A Stunning Look at the Hidden Mysteries of Glacier Caves - The New York Times

As my eyes adjusted to the lower light, I found myself staring down into a chasm that was far bigger than anything I thought we might find beneath the surface of the Greenland ice sheet.

It was 2018, and I was on an expedition with Will Gadd, a Canadian adventure athlete, to explore moulins, or giant vertical caves, in the Greenland ice sheet.

While I was skipping classes to explore and map caves near campus, Doug was studying how the warming climate was melting Mount Everest’s glaciers into networks of lakes.

Between climbs, and later over beers, Doug and I became convinced that we could understand how glacier caves in the Everest region were forming — if only we could explore and map them.

The discoveries we made scampering beneath the world’s glaciers over the next decade helped us document the role that glacier caves play in mediating how glaciers respond to climate change.

In Nepal, where thick blankets of debris on glacier surfaces should insulate glaciers from melting, we found glacier caves were melting ice below the debris.

In other parts of the world, including in Alaska and Svalbard, glacier caves followed fractures in the ice and funneled rivers of meltwater to glacier beds.

While I’d explored glacier caves around the world before working with Will, there was one place I hadn’t gotten to explore: the inside of the Greenland ice sheet.

Each summer, rising temperatures transform the frozen surface of the edge of the Greenland ice sheet into a network of rivers and lakes.

As the flow of meltwater into that interface increases, friction between the ice and bed is reduced, and the ice sheet speeds up, sending ice into the ocean faster than in winter.

Some glaciologists are worried that as climate warming triggers more melting, and new caves form in areas of the ice sheet that didn’t previously melt, increased lubrication might cause the ice sheet to dump ice into the ocean and raise sea levels faster than expected.

With funding from the National Science Foundation, I was able to establish remote camps to study how the water flow into caves was affecting the motion of the ice sheet during summer.

I wanted to see if the ideas I’d developed about glacier caves from other glaciers worked on Greenland.

But as I dangled in the middle of that massive, icy shaft in the Greenland ice sheet, perplexed by its sheer size, I realized that glacier caves still held surprises for me, and that there were more mysteries left to solve.