A landscape in motion
The Mackenzie River Delta is the second-largest in the Arctic, a sprawling 13,000-square-kilometer labyrinth of channels and wetlands. Beneath this vast plain lies a foundation of permafrost—permanently frozen ground—that is in some places over 100 meters thick. This frozen earth is not static; it is a dynamic landscape shaped by a process called thermokarst. As pockets of ice-rich permafrost thaw, the ground surface collapses and subsides, creating a pockmarked terrain of hummocks and water-filled depressions.
This process gives rise to the delta's most numerous feature: its lakes. There are tens of thousands of them, constantly forming, shifting, and disappearing. Some lakes can drain with astonishing speed when a thawing ice wedge opens a new channel, an event known as catastrophic drainage. The landscape is also sculpted by retrogressive thaw slumps, a type of landslide that occurs when thawing ground-ice on a slope turns the soil into a muddy slurry. These slumps can retreat several meters in a single summer, dumping huge amounts of sediment and dissolved minerals into adjacent lakes and altering their water chemistry.
Archives of ice and gas
The permafrost of the Mackenzie Delta is frozen soil; it is a high-fidelity archive of past climates. Cryostratigraphy, the study of layered ice, reveals this history. Within the permafrost are massive wedges of ice, formed over millennia as meltwater filled thermal contraction cracks in the ground each spring and refroze. These ice wedges preserve air bubbles, pollen, and other organic matter, while the isotopic composition of the ice itself is a thermometer, recording past winter temperatures.
This frozen ground also holds an immense quantity of organic carbon. As the permafrost thaws, microbes begin to decompose this long-frozen material, releasing carbon dioxide and methane. The methane release is sometimes visible as ebullition—streams of bubbles rising to the surface of the delta's many lakes. In areas with high concentrations of this seeping gas, the bubbles can be ignited, creating flames that dance across the water's surface. This phenomenon occurs where the methane bubbling through the water is dense enough to sustain a flame, a sign of the changes happening deep within the Arctic ground.