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Abstract: The boreal biome represents approximately one third of the world's forested area and plays an important role in global biogeochemical and energy cycles. Numerous studies in boreal Alaska have concluded that growth of black and white spruce is declining as a result of temperature‐induced drought stress. The combined evidence of declining spruce growth and changes in the fire regime that favor establishment of deciduous tree species has led some investigators to suggest the region may be transitioning from dominance by spruce to dominance by deciduous forests and/or grasslands. Although spruce growth trends have been extensively investigated, few studies have evaluated long‐term radial growth trends of the dominant deciduous species (Alaska paper birch and trembling aspen) and their sensitivity to moisture availability. We used a large and spatially extensive sample of tree cores from interior Alaska to compare long‐term growth trends among contrasting tree species (white and black spruce vs. birch and aspen). All species showed a growth peak in the mid‐1940s, although growth following the peak varied strongly across species. Following an initial decline from the peak, growth of white spruce showed little evidence of a trend, while black spruce and birch growth showed slight growth declines from ~1970 to present. Aspen growth was much more variable than the other species and showed a steep decline from ~1970 to present. Growth of birch, black and white spruce was sensitive to moisture availability throughout most of the tree‐ring chronologies, as evidenced by negative correlations with air temperature and positive correlations with precipitation. However, a positive correlation between previous July precipitation and aspen growth disappeared in recent decades, corresponding with a rise in the population of the aspen leaf miner (Phyllocnistis populiella), an herbivorous moth, which may have driven growth to a level not seen since the early 20th century. Our results provide important historical context for recent growth and raise questions regarding competitive interactions among the dominant tree species and exchanges of carbon and energy in the warming climate of interior Alaska. [ABSTRACT FROM AUTHOR]

Alaska is one of the most seismically active regions of the world. Coincidentally, the state has also experienced dramatic impacts of climate change as it is warming at twice the rate of the rest of the United States. Through mechanisms such as permafrost thaw, water table fluctuation, and melting of sea ice and glaciers, climatic-driven changes to the natural and built-environment influence the seismic response of infrastructure systems. This paper discusses the challenges and needs posed by earthquake hazards and climate change to Alaska's infrastructure and built environment, drawing on the contributions of researchers and decision-makers in interviews and a workshop. It outlines policy, mitigation, and adaptation areas meriting further attention to improve the seismic resilience of Alaska's built environment from the perspectives of engineering and complementary coupled human-environmental systems., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Turner et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

In a time of multiple, competing, and nested crises, the draw to storytelling is intuitive. Stories help us make sense of the world around us. People are drawn to stories because of their emphasis on community, and the way they create possibilities when it feels like there are none. This paper builds upon geographic research on storytelling, articulating how stories are critical for creating meaning in light of crises. Based on 14 months of fieldwork with storytellers in Appalachia and Alaska, two regions facing profound social, climatic, and economic change and with culturally rich storytelling traditions, research for this paper discusses the practice of storytelling, as told by storytellers, and how different approaches to storytelling help address the climate crisis specifically with notes for crises more broadly. Further, considering calls to use storytelling to address climate change, this paper examines and critiques the stories that are currently being told and valued. Finally, this paper outlines the kinds of stories that could be told to address crises, noting specifically how stories are sites of cultural and political struggle. [ABSTRACT FROM AUTHOR]

As the Arctic and its rivers continue to warm, a better understanding of the possible future impacts on people would benefit from close partnership with Indigenous communities and scientists from diverse fields of study. We present efforts by the Arctic Rivers Project to conduct community‐engaged research to increase collective understanding of the historical and potential future impacts of climate change on rivers, fish, and Indigenous communities. Working in central to northern Alaska and the Yukon Territory in Canada, the project seeks to engage with Indigenous communities in ethical and equitable ways to produces science that is useful, useable, and used that may serve as an example for future research efforts. Toward this goal, we formed an Indigenous Advisory Council and together developed project‐specific knowledge co‐production protocols. This paper provides a novel model of design and implementation to co‐produce knowledge with communities across a large study domain. Plain Language Summary: The Arctic and rivers located in the Arctic and subarctic are warming due to climate change. To understand the impacts this warming will have on people, partnering with impacted Indigenous communities in the region is important. It is also important that these partnerships are ethical and equitable and produce science that is actionable. This paper discusses efforts undertaken by a specific project, the Arctic Rivers Project, to conduct ethical and equitable research with Indigenous communities and generate science that is useful to those communities. Through this research our goal is to better understand potential future impacts of climate change on rivers, fish, and Indigenous communities in central northern Alaska and the Yukon Territory in Canada. To achieve this goal, the project formed an Indigenous Advisory Council (IAC) and together developed guidelines for how we can work collaboratively with Indigenous communities. Our specific process of forming an IAC and guidelines is, to our knowledge, a new way to approach collaborative research when working across a large geographic area. We present our process here so that it may provide an example for other research efforts. Key Points: Arctic climate information can be made useful, useable, and used by equitably accounting for diverse community adaptation needs through knowledge co‐productionInstitutional and community capacity, including means and ability, is necessary for equitable knowledge co‐production to occurWe present an approach for co‐producing knowledge with Indigenous communities that can serve as an example for other scientific efforts [ABSTRACT FROM AUTHOR]

Time‐lapse cameras have been widely used as a tool to monitor the timing of seasonal vegetation growth. These simple, relatively inexpensive systems can provide high‐frequency observations of leaf development and demography which are critical data sets needed to characterize plant phenology from species to landscapes. This is important for understanding how plants are responding to global changes, as well as for validating satellite‐derived phenology products.However, in remote regions including the high‐latitude Arctic, deploying time‐lapse cameras could be challenging. The remoteness and lack of widespread power and telecommunications infrastructure limit options for the installation, maintenance and retrieval of data and equipment, and make it difficult for cameras to survive in extreme weather (e.g. long cold winters). To improve our understanding of Arctic phenology, new technologies are required to address these challenges.Here, we present a novel, low‐power, compact, lightweight time‐lapse camera system, called power‐interval camera automation module (PiCAM). The PiCAM was designed with explicit consideration to simplify deployment (i.e. without a need for external power supplies) of camera systems and to address the challenges of camera survival in harsh Arctic environments. In this paper, we describe the design, setup and technical details of the PiCAM and provide a roadmap for how to build and operate these systems. As proof of concept, we deployed 26 PiCAMs at three low‐Arctic tundra sites on the Seward Peninsula, Alaska in early August 2021 for characterizing Arctic plant phenology.Of the 26 PiCAMs, 70% remained active at the point of our revisit in late July 2022 despite the extreme winter temperatures they experienced (< −30°C, heavy snow cover). We extracted key plant phenology metrics from the PiCAMs and captured strong differences across key Arctic plant species. We showed that the PiCAM has the potential to be widely used for monitoring plant phenology across the broader Arctic region, addressing the need for ground‐based understanding of Arctic phenological diversity to develop knowledge of plant response to climate change and to validate remote sensing products. [ABSTRACT FROM AUTHOR]

• Political ecology has largely been reactive. • Political ecology should be more proactive. • Experimentation helps political ecology address ongoing and future issues. • Storytelling is a useful method for engaging climate knowledge. • This paper includes lessons for doing experimental political ecology scholarship. Political ecology emphasizes critique, and, through critique, its ability to better understand nature-society relations. Recently, calls have been made from within the sub-discipline to move beyond critique, and towards engaging nature-society relations more experimentally. This paper asks: is it possible for political ecology to be less reactive and more proactive? Rather than studying events that have already happened, is it possible to study events currently happening or that have not yet happened? This paper is an attempt to do political ecology more experimentally by staging an intervention and studying its outcomes. Given the abstract nature of climate change, and given storytelling's capacity for helping people make sense of the world around them, this project combined political ecology analysis and storytelling, resulting in an experimental process of collaborative climate knowledge production in regions, and with people, central to the changing climate. Research for this paper took place over fourteen months in Appalachia and Alaska, climate-vulnerable regions with economies tied to fossil fuel industries and with culturally rich storytelling traditions. The aim of this paper is threefold. First, I will examine political ecology scholarship that already engages with experimentation as a way of making the case for a more experimental political ecology. Second, I will discuss the process and outcomes from my experimental research, namely that storytelling is a meaningful way of building climate knowledge. Finally, by outlining the challenges of doing this research, this paper ends with lessons for future iterations of more experimental research. [ABSTRACT FROM AUTHOR]

Despite perceptions of high water availability, adequate access to sufficient water resources remains a major challenge in Alaska. This paper uses a participatory modeling approach to investigate household water vulnerability in remote Alaska and to examine factors that affect water availability and water access. Specifically, the work asks: how do water policy stakeholders conceptualize the key processes that affect household water vulnerability in the context of rural Alaska? Fourteen water policy stakeholders participated in the modeling process, which included defining the problem of household water vulnerability and constructing individual causal loop diagrams (CLDs) that represent their conceptualization of household water vulnerability. Individual CLDs were subsequently combined and five sub-models emerged: environmental, economic, infrastructure, social, and health. The environmental and economic sub-models of the CLD are explored in depth. In the environmental sub-model, climate change and environmental barriers due to geography influence household water vulnerability. In the economic sub-model, four processes and one feedback loop affect household water vulnerability, including operations and maintenance funding, the strength of the rural Alaskan economy, and the impact of regulations. To overcome household water vulnerability and make households more resilient, stakeholders highlighted policy solutions under five themes: economics, social, regulatory, technological, and environmental.

Arctic freshwater ecosystems and fish populations are largely shaped by seasonal and long‐term watershed hydrology. In this paper, we hypothesize how changing air temperature and precipitation will alter freeze and thaw processes, hydrology, and instream habitat to assess potential indirect effects, such as the change to the foraging and behavioral ecology, on Arctic fishes, using Broad Whitefish Coregonus nasus as an indicator species. Climate change is expected to continue to alter hydrologic pathways, flow regimes, and, therefore, habitat suitability, connectivity, and availability for fishes. Warming and lengthening of the growing season will likely increase fish growth rates; however, the exceedance of threshold stream temperatures will likely increase physiological stress and alter life histories. We expect these changes to have mixed effects on Arctic subsistence fishes and fisheries. Management and conservation approaches focused on preserving the processes that create heterogeneity in aquatic habitats, genes, and communities will help maintain the resilience of Broad Whitefish and other important subsistence fisheries. Long‐term effects are uncertain, so filling scientific knowledge gaps, such as identifying important habitats or increasing knowledge of abiotic variables in priority watersheds, is key to understanding and potentially mitigating likely impacts to Arctic fishes in a rapidly changing landscape. [ABSTRACT FROM AUTHOR]

Indigenous Peoples in the Arctic have for millennia relied on freshwaters for drinking water and freshwater species that comprise important subsistence harvests, which promotes a strong connection to the land and unique understanding of organisms and ecosystem processes and changes. Despite the importance of freshwater biodiversity and ecosystem services to Arctic Indigenous communities, there have been limited attempts to summarise available Indigenous Knowledge (IK) regarding Arctic freshwater systems and to understand how conservation can benefit from this knowledge base.This paper presents a systematic review of literature documenting circumpolar Arctic IK with a focus on freshwater biodiversity in Canada, Greenland, Fennoscandia (Norway, Sweden, and Finland), Russia, and the U.S.A. (Alaska). Standardised search terms and methodologies were used to locate relevant documents using Google Scholar and Google Advanced search engines. Thematic coding was used to identify freshwater biodiversity themes within the identified documents.Documented IK of freshwater biodiversity was found from all five geographic regions and included data on both species presence and habitat changes with potential to affect biodiversity. Canada had the highest number of relevant documents (n = 127), followed by the U.S.A. (Alaska; n = 116), Fennoscandia (n = 38), Russia (n = 27), and Greenland (n = 5). The number of relevant documents with IK published per year was highest in most recent years, from 2010 onwards, in all geographic regions.Fish represented the highest number of faunal observations with 59 species observed, approximately half of which were Salmonidae (29 species). Local‐scale assessment of fish diversity found observations of the highest number of species (11–25) in Alaska, and individual observations of 6–10 species were found throughout Alaska, mainland areas of Canada, and the Kola Peninsula in Russia. Documented IK also contributed new information on historical fish diversity and indicated local‐scale loss or gain of species. Such information is of vital importance to provide long‐term records of fish composition and abundance, especially when this information does not exist in other knowledge bases such as western science datasets.Indigenous Knowledge included observations of changes in freshwater and terrestrial habitat associated with a warming climate, such as: decreasing water levels and more draining/drying of lakes and rivers, a shorter period of ice cover (late freeze and early break‐up), decreasing ice thickness, and increasing occurrence of permafrost thaw and eroding banks. Such observations by those who actively rely on Arctic freshwater ecosystem services are important because they signify that change is occurring and that action is needed to mitigate the impacts on freshwater habitats and the biodiversity therein.This study demonstrates that previously documented IK provides valuable information towards determining freshwater biodiversity baselines and patterns of change in the circumpolar Arctic. However, these results do not sufficiently cover the depth and breadth of IK on freshwater biodiversity and ecology held by Indigenous communities. Further work incorporating Indigenous worldviews around freshwater ecology would provide context to the knowledge collected and a deeper understanding of Arctic circumpolar freshwater environments. [ABSTRACT FROM AUTHOR]

Institutions are influential in mediating the impact of adaptation initiatives at the local level, yet there are disconnects between the goals of multi-scale planning initiatives and community priorities. Research to address this challenge primarily focuses on reform to formal institutions in environmental governance. Meanwhile, knowledge of the specific role informal institutions play in governance processes remains limited. This study increases understanding of the interactions between informal institutions and adaptation using a case study of the Native Village of Wainwright on Alaska's North Slope. Qualitative contextual analysis was employed to identify patterns of informal institution and adaptation associations in historic and contemporary situations in Wainwright. The Adaptation Institutional Analysis Framework developed in this paper extends Elinor Ostrom's Institutional Analysis and Development Framework and is used as a tool to analyse and describe these dynamics. Four primary findings resulted from this analysis (1) identification of informal institutions that have a bearing on adaptation to environmental change and adaptive capacity in Wainwright, (2) insight into how the identified institutions relate to each other and to different aspects of local adaptation, (3) identification of changes in informal institutions that have occurred over time and the potential implications of these changes for local adaptive capacity, and (4) potential opportunities to leverage knowledge of informal institution and adaptation relationships in targeted formal initiatives. The outcomes of this study contribute to an improved understanding of the function and potential of informal institutions in adaptation processes, the benefits of which extend beyond the local context of Wainwright. [ABSTRACT FROM AUTHOR]

The Kuparuk River, located on Alaska's North Slope, is one of the most studied rivers in the Arctic. For nearly 40 seasons, physical, chemical, and biological parameters have been monitored continuously in a 5 km, 4th‐order reach of the river during the short summer season when there is flow in this river. Flow decreases as the tundra begins to refreeze in the late autumn and these streams normally remain frozen until the spring freshet. The monitoring program has supported a 34‐year phosphorus enrichment experiment conducted by the Arctic Long Term Ecological Research (LTER) program. Enrichment with phosphorus dramatically changed the structure and function of the primary producer community in the fertilized reach, with cascading effects in higher trophic levels. The datasets generated by this experiment have revealed significant increases in flow‐weighted mean concentrations of nitrate and significant decreases in flow‐weighted mean concentrations of dissolved organic N and P over time. In this paper, we present an overview of the nutrient concentration, discharge, macroinvertebrate, and Arctic grayling population datasets we have collected. The purposes of these datasets are to track changes resulting from the enrichment experiment, support ancillary research on responses of an Arctic stream to climate warming and permafrost thaw, and to provide input and validation data for models to predict future changes in Arctic streams. [ABSTRACT FROM AUTHOR]

There is myriad evidence that global warming is exerting a profoundly disruptive influence on the lifeways of modern native (Yup'ik) communities living in the Yukon-Kuskokwim (Y-K) delta of southwestern Alaska. Yup'ik subsistence is intimately tied to seasonal change and the ability to accurately predict the availability of plant and animal resources. It therefore seems reasonable to suggest that periods of climatic instability such as the Little Ice Age (LIA) may have had a deleterious effect on Yup'ik communities in the past. However, at present there are no palaeotemperature records that document the localised climatic changes of the last millennium in the Y-K Delta region. This lack of data hinders our understanding of the archaeological record from the site of Nunalleq, which is situated at the heart of the delta and was occupied during the LIA. To address this oversight, this paper presents the results of a Coleoptera (beetle) based climate reconstruction from a peat profile in the vicinity of Nunalleq to investigate the magnitude of Late Holocene climatic changes. Using the Mutual Climatic Range (MCR) method, we reconstruct mean summer and winter temperatures from the mid-15th to late-19th centuries. The results indicate that the past environments of Nunalleq were characterised by a climate significantly cooler than the present. The earliest definitive evidence for Little Ice Age cooling dates from the late 16th century, when mean summer temperatures were at least 1.2ᵒC below the modern mean. Temperatures appear to have remained lower than modern until the early 19th century. The coolest Nunalleq record – 1.3ᵒC below the modern mean summer temperatures – is centred on AD 1815, after which there is evidence for climatic amelioration. These data present differences with observations from other regions of Alaska and underline the importance of more local palaeoclimate reconstructions, particularly when interrogating the relationships between past climatic and social change. [ABSTRACT FROM AUTHOR]

Northern communities are experiencing greater climate variability, with extreme climate impacts occurring more frequently and with more intensity; with the need for adaptation to reduce the risk becoming more immediate. Specific stressors and decision dynamics surrounding the nature of local government policy and planning for climate adaptation are underrepresented in the scholarship. This paper seeks to contribute to the literature by exploring the case of Homer, Alaska. Through narratives of key informants connected to the community's climate change agenda, this research explores primary climate stressors and the nature of adaptation policy integration. Findings suggests that while Homer is experiencing a variety of climate change impacts, adaptation remains a low priority for city officials. This study sheds light on some of the challenges of integrating climate adaptation policy with strategic community planning, and in turn provides decision-makers with insight into considerations for mainstreaming resilience thinking at a local government scale. [ABSTRACT FROM AUTHOR]

The authors of this paper attempted to develop a database that would serve to track social changes brought about by the expansion of arctic tourism resulting from climate change. In this paper we review and assess the state of data used to describe and monitor tourism trends in the pan-arctic and their potential social effects. We selected 12 potential indicators for long-term assessment and monitoring changes in arctic tourism. We attempted to collect consistent data from 1980 to 2008 for Alaska, Canada, Norway, Greenland, Lapland and Iceland. In addition to visitor counts of various types, the database includes tourism-related employment and earnings at the place and regional levels, though the data are not consistent or complete for all the countries. The World Tourism Organization provides relatively standardized tourism data definitions. However, data collection by national agencies varies across the arctic countries and data are not available for all selected indicators. A significant problem is that most jurisdictions use sampling and reporting protocols that result in statistically unreliable estimates for remote rural areas. These same areas may also be most vulnerable to potential impacts and changes brought about by expanding tourism development. We discuss the critical need for an arctic tourism observation system. Standardization or comparability of time series data sets will be important for the future monitoring and modeling of changes in the arctic environment and associated impacts of expanding tourism, especially as diminishing sea ice cover increases visitor access. [ABSTRACT FROM AUTHOR]

The climate in Alaska is changing with temperatures and precipitation increasing, and experts say those changes will continue. The changing climate will, among other kinds of social and economic effects, damage public infrastructure throughout Alaska, adding to maintenance costs and shortening the lifespan of everything from schools to sanitation systems. The question of how much cost impact this change will have and when the costs are expected to occur is the question of significant concern and debate. One approach to answering this question is addressed in this paper. Based on a probabilistic model, the results in this paper estimate how much climate change will add to future costs of public infrastructure in Alaska. Based on a database of public infrastructure throughout Alaska and the estimated replacement costs and lifespans for the various types of infrastructure statewide, the model provides a first analysis of climate impact on infrastructure costs. As an additional refinement of the model, the paper presents two potential adaptation approaches to reduce the impacts of climate change on the adaptation process. Code adaptation and event adaptation are introduced as two potential processes, based on existing responses to natural disasters, that may be employed to adapt to climate change. These adaptation approaches have the potential to reduce climate change costs by 10–45%. This is significant when the total potential cost impact to infrastructure from climate change is projected to add 10–20% to infrastructure costs by 2030 and 10–12% by 2080 under different climate projections and taking design adaptations into account. [ABSTRACT FROM AUTHOR]

Abstract: Climate change exerts influence on the globe over relatively long temporal and at broad spatial scales. However, at the local scale in which communities undertake their daily activities, changes in land-use may result in changes that accumulate and manifest more quickly in the landscape. In this paper we set out a methodology for identifying social–ecological system (SES) vulnerabilities in the landscape with respect to freshwater resources for Arctic communities. A multiple-scale approach is used at regional and watershed scales and is demonstrated for the Seward Peninsula region, Alaska and the Fish River watershed on Seward Peninsula but may be applied elsewhere. The approach includes change in permafrost distribution as an important effect of climate change, and change in mining activity as an important land-use effect. Vulnerability in the SES is identified as a consequence of spatially coinciding values. The resulting patterns of vulnerability highlight the interaction between changes, which act on slower temporal scales (e.g., permafrost distribution) and changes which act more quickly (e.g., downstream aggregation of mining activity). These results are discussed in the context of using the integration approach outlined in this paper to better enable communities’ responses to change at local scales in such a way that they are both adaptive and resilient. [Copyright &y& Elsevier]

In the face of increasing temperature at high latitudes, ecosystem respiration (RE) is a key to determining sink and source dynamics of a boreal forest. In this paper, we analyzed four-year RE data obtained in an open black spruce forest—a typical boreal forest ecosystem with permafrost in Interior Alaska. RE measured as nighttime CO 2 effluxes for both the ecosystem and the forest floor were clearly situated along the exponential temperature-dependent curve, except for the data obtained in extremely dry conditions in mid-summer. More than 93 % of RE data measured at nighttime with high vapor pressure deficit (VPD > 400 Pa) were lower than the values predicted from the temperature-dependent curve. Consequently, the year 2013 (with an unusually dry summer) had a 15 % lower amount of annual RE than that could be expected from the temperature-dependent curve without considering the effect of high VPD. The suppression of RE under dry conditions was also related to decreases in soil moisture and net ecosystem productivity. Finally, assuming daytime RE could be extrapolated from the temperature-dependent curves, annual daytime RE estimated with the effect of high VPD was decreased by up to 62% from RE estimated without the VPD effect. The down-regulation of RE presented in this study postulates a possible negative feedback for the carbon budget of boreal forests in response to climate warming. [ABSTRACT FROM AUTHOR]

Scenario planning is a flexible tool used to assess a broad range of plausible, relevant, divergent, and challenging futures, for short-term responses and long-term planning. Scenario planning has gained popularity in natural resource management for addressing uncertainties associated with climate change, but the literature contains few retrospective assessments of scenario planning. In this paper, we use a case study of a climate change scenario planning process conducted by National Park Service in Alaska to evaluate this tool and its outcomes. Five planning workshops, each addressing an Inventory and Monitoring Network in Alaska, were held between 2010 and 2012. In 2015, we conducted 30 interviews with workshop participants to evaluate the outcomes of these workshops. Participants described individual outcomes, including increased knowledge of climate change, increased awareness of uncertainty, and the ability to learn from others across disciplines and backgrounds. Challenges include ensuring adequate feedback and follow-through after the initial process, making products tangible and meaningful to participants, and providing specific mechanisms for applying the process beyond the workshop. The evaluation showed that the workshops were well organized and facilitated, and that they fostered individual learning and helped participants develop adaptive capacity. Suggestions for improvement included institutionalizing the process so that it can have more impact at the organizational level, and recognizing and preparing for the challenges of co-production of knowledge. [ABSTRACT FROM AUTHOR]

Research on the human dimensions of global climate change should consider the way at-risk populations confront uncertainty through cultural practices. This is a vital point for indigenous peoples around the world, but particularly for those in the Arctic region where the effects of climate change are most dramatic. The Iñupiat of Arctic Alaska are especially susceptible to climatic and associated environmental changes, because they rely on sea ice to hunt the bowhead whale. Employing a humanistic approach, this paper reveals Iñupiaq cultural resilience by exploring how collective uncertainty tied to the effects of climate change is manifested in Iñupiaq lives. These experiences show how the human dimensions of climate change, cultural resilience, and identity politics are integrated in the Arctic. By reinforcing their cultural relationship with the bowhead whale, these Iñupiat better cope with an unpredictable future. [ABSTRACT FROM AUTHOR]

Permafrost is very sensitive to climate factors, with warm permafrost particularly vulnerable to climate change. This paper aims to provide a detailed case study of climate trends of a high-latitude Alaskan site underlain by warm permafrost based on historical data and predictions from the Coupled Model Intercomparison Project Phase 5 (CMIP5). The climate data, including air temperature, precipitation, wind speed, and their annual and seasonal trends from 1950 to 2099, are presented for Bethel, Alaska. The downscaled data are compared with the historical data in the overlap period. Both air and design freezing and thawing indices are calculated using various methods. In comparison, the downscaled model predictions align well with air temperature and wind speed records but not for precipitation, indicating the need for further downscaling at a finer resolution. The historical annual temperature records show a warming rate of 0.40 °C per decade, which is predicted to almost double to 0.78 °C per decade in the 21st century, leading to shorter winters and longer summers. The historical annual precipitation increased by a rate of 14.8 mm per decade from 1950 to 2020, and this trend is predicted to continue but at a slightly lower rate. The wind speed decreased consistently from 1984 to 2020 by 0.9 km/h per decade. However, the CMIP5 predicts that such a trend will diminish, with the mean annual wind speed remaining almost unchanged in this century. The air freezing index exhibits a consistent downtrend from 1950 to 2020, whereas the air thawing index remained flat until 1980 and rose afterward; the CMIP5 predicts that both trends will continue in the 21st century. The design air freezing and thawing indices are sensitive to the assessment periods for both methods. An assessment period shorter than 30 years, e.g., ten years, is recommended to find design indices. It is conservative to use the monthly mean air temperature method for evaluating the design air freezing index and apply the extreme event method for the design thawing index. • Compare downscaled model data at a finer resolution with other models in CMIP5. • Assess the design freezing and thawing indices by two methods with varying periods. • Recommend methods and periods for evaluating design freezing/thawing indices. • Discuss climate change effects on infrastructure, design strategies, future studies. [ABSTRACT FROM AUTHOR]

Given current and projected warming trends in the Arctic and the important role played by subsistence hunting and fishing in the life of northern rural communities, it is increasingly important to document local observations of climate change and its impacts on livelihood practices. We describe ethnographic research exploring local observations of climate changes and related impacts on subsistence fisheries in three Iñupiat communities in northwest Alaska and six Athabascan communities in the Yukon River drainage. We found consistent agreement among perceptions concerning a broad range of environmental changes affecting subsistence practices in these communities. These observations of environmental changes are not experienced in isolation but within the context of accompanying social changes that are continually reshaping rural Alaskan communities and subsistence economies. In this paper we reflect on our research approach combining multiple methods of inquiry. Participant observation and semidirected interviews provided the conceptual framework for broadening our focus from climate and environmental change to community residents' understanding of climate change in the context of their holistic human-environment worldview. Cultural consensus analysis allowed us to assess the extent to which perceptions of change are shared among hunters and fishers within and between villages and regions and to identify those phenomena occurring or experienced at smaller scales. Reflecting on this multimethods approach, we highlight important questions that have emerged about how we understand, synthesize, and represent local knowledge, especially as it is used in regulatory or management arenas. [ABSTRACT FROM AUTHOR]

Coastal regions of Alaska are regularly affected by intense storms of ocean origin, the frequency and intensity of which are expected to increase as a result of global climate change. The Yukon-Kuskokwim Delta (YKD), situated in western Alaska on the eastern edge of the Bering Sea, is one of the largest deltaic systems in North America. Its low relief makes it especially susceptible to storm-driven flood tides and increases in sea level. Little information exists on the extent of flooding caused by storm surges in western Alaska and its effects on salinization, shoreline erosion, permafrost thaw, vegetation, wildlife, and the subsistence-based economy. In this paper, we summarize storm flooding events in the Bering Sea region of western Alaska during 1913 - 2011 and map both the extent of inland flooding caused by autumn storms on the central YKD, using Radarsat-1 and MODIS satellite imagery, and the drift lines, using high-resolution IKONOS satellite imagery and field surveys. The largest storm surges occurred in autumn and were associated with high tides and strong (> 65 km hr-1) southwest winds. Maximum inland extent of flooding from storm surges was 30.3 km in 2005, 27.4 km in 2006, and 32.3 km in 2011, with total flood area covering 47.1%, 32.5%, and 39.4% of the 6730 km2 study area, respectively. Peak stages for the 2005 and 2011 storms were 3.1 m and 3.3 m above mean sea level (amsl), respectively-almost as high as the 3.5 m amsl elevation estimated for the largest storm observed (in November 1974). Several historically abandoned village sites lie within the area of inundation of the largest flood events. With projected sea level rise, large storms are expected to become more frequent and cover larger areas, with deleterious effects on freshwater ponds, non-saline habitats, permafrost, and landscapes used by nesting birds and local people [ABSTRACT FROM AUTHOR]

Over the past 50 years, the number and size of high-latitude lakes have decreased throughout many regions; however, individual lake trends have been variable in direction and magnitude. This spatial heterogeneity in lake change makes statistical detection of temporal trends challenging, particularly in small analysis areas where weak trends are difficult to separate from inter- and intra-annual variability. Factors affecting trend detection include inherent variability, trend magnitude, and sample size. In this paper, we investigated how the statistical power to detect average linear trends in lake size of 0.5, 1.0 and 2.0 %/year was affected by the size of the analysis area and the number of years of monitoring in National Wildlife Refuges in Alaska. We estimated power for large (930-4,560 sq km) study areas within refuges and for 2.6, 12.9, and 25.9 sq km cells nested within study areas over temporal extents of 4-50 years. We found that: (1) trends in study areas could be detected within 5-15 years, (2) trends smaller than 2.0 %/year would take >50 years to detect in cells within study areas, and (3) there was substantial spatial variation in the time required to detect change among cells. Power was particularly low in the smallest cells which typically had the fewest lakes. Because small but ecologically meaningful trends may take decades to detect, early establishment of long-term monitoring will enhance power to detect change. Our results have broad applicability and our method is useful for any study involving change detection among variable spatial and temporal extents. [ABSTRACT FROM AUTHOR]

Background. Indigenous residents of Alaska's Bering Strait Region depend, both culturally and nutritionally, on ice seal and walrus harvests. Currently, climate change and resultant increases in marine industrial development threaten these species and the cultures that depend on them. Objective. To document: (a) local descriptions of the importance of marine mammal hunting; (b) traditional methods for determining if harvested marine mammals are safe to consume; and (c) marine mammal outcomes that would have adverse effects on community health, the perceived causes of these outcomes, strategies for preventing these outcomes and community adaptations to outcomes that cannot be mitigated. Design. Semi-structured interviews and focus groups were conducted with 82 indigenous hunters and elders from the Bering Strait region. Standard qualitative analysis was conducted on interview transcripts, which were coded for both inductive and deductive codes. Responses describing marine mammal food safety and importance are presented using inductively generated categories. Responses describing negative marine mammal outcomes are presented in a vulnerability framework, which links human health outcomes to marine conditions. Results. Project participants perceived that shipping noise and pollution, as well as marine mammal food source depletion by industrial fishing, posed the greatest threats to marine mammal hunting traditions. Proposed adaptations primarily fell into 2 categories: (a) greater tribal influence over marine policy; and (b) documentation of traditional knowledge for local use. This paper presents 1 example of documenting traditional knowledge as an adaptation strategy: traditional methods for determining if marine mammal food is safe to eat. Conclusions. Participant recommendations indicate that 1 strategy to promote rural Alaskan adaptation to climate change is to better incorporate local knowledge and values into decision-making processes. Participant interest in documenting traditional knowledge for local use also indicates that funding agencies could support climate change adaptation by awarding more grants for tribal research that advances local, rather than academic, use of traditional knowledge. [ABSTRACT FROM AUTHOR]

This paper discusses the relationship between climate change and subsistence behaviors of indigenous peoples in Arctic regions of North America. It is noted that those most affected by such change are, typically, those peoples who continue to carry out subsistence practices through which they acquire a significant percentage of food from the land. It is these very peoples who also may offer valuable observations about changes which they are personally witnessing. A case study example, the Nets'aii Gwich'in community of Arctic Village, Alaska, is presented. Using Traditional Ecological Knowledge (TEK) and villagers' observations as the primary data source, it is shown that levels of subsistence activity in this community are decreasing. Villagers believe that climate changes are playing a key role in the ability to access country foods. They believe too that there are fewer animals and that the food now available is of poorer quality than in the past. It is concluded that the information and data presented here concerning villager perceptions should be viewed as only part of the explanation for changes in subsistence behaviors. More research in the coming years is called for to further help distinguish the impacts of climate change upon subsistence activities from other social and economic forces which also are playing a role in such indigenous communities. [ABSTRACT FROM AUTHOR]

This paper deals with the analysis of monthly temperatures in 19 meteorological stations in Alaska during the last 50 years. For this purpose, we employ a procedure that permits us to examine in a single framework several features observed in climatological time series such as time trends, long-range persistence and seasonality. The results indicate that the highest degrees of persistence are observed in stations located in the southern regions and seasonality appears as a major issue in all cases. Removing the seasonal structure and focussing on the anomalies with respect to the monthly means, the time trend coefficients appear significantly positive in the majority of the cases, implying that temperatures have increased during the last 50 years. [ABSTRACT FROM AUTHOR]

We present the results of a reconnaissance investigation of unusual debris mass-movement features on permafrost slopes that pose a potential infrastructure hazard in the south-central Brooks Range, Alaska. For the purpose of this paper, we describe these features as frozen debris-lobes. We focus on the characterisation of frozen debris-lobes as indicators of various movement processes using ground-based surveys, remote sensing, field and laboratory measurements, and time-lapse observations of frozen debris-lobe systems along the Dalton Highway. Currently, some frozen debrislobes exceed 100m in width, 20m in height and 1000m in length. Our results indicate that frozen debris-lobes have responded to climate change by becoming increasingly active during the last decades, resulting in rapid downslope movement. Movement indicators observed in the field include toppling trees, slumps and scarps, detachment slides, striation marks on frozen sediment slabs, recently buried trees and other vegetation, mudflows, and large cracks in the lobe surface. The type and diversity of observed indicators suggest that the lobes likely consist of a frozen debris core, are subject to creep, and seasonally unfrozen surface sediment is transported in warm seasons by creep, slumping, viscous flow, blockfall and leaching of fines, and in cold seasons by creep and sliding of frozen sediment slabs. Ground-based measurements on one frozen debris-lobe over three years (2008--2010) revealed average movement rates of approximately 1 cm day-1, which is substantially larger than rates measured in historic aerial photography from the 1950s to 1980s. We discuss how climate change may further influence frozen debris-lobe dynamics, potentially accelerating their movement. We highlight the potential direct hazard that one of the studied frozen debris-lobes may pose in the coming years and decades to the nearby Trans Alaska Pipeline System and the Dalton Highway, the main artery for transportation between Interior Alaska and the North Slope. [ABSTRACT FROM AUTHOR]

The effects and severity of anthropogenic climate change are being increasingly realized, with international efforts through the United Nations Framework Convention on Climate Change (UNFCCC) aimed at mitigation of greenhouse gas emissions and adaptation to current and future changes. Many of these adaptation measures focus on helping communities in developing nations, grounded in an inter-national framework that notes national disparities in responsibility and impact. While consideration of international inequality is an important and salient framework, it can have the unintentional effect of masking intra-national inequality, and eclipsing the role that factors such as race, class, and gender also play in shaping individual and community vulnerability to climate change. To highlight the role of such social factors in vulnerability, this paper looks at the Alaska Native village of Kivalina, an Inupiat community that must relocate due to climate change. It will be argued that while Kivalina shares many similarities with other global communities heavily impacted by climate change, due to common historic injustices, Kivalina also faces unique challenges by being located in the US, including longstanding resistance by US government and corporate interests to recognizing and acting on climate change, lack of adaptation measures, and cuts to federal disaster management. These challenges raise questions about how governments in "developed" countries can be held accountable when they do not adequately assist their people in danger from climate change. [ABSTRACT FROM AUTHOR]

Abstract: Human response to climatic conditions during the turbulent terminal Pleistocene has long concerned archaeologists and paleoecologists alike, especially with regards to the Younger Dryas. In some regions of the Northern Hemisphere the Younger Dryas was not significantly felt; however, in far northern regions affects of climate change are often acute. This paper focuses on the central Alaskan record to explore human–environment interactions during the terminal Pleistocene and tackle questions regarding human response to the Younger Dryas. This region of Beringia preserves a wealth of both paleoecological and archaeological data. Relative to other northern landscapes, proxy data from central Alaska indicate the Younger Dryas signal was somewhat muted but still characterized by return to cooler and/or more arid conditions. This phenomenon likely affected distributions and character of both floral and faunal resources, altering human perception of the surrounding landscape and potentially leading to reorganization of technologies, subsistence behavior, and land-use strategies. [Copyright &y& Elsevier]

This paper compares two case studies in Alaska, one on commercial fishers of the Bering Sea and Aleutian Islands region and the other on moose hunters of Interior Alaska, to identify how governance arrangements and management strategies enhance or limit people's ability to respond effectively to changing climatic and environmental conditions. The two groups face similar challenges regarding the impacts of a changing climate on wild fish and game, but they tell very different stories regarding how and under what conditions these impacts challenge their harvest activities. In both regions, people describe dramatic changes in weather, land, and seascape conditions, and distributions of fish and game. A key finding is that the "command-and-control" model of governance in the Alaska Interior, as implemented through state and federal management tools such as registration hunts and short open seasons, limits effective local responses to environmental conditions, while the more decentralized model of governance created by the Limited Access Privilege systems of the Bering Sea allows fishers great flexibility to respond. We discuss ways to implement aspects of a decentralized decision-making model in the Interior that would benefit hunters by increasing their adaptability and success, while also improving conservation outcomes. Our findings also demonstrate the usefulness of the diagnostic framework employed here for facilitating comparative crossregional analyses of natural resource use and management. [ABSTRACT FROM AUTHOR]

Alessa, Lilian, Mark Altaweel, Andrew Kliskey, Christopher Bone, William Schnabel, and Kalb Stevenson, 2011. Alaska's Freshwater Resources: Issues Affecting Local and International Interests. Journal of the American Water Resources Association (JAWRA) 47(1):143-157. DOI: 10.1111/j.1752-1688.2010.00498.x The State of Alaska faces a broad range of freshwater challenges including limited resource access in rural communities, increasing freshwater use, and a pressing need to better understand and prepare for climate-driven change. Despite these significant issues, Alaska is relatively water-rich and far more equipped to address its water resource concerns compared with other regions of the world. Globally, simultaneous and rapid water stresses have influenced and complicated conflicts and are motivating nations to develop markets and trade as one of the primary means to manage their needs for this resource. This paper presents these interacting issues in the context of Alaska's relationship with a world undergoing significant social and ecological changes that affect freshwater supplies. We present the challenges faced by Alaska in the context of a larger global perspective, and briefly explore the relative effects these issues have on local, regional, and global scales. We present the argument that Alaska needs to develop more robust institutions and policies that can alleviate both household concerns and ensure that Alaska plays a significant role in the international freshwater arena for its long-term resilience. [ABSTRACT FROM AUTHOR]

This paper assesses the resilience of Alaska's boreal forest system to rapid climatic change. Recent warming is associated with reduced growth of dominant tree species, plant disease and insect outbreaks, warming and thawing of permafrost, drying of lakes, increased wildfire extent, increased postfire recruitment of deciduous trees, and reduced safety of hunters traveling on river ice. These changes have modified key structural features, feedbacks, and interactions in the boreal forest, including reduced effects of upland permafrost on regional hydrology, expansion of boreal forest into tundra, and amplification of climate warming because of reduced albedo (shorter winter season) and carbon release from wildfires. Other temperature-sensitive processes for which no trends have been detected include composition of plant and microbial communities, long-term landscape-scale change in carbon stocks, stream discharge, mammalian population dynamics, and river access and subsistence opportunities for rural indigenous communities. Projections of continued warming suggest that Alaska's boreal forest will undergo significant functional and structural changes within the next few decades that are unprecedented in the last 6000 years. The impact of these social-ecological changes will depend in part on the extent of landscape reorganization between uplands and lowlands and on policies regulating subsistence opportunities for rural communities. [ABSTRACT FROM AUTHOR]

This paper integrates dendrochronological, demographic, and experimental perspectives to improve understanding of the response of white spruce (Picea glauca (Moench) Voss) tree growth to climatic variability in interior Alaska. The dendrochronological analyses indicate that climate warming has led to widespread declines in white spruce growth throughout interior Alaska that have become more prevalent during the 20th century. Similarly, demographic studies show that white spruce tree growth is substantially limited by soil moisture availability in both mid- and late-successional stands. Interannual variability in tree growth among stands within a landscape exhibits greater synchrony than does growth of trees that occupy different landscapes, which agrees with dendrochronological findings that the responses depend on landscape position and prevailing climate. In contrast, the results from 18 years of a summer moisture limitation experiment showed that growth in midsuccessional upland stands was unaffected by moisture limitation and that moisture limitation decreased white spruce growth in floodplain stands where it was expected that growth would be less vulnerable because of tree access to river water. Taken together, the evidence from the different perspectives analyzed in this study clearly indicates that white spruce tree growth in interior Alaska is vulnerable to the effects of warming on plant water balance. [ABSTRACT FROM AUTHOR]

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Peak oil and global warming have both been vilified and then vindicated. When the small community of Haines, Alaska, dependent for food, fuel and social services on the increasingly less viable fossil fuel economy, began noticing deficits in early 2007, its Borough Assembly engaged the volunteer Haines Energy Task Force to research and make recommendations on alternative energy sources for heating and transportation, local food production and harvesting of subsistence resources, social services and economic change. As a long-term resident and property owner, I found myself in a zone of identification (Burke 1950) as part of a nexus of practice (NOP) of citizens thinking about the future of reduced and alternative energy consumption and taking action toward bringing about the envisioned future. As part of this NOP, my analysis constituted social action by transforming the NOP in engaging the NOP, the opening move in a nexus analysis (Scollon and Scollon 2004: 9). This paper is an account of the ways and extent to which the task force was able to bring about change in the community. It is not a nexus analysis as such but a summary report. [ABSTRACT FROM AUTHOR]

Abstract: As part of a project comparing the structure and function of four marine ecosystems off Norway and the United States, this paper examines the oceanographic responses to climate forcing, with emphasis on recent changes. The four Northern Hemisphere ecosystems include two in the Pacific Ocean (Bering Sea and Gulf of Alaska) and two in the Atlantic Ocean (Georges Bank/Gulf of Maine and the Barents/Norwegian Seas). Air temperatures, wind forcing and heat fluxes over the four regions are compared as well as ocean hydrography and sea-ice conditions where seasonal sea ice is found. The long-term interannual variability in air temperatures, winds and net heat fluxes show strong similarity between adjacent ecosystems and within subregions of an ecosystem, but no significant correlations between Pacific and Atlantic ecosystems and few across the Atlantic. In spite of the lack of correlation between climate forcing and ocean conditions between most of the ecosystems, recent years have seen record or near record highs in air and sea temperatures in all ecosystems. The apparent causes of the warming differ. In the Atlantic, they appear to be due to advection, while in the Pacific temperatures are more closely linked to air-sea heat exchanges. Advection is also responsible for the observed changes in salinity in the Atlantic ecosystems (generally increasing salinity in the Barents and Norwegian Seas and decreasing in the Gulf of Maine and Georges Bank) while salinity changes in the Gulf of Alaska are largely related to increased local runoff. [Copyright &y& Elsevier]

Abstract: Assessment of the response of the carbon cycle to climate change is important for predicting future climate, especially in northern high latitudes, where the warming may be highly pronounced. In this paper, three years of data measured by the eddy covariance method were used to verify the carbon dynamics of a black spruce forest in interior Alaska with the BIOME-BGC model. The model was modified and calibrated to the cold regions. The calibrated model simulation satisfactorily performed reproduction of the observed net ecosystem exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (RE). The daily output of the model also correlated with field-based estimates of NEE (42%), GPP (89%), and RE (89%). The model simulation showed that the heterotrophic respiration occupied a substantial portion of total carbon exchange, and that inter-annual variation of the heterotrophic respiration determined the sink/source strength of carbon. According to our simulation, the black spruce forest in interior Alaska was a net carbon sink between 1949 and 2005, and the trend of the projected sink strength was not obvious in the recent climate warming. The model analysis suggested that the change in the seasonal weather pattern strongly affected the carbon balance. A potentially increased carbon sink due to future warming climate and elevated CO2 will be at least partly offset by a concurrent increase of VPD, since the response of the stomatal conductance to increased VPD could increase the soil moisture, and thus stimulate heterotrophic respiration, rather than net primary productivity. The results of this study should be useful to forecast the response of the carbon cycle to warming in black spruce forests of interior Alaska. [Copyright &y& Elsevier]

This paper explores whether fundamental differences exist between urban and rural vulnerability to climate-induced changes in the fire regime of interior Alaska. We further examine how communities and fire managers have responded to these changes and what additional adaptations could be put in place. We engage a variety of social science methods, including demographic analysis, semi-structured interviews, surveys, workshops and observations of public meetings. This work is part of an interdisciplinary study of feedback and interactions between climate, vegetation, fire and human components of the Boreal forest social–ecological system of interior Alaska. We have learned that although urban and rural communities in interior Alaska face similar increased exposure to wildfire as a result of climate change, important differences exist in their sensitivity to these biophysical, climate-induced changes. In particular, reliance on wild foods, delayed suppression response, financial resources and institutional connections vary between urban and rural communities. These differences depend largely on social, economic and institutional factors, and are not necessarily related to biophysical climate impacts per se. Fire management and suppression action motivated by political, economic or other pressures can serve as unintentional or indirect adaptation to climate change. However, this indirect response alone may not sufficiently reduce vulnerability to a changing fire regime. More deliberate and strategic responses may be required, given the magnitude of the expected climate change and the likelihood of an intensification of the fire regime in interior Alaska. [ABSTRACT FROM AUTHOR]

Central Alaska and Yukon represent the longest continuously inhabited region in the Americas, with a rich record of research on technology, subsistence, and decision-making spanning over 14,000 years. Still, archaeologists debate whether the changes observed in the material and paleodemographic record can be interpreted as the result of environmental influences. This paper presents a multivariate analysis of regional occupation chronology, paleodemography, site placement, and climate data to investigate how past populations were affected by climate change. This research shows that populations were larger than expected at some of the earliest periods and that significant climatic and environmental events do not correspond with significant population decreases as researchers have previously argued. Changes in land use were gradual and unidirectional, with decreases in average site slope, increases in average site size, and consistent average site elevation through time. Trends in land use and paleodemography correspond to cultural phases assigned by regional experts, though environmental shifts undoubtedly played a role in shaping land use and culture throughout the past. This research has possible implications for our understanding of important cultural moments in the region's history, such as initial and subsequent migrations throughout the Americas. • Modeling climate impacts on land use and paleodemography in central Alaska and Yukon using settlement patterning data. • Long-term trends in human population from the late Pleistocene to the late Holocene (14,000–100 calibrated years BP). • Comparison of continuous and categorical data shows gradual changes in land use, population size, and climate. • Cultural intervals align with changes in land use and settlement patterning. [ABSTRACT FROM AUTHOR]

Calls to list polar bears as a threatened species under the United States Endangered Species Act are based on forecasts of substantial long-term declines in their population. Nine government reports were written to help US Fish and Wildlife Service managers decide whether or not to list polar bears as a threatened species. We assessed these reports based on evidence-based (scientific) forecasting principles. None of the reports referred to sources of scientific forecasting methodology. Of the nine, Amstrup et al. [Amstrup, S. C., B. G. Marcot, D. C. Douglas. 2007. Forecasting the rangewide status of polar bears at selected times in the 21st century. Administrative Report, USGS Alaska Science Center, Anchorage, AK.] and Hunter et al. [Hunter, C. M., H. Caswell, M. C. Runge, S. C. Amstrup, E. V. Regehr, I. Stirling. 2007. Polar bears in the Southern Beaufort Sea II: Demography and population growth in relation to sea ice conditions. Administrative Report, USGS Alaska Science Center, Anchorage, AK.] were the most relevant to the listing decision, and we devoted our attention to them. Their forecasting procedures depended on a complex set of assumptions, including the erroneous assumption that general circulation models provide valid forecasts of summer sea ice in the regions that polar bears inhabit. Nevertheless, we audited their conditional forecasts of what would happen to the polar bear population assuming, as the authors did, that the extent of summer sea ice would decrease substantially during the coming decades. We found that Amstrup et al. properly applied 15 percent of relevant forecasting principles and Hunter et al. 10 percent. Averaging across the two papers, 46 percent of the principles were clearly contravened and 23 percent were apparently contravened. Consequently, their forecasts are unscientific and inconsequential to decision makers. We recommend that researchers apply all relevant principles properly when important public-policy decisions depend on their forecasts. [ABSTRACT FROM AUTHOR]

Background: Wildfires are an increasingly important component of the forces that drive the global carbon (C) cycle and climate change as progressive warming is expected in boreal areas. This study estimated C emissions from the wildfires across the Alaskan Yukon River Basin in 2004. We spatially related the firescars to land cover types and defined the C fractions of aboveground biomass and the ground layer (referring to the top 15 cm organic soil layer only in this paper) consumed in association with land cover types, soil drainage classes, and the C stocks in the ground layer. Results: The fires led to a burned area of 26,500 km² and resulted in the total C emission of 81.1 ± 13.6 Tg (Tg, Teragram; 1 Tg = 1012 g) or 3.1 ± 0.7 kg C m-2 burned. Of the total C emission, about 73% and 27% could be attributed to the consumption of the ground layer and aboveground biomass, respectively. Conclusion: The predominant contribution of the ground layer to the total C emission implies the importance of ground fuel management to the control of wildfires and mitigation of C emissions. The magnitude of the total C emission depends on fire extent, while the C loss in kg C m-2 burned is affected strongly by the ground layer and soil drainage condition. The significant reduction in the ground layer by large fires may result in profound impacts on boreal ecosystem services with an increase in feedbacks between wildfires and climate change. [ABSTRACT FROM AUTHOR]

Late Pleistocene Beringia had herb-dominated vegetation with abundant grasses (Poaceae), and it was inhabited by an impressive assemblage of large grazing mammals. This paper reconstructs the list of most probable late Pleistocene Beringian lowland grass species from biogeographical evidence. Late Pleistocene eolian sediments and buried soils indicate that large areas of the Beringian lowlands had nutrient-rich, silty soils that occurred over ice-rich permafrost but were generally not waterlogged. A list of likely grasses was compiled from all species that have been recorded on similar fine-grained, mesic-to-dry lowland soils (i.e., presumed refugia) and are distributed at least sporadically across the whole region today. Grasses from 13 genera met these criteria, including most of the taxa that have been identified as late Pleistocene fossils from the study area. Most of these grasses are high-latitude species of genera that are also common in temperate latitudes (e.g., Elymus, Festuca, and Poa). This diverse group of plants has a wide range of adaptations today, suggesting that grasses would have been available to occupy a variety of habitats through Pleistocene climatic fluctuations. Among these grasses are a number of highly productive forage species. [ABSTRACT FROM AUTHOR]

The 1976 Pacific climate shift is examined, and its manifestations and significance in Alaskan climatology during the last half-century are demonstrated. The Pacific Decadal Oscillation index shifted in 1976 from dominantly negative values for the 25-yr time period 1951–75 to dominantly positive values for the period 1977–2001. Mean annual and seasonal temperatures for the positive phase were up to 3.1°C higher than for the negative phase. Likewise, mean cloudiness, wind speeds, and precipitation amounts increased, while mean sea level pressure and geopotential heights decreased. The pressure decrease resulted in a deepening of the Aleutian low in winter and spring. The intensification of the Aleutian low increased the advection of relatively warm and moist air to Alaska and storminess over the state during winter and spring. The regime shift is also examined for its effect on the long-term temperature trends throughout the state. The trends that have shown climatic warming are strongly biased by the sudden shift in 1976 from the cooler regime to a warmer regime. When analyzing the total time period from 1951 to 2001, warming is observed; however, the 25-yr period trend analyses before 1976 (1951–75) and thereafter (1977–2001) both display cooling, with a few exceptions. In this paper, emphasis is placed on the importance of taking into account the sudden changes that result from abrupt climatic shifts, persistent regimes, and the possibility of cyclic oscillations, such as the PDO, in the analysis of long-term climate change in Alaska. [ABSTRACT FROM AUTHOR]

A correction to this paper has been published: https://doi.org/10.1007/s00382-021-05756-2 [ABSTRACT FROM AUTHOR]

The progress made in the Land--Atmosphere--Ice Interactions Flux Study over the past 4 yr to fully characterize the biophysical fluxes in the snow-free tundra ecosystem and their relationship to climate and climate change is described. This paper is the result of a synthesis effort to bring together the measurements of surface fluxes at various sites on the North Slope of Alaska in the snow-free period of 1995 with the results of modeling efforts for this region. It is found that methodological and site dissimilarities contribute to measurement dif-ferences at least as much as instrument and sampling error, even for closely collocated and similarly vegetated sites. The regional climate model employed in this study generally simulates fluxes that are within the range of measured fluxes, but tends to overestimate both net radiation and latent heat fluxes. The regional model also captures site to site variations quite well, which appear to be more sensitive to mesoscale meteorological conditions than on specifics of site characteristics. The active layer model employed in this study performs well in estimating ground heat flux but rather more poorly in simulating turbulent fluxes. The global climate model is unable to capture the broad-scale response of the land surface sensible heat flux and net radiation, although it performs rather better in the simulation of latent and ground heat fluxes. Finally, the intended purposes and applications of both data and model simulations have a strong impact on their applicability to other studies. [ABSTRACT FROM AUTHOR]

Climate variability is not a new challenge for coastal communities. However, because climate variability is manifesting with more extreme climate impacts, occurring with greater frequency and with more intensity, the necessity for adaptation to minimize risk is becoming more pronounced. Though this is true of coastal communities around the globe, it is an acutely important concern for coastal communities in high northern latitudes, where the impacts of climate change are occurring at a disproportionate rate. With Homer, Alaska, as a case study, and through the lens of evolutionary governance, this research investigates coastal stressors (eg. storm surges, bluff instability) and subsequent decision dynamics around local government policy and planning for climate adaptation. In particular, the paper explores the relationship between actors and institutions, the connection between power and knowledge, as well as the challenges of path and goal dependencies. Narratives from key informants associated with Homer's climate change agenda highlight that while some stakeholders are keen to mainstream adaptation thinking into long-term strategic planning, adaptation policy remains a low priority (with a focus instead on mitigation). Uptake is further hindered by a belief among key decision-makers that the threat of climate change is a concern for the future. This in turn has resulted in diminished internal capacity (eg. institutions, knowledge) to effectively prepare for climate variability in general. Drawing insights through evolutionary governance theory, this study may provide coastal community decision-makers with an appreciation of the value (and nuanced challenges) of embedding climate adaptation thinking into strategic community planning. • The City lacks necessary institutions to build climate resilience through adaptation. • Leadership believes that climate change risks are too uncertain to motivate response. • Decision-makers view climate change adaptation as a low priority. • Adaptation remains a peripheral agenda; focus instead is on climate change mitigation. [ABSTRACT FROM AUTHOR]

Deep-sea coral and sponge ecosystems are widespread throughout most of Alaska's marine waters, and are associated with many different species of fishes and invertebrates. These ecosystems are vulnerable to the effects of commercial fishing activities and climate change. We compared four commonly used species distribution models (general linear models, generalized additive models, boosted regression trees and random forest models) and an ensemble model to predict the presence or absence and abundance of six groups of benthic invertebrate taxa in the Gulf of Alaska. All four model types performed adequately on training data for predicting presence and absence, with regression forest models having the best overall performance measured by the area under the receiver-operating-curve (AUC). The models also performed well on the test data for presence and absence with average AUCs ranging from 0.66 to 0.82. For the test data, ensemble models performed the best. For abundance data, there was an obvious demarcation in performance between the two regression-based methods (general linear models and generalized additive models), and the tree-based models. The boosted regression tree and random forest models out-performed the other models by a wide margin on both the training and testing data. However, there was a significant drop-off in performance for all models of invertebrate abundance (~50%) when moving from the training data to the testing data. Ensemble model performance was between the tree-based and regression-based methods. The maps of predictions from the models for both presence and abundance agreed very well across model types, with an increase in variability in predictions for the abundance data. We conclude that where data conforms well to the modeled distribution (such as the presence-absence data and binomial distribution in this study), the four types of models will provide similar results, although the regression-type models may be more consistent with biological theory. For data with highly zero-inflated distributions and non-normal distributions such as the abundance data from this study, the tree-based methods performed better. Ensemble models that averaged predictions across the four model types, performed better than the GLM or GAM models but slightly poorer than the tree-based methods, suggesting ensemble models might be more robust to overfitting than tree methods, while mitigating some of the disadvantages in predictive performance of regression methods. [ABSTRACT FROM AUTHOR]