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Glaciers shape the land and lives of Alaskans — carving mountains, funneling cold freshwater into rivers, carrying nutrients to the sea and reflecting sunlight back to space. 

Friday marked the first-ever World Day for Glaciers, a day observed by the United Nations to sound the alarm on the accelerating pace of global melting. Scientists who study Alaska glaciers spoke about their research to uncover how these rapidly changing systems affect our world. 

Kiya Riverman studies what makes glaciers flow as a glaciologist and associate director of the Juneau Icefield Research Program. 

“Often we have this sense that glaciers are this really static thing,” she said.  

Before and after pictures show glaciers retreating, sure, but usually over the span of years and decades. It’s much faster than that, she said. 

“They’re almost like living, breathing creatures that change a little bit every day,” she said. 

They speed up in the heat of the day, and slow down as they cool at night. 

Glaciers make up an area of land in Alaska nearly equal to the size of West Virginia — but we’re losing them quickly. The state is warming two or three times faster than the global average, and glaciers here have shrunk more — in gigatons per year — than anywhere else since the turn of the century.

As the ice melts, the average global sea level rises. Although this doesn’t directly affect much of Southeast Alaska, where the land is rising faster than the sea as it sheds the weight of glaciers. That’s called isostatic rebound, and it’s one reason why rising seas won’t lap up to every coastal community the same way. 

Riverman said it’s challenging to predict and quantify the extent to which melting glaciers cause sea level rise.

“So we know that glaciers are changing, we know that the ocean is changing, but how those two impact each other is kind of the edge of the field still, and that’s a problem” because low-lying areas by the sea will get hit hard and that will impact millions of people worldwide, Riverman said. Alaska’s glacial meltwater has already contributed significantly to sea level rise, and scientists predict that will continue. 

To understand what’s happening under the ice, Riverman and her team ski out onto the Juneau icefield every summer and put out seismometers that measure vibrations. 

They strike the ice surface with a sledgehammer or shoot it with blank shotgun shells.

“We use those miniature earthquakes to study how thick the ice is and what materials sit underneath,” she said.

She also uses radar to pinpoint where pockets of water have formed, since water lubricates the ice and makes it flow faster. 

Other scientists look at glacier mass, a measure of how much glacier matter there is. Louis Sass is part of the oldest study of glacier mass in North America as a glaciologist with the U.S. Geological Survey’s Alaska Science Center. It’s called the Benchmark Glacier Project, and it started tracking a few of Alaska’s glaciers — Lemon Creek in Juneau, Wolverine on the Kenai Peninsula and Gulkana in the Alaska Range — in the 1950s and 60s.

Back then, Sass said, it wasn’t clear whether Alaska’s glaciers were retreating continuously, or if they had just retreated some after the Little Ice Age and then stabilized. 

“People didn’t really know what was happening, because people hadn’t paid really close attention,” Sass said. “There were just very few glaciers that had any sort of picture record or enough data.”

Sass and his team venture out to the same survey sites each spring and fall to calculate the change in mass. They dig pits into the snow or take cores and weigh it. Then they drill long stakes down into the glacier to measure the levels of snow and ice. This is all very similar to what was done back in the 1960s, Sass said.

But now, using satellite imagery, they calibrate that data with the elevation changes of those survey sites as they slide down toward the ocean — since ice melts faster at lower, hotter elevations. The sliding poses a research challenge, Sass said. 

On Wolverine Glacier in the Kenai Mountains, “a sinkhole opened up, and that section of the glacier just sort of disintegrated, and the ice beyond it all melted away” so they lost the survey site stationed there, Sass said. “We’ve had to replace sites that have disappeared on all the glaciers now, as they melted out — and it’s changing so much faster.”

Rapid melting has created a relatively new problem for people who live in the path of the freezing water’s path: glacial outburst floods. 

In Juneau, Suicide Basin is a pool contained in steep rock and dammed by Mendenhall Glacier. During the summer, the pool fills with meltwater and puts pressure on the ice dam until it suddenly breaks and drains into Mendenhall Lake, which then floods parts of the neighborhood in the surrounding valley. 

Jamie Pierce is a hydrologist at the U.S. Geological Survey who monitors Suicide Basin. 

Equipment stationed in Mendenhall Lake shows Pierce early warning signs when a flood is coming. 

“Water temperature will plummet, that’s a big one,” he said. “Then, of course, the lake stage will start rising precipitously.”

One summer day in late June of 2018, when he was setting up some monitoring gear in Suicide Basin, he thought he was witnessing the dam break in real-time. Bubbles started to rise up to the water’s surface among floating icebergs. It was noisy — crackling and popping. 

“And then all of a sudden, a massive iceberg started to overturn, and it kind of set off a chain reaction,” Pierce said.

The glacier calved off a chunk of ice roughly 100 feet deep and 200 feet long. Pierce and his colleagues thought it was going to trigger the big release. It didn’t, but it showed the huge scale of change the glacier is going through, and meant that the ice dam went quite deep. 

Major questions remain about Alaska’s glaciers. How long will they last? How big can glacial outburst floods get? And what will happen when the ice is gone?

Researchers are chasing answers to help Alaskans navigate a rapidly changing relationship with ice.