Laki eruption of 1783, tree rings, and disaster for northwest Alaska Inuit

Environmental conditions for trees that established in central Fennoscandia shortly after the final retreat of the Weichselian ice sheet remain poorly understood. In this study we examine tree rings of five well-preserved Pinus sylvestris (Scots pines) that grew in the area in front of the retreating ice sheet in northern Sweden. They became buried in flood sediments deposited by a glacial outburst flood (jökulhlaup) about 9.5–9.9 kyr cal bp and the aim of our study was to search for information regarding damage from fires and bioclimatic conditions in their ancient tree ring records. Our analysis, providing a glimpse into the local early Holocene environment in north-central Sweden, suggests that: 1, there were repeated fires (four fire events detected) during the early Holocene; and 2, bioclimatic conditions when the ancient pines were growing resembled those of modern sub-alpine pine woods. The latter is indicated by their patterns of tree ring growth (growth rate and variation), which were statistically similar to those of pines growing in sub-alpine woods with an open canopy, but different from pines in protected and managed boreal forests. Lower δ13C for the ancient latewood in comparison to pine wood from trees growing near the Scandinavian mountains before the 1850s were probably caused both by stomata fractionation due to lower atmospheric CO2 during the early Holocene and by the moist local environment created by the nearby ancient Ancylus lake, which preceded the Baltic Sea. Periods with cloudy and cold summers were also indicated by the occurrence of ‘false rings’. Finds of charred fragments of Calluna vulgaris (heather, ling), an understory shrub that can burn even with a relatively high moisture content, suggest that heath vegetation was crucial to make fire a reoccurring ecological factor in the area during the early Holocene.

Readings in Times of Crisis: New Interpretations of Stories about the Settlement of Iceland

Caribou (Rangifer tarandus granti) use lichens, when available, as primary forage on their winter range. In boreal forest habitats, wildland fires effectively destroy lichens, and overwintering caribou are known to avoid burned areas for decades while lichen communities regenerate. However, little has been published about caribou response to burned habitat in tundra ecosystems. To assess the relationship between winter caribou distribution and burned areas, we instrumented Western Arctic Herd caribou with satellite telemetry collars and evaluated their locations in relation to recent burns of known age (? 55 years old) across northwestern Alaska. We analyzed caribou distribution for different habitat types (tundra and boreal forest), age categories of burns, and possible edge effects. We also reanalyzed the data, limiting available habitat to a uniform traveling distance (5658 m) from daily satellite locations. Using selection indices that compared caribou use of burns and buffers to their availability, we found that caribou strongly selected against burned areas within the tundra ecosystem. Recent burns were selected against at both large (range-wide) and intermediate (5658 m) spatial scales. Caribou particularly selected against 26- to 55-year-old burns and the interior (core) portions of all burns. We found that caribou were more likely to select burned areas in the late fall and early spring than midwinter. Increased fires in northwestern Alaska could decrease the availability and quality of winter habitat available to the herd over the short term (up to 55 years), potentially influencing herd population dynamics and reducing sustainable harvest levels. We recommend that fire managers consider caribou midwinter range condition and extent: however, management that achieves a mosaic pattern of fire history may benefit a wide array of species, including caribou. A better understanding of the current regional fire regime and the distribution of available winter range will be required before practicable management recommendations can be developed for this herd.

Ten years of measurements and modeling of soil temperature changes and their effects on permafrost in Northwestern Alaska

Considering the Revolution

We present radiocarbon (14C) in tree rings from Mexico City and a reconstruction of fossil CO2concentrations for the last five decades, as part of a research program to understand the14C dynamics in this complex urban area. Background values were established by14C concentrations in tree rings from a nearby clean area. Agreement between background and NH-zone 2 values indicateTaxodium mucronatumis a good biomonitor for annual atmospheric14C variations. Values for the urban tree rings were significantly lower than background values, indicating a14C depletion from fossil CO2emissions. There is an increasing trend of fossil CO2between 1960 and 1990, in agreement with the population growth and the increasing demand for fossil fuels in Mexico City. Between 1990 and 2000, there is an apparent decrease in fossil CO2concentration, increasing again after 2000. The decrease in 2000, despite being of the same magnitude as the overall uncertainty, may reflect environmental policies that improved the energy efficiency and reduced CO2emissions in the area. The increase in fossil CO2concentration between 2000 and 2010 may be attributable to the significant growth of motor vehicle usage in Mexico City, which made transportation the main energy-demanding and -emitting sector.

The longest chronology from New Zealand so faris from Libocedrus bidwillii Hook. f. (i.e.,from AD 1992 back to AD 1140, a span of 853 years). A subset of 11 chronologies was selected from anetwork of 23 sites to reconstruct past temperaturesbased on the similarity of significant responsefunctions. A comparison of climate data overdifferent seasons with these 11 chronologies wascarried out using a bootstrap transfer function. Average late-summer (February–March) temperature wasselected for reconstruction based on independentverification results. The reconstructed temperaturewas then presented for the period back to AD 1720. The chronologies reconstructed years experiencing hotsummers better than cold summers. The power spectrumof the reconstructed temperatures showed periodicitiessimilar to those of the observed temperatures. Reconstructed temperatures were significantlycorrelated with other proxy climate reconstructionsderived from tree rings in New Zealand. However,unlike the other tree ring-based reconstructions, theLibocedrus bidwillii series reconstructed boththe 1950s and 1970s warming periods. The resultsalso compared very favourably with other palaeoclimateevidence.

Dendrochronology reveals the construction history of an early 19th century farm settlement, southwestern Virginia, USA

Numerous exposures of Pleistocene sediments occur in the Noatak basin, which extends for 130 km along the Noatak River in northwestern Alaska. Nk-37, an extensive bluff exposure near the west end of the basin, contains a record of at least three glacial advances separated by interglacial and interstadial deposits. An ancient river-cut bluff and associated debris apron is exposed in profile through the central part of Nk-37. The debris apron contains a rich biotic record and represents part of an interglaciation that is probably assignable to marine-isotope stage 5. Pollen spectra from the lower part of the debris apron closely resemble modern samples taken from the Noatak floodplain in spruce gallery forest, and macrofossils of spruce are also present at this level. Fossil bark beetles and carpenter ants occur higher in the debris apron. Mutual Climatic Range (MCR) estimates from the fossil beetles suggest temperatures similar to or warmer than today. Together, these fossils indicate the presence of an interglacial spruce forest in the western part of the Noatak Basin, which lies about 80 km upstream of the modern limit of spruce forest.

Between 1993 and 1995, marine and terrestrial animal samples were collected from the Beaufort Sea and northwest Alaska. These samples were analyzed at Los Alamos National Laboratory for the presence of the anthropogenic radionuclides, {sup 90}Sr, {sup 137}Cs, {sup 238}Pu, {sup 239+240}Pu, and {sup 241}Am. The measurement data were combined with food consumption rates based on survey results for populations residing in three northwest Alaskan communities and published age-dependent ingestion dose coefficients to estimate potential radiological impacts from the consumption of traditional animal foods harvested in this region. The results of this study indicate that committed equivalent doses to adults from {sup 90}Sr and {sup 137}Cs, due to consumption of traditional food sources are consistent with currently accepted estimates of average doses to adults in North America due to atmospheric nuclear weapons testing fallout.

Our study applied the Community Voice Method, a film-based community engagement approach, in a primarily Indigenous Arctic community to amplify voices of hunters regarding management of subsistence resources. Over a 30-month period we applied transdisciplinary methods to collaborate with the community of Kotzebue in northwestern Alaska on an original film. The goals of the film were to illustrate how Iñupiaq values and knowledge guide subsistence hunting practices through stories, educate youth and foster intergenerational dialog, and initiate discussions about inclusion of Indigenous values and knowledge in resource management. Here, we describe our application of this method and reflect on our successes and challenges, in hope that other practitioners can use this methodology to proactively identify community issues around natural resource management and, through an audiovisual medium, facilitate stakeholder empowerment in Indigenous communities.

Arctic ecosystems are undergoing rapid changes as a result of global climate change, with significant implications for the livelihoods of Arctic peoples. In this paper, based on ethnographic research conducted with the Inupiaq communities of Noatak and Selawik in northwestern Alaska, we detail prominent environmental changes observed over the past twenty to thirty years and their impacts on subsistence-based lifestyles. However, we suggest that it is ultimately insufficient to try to understand how Arctic communities are experiencing and responding to climate change in isolation from other stressors. During interviews and participant observation documenting local observations of climatic and related environmental shifts and impacts to subsistence fishing practices, we find the inseparability of environmental, social, economic, cultural, and political realms for community residents. Many of our informants, who live in a mixed economy based on various forms of income and widespread subsistence harvesting of fish and game, perceive and experience climate change as embedded among numerous other factors affecting subsistence patterns and practices. Changing lifestyles, decreasing interest by younger generations in pursuing subsistence livelihoods, and economic challenges are greatly affecting contemporary subsistence patterns and practices in rural Alaska. Observations of climate change are perceived, experienced, and articulated to researchers through a broader lens of these linked lifestyle and cultural shifts. Therefore, we argue that to properly assess and understand the impacts of climate change on the subsistence practices in Arctic communities, we must also consider the total environment of change that is dramatically shaping the relationship between people, communities, and their surrounding environments.

With industrial development expanding in the Arctic, there is increasing interest in quantifying the impacts of development projects on barren ground caribou (Rangifer tarandus granti). The primary data source to assess caribou distribution and predict impacts in remote areas of Alaska has shifted in recent decades from aerial survey data to telemetry data, but these techniques have different strengths and weaknesses. The ranges of two caribou herds, the Western Arctic Herd and the Teshekpuk Herd, overlap in northwest Alaska between Wainwright and Atqasuk, Alaska. Based on long-term telemetry data sets, this region was thought to be outside of the core calving ranges of both herds. Calving has long been reported to occur in this general area, but early reports assumed caribou were from the Western Arctic Herd and only one systematic aerial survey of caribou density and distribution during calving has been conducted in this area in recent decades. Following interest in industrial development in this area, we conducted aerial strip-transect surveys during early to mid-June 2013–2015 to directly assess the density and distribution of caribou in the area and we used existing telemetry data to compare our results to the seasonal distribution of both herds. Total caribou densities varied between 0.36 and 1.06 caribou/km² among years, and calf densities varied 0.04 and 0.25 calves/km² among years. Contrary to assumptions by early researchers in the area, telemetry data indicated that caribou in this area during early to mid-June were from the Teshekpuk Herd. The use of telemetry data alone underestimated the importance of this area for calving, but the combination of aerial surveys and telemetry data provided complementary information on caribou use of this area showing the importance of collecting the appropriate types of data for assessing potential impacts of development on caribou.

We explored patterns in soil nitrogen (N) availability in five ecosystems in the Noatak National Preserve in northwestern Alaska, and the potential response of N availability to changes in soil moisture and temperature. Nitrogen availability appeared to be highest in an ecosystem dominated by Alnus crispa (Ait.) Pursh, and lowest in ecosystems dominated by willows or by cotton grass tussocks. All soils responded strongly to changes in moisture; repeated watering during 30-day incubations raised net N mineralization rates by 1.5 to 3.0 fold. Net N mineralization at 12°C was 5 to 10 fold greater than at 5°C. The responses of net mineralization rates derived from strong effects of treatments on both microbial mineralization (release) of N, and microbial immobilization (uptake) of N. For example, incubation of soils from the alder site at 12°C slightly increased gross mineralization of N, more than doubled microbial immobilization of N, reduced gross nitrate production by more than 80%, and more than ...

Architectural wood elements are well-preserved in cold soils and archaeological Thule/Iñupiat sites of the early 2nd millennium CE in northwestern Alaska. These organic remains, at the intersection of archaeology, palaeoclimatology, and ecology, offer an annual and local resolution rarely accessible to archaeologists, providing insights on past climate variations. In a context where cultural variations of past arctic people are often interpreted as responses to climatic and environmental changes, this paper is a state-of-the-art examination of the dendroclimatic potential of Iñupiat architectural wood remains based on current knowledge. The focus is especially on current possibilities and limits of early Iñupiat architectural wood remains and the need to build a finer sequence for the period of the Medieval Climate Anomaly [MCA] (9th-13th century) to contribute to a broader understanding of the climatic framework of the early 2nd millennium and of early Iñupiat socio-ecological dynamics in Northwest Alaska for future research.