Prologue A Certain Type of Fun, July 10-12, 2022 Kalulutok Creek would be called a river in most parts of the world. Here in Gates of the Arctic National Park and Preserve, amid the largest span of legislated wilderness in the United States, it''s just a creek compared to the massive Noatak River that we''re bound for. But in my mind--while we splash-walked packrafts and forded its depths at least thirty times yesterday--Kalulutok will always be an ice-cold, wild river. It drains the Endicott and Schwatka Mountains, which are filled with the most spectacular granite and limestone spires of the entire Brooks Range. One valley to the east of us is sky-lined with sharp, flinty peaks called the Arrigetch, or "fingers of the outstretched hand" in Iñupiaq. As the continent''s most northerly mountains, the sea-fossil-filled Brooks Range--with more than a half-dozen time-worn peaks over 8,000 feet high--is seen on a map as the last curl of the Rocky Mountains before they stairstep into foothills and coastal plains along the Arctic Ocean. The Brooks Range stretches 200 miles south to north and 700 miles to the east, where it jabs into Canada. Although there are more than 400 named peaks, since the Brooks Range is remote and relatively untraveled, it''s rare that anyone bothers to climb these mountains.

My river-slogger companion, Chris, and I will be one of the summer''s handful of exceptions. We carry a water filter, but it would be silly to use it. We''re higher and farther north than giardiasis-infected beavers and there is no sign of the pellet-dropper deer known as caribou. The creek is fed from the pure ice of shrunken glaciers above and ancient permafrost in the ground below. In what seems like prodigious heat for the Arctic, the taps here are all wide-open. When we get thirsty, we luxuriate in one of the freedoms of a journey through pristine wilds: we kneel, cup our hands and drink directly from the ice-cream-headache water of the Kalulutok. Its root name, from the word for fish, kaluk, has been lost to most Iñupiat, who now mostly speak English. Yet there''s no question that the stream is full of grayling, or sulupaugak, that flit about as sun-blinkered shadows through the eddies.

If I stand still under a twenty-degree angle from the horizon, the grayling won''t see me. A grayling''s eyes are remarkably similar to mine--except they can simultaneously focus on near and far-away objects like a hawk--but the optics and underwater reflections limit their vision. I love their eyes: the rim of sparkly gold iris that surrounds the black, teardrop-shaped pupils. When you snatch the fish from their watery world, they stare back with such wide-eyed purity that you wouldn''t want to dismiss the presence of their soul. I also admire their finely sculpted, streamlined form and iridescent blue scales. I repeatedly study these creatures that I share the water with as they restively hold the current in the same way that I stand against a strong wind. They erect their distinctive, sail-shaped dorsal fins and anchor themselves in place against the flow. Then they can be seen as vividly as a worm in mezcal.

Usually less than a foot long and found in northern waters, the grayling is a keystone species, a veritable canary in the coal mine in an era when the Arctic now warms nearly four times faster than the rest of the world. In their migrations up and down tens of thousands of small streams, they provide nutrients throughout the ecosystem and are often the only fish--lithe and muscular--that can wriggle up countless narrow drainages that won''t fit the stouter salmon and trout. While that''s the beta from the appreciative fish biologists, they also wonder if this supremely adapted cold-water species will go belly up as the world overheats, streams in the Arctic dry, and summer seasons elongate.1 A couple months from now, as this river-creek begins to crackle with ice buildup, hundreds of sulupaugak will migrate downstream into the 400-foot-deep waters of Walker Lake. They''ll congregate there until spring, preyed upon by the tubby, bully lake trout--akin to grizzlies amid ground squirrels. I watch the grayling here in the headwaters of Walker Lake and the Kobuk River as I study birds on the wing and other wildlife signs: the wide bear trails bulldozed through the alder thickets, moose scat remarkably like Milk Duds, and, in the willows, the ptarmigan excreta like coarse hamburger curls extruded from the meat grinder. On the river bars, braided-rope-shaped wolf feces are also strewn hither and yon. "TMI, Jon," many people would say.

Too Much Information, to stop and talk about and pull apart every piece of animal fecal matter as if it were Play-Doh. Or to badger the Fish and Wildlife Service worker back in Fairbanks on the misconceptions about Arctic char and Dolly Varden. "Char only exist in Alaskan lakes," I insisted, while Chris quietly exited the federal offices, chagrined at my compulsion to debate such arcane details. My disclaimer: Thirty-nine years ago, I decided to learn all I could about life above the Arctic Circle. As a climber, I traded my worship of high mountains for the High Arctic. I substituted bears and mosquitoes for crevasses and avalanches, but more importantly--like the study of crevasse extrication and avalanche avoidance--you couldn''t just read about the Arctic or sign up for classroom courses. You have to go on immersive journeys and figure out how the interlocked parts of the natural world fit together. Without guides or someone to hold your hand.

Best to hit the ragged edge of exhaustion and make mistakes so that you learn what''s important. And to go alone at least once. Along this path, acts of curiosity out on the land and the water can open an earned universe of wonders. But you must spend time in the villages, too, with the kindhearted people of the North to make sure you get it right. And you can''t call the Arctic "the Far North"--it is "home" rather than "far" to the many people who live there. So, after twoscore of Arctic journeys, in the summer of 2022, I''m on one more trip. I could not be on such an ambitious trip without all the previous experiences, which I''ll use to sculpt a cohesive, whole, and fully developed sense of place. (Disclaimer 2: The more I learn, it sometimes feels like the less I know about the Arctic.

) But this time the agenda is different. I hope to better understand the climate crisis. Chris and I are here to document it however we can. Since my first trip above the Arctic Circle in 1983, I have seen extraordinary changes in the landscape. Only three days underway and we''ve already flown over a wildfire to access our Walker Lake drop-off point. And yesterday we trudged underneath several bizarre, tear-drop-shaped landslide thaw slumps--a.k.a.

thermokarsts--caused by the permafrost thaw. In much of Alaska, the Arctic Monitoring and Assessment Programme (AMAP) says that permafrost thaw from 2005 to 2010 has caused the ground to sink more than four inches, and in places to the north of us, twice that. The land collapses as the permafrost below it thaws like logs pulled out from beneath a woodpile. AMAP believes this will amount to a "large-scale degradation of near-surface permafrost by the end of the twenty-first century." This means that roads and buildings and pipelines--along with hillsides, Iñupiat homes, forests, and even lakes--will fall crazy aslant, or get sucked into the ground as if taken by an earthquake. Our hoped-for documentation of the climate crisis isn''t likely to be easy on this remote wilderness trip. We don''t expect a picnic--known as Type 1 Fun to modern-day adventurers. A journey across the thaw on foot and by packraft for 500-plus miles won''t be like a backcountry ski trip or a long weekend backpack on Lower 48 trails.

We have planned for Type 2 Fun: an ambitious expedition that will make us suffer and give us the potential to extend ourselves just enough that there will be hours, or even days, that won''t seem like fun until much later when we''re back home. Then our short-circuited memories will allow us to plan the next trip as if nothing went wrong on this one. As if it was all just great Fun with a capital F. Ultimately an important part of wilderness mastery is to avoid Type 3 Fun: a wreckage of accidents, injuries, near-starvation, or rescue. We''ve both been on Type 3 Fun trips that we''d rather forget. I have more than a few outdoor expert friends who claim that the real trick of expeditions is always to be in control, regardless of calculated risk activity, and to avoid the proverbial "adventure." But I''ve never really succeeded. No matter how hard I try, on my trips in the North, things sometimes simply go south: someone forgets the stove, you fall and dislocate a shoulder, you forget to tighten the pee bottle in a crowded tent in a storm, you miscalculate a crevasse jump, you shower yourself with bear spray, or someone (not me) lets the tent blow away.

You try to avoid these rookie moves, but sooner or later, particularly on a long expedition, the odds are that you or one of your partners will screw up, or the weather will thrash you, and you''ll have an adventure. Yesterday, in the first hour of our day, while we forded the Kalulutok I tripped, fell in face-first, performed a splashy left-handed push-up in three feet of water, clambered upright--my packraft clutched by its bowline like a leashed dog yanked me backward in the current--and continued the hurried, bowlegged-swagger necessary to stay upright in.