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Exploring Wisconsin’s rare Lake Superior ice caves.

A few of the caves are big enough to crawl inside. Photo by Eric Holthaus

Last week, my wife and I headed north from our Wisconsin home to the shore of frozen Lake Superior. There, we found ourselves a palace of ice and snow at the edge of the largest freshwater lake in the world—an increasingly rare sight in an era of warming climates.

Huge waves are frozen in place where the beach should be. Icicles as long as a Winnebago dangle perilously above your head. When you step out on the ice, the snow doesn’t crunch. It squeaks. Perhaps snow, too, gets too cold sometimes.

In the summer the caves look quite different. However, after weeks of polar vortex–induced chill, ice along the shores of the Great Lakes has frozen to such an extent that groundwater seeping through cracks in the local sandstone—the same brownstone used to construct some of the iconic buildings in Chicago and Minneapolis—has formed natural ice sculptures, magnificent and temporary. Aficionados of winter visit the caves by walking on foot over about a mile of Lake Superior’s frozen surface.

From the National Park Service:

One of the benefits of the severe cold temperatures we have had is the hoarfrost we are finding on icicles in some of the sea caves. These needle-like crystals form from direct condensation from the air at very low temperatures. The crystals are very delicate and will not last once temperatures begin to moderate.

This is the first year the caves have been safely accessible since 2009, according to a National Park Service FAQ, and they’re drawing visitors from all over. “Ice caves go viral,” a headline from the Duluth News Tribune touted during our visit. Photo collages have popped up on the Atlantic and in Smithsonian magazine. Attendance is at an all-time high and is expected to top that record again this weekend. The park service is shifting staff over from nearby national parks to manage the influx, says Wisconsin Public Radio.

For the past few weeks, it’s been possible to walk on Lake Superior itself.

Photo by Eric Holthaus

Giant icicles towered above our heads. Photo by Eric Holthaus

Over coffee, later that morning, we heard locals ranting about the influx of tourists over the preceding days. Our hotel was sold out the weekend before our visit. We counted cars from nine states in the parking lot the Monday of our stay. Needless to say, February is normally the low season for tourists in northern Wisconsin. 

By the time we got to the ice itself, we weren’t prepared for just how spine-tinglingly cold it was.

I mean, we were prepared: wool socks, long underwear, down vest, balaclavas (yeah, we didn’t know that’s what they were called either, before we moved here from Arizona a few months ago), Gore-Tex gloves. We even brought those little air-activated hand warmer packets (in each glove and inside each sock). Praise you, sweet baby Jesus, for inventing chemistry.

And, of course, we picked one of the coldest days of the year: my 33rd birthday, the day that the high temperature was 0 degrees Fahrenheit with a wind chill of 20 below.

So, why go? Because it’s there. And, quite frankly, it may be a long time before these ice caves return.

Map courtesy of the Canadian Ice Service

Satellite data showed that at the time of our visit, the amount of ice on the Great Lakes reached a level not seen in 20 years. Via Climate Central:

This year’s ice is far from the norm as the long-term trend has been toward a dramatically reduced ice coverage over the past 40 years, in step with general warming trends in temperatures, particularly winter temperatures.

It continues: “This is a blip on the long-term trend.”

But what a beautiful blip it is.

Hidden inside some of the caves, protected from the harsh winds, are forests of intricate ice crystals known as hoarfrost.

Photo by Eric Holthaus

Some of the caves resemble cathedrals of icy stalactites. Photo by Eric Holthaus
Taking photos was the biggest challenge: Our fingers could only last a few seconds outside of our gloves.

Photo by Eric Holthaus

Simply put, this was one of the most magical walks I have ever experienced. Just for the fact that it will become increasingly rare in the future.

Taking the pictures was the worst. The longest I dared to take my hand out of my glove was about 30 seconds. We were saved, saved by those hand warmer packets. So, most of the experience will remain a memory.

About an hour in, we got too cold, so we turned back. But then I saw a small cave no one was near and decided to crawl in. I sat there mesmerized. The world had a bluish glow as sunlight filtered in, low and feeble on the horizon. Close in, the detail of the frost on the ice itself had a fractal quality. Inside, it seemed every icicle had needles of growth, and every needle had its own story to tell. It was easy to lose track of time.

On our way home from the caves, we detoured to the ferry terminal at Bayfield. There, traffic cones marked the mile or so of temporary track over the ice between the mainland and Madeline Island—a summer destination accessible by car this frozen winter.

We drove our car out onto frozen Lake Superior, past ice fishing huts and empty summer homes, just because we could. For that moment, we were caught in between: a relic of a former, cooler world, on a transition to an uncertain future.

Many of the “caves” were actually open to the air on top, with ice cascading off the cliffs above our heads.

Photo by Eric Holthaus

There’s no horizon on Lake Superior this time of year, only infinite snow and ice. Photo by Eric Holthaus
Blocks of ice from frozen waves littered the edge of the Lake Superior ice caves. Photo by Eric Holthaus
No, this isn’t Antarctica. It’s Wisconsin. Our faces had frost on them too, by the time we were done. Photo by Eric Holthaus

This article is part of Future Tense, a collaboration among Arizona State University, the New America Foundation, and SlateFuture Tense explores the ways emerging technologies affect society, policy, and culture. To read more, visit the Future Tense blog and the Future Tense home page. You can also follow us on Twitter.