Brooks Range In Alaska Research Articles

Unrecorded Tundra Fires of the Arctic Slope, Alaska USA

Few fires are known to have burned the tundra of the Arctic Slope north of the Brooks Range in Alaska, USA. A total of 90 fires between 1969 and 2022 are known. Because fire has been rare, old burns can be detected by the traces of thermokarst and distinct vegetation they leave in otherwise uniform tundra, which are visible in aerial photograph archives. Several prehistoric tundra burns have been found in this way. Detection of tundra fires in this sparsely populated and remote area has been historically inconsistent and opportunistic, relying on reports by aircraft pilots. Fire reports have been logged into an administrative database which, out of necessity, has been used to scientifically evaluate changes in the fire regime. To improve the consistency of the record, we completed a systematic search of Landsat Collection 2 for the Brooks Range Foothills ecoregion over the period 1972–2022. We found 57 unrecorded tundra burns, about 41% of the total, which now numbers 138. Only 15% and 33% of all fires appear in MODIS and VIIRS satellite-borne thermal anomaly products, respectively. The fire frequency in the first 37 years of the record is 0.89 y−1 for natural ignitions that spread ≥10 ha. Frequency in the last 13 years is 2.5 y−1, indicating a nearly three-fold increase in fire frequency.

The Seasonality of In‐Stream Nutrient Concentrations and Uptake in Arctic Headwater Streams in the Northern Foothills of Alaska's Brooks Range

AbstractOver the past 30 plus years, the Arctic has warmed at a rate of 0.6°C per decade. This has resulted in considerable permafrost thaw and alterations of hydrological and biogeochemical processes. Coincident with these changes, recent studies document increases in annual fluxes of inorganic nutrients in larger Arctic rivers. Changing nutrient fluxes in Arctic rivers have been largely attributed to warming‐induced active layer expansion and newly exposed subsurface source areas. However, the ability of Arctic headwater streams to modulate inorganic nutrient patterns manifested in larger rivers remains unresolved. We evaluated environmental conditions, stream ecosystem metabolism, and nutrient uptake in three headwater streams of the Alaskan Arctic to quantify patterns of retention of inorganic nitrogen (N) and phosphorous (P). We observed elevated ambient nitrate‐N (NO3‐N) concentrations in late summer/early fall in two of three experimental stream reaches. We observed detectable increases in uptake as a result of nutrient addition in 88% of PO4‐P additions (n = 25), 38% of NH4‐N additions (n = 24), and 24% of NO3‐N additions (n = 25). We observed statistically significant relationships between NH4‐N uptake and ecosystem respiration, and PO4‐P uptake and gross primary productivity. Although these headwater streams demonstrate ability to control downstream transport of PO4‐P, we observed little evidence the same holds for dissolved inorganic N. Consequently, our results suggest that continued increases in terrestrial to aquatic N transfer in Arctic headwater landscapes are likely to be evident in larger Arctic rivers, in‐network lakes, and coastal environments.

Extent Changes in the Perennial Snowfields of Gates of the Arctic National Park and Preserve, Alaska

Perennial snowfields in Gates of the Arctic National Park and Preserve (GAAR) in the central Brooks Range of Alaska are a critical component of the cryosphere. They serve as habitat for an array of wildlife, including caribou, a species that is crucial as a food and cultural resource for rural subsistence hunters and Native Alaskans. Snowfields also influence hydrology, vegetation, permafrost, and have the potential to preserve valuable archaeological artifacts. By deriving time series maps using cloud computing and supervised classification of Landsat satellite imagery, we calculated areas and evaluated extent changes. We also derived changes in elevations of the perennial snowfields that remained stable for at least four years. For the study period of 1985 to 2017, we found that total areas of perennial snowfields in GAAR are decreasing, with most of the notable changes in the latter half of the study period. Equilibrium areas, or bright areas, of the snowfields are shrinking, while ablation, or dark areas, are growing. We also found that the snowfields occur at higher elevations over time. Climate change may be altering the distribution, elevation, and extent of perennial snowfields in GAAR, which could affect caribou populations and subsistence lifestyles in rural Alaska.

U-Pb and oxygen isotope characteristics of Timanian- and Caledonian-age detrital zircons from the Brooks Range, Arctic Alaska, USA

AbstractThe Devonian connection between the Brooks Range of Alaska, USA, with the continental margin of Arctic Canada and its subsequent Jurassic–Cretaceous counterclockwise rotation to form the Amerasian Basin, is a highly debated topic in Arctic tectonics. This resource-rich region was assembled from terranes that formed part of Laurentia or Baltica, or were juvenile oceanic arcs in the early Paleozoic that were brought together during Caledonian Orogenesis and the subsequent collision that formed Pangea (Uralide Orogeny). Elements of these orogens, as well as older ones, are predicted to occur in the Brooks Range of Arctic Alaska. This study presents the first combined zircon U-Pb and oxygen data from six Brooks Range metasedimentary units with assumed Neoproterozoic to Devonian ages. Three distinct detrital zircon patterns are identified in these units: (1) those with Neoproterozoic maximum depositional ages characteristic of the Timanide Orogen of northern Baltica and adjacent parts of Siberia, (2) an almost unimodal Siluro–Ordovician (443.5 ± 2.3 Ma) detrital zircon population consistent with the oceanic Apoon arc believed to have existed off shore of northern Laurentia and to have accreted to the North Slope subterrane during the Caledonian event, and (3) those with Middle Devonian maximum depositional ages consistent with post-accretion extension during the final (Scandian) phase of Caledonian Orogenesis. Oxygen isotopes from the same zircons reveal minor to significant crustal contamination with approximately two thirds (n = 255/405) having δ18O values >5.9‰ (above the mantle field of 5.3 ± 0.6‰). Pattern 1 units exhibit a progressive increase in δ18O values throughout the Proterozoic (5.99 to 9.29‰) indicative of increasing crustal growth and Timanide age zircons yield average δ18O values of 7.18 ± 0.64‰ (n = 26) suggestive of more crustal influence than Caledonian age zircons, possibly reflecting northern Baltica signatures. The unimodal population in Pattern 2 yields average δ18O values of 5.49 ± 0.66‰ (n = 17) and 6.02 ± 0.27‰ (n = 23) prior to and during, respectively, the main Caledonian event and suggest derivation from Devonian juvenile arc sources possibly representing the initiation of the collision between Laurentia and Baltica. Similar to Pattern 1, the δ18O values associated with Pattern 3 show a progressive increase in δ18O values throughout the Proterozoic (5.00 to 9.39‰). However, Pattern 3 also exhibits a distinct juvenile fingerprint (6.13 ± 0.24‰, n = 51) during the main Caledonian event and a slight increase to 7.12 ± 1‰ (n = 7) in post-Caledonian zircons possibly suggest correlating with a post-accretion phase in which proximally sourced zircon-bearing detritus was deposited in extension-related basins marking the joining of Laurentia and Baltica.

Weatherscapes: Alaska's Brooks Range: Fortress of the Arctic

Rising into the frigid air of northern Alaska, situated in its entirety above the Arctic Circle, the virtually uninhabited 700-mile-long Brooks Range is one of the least visited, wildest, most aust...

Management implications of highly resolved hierarchical population genetic structure in thinhorn sheep

Patterns of genetic variation of a species can be shaped by events that occur at wide temporal and geographic scales. Geophysical processes, such as continental glaciations, can affect species vicariance at wide scales whereas processes that act at finer scales, such as gene flow between populations, can have more localized effects. Recent studies have shown that contemporary population structure should be interpreted within the context of historical events, such as ice-age vicariance, due to the hierarchical nature of genetic variation found in many species. The thinhorn sheep (Ovis dalli) is a mountain specialist found in northwestern North America, from the Brooks Range in Alaska, east through Yukon to the Mackenzie Mountains of Northwest Territories and south to the Rocky and Coastal Mountains of British Columbia. In this study, we examined the population genetic structure of thinhorn sheep in light of genetic evidence regarding the glacier driven evolution of the two thinhorn sheep subspecies, O. d. dalli and O. d. stonei, using 153 biallelic single-nucleotide polymorphisms genotyped in over 2800 thinhorn rams. We found patterns of genetic variation to be generally consistent with genetic subspecies boundaries at the species-wide level, and mountain range and river valley boundaries at finer scales. By taking in account historical vicariance by conducting hierarchical analyses of population genetic structure, we revealed the presence of three previously unreported Stone’s sheep genetic clusters in the Stikine/Skeena, Cassiar and Rocky Mountains and identified a new geographic range for Stone’s sheep that is much more restricted than currently accepted subspecies maps indicate, and is almost exclusively confined within British Columbia. Our results indicate that contemporary patterns of genetic variation can be influenced by events acting over a range of spatial and temporal scales, and thus the importance of interpreting the findings of present-day genetic structure in light of the phylogeographical history of the species in question.

Ophiolitic Complex of the Matachingai River on Eastern Chukotka: Fragment of Lithosphere in Mesozoic Back-Arc Basin

The Matachingai River basin is known among the few ophiolitic complexes on eastern Chukotka as the southern boundary of the Chukotka Fold System (in terms of tectonics, the Chukotka microcontinent or a fragment of the Arctic Alaska–Chukotka microplate). This complex comprises tectonic blocks of residual spinel harzburgite with dunite bodies and pyroxenite, olivine gabbro, and leucogabbro veins; blocks of hornblende gabbro, diorite, and plagiogranite; and Upper Jurassic–Lower Cretaceous basaltic–cherty and cherty–carbonate rocks. The geological relationships of rocks within tectonic blocks, the compositions of primary minerals, the bulk geochemistry of rocks, as well as the strontium, neodymium, and lead isotopic compositions, make it possible to consider individual tectonic blocks of the complex as fragments of a disintegrated oceanic-type lithosphere that formed in a back-arc spreading center. The melts, crystallization products of which are represented by hornblende gabbro of blocks, olivine gabbro of veins, and basalts, separated from geochemically and isotopically heterogeneous mantle. Blocks composed of rocks with various modal composition are likely relicts of an oceanic lithosphere of different segments of a back-arc basin. The studied complex may be a lithosphere of one of the Middle–Late Jurassic back-arc basins. Fragments of these basins are retained in ophiolitic complexes on Great Lyakhovsky Island of the New Siberian Islands Archipelago, western Chukotka, and the Brooks Range in Alaska.

A new species of Idiognathoides (conodont) in the Lower Pennsylvanian Ladrones Limestone of the Alexander terrane, southeast Alaska, and its paleogeographic significance

The Peratrovich Formation and overlying Ladrones Limestone in the Craig C4 quadrangle of the Prince of Wales Island, Alaska, record the accumulation of Carboniferous carbonates behind the remnants of a Late Devonian volcanic arc in the Alexander terrane. The occurrences of declinognathodid elements in the lower Ladrones Limestone suggest the possibility of a conformable Mississippian-Pennsylvanian boundary near the base of the Ladrones Limestone. The recovery of the Early Pennsylvanian conodont Idiognathoides chaagulootus n. sp. in the lower part of the Ladrones Limestone helps to constrain current models of the paleogeographic position of the Alexander terrane during the Carboniferous because of its limited occurrence within the Uralian Seaway. The presence of Id. chaagulootus n. sp. in the Alexander terrane, the Brooks Range of Alaska, and Novaya Zemlya indicates a species level biogeographic connection between these regions that shows that the Alexander terrane remained in the Uralian Seaway until at least the Middle Pennsylvanian.

Predicting movement using internal deformation dynamics of a landslide in permafrost

Within the Brooks Range of Alaska, several frozen debris lobes (FDLs) – or slow-moving landslides in permafrost – are approaching critical infrastructure. FDL-A, the largest and closest of these features, was 32.3m from the toe of the Dalton Highway as of October 2016. Here we present the analysis of nearly three years of data from a MEMS-based in-place inclinometer installed within FDL-A. Analysis of the strain within the active layer indicates that it is closely tied to air temperature and water, suggesting that cooling and/or draining the FDL may be effective mitigation techniques. Within the lobe body, strain rates are comparable to those measured within rock glaciers. Using the cyclical pattern and phase lag identified within the strain data, and surface movement rates 1) derived from historic imagery analysis and InSAR data, and 2) measured using a differential GPS system, we developed and vetted a predictive function for surface movement of FDL-A. The predictive function indicates that FDL-A moves at an average rate of 4.9myr−1, reaching a maximum velocity of 7.9myr−1 during the fall, and falling to 1.9myr−1 in the early spring. We hypothesize that the seasonal movement pattern is due to the infiltration of snow melt, and the subsequent reduction of effective stress within the shear zone. Using the predictive function and the measured October 2016 distance, we predict that FDL-A will reach the current Dalton Highway embankment during early 2023.

Nest-site selection and nest success of an Arctic-breeding passerine, Smith's Longspur, in a changing climate

ABSTRACT Despite changes in shrub cover and weather patterns associated with climate change in the Arctic, little is known about the breeding requirements of most passerines tied to northern regions. We investigated the nesting biology and nest habitat characteristics of Smith's Longspurs (Calcarius pictus) in 2 study areas in the Brooks Range of Alaska, USA. First, we examined variation in nesting phenology in relation to local temperatures. We then characterized nesting habitat and analyzed nest-site selection for a subset of nests (n = 86) in comparison with paired random points. Finally, we estimated the daily survival rate of 257 nests found in 2007–2013 with respect to both habitat characteristics and weather variables. Nest initiation was delayed in years with snow events, heavy rain, and freezing temperatures early in the breeding season. Nests were typically found in open, low-shrub tundra, and never among tall shrubs (mean shrub height at nests = 26.8 ± 6.7 cm). We observed weak nest-site select...

Dispersal and survival of a polygynandrous passerine

ABSTRACT Although sex biases in survival and dispersal are thought to be linked to avian mating systems, little is known about these demographic patterns in less common mating strategies such as polygynandry. We investigated breeding-site fidelity, natal philopatry, and apparent survival of the polygynandrous Smith's Longspur (Calcarius pictus) over a 7-yr period at 2 areas in Alaska's Brooks Range. We used capture–recapture histories of 243 color-banded adults and 431 juveniles to estimate annual survival and determined dispersal patterns from 34 adults that were found breeding within the study areas over multiple years. Most adults (88%) returned to nest in the same breeding neighborhood as in previous years; mean dispersal distance was 300.9 ± 74.2 m and did not differ between sexes. Juveniles exhibited low natal philopatry; only 4% of banded hatch-year birds were resighted as adults during subsequent years. Those that did return dispersed, on average, 1,674.4 ± 465.8 m from their natal nests (n = 6). ...

Using satellite image analysis for locating prehistoric archaeological sites in Alaska's Central Brooks Range

In this pilot study, we apply satellite image analysis to archaeological site prospection in Alaska's Brooks Range. Our goal was to test whether satellite remote sensing, which has been successful in locating large archaeological features associated with sedentary peoples, could be applied to arctic interior sites associated with mobile hunter–gatherers. In particular, we strove to develop a relatively straightforward and inexpensive model using existing data which could be used to help guide archaeology surveys. Using 1-m resolution IKONOS imagery of Lake Matcharak along the upper Noatak River, we produced a Normalized Difference Vegetation Index (NDVI) and tasseled cap transformation of the study area and stacked these five vegetation indices into one image. We then applied unsupervised and supervised classifications to the image first, to test for the presence of a site-specific spectral class and second, determine the nature of that class. Through a visual analysis of the unsupervised classification, a spectral phenomenon was seen to co-occur with archaeological sites in the study area. The supervised classification provided a high-resolution land cover map used to identify the signature as the ecotone between un-vegetated sediments and dense willow (Salix sp.) stands. Dense willow stands along the Lake Matcharak shore visually correlate with most of the known archaeological sites, possibly reflecting landform and/or vegetation characteristics that would have appealed to past inhabitants. The methods described here could contribute to building better survey strategies and archaeological predictive models for elsewhere in the Brooks Range and Alaska.

Isoprene emissions from a tundra ecosystem

Abstract. Whole-system fluxes of isoprene from a moist acidic tundra ecosystem and leaf-level emission rates of isoprene from a common species (Salix pulchra) in that same ecosystem were measured during three separate field campaigns. The field campaigns were conducted during the summers of 2005, 2010 and 2011 and took place at the Toolik Field Station (68.6° N, 149.6° W) on the north slope of the Brooks Range in Alaska, USA. The maximum rate of whole-system isoprene flux measured was over 1.2 mg C m−2 h−1 with an air temperature of 22 °C and a PAR level over 1500 μmol m−2 s−1. Leaf-level isoprene emission rates for S. pulchra averaged 12.4 nmol m−2 s−1 (27.4 μg C gdw−1 h−1) extrapolated to standard conditions (PAR = 1000 μmol m−2 s−1 and leaf temperature = 30 °C). Leaf-level isoprene emission rates were well characterized by the Guenther algorithm for temperature with published coefficients, but less so for light. Chamber measurements from a nearby moist acidic tundra ecosystem with little S. pulchra emitted significant amounts of isoprene, but at lower rates (0.45 mg C m−2 h−1) suggesting other significant isoprene emitters. Comparison of our results to predictions from a global model found broad agreement, but a detailed analysis revealed some significant discrepancies. An atmospheric chemistry box model predicts that the observed isoprene emissions have a significant impact on Arctic atmospheric chemistry, including a reduction of hydroxyl radical (OH) concentrations. Our results support the prediction that isoprene emissions from Arctic ecosystems will increase with global climate change.

Wind Field Climatology, Changes, and Extremes in the Chukchi–Beaufort Seas and Alaska North Slope during 1979–2009

Abstract Wind field climatology, changes, and extremes at ~32-km resolution were analyzed for the Chukchi–Beaufort Seas and Alaska North Slope region using 3-hourly North American Regional Reanalysis (NARR) from 1979 to 2009. The monthly average wind speeds show a clear seasonal cycle with a minimum of 2–4 m s−1 in May and a maximum up to 9 m s−1 in October. The 95th percentile winds show a similar seasonality with a maximum up to 15 m s−1 in October. The 31-yr domain averaged 3-hourly wind speeds display a clear diurnal cycle over land and sea ice areas during the warm seasons. Weaker radiation during winter and larger heat capacity over open water reduce the diurnal signal in the wind field diurnal variations. There were increasing trends of areal averaged monthly mean and 95th percentile wind speeds for July through November. The strongest increase in the areal averaged 95th percentile wind speeds occurred in October from 7 m s−1 in 1979 to 10.5 m s−1 in 2009. The frequency of extreme wind events (speed above the 95th percentile winds) shows an increasing trend in all months, with the greatest increase occurring in October, showing 8% more extreme wind events in 2009 comparing to 1979. The prevailing wind direction was northeast with a frequency of 40%–60% for most of the year. The frequency for southwest and northwest winds was small (<20%) except for two anomalous areas along the Brooks Range in Alaska and the Chukotka Mountains in easternmost Russia where the frequency has increased to 35%–50% during the cold season months.

Variability of in‐stream and riparian storage in a beaded arctic stream

AbstractThe extent and variability of water storage and residence times throughout the open water season in beaded arctic streams are poorly understood. Data collected in Imnavait Creek, a beaded stream located north of the Brooks Range in Alaska, were used to better understand the effects of in‐pool and riparian storage on heat and mass movement through beaded streams. Temperature data of high spatial resolution within the pools and surrounding sediments were used with volumetric discharge and electrical conductivity to identify storage areas within the pools, banks, and other marshy areas within the riparian zone, including subsurface flow paths that connect the pools. These subsurface flows were found to alter water conductivity and the character of dissolved organic matter (DOM) in short reaches (10 s of m) while influencing the chemistry of downstream pools. During low flow periods, persistent stratification occurred within the pools due to absorption of solar radiation by DOM coupled with permafrost below and low wind stress at the pool surface. Additionally, one of the shallow pools (<0.5 m depth) remained stratified during higher flow periods and lower radiation inputs due to dense subsurface flows entering the bottom of the pools. This consistent separation of surface and bottom water masses in each pool will increase the travel times through this and similar arctic watersheds, and therefore will affect the evolution of water chemistry and material export. Copyright © 2011 John Wiley & Sons, Ltd.

Snow-mediated ptarmigan browsing and shrub expansion in arctic Alaska

Large, late-winter ptarmigan migrations heavily impact the shoot, plant, and patch architecture of shrubs that remain above the snow surface. Ptarmigan browsing on arctic shrubs was assessed in the vicinity of Toolik Lake, on the north side of the Brooks Range in Alaska. Data were collected in early May 2007, at maximum snow depth, after the bulk of the ptarmigan migration had passed through the area. In an area of tall shrubs, half of the buds on Salix alaxensis were browsed by ptarmigan. Three percent of the buds that were buried beneath the snow were browsed, 90% of the buds that were less than 30 cm above the maximum snow level were browsed, and 45% of the buds above that height were browsed. Ptarmigan browsing was found to be a major height limiter for tall shrubs, thereby controlling shrub architecture by brooming stems at the snow surface and inducing stump shoots. These results were qualitatively extrapolated by photographing shrub morphology over a region approximately 300 km wide across a series of north-flowing arctic rivers with headwaters in the Brooks Range. Ptarmigan “hedging” of shrub patches, and shrub growth under a warmer climate, are opposing forces mediated by snow distribution.

White Spruce Seedling (<i>Picea glauca</i>) Discovered North of the Brooks Range Along Alaska's Dalton Highway

A white spruce seedling, Picea glauca (Moench) Voss, was found at the northern edge of the Brooks Range in Alaska, more than 50 km north of the latitudinal tree line. The seedling, 19 cm tall and about nine years old, was growing at the side of the Dalton Highway to Prudhoe Bay. It most likely sprouted from a seed transported across the Brooks Range on a vehicle and has survived on the well-drained gravel road berm, where site conditions are more favorable for germination and survival than in the surrounding tundra. This spruce has survived for about a decade under current climatic conditions. Even with a warming climate, natural seed dispersal is severely hampered by the rugged topographic barrier of the Brooks Range. Considering the amount of vehicle traffic on the Dalton Highway, however, it is likely that more pioneering spruce seedlings will turn up along this corridor. Once over the Brooks Range, a spruce population can potentially develop and expand.

Dietary Fatty Acid Composition and the Hibernation Patterns in Free‐Ranging Arctic Ground Squirrels

Laboratory experiments have demonstrated that the amount of polyunsaturated fatty acids (PUFAs) in the diet before hibernation influences patterns of mammalian torpor. The hibernation ability of ground squirrels is greatest (longest torpor bouts, greatest number of animals entering torpor) when the PUFA content of their fall diets is 33-74 mg/g, under laboratory conditions. The extent to which natural fall diets both (a) vary in PUFA content and (b) influence the torpor patterns of free-ranging populations of hibernating mammals is unknown, however. We conducted a 3-yr study on the diet PUFA contents and subsequent hibernation patterns of free-ranging arctic ground squirrels (Spermophilus parryii) in the Brooks Range of Alaska. We found that the PUFA contents of fall diets varied more than threefold among individuals. Our study also revealed that arctic ground squirrels that consumed a moderate-PUFA (33-74 mg/g) diet had (a) longer torpor bouts, (b) fewer arousals from torpor, (c) shorter arousal periods, (d) more days in torpor, and (e) greater probability of persisting in the population than those that consumed a high-PUFA (>74 mg/g) diet during the fall. No animals were demonstrated to have consumed a diet representing low-PUFA (<33 mg/g) values. Our study is therefore the first to demonstrate that estimated dietary PUFA levels of a free-ranging hibernator influence subsequent torpor patterns.

Hyporheic exchange and water chemistry of two arctic tundra streams of contrasting geomorphology

The North Slope of Alaska's Brooks Range is underlain by continuous permafrost, but an active layer of thawed sediments develops at the tundra surface and beneath streambeds during the summer, facilitating hyporheic exchange. Our goal was to understand how active layer extent and stream geomorphology influence hyporheic exchange and nutrient chemistry. We studied two arctic tundra streams of contrasting geomorphology: a high‐gradient, alluvial stream with riffle‐pool sequences and a low‐gradient, peat‐bottomed stream with large deep pools connected by deep runs. Hyporheic exchange occurred to ∼50 cm beneath the alluvial streambed and to only ∼15 cm beneath the peat streambed. The thaw bulb was deeper than the hyporheic exchange zone in both stream types. The hyporheic zone was a net source of ammonium and soluble reactive phosphorus in both stream types. The hyporheic zone was a net source of nitrate in the alluvial stream, but a net nitrate sink in the peat stream. The mass flux of nutrients regenerated from the hyporheic zones in these two streams was a small portion of the surface water mass flux. Although small, hyporheic sources of regenerated nutrients help maintain the in‐stream nutrient balance. If future warming in the arctic increases the depth of the thaw bulb, it may not increase the vertical extent of hyporheic exchange. The greater impacts on annual contributions of hyporheic regeneration are likely to be due to longer thawed seasons, increased sediment temperatures or changes in geomorphology.

Modeling biogeophysical interactions in nonsorted circles in the Low Arctic

We investigate biogeophysical processes that cause differential frost heave in nonsorted circles north of the Alaska's Brooks Range. The main objective is the development of a numerical thermo‐mechanical model of a nonsorted circle. The presented model includes mass, momentum and energy conservation laws for water, ice and soil. We applied this model to simulate differential frost heave at the Franklin Bluffs site and obtained a good quantitative agreement with measured dynamics of soil temperature, water content, and frost heave. For other locations such as at the Sagwon Hills and Howe Island sites we obtained qualitative agreement with frost‐heave measurements. Sensitivity analysis shows that the most active development of differential frost heave occurs for nonsorted circles within waterlogged areas, as observed in field measurements. For well drained sites, model results and field observations show that the differential frost heave is much smaller in magnitude comparing to that of the water‐logged sites. Sensitivity of the model to alternation of the vegetation cover shows that a strong heterogeneity in the vegetation cover promotes active development of the differential frost heave. For nonsorted circles with vegetation on top of the circle, the computed differential heave is less pronounced. The radius of the nonsorted circle influences the magnitude of the frost heave. The computed maximum frost heave in the center of the circle corresponds to 1–1.5 meter diameter nonsorted circles. For nonsorted circles with larger diameters, computed frost heave in the center of a circle is smaller compared to the heave at the circle circumference.