Driving the Dalton: A Tour of North Slope Glacial History

The Dalton Highway and surrounding landscape are icy in March (Source: Emma Boone).

The only road in the United States that crosses the Arctic Circle is the Dalton Highway: a remote, potholed, perilous path that begins north of Fairbanks and terminates at the Arctic Ocean. For some, driving the Dalton is a bold, lonely adventure, and for others, it’s just a long commute to work. Molly Timm, field operations assistant at University of Alaska’s Toolik Field Station, has driven the Dalton over ninety times. “It’s nicer in winter because there are fewer potholes,” she told GlacierHub.

No matter what brings you to the bumps and beauty of the Dalton, driving the young “Haul Road,” built in 1974, is a journey through time. The North Slope landscape is filled with features that date back to a series of glaciations beginning 2.6 million years ago. If you decide to stretch your legs, any given hike in the Brooks Range will likely involve scrambling over moraine rocks, and navigating the hill-sized heaps of gravel called kames that dot the tundra. Easier stretches will have you striding over the rolling heath, its crests and troughs the result of depression by glacial ice.

About a quarter of the Dalton Highway, such as this section looking north to Sukakpak Mountain, is paved (Source: Henry Masters).

“Really, the entire Arctic landscape is shaped by glacial activity, past and present,” Ruby An, terrestrial research assistant at Toolik Field Station, reflected on the North Slope. “If you look at Google Maps, you see a spiderweb of lakes all along the coastline.” In fact, some regions of the coastal plain consist of lakes and ponds formed on top of old, drained lakes, a sign of the permafrost layer that belies the tundra.

My drive up the Dalton begins, like all others, in Fairbanks. I am headed north with two other scientists to study kettle ponds, formed when glaciers dropped large chunks of ice as they receded. Dan, Kyle, and I spend our first morning together running around Interior Alaska’s largest city (population 33,188), loading the truck with scientific equipment, spare tires, beer, gasoline, water and food.

Musk oxen first colonized Alaska during the Pleistocene (Source: Henry Masters).

During the last glacial maximum, about 20,000 years ago, Interior Alaska was an ice-free grassland inhabited by animals like steppe bison, American lions, and giant short-faced bears. The Fairbanks area today is characterized by boreal forest and granite tors, large rock formations that persist as testaments to the lack of local glaciation.

The Dalton starts slow. I doze in the back as Kyle drives our heavily-provisioned truck through the birch-covered slopes outside of Fairbanks, which slowly yield to a spruce forest, scraggly and crooked on the frozen loess, a silty clay layer that covers much of Interior Alaska. North of Coldfoot, a town with a gas station, diner, and population of 11, everything changes. The trees disappear, granting us clear views of hills that grow as we creep north to the foothills of the Brooks Range.

The historic glaciations of the North Slope impact the distribution of plant species on the North Slope today (Source: Henry Masters).

It’s June 8th, and as we drive north through Alaska, we also move back through the year, from high summer in Fairbanks to early spring on the North Slope. At elevation, the foothills and mountains of the Brooks Range are shrouded in snow, and brown tundra peaks out below. Dryas octopetala—the frail yet hardy white-blossomed plant eponymous of the Ice Age’s Younger Dryas period—is one of the only alpine flowers in bloom. When summer eventually takes hold, the vegetation patterns on the tundra will reflect the effects of the historic glaciations of the region, according to An. The more time has passed since a given piece of ground was uncovered by ice, the older the bedrock, and the more acidic the soil, an important factor in shaping where plants live. The glaciers have been gone for millennia, but they still influence the plant species composition of the landscape.

Melting permafrost, another relic of the last ice age, causes problems throughout Interior Alaska—“drunken” spruce trees are destabilized and fall over, ground subsides, house foundations crack. Along the Dalton, this melt is even more menacing. We pass hills on which frozen debris lobes creep downslope about 1.5 cm per day, slowly approaching the Dalton, and creating what Timm calls “a lot of hubbub” about the economic giant of the Trans-Alaska Pipeline, which pumps oil 800 miles between Prudhoe Bay and Valdez.

A bull moose drinks from a pond on the side of the Dalton near Coldfoot (Source: Henry Masters).

“Four-wheeler coming up Atigun Pass,” my boss Dan calls over the CB radio. With no response and no semis visibly barreling towards us, we start up the narrow, steep pass, and enter true glacial terrain. The Atigun River Valley, like dozens of others in the Brooks Range, curves in a classic U shape, carved by glacial scour during the last glacial maximum. We pass the campground and airstrip at Galbraith Lake, formed by the damming action of a glacier’s terminal moraine.

“That’s Gates,” Dan points, using the unofficial nickname of a cirque glacier in the distance. “It’s a great day hike to the top. Takes about eighteen hours,” he mentions, so casually that I can’t tell whether he’s joking. He isn’t.

Driving through Atigun Pass in September is a challenge with limited visibility (Source: Emma Boone).

Gates is a prominent cirque glacier in the Brooks Range, located on the northern boundary of the remote Gates of the Arctic National Park. Like other high mountain glaciers in the region, Gates is one of the last remnants of a long, icy history. The entire North Slope landscape tells the story of successive, repeated glaciations, beginning over 2.6 million years ago in the late Pliocene. Passing through this landscape, the significance of these glaciations feels all the more immediate because they bear the names of nearby major rivers: Anaktuvuk, Sagavanirktok, Itkillik. Around 11,500 years ago, the glaciers of the Itkillik II advance made their last retreat to the mountain cirques of the Brooks Range, where they remain, feeding local streams and rivers with seasonal melt.

“Oh look, a siksik,” Dan says, referring to the ground squirrel running straight at our tires by its Inupiaq name. Kames are important habitat for ground squirrels and voles, who burrow easily into the dry mounds. This rodent distribution is apparent around our destination, Toolik Lake, a complex kettle pond surrounded by kames.

As we turn into Toolik Field Station’s driveway, our 285 mile jaunt on the Dalton ends, and the field season begins. The Haul Road continues on to Prudhoe Bay, past more glacial valleys, more moraines, and pingos, ice-cored hills that form in periglacial terrain.

Numerous kettle ponds are visible from the ridge system overlooking Galbraith Lake (Source: Rachel Kaplan).

We, however, will stay here, to spend the summer studying kettle ponds and biogeochemical cycling in the Toolik region, which is another way of studying the historic glaciations of the North Slope. When we sample different lakes, the various times of glacial retreat will leave a signature in the water chemistry. Thermokarsts, defined as sunken land formed by melting ice wedges, cause the tundra to slump into some of our study lakes, impacting their nutrient cycling and discharging carbon into the atmosphere.

But as we drive toward Toolik Field Station for the first time, I know little of this. All I know is that at 68’38”, I am the furthest north I have ever been, in true glacial terrain. This landscape is vast and wild, and after the drive north, I have many questions to ask of it.

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