Prudhoe Bay Research Articles

Improving People’s Lives: Minimizing Impact

President's column Last December I had the pleasure of returning to the Kingdom of Saudi Arabia and touring the giant Manifa oil field. Manifa produces a heavy, sour crude oil from six, long (up to 40 km), stacked reservoirs in shallow water (Arukhe 2014). The shallow waters have abundant sea grasses and corals and are teeming with marine life. Shrimping and fishing are important parts of the local economy. The development of the Manifa field is a fascinating story showing how creative solutions can minimize impact on the environment. Manifa was discovered by Saudi Aramco in 1957. The discovery well targeted both the shallower formations productive in the large Safaniya coastal field and the deeper Arab formations so productive onshore. Neither zone was productive; however, the discovery found excellent productive layers in between, including three that were only produced in small volumes onshore and three that had never before proved productive. The heavy, sour crude was similar to Khursaniyah, one of the three major types of crude present in large quantities in the Kingdom. Demand was less for this crude than for Safaniya and Arab crudes but the market for heavy sour crudes was improving (Aramco World 1963). The first development was in 1962, and the field was brought on stream in 1964. The field produced for 20 years before being mothballed in 1985 because of low demand (Aldossary 2015). Manifa’s history can be contrasted with that of Prudhoe Bay in Alaska. While specific reserve estimates for Manifa are not public information, both fields are very large. The Prudhoe Bay field was discovered in 1968 and did not begin production until 1977. Prudhoe production peaked at about 1.5 million BOPD in 1989. Prudhoe Bay crude averages 27.6 °API and had a significant domestic market to serve. Manifa crude is 26–31 °API and has from 2.8% to 3.7% sulfur content (Croft and Patzek 2009), with less of a market at the time. It is fairly astonishing that roughly comparable fields would go down such radically different paths. Manifa would remain mothballed until 2006. Saudi Aramco redeveloped the field consistent with a very long life production time horizon for its large reservoirs (Saudi Aramco 2016). But the old way of approaching shallow offshore fields would not be acceptable. The use of jackup rigs in these shallow waters would have required excessive dredging, and the size of the reservoir eliminated the possibility of effective development from the shore. A new approach to development would be needed. A creative plan to develop man-made islands connected by a causeway would allow conventional onshore rigs to be used to develop this offshore field. A long causeway was considered, but early designs would have decreased water circulation vital to distributing nutrients and oxygen vital to marine life. With more than 4 million man-hours of work in the design phase, a solution was developed to build 27 man-made islands connected by 41 km of causeways. To ensure needed water circulation, the causeway does not go all the way across the bay and 14 bridges were built into the causeway to further improve circulation (Aldossary 2015). Production commenced in 2012 ahead of schedule and under budget in a development that earned a UNESCO Environmental Responsibility Award nomination. It is an impressive development of which Saudi Aramco is rightly proud, with eventual production capacity of 900,000 BOPD or more. As our helicopter approached the massive processing facility, I looked at the three large flare stacks. There was nothing being flared. Was the field shut in? No, the design and normal operations of the field use all of the produced gas and creative operations practices mean that almost no gas is flared. Excess electricity produced by the facilities goes into the power grid.

Trace Elements in Sea Ducks of the Alaskan Arctic Coast: Patterns of Variation Among Species, Sexes, and Ages.

Climate change and increasing industrialization in the Arctic call for the collection of reference data for assessing changes in contaminant levels. For migratory birds, measuring and interpreting changes in traceelement burdens on Arctic breeding areas require insights into factors such as sex, body size, or wintering area that may modify patterns independently of local exposure. In the Alaskan Arctic, we determined levels of trace elements in liver and kidney of common eiders (Somateria mollissima) and long-tailed ducks (Clangula hyemalis) from the Prudhoe Bay oil field and of king eiders (S. spectabilis) and threatened spectacled eiders (S. fischeri) and Steller's eiders (Polystica stelleri) from near the town of Barrow. Small-bodied Steller's eiders and long-tailed ducks from different locations had similarly low levels of selenium (Se), cadmium (Cd), and copper (Cu), perhaps reflecting high mass-specific rates of metabolic depuration during long spring migrations through areas of low exposure. In larger species, Se, Cd, and Cu concentrations were higher in adults than juveniles suggesting that these elements were acquired in nonbreeding marine habitats. Adult male spectacled eiders had exceptionally high Se, Cd, and Cu compared with adult females, possibly because of depuration into eggs and longer female occupancy of nonmarine habitats. Adult female common eiders and juvenile long-tailed ducks at Prudhoe Bay had high and variable levels of Pb, potentially due to local exposure. Explanations for substantial variations in Hg levels were not apparent. Further research into reasons for differing element levels among species and sexes will help clarify the sources, pathways, and risks of exposure.

Stable isotopes in the closed-system Weather Pingo, Alaska and Pestsovoye Pingo, northwestern Siberia

High-resolution records of the stable isotopic (δ18O and δD) composition of ice within two closed system (hydrostatic) pingos indicate a complex history of ice formation by segregation and injection and pingo growth. Physical properties and internal structure of continuous ice cores in the center of the Weather Pingo near Prudhoe Bay, Alaska, and the Pestsovoye Pingo, in northwestern Siberia, were described and then sub-sampled for analysis of the isotopic composition. Changes in the isotopic signature and physical properties of ice with depth reveal distinct patterns in both pingos indicative of ice growth as permafrost aggraded into the drained lake basin. In the initial stages following active layer deepening and initial freeze back, in-situ water migrating toward the freezing front froze at a relatively rapid rate as revealed by a complex isotopic record and small ice crystal size in the cores of Weather Pingo. Once the water supply became limited, freezing under equilibrium conditions resulted in an isotopic composition consistent with Rayleigh-type fractionation and δ18O and δD values that become more negative with depth. The data for the Pestsovoye Pingo reveal similar trends related to the initial stages of water migration and freezing, followed by isotopic fractionation under equilibrium conditions as unfrozen water available in the talik beneath the pingo became limited. Most of the ice in both pingos (~50%) formed during this final stage of permafrost aggradation. Thus temporal variability in water migration and freezing rate at the base of each pingo created a complex isotopic stratigraphy and ice growth history.

Ambient loading and modal parameters for the Chulitna River Bridge

The Chulitna River Bridge is a 790-ft five girder, five-span steel bridge on the Parks Highway between Fairbanks and Anchorage, Alaska. This bridge was built in 1970 and widened in 1993. Under the no-live load condition, five support bearings are not in contact. Heavily loaded trucks often travel across this bridge to the oil fields in Prudhoe Bay, Alaska. A virtual finite element modeling, dynamic field testing of the “ambient vibrational response,” and structural health monitoring system are used to analyze, evaluate, and monitor the structural performance. As the first stage of the research, this article presents results from the dynamic testing and evaluation of the structural responses of the bridge. In the dynamic field testing, 15 portable accelerometers were placed on centerline along the bridge length to record the structural response, and an ambient free-decay response was used to evaluate the dynamic properties of the bridge structure. Natural frequencies and modal damping ratios were identified and characterized using Hilbert–Huang transform and fast Fourier transform methods. Compared with conventional approaches, this study demonstrates that (1) the Hilbert–Huang method was found to be effective and suitable for modal parameter identification of a long steel girder bridge using ambient truck loading; (2) the nonlinear damping was, for the first time, identified based on Hilbert–Huang transform’s amplitude–time slope; (3) modal frequencies are very sensitive to sensor location so their position should be optimized.

Haul Road Stories

Haul Road Stories Annie Olson (bio) 1 The James W. Dalton Highway stretches 414 miles north from Fairbanks to Prudhoe Bay—that is, 414 miles across the Arctic and beyond the reach of civilization in Alaska. When my boyfriend Mike and I quit our summer jobs on the Kenai Peninsula with a fishing out-fitter, we wanted to be beyond reach. We were tired of earning less than minimum wage and even more tired of the summer tourism season in south central Alaska: thousands of trailers lined bumper to bumper on the Sterling Highway, the passengers snapping pictures from their windows of rivers and mountains. It wasn’t the Alaska I wanted to show Mike while we were still twenty-six and untethered. So we set forth, in June of 2007, to find out if frontiers still existed. We applied to job postings on a bench outside a coffee shop in Homer, connecting and reconnecting to a feeble wireless signal. Out of money, we left for the Arctic before Northern Alaska Tour Company officially hired us. The distance we traveled from the Kenai Peninsula to the Yukon River is equivalent to a road trip from Wisconsin to Oklahoma. [End Page 31] 2 I do not keep travel journals—at least not good ones—but I love to read them. Classics like Darwin or Heyerdahl or the diaries of prospectors from the Alaskan Gold Rush. Before Darwin ever reached the Galápagos Islands, he sailed around Cape Horn several times. Many of his early letters describe the wind: that “grand spectacle” of “all nature thus raging.” He was enthralled by the “savage, solitary character” of southern Argentina, where “no European had ever trod.” But I do not mind if others have gone before me. Even the best expedition journals are brief moments in the story of a place. 3 In the 1970s the Trans-Alaska Pipeline was built to funnel oil from the fields in Prudhoe Bay to Fairbanks, with the Dalton Highway constructed alongside. The Arctic icecap makes shipping to Prudhoe nearly impossible, so the Dalton or “Haul Road” is the only way to transport supplies: machinery, ATCO trailers, enough food to sustain workers at the oil rigs. Seventy-five percent of the road is unpaved. The truckers who work the Dalton are a tight and insular clan, having run the same route for years. Most live in Fairbanks and make two “turns” per week—trips up to Prudhoe and back. When I worked in the Arctic, the trucking family included about three hundred regular drivers and two hundred part-timers. Small communities of seasonal workers and homesteaders live along the Dalton. Yukon River Camp, at milepost 56, is the first stop going north. There are two restaurants, a dorm for construction crews, and a visitor center. Camp is only open mid-June through early September. The Arctic Circle is next, at milepost 115. It is marked with a single sign. [End Page 32] Coldfoot, at milepost 175, is considered the halfway point for truckers. There is a restaurant, dormitory, airport, and motel. Property management varies—currently Northern Alaska Tour Company operates Coldfoot Camp—but all managers are contractually obligated to keep the restaurant and fuel pumps running twenty-four hours a day, year-round. It’s the only truck stop in 414 miles. The unofficial lowest temperature ever recorded in Coldfoot, which locals consider accurate, is negative eighty-one degrees Fahrenheit. Most winters see lows in the negative sixties. Truckers stop articulating the minus sign by the end of October, at which point “thirty” translates to “thirty degrees below zero.” There is little difference between the twenties and the thirties, but gasoline freezes and will not pump in the forties. When temperatures fall into the fifties, it is very dangerous to drive. 4 Mike and I were initially hired by Northern Alaska for a two-month contract at Yukon River Camp. Getting there was the first obstacle. Our new employers offered us a ride up in a tour van, but we insisted on bringing our Chevy Blazer. Ostensibly, we understood the risks. Guidebooks warn against driving a personal vehicle on the Dalton. It’s poorly maintained, and mostly dirt...

Snow retention for increased water supply of shallow Arctic lakes

Throughout the year, water availability in the Arctic is marginal because of the cold climate, presence of permafrost, and low precipitation. Recent resource development and improvements in living conditions of the expanding population have placed additional stresses on the annual local water supply of communities and industry located in this region. This study implemented a snow control practice to enhance snowdrift growth as a local water source at a shallow Arctic lake located on Alaska's Coastal Plain, 50km south of Prudhoe Bay, USA. A 130m long and 3m tall snow fence was placed next to a lake for the winters of 2009–2010 and 2010–2011. This snow fence retained large quantities of snow transported by wind during the winter, forming a sizable snowdrift. In this region of the Arctic, lakes receive most of their water from seasonal snowpack melt in late May and early June, with subsequent drying of the lakes after snowmelt. The artificially created snowdrift at the experimental lake contributed meltwater until early July during both summers of the study period and effectively offset summer lake drying. At summer's end, the additional lake volume from the fence snowdrift was 21% and 29% in 2010 and 2011, respectively. While techniques such as snow fences can be used to address existing needs for enhanced water supplies, they can also serve as a tool for assessing lake response to a future climate scenario in which summers are warmer and both evaporation and winter precipitation increase.

Role of ground ice dynamics and ecological feedbacks in recent ice wedge degradation and stabilization

AbstractGround ice is abundant in the upper permafrost throughout the Arctic and fundamentally affects terrain responses to climate warming. Ice wedges, which form near the surface and are the dominant type of massive ice in the Arctic, are particularly vulnerable to warming. Yet processes controlling ice wedge degradation and stabilization are poorly understood. Here we quantified ice wedge volume and degradation rates, compared ground ice characteristics and thermal regimes across a sequence of five degradation and stabilization stages and evaluated biophysical feedbacks controlling permafrost stability near Prudhoe Bay, Alaska. Mean ice wedge volume in the top 3 m of permafrost was 21%. Imagery from 1949 to 2012 showed thermokarst extent (area of water‐filled troughs) was relatively small from 1949 (0.9%) to 1988 (1.5%), abruptly increased by 2004 (6.3%) and increased slightly by 2012 (7.5%). Mean annual surface temperatures varied by 4.9°C among degradation and stabilization stages and by 9.9°C from polygon center to deep lake bottom. Mean thicknesses of the active layer, ice‐poor transient layer, ice‐rich intermediate layer, thermokarst cave ice, and wedge ice varied substantially among stages. In early stages, thaw settlement caused water to impound in thermokarst troughs, creating positive feedbacks that increased net radiation, soil heat flux, and soil temperatures. Plant growth and organic matter accumulation in the degraded troughs provided negative feedbacks that allowed ground ice to aggrade and heave the surface, thus reducing surface water depth and soil temperatures in later stages. The ground ice dynamics and ecological feedbacks greatly complicate efforts to assess permafrost responses to climate change.

Ontogenetic and spatial variability in trophic biomarkers of juvenile saffron cod (Eleginus gracilis) from the Beaufort, Chukchi and Bering Seas

Climate models indicate the Arctic will undergo dramatic environmental change with forecasted increases in temperature and river runoff. Saffron cod (Eleginus gracilis) is abundant in nearshore waters and appears in the diet of many Arctic sea birds and marine mammals; however, little is known about its early ecology and consequently how they might be affected by environmental changes. We aimed to characterize the mechanisms of spatial and ontogenetic variation in trophic biomarkers (lipid classes, fatty acids and bulk C and N stable isotopes) of saffron cod from the Western Arctic, Chukchi and Bering Seas. Size-standardized analyses showed a significant difference in lipid condition metrics and trophic biomarkers as a function of survey location. Both ontogeny and sampling location played an important role in determining lipid stores with elevated levels in both small offshore juveniles ( 75 mm). Higher lipid storage in Arctic juveniles was associated with elevated levels of diatom fatty acid markers, but not with nearshore carbon input. Increased lipids were found in age-1 juveniles from Prudhoe Bay in the Western Beaufort that were feeding at a lower trophic level than similarly sized age-0 juveniles from surface trawls in the Bering Sea. The use of otolith annuli revealed two discrete patterns of growth that help explain the trade-offs between energy storage and rapid growth that diverge between the Arctic and Bering Sea. Laboratory temperature-growth experiments confirmed that saffron cod have a eurythermal growth response and are able to store excess lipids at temperatures as high as 20 °C.

Permafrost Carbon: What soil science has to say about its distribution and fate

Permafrost Carbon: What soil science has to say about its distribution and fate

The NO<sub><i>x</i></sub> dependence of bromine chemistry in the Arctic atmospheric boundary layer

Abstract. Arctic boundary layer nitrogen oxides (NOx = NO2 + NO) are naturally produced in and released from the sunlit snowpack and range between 10 to 100 pptv in the remote background surface layer air. These nitrogen oxides have significant effects on the partitioning and cycling of reactive radicals such as halogens and HOx (OH + HO2). However, little is known about the impacts of local anthropogenic NOx emission sources on gas-phase halogen chemistry in the Arctic, and this is important because these emissions can induce large variability in ambient NOx and thus local chemistry. In this study, a zero-dimensional photochemical kinetics model was used to investigate the influence of NOx on the unique springtime halogen and HOx chemistry in the Arctic. Trace gas measurements obtained during the 2009 OASIS (Ocean – Atmosphere – Sea Ice – Snowpack) field campaign at Barrow, AK were used to constrain many model inputs. We find that elevated NOx significantly impedes gas-phase halogen radical-based depletion of ozone, through the production of a variety of reservoir species, including HNO3, HO2NO2, peroxyacetyl nitrate (PAN), BrNO2, ClNO2 and reductions in BrO and HOBr. The effective removal of BrO by anthropogenic NOx was directly observed from measurements conducted near Prudhoe Bay, AK during the 2012 Bromine, Ozone, and Mercury Experiment (BROMEX). Thus, while changes in snow-covered sea ice attributable to climate change may alter the availability of molecular halogens for ozone and Hg depletion, predicting the impact of climate change on polar atmospheric chemistry is complex and must take into account the simultaneous impact of changes in the distribution and intensity of anthropogenic combustion sources. This is especially true for the Arctic, where NOx emissions are expected to increase because of increasing oil and gas extraction and shipping activities.

Phylogenetic and pathogenic characterization of novel adenoviruses isolated from long-tailed ducks (Clangula hyemalis)

Novel adenoviruses were isolated from a long-tailed duck (Clangula hyemalis) mortality event near Prudhoe Bay, Alaska in 2000. The long-tailed duck adenovirus genome was approximately 27kb. A 907bp hexon gene segment was used to design primers specific for the long-tailed duck adenovirus. Nineteen isolates were phylogenetically characterized based on portions of their hexon gene and 12 were most closely related to Goose adenovirus A. The remaining 7 shared no hexon sequences with any known adenoviruses. Experimental infections of mallards with a long-tailed duck reference adenovirus caused mild lymphoid infiltration of the intestine and paint brush hemorrhages of the mucosa and dilation of the intestine. This study shows novel adenoviruses from long-tailed ducks are diverse and provides further evidence that they should be considered in cases of morbidity and mortality in sea ducks. Conserved and specific primers have been developed that will help screen sea ducks for adenoviral infections.

Coiled-Tubing-Deployed Shutoffs in Alaska With a Polymer Gel and Microfine Cement

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 173655, “Coiled-Tubing-Deployed Gas and Water Shutoffs in Alaska With a Polymer Gel and Microfine Cement,” by D.B. Robertson, SPE, BP; M.A. Brown, Petrotechnical Resources of Alaska; L.H. Duong, SPE, BP; O.V. Ivanova, Schlumberger; and A. Tambe, SPE, BP, prepared for the 2015 SPE Coiled Tubing and Well Intervention Conference and Exhibition, The Woodlands, Texas, USA, 24–25 March. The paper has not been peer reviewed. A common problem in oil and gas wells is excess free gas or water production from only certain portions of the completed interval. A coiled-tubing-deployed profile-modification technique was developed primarily to shut off excess free-gas production from the heel of cased-and-perforated horizontal oil wells. The technique has also been used for water and gas shutoff in both vertical and horizontal wells in a variety of lower-completion types. Introduction Coiled-tubing work has a well- established track record in North Slope of Alaska oil fields involving several thousand interventions of various types. Fig. 1 is a photograph of a typical Arctic-winter coiled-tubing operation. Most of the approximately 1,700 wells in the Prudhoe Bay field penetrate either an extensive gas cap or the aquifer in the sandstone reservoir. Mechanisms for excess free-gas or water production can be related to poor primary-cement jobs of production liners, fluid-contact movements over time, coning, or corroded or damaged liners. In general, any through-tubing-profile modification that can be performed to reduce excess free-gas and water rates and increase oil rate or time on production is beneficial to overall field production. With many candidate wells, there has been a continuous evolution in job design and execution techniques over the years.

In the Warming Arctic Seas

In the Warming Arctic Seas

PREVALENCE AND SPATIO-TEMPORAL VARIATION OF AN ALOPECIA SYNDROME IN POLAR BEARS (URSUS MARITIMUS) OF THE SOUTHERN BEAUFORT SEA

Alopecia (hair loss) has been observed in several marine mammal species and has potential energetic consequences for sustaining a normal core body temperature, especially for Arctic marine mammals routinely exposed to harsh environmental conditions. Polar bears (Ursus maritimus) rely on a thick layer of adipose tissue and a dense pelage to ameliorate convective heat loss while moving between sea ice and open water. From 1998 to 2012, we observed an alopecia syndrome in polar bears from the southern Beaufort Sea of Alaska that presented as bilaterally asymmetrical loss of guard hairs and thinning of the undercoat around the head, neck, and shoulders, which, in severe cases, was accompanied by exudation and crusted skin lesions. Alopecia was observed in 49 (3.45%) of the bears sampled during 1,421 captures, and the apparent prevalence varied by years with peaks occurring in 1999 (16%) and 2012 (28%). The probability that a bear had alopecia was greatest for subadults and for bears captured in the Prudhoe Bay region, and alopecic individuals had a lower body condition score than unaffected individuals. The cause of the syndrome remains unknown and future work should focus on identifying the causative agent and potential effects on population vital rates.

Underwater Conventional and Unconventional Oil and Gas in the Arctic

Introduction Hydrocarbons under the Arctic and sub-Arctic seas have been known about for a long time. Gas and oil were found first in the northward extension of the Prudhoe Bay province and in the Canadian Arctic Islands. Those discoveries were followed by further finds in the Barents Sea, the Pacific to the east of Sakhalin, off Newfoundland and in Davis Strait, and in the northern Caspian Sea (where despite its low latitude many of the ice problems found further north are still present). Many areas of the Arctic seas have not been explored. Currently there is exploration in the Kara Sea and the Chukchi Sea. The potential difficulties are formidable. It will be essential that production schemes be safe against any possibility of environmental pollution. Some environmental campaigners are viscerally opposed to any Arctic development. They can reliably be anticipated to oppose every project on principle and will deploy every argument that can be dreamed up, whether scientifically credible or not. The curre...

Understanding the impact of open-framework conglomerates on water–oil displacements: the Victor interval of the Ivishak Reservoir, Prudhoe Bay Field, Alaska

The Victor Unit of the Ivishak Formation in the Prudhoe Bay Oilfield is characterized by high net-to-gross fluvial sandstones and conglomerates. The highest permeability is found within sets of cross-strata of open-framework conglomerate (OFC). These cross-strata are preserved within unit-bar deposits and assemblages of unit-bar deposits within compound (braid)-bar deposits, and may form thief zones limiting enhanced oil recovery. We incorporate recent research that has quantified important attributes of preserved sedimentary architecture into high-resolution models. Waterflooding experiments using these models demonstrate the control that such architecture has on oil production rate, water breakthrough time, and spatial and temporal distribution of residual oil saturation. We found that when the pressure gradient is orientated perpendicular to the palaeoflow direction, the total oil production and the water breakthrough time are larger, and the remaining oil saturation is smaller, than when it is orientated parallel to palaeoflow. The pressure difference between production and injection wells does not affect sweep efficiency, although the spatial distribution of oil remaining in the reservoir critically depends on this value. Oil sweep efficiency decreases slightly with increase in the proportion of OFC cross-strata. Whether or not clusters of connected OFC span the domain does not visibly affect sweep efficiency.

Lateral Pile Analysis Frozen Soil Strength Criteria

This paper presents a design approach to analyze the effects of lateral loads on piles embedded in a layered frozen soil profile. This design approach makes use of a commercially available computer program that uses p-y curves to model lateral pile loading and soil interaction. Shear strength and strain criteria for both fine-grained and coarse-grained frozen soil are presented for use in constructing p-y curves. These strength criteria are parameterized based on frozen soil temperature and load duration. Inuvik lateral pile load test measurements and deflections calculated using the strength criteria are compared. This comparison indicates that reducing shear strengths by a safety factor of 1.22 will ameliorate most unaccounted-for variations in soil profile. Deflections and moments are also calculated using the strength criteria for two Prudhoe Bay, Alaska, lateral pile load cases.

Anthropogenic food use and diet overlap between red foxes (Vulpesvulpes) and arctic foxes (Vulpeslagopus) in Prudhoe Bay, Alaska

Red foxes (Vulpes vulpes (L., 1758)) recently expanded into the oil fields at Prudhoe Bay, Alaska, USA, and we hypothesized that the availability of anthropogenic foods may contribute to their success and persistence there. This study assessed the importance of anthropogenic foods to the diets of red foxes and arctic foxes (Vulpes lagopus (L., 1758)), and competition for food resources between the two species in Prudhoe Bay. We used stable isotope analysis of fox tissues to infer diet during summer and winter for both red and arctic foxes, and lifetime diet for red fox. While the contribution of anthropogenic foods in late summer for both species’ diets was low (~10% to 15%), the contribution in late winter was higher and varied between species (red foxes = 49%; arctic foxes = 39%). Estimates of lifetime diet in red foxes suggest consistent use of anthropogenic foods. We found moderate overlap of fox diets, although red foxes appeared to be more specialized on lemmings, whereas arctic foxes had a more diverse diet. Availability and consumption of anthropogenic foods by red foxes, particularly in winter, may partially explain their year-round presence in Prudhoe Bay.

Ecotypic differentiation in photosynthesis and growth of Eriophorum vaginatum along a latitudinal gradient in the Arctic tundra

Ecotypic differentiation reduces climatic niche breadth at the population level relative to a species’ spatial distribution. For species that form climatic ecotypes, if future climate exceeds local population tolerance, climate change will precipitate the decline of extant populations range-wide. Here, we examine the variation in physiological and morphological traits of Eriophorum vaginatum L. collected from a 30-year-old reciprocal transplant experiment, in which six populations of E. vaginatum were transplanted along a latitudinal gradient from Eagle Creek to Prudhoe Bay, Alaska. We tested for ecotypic differentiation of photosynthesis, respiration, chlorophyll fluorescence, and biomass per tiller, which is a metric correlated with population growth in E. vaginatum. The light-saturated photosynthetic rate (Amax) showed homesite advantage in that tussocks in their homesites had significantly higher values of Amax relative to nonlocal populations. This pattern of homesite advantage was also observed for biomass per tiller, but not for fluorescence and respiration. Photosynthetic rate was positively correlated with biomass per tiller and survival, suggesting that adaptations related to photosynthesis may optimize performance of local populations to homesite conditions. Taken together, these findings indicate that a rapidly changing climate may elicit population decline of E. vaginatum, rendering this species at a competitive disadvantage to shrubs and boreal forest species, which are expanding northward as the climate changes. Transition from tussock-sedge tundra to boreal forest and shrubland alters features, such as albedo, soil temperature, and water-table depth, in ways that may accelerate climate change.

Shifts in Fox Den Occupancy in the Greater Prudhoe Bay Area, Alaska

Although shifts in the distribution of red foxes into areas previously dominated by Arctic foxes have been documented over wide areas of the circumpolar North, no such documentation exists yet for the Alaskan Arctic. Fox research in the greater Prudhoe Bay area from the 1970s through the early 1990s focused primarily on Arctic foxes in relation to oil development because red foxes were uncommon. A monitoring program in 2005–12 included annual surveys of 31–48 fox dens within 2 km of the road system. In 2005, 2006, and 2008, Arctic fox dens outnumbered those of red foxes, but from 2010 onward, the reverse was true. There is greater distance between natal dens of Arctic foxes and those of red foxes than between natal dens within each species, suggesting that Arctic foxes avoid red fox denning territories. Of dens in our study that were used by Arctic foxes prior to 2005, 50% have since been occupied by red foxes. Red foxes displaced Arctic foxes from dens closest to oil field camps, pads, and other facilities, and preyed on their pups. Access to anthropogenic food sources probably supports red foxes in the area. Predictions from climate change studies indicate the displacement of Arctic foxes by red foxes will continue in the Alaskan Arctic, although the change may be slower away from areas of human occupation and anthropogenic foods.