Coastal sea ice also absorbs ocean wave energy. When it melts, or doesn’t solidify for as long in the winter, waves crash directly into the shore, erode the land, and carve off chunks of earth. In Alaska, for example, the shorelines of many northern and western communities are shrinking by more than 3 feet a year. Several villages along the state’s rivers and coasts have engaged in costly relocation efforts as they’ve watched their waters deluge local infrastructure.
Less sea ice paired with warmer ocean temperatures could also contribute to milder cold snaps, a concern because of the rain-on-snow events that can ensue. The resulting crusty ground conditions can have dire consequences for Arctic wildlife, including reindeer herds—as well as for the communities that rely on them.
A recently published study in Geophysical Research Letters suggests that “Arctic warming and sea ice loss are already impacting the Arctic communities, whose lifestyles and livelihoods were adapted to cold weather through generations of lived knowledge.” That’s the case for the Inuit communities of Alaska’s North Slope, who can no longer rely on year-round underground ice cellars to store the meat from their hunts and ensure a consistent food supply.
Arctic sea ice loss also disrupts marine ecosystems. Researchers who investigated very cold water in the Bering Sea found that less sea ice could constrict shellfish production. The snow crab is a prime example—the fishery, estimated to be worth $227 million annually, crashed in 2018–2019. It still hasn’t fully recovered, nor have the fishing communities who depend on it; a recent study by NOAA Fisheries scientists suggests that the crabs may never come back.
In Antarctica, on the other hand, the effects are quite different. Ice is now melting from below, thanks to warming seas. The impacts of climate change there are “insidiously indirect,” says MacAyeal. Ice is melting “around the fringe of the continental ice sheet where it’s running into the ocean.” That also destabilizes ice shelves and contributes to rising seas.
Scientists have been sounding the alarm bells on West Antarctica’s 80-mile-wide Thwaites Glacier, which is increasingly losing structural integrity, and may very well shatter in as little as five years. The resulting chain of effects would trigger global sea level rise that impacts millions of people.
The Great Lakes: From sedimentation to algal blooms
Ice coverage across the Great Lakes, the largest freshwater system in the world, plays an important role in regulating regional weather patterns across a vast swath of the United States and Canada. But as global warming accelerates, scientists predict there will routinely be less ice atop the lakes in the winter. The changing conditions have significant implications for local ecosystems and economies.
As the ice serves as a cap on the waters to contain water vapor from escaping into the air, less ice means more evaporation, lowering water levels. In turn, lake-effect precipitation increases, which then increases water levels. Without enough ice, the coastlines are more vulnerable to flooding and the effects of strong storms—which can include sedimentation and erosion. Researchers at Michigan State University (MSU) have found that diminishing ice cover near the shore allows waves to scour the lake bottom and transport sand from the shoreline into the lake.
Cities and towns near the lakeshore are taking protective measures to keep water from destroying infrastructure. Illinois officials recently invested $73 million to safeguard the 2.2-mile Illinois Beach State Park shoreline on Lake Michigan and preserve it for people and wildlife. Concerned officials in South Haven, Michigan, took more drastic measures in 2020 when lake levels reached record-breaking highs. They installed barriers that cost the community more than $30,000 to protect a drinking water storage tank and a wastewater treatment plant.
Ethan Theuerkauf, an MSU geography, environment, and spatial sciences professor, says these changes come as a surprise to many local officials tasked with managing the Great Lakes coasts. “Ice, even though we know it’s prevalent along the Great Lakes’ coasts, really wasn’t considered as a factor in terms of lake management and, more specifically, modeling and forecasting of coastal change in the future,” he says.
Some aquatic residents, too, like the yellow perch that rely on ice cover to survive, are also struggling to adapt. Without reliable ice coverage, incubating fish eggs have less protection from the sun’s rays and waves over the winter. Algae could also bloom more often, which poses health risks for wildlife and people.
And there will be fewer opportunities to practice cultural traditions like ice fishing, a hallmark of life in northern lakes. On Wisconsin’s storied Lake Winnebago, the ice was honeycombed by January last winter.
Scientists began measuring the percent of ice coverage on the Great Lakes in 1973. By midwinter, the ice is typically many inches thick—basin-wide, average annual ice coverage reaches a maximum of about 53 percent. But last February, the lakes were essentially ice-free. Scientists with NOAA’s Great Lakes Environmental Research Laboratory found it had plummeted to a new record low: just 2.7 percent.
Reflecting on the data, the researchers noted, “we’ve crossed a threshold.” What’s on the other side remains less clear.
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