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The Arctic is one of the few underexplored frontiers on the Earth. The present NJG issue consists of papers presented at the Arctic Conference Days in Tromsø in September 2007. The 10 papers presented herein are from the ICAM V sessions of the conference, and thus represents a continuation of proceedings from the previous ICAM conferences held in 1992 in Anchorage, 1994 in Magadan, 1998 in Celle and in 2003 in Dartmouth. [ABSTRACT FROM AUTHOR]

This paper examines search and rescue and backcountry medical response constraints in the Canadian Arctic and potential for unmanned aerial vehicles (UAV) to aid in response and preparedness. Semi-structured interviews (n = 18) were conducted with search and rescue responders, Elders, and emergency management officials to collect data on current emergency response and potential for UAV use. UAV test flights (n = 17) were undertaken with community members. We analyzed five years of weather data to examine UAV flight suitability. Numerous challenges face Arctic search and rescue and backcountry emergency response. Changing social and environmental conditions were described as increasing vulnerability to backcountry emergencies. Responders desired additional first aid and emergency training. Legal and weather restrictions were found to limit where, when and who could fly UAVs. UAVs were demonstrated to have potential benefits for hazard monitoring but not for SAR or medical response due to legal restrictions, weather margins, and local capacity. We find that communities are ill-prepared for ongoing SAR demands, let alone a larger disaster. There are numerous limitations to the use of consumer UAVs by Arctic communities. Prevention of backcountry medical emergencies, building resilience to disasters, and first responder training should be prioritized over introducing UAVs to the response system. [ABSTRACT FROM AUTHOR]

This paper examines the development of a geographical sensibility amongst field scientists involved in the Polar Continental Shelf Project (PCSP) during the late 1950s and early 1960s. This is achieved by using oral histories collected from scientists and other field personnel. These oral testimonies reveal a number of important issues for historians of geography. These include the interrelation of scientific practices in the field and the association of an interdisciplinary stance towards Arctic science with a particular understanding of geographical identity. It appears that the community of actors taking vocational and professional meaning from the practice of geography is much larger than is usually considered to be the case. The paper concludes by discussing the implications for debates about disciplinary identity and belonging in geography. [ABSTRACT FROM AUTHOR]

The Barmur Group (informally Tjörnes beds) sedimentary succession of northern Iceland is key to reconstructing the opening of the Bering Strait oceanic gateway because these rocks record migration of bivalve molluscs from the Pacific to the Atlantic via the Arctic. However, the timing of the migration event is poorly constrained owing to a lack of reliable absolute ages. To address this problem, we present the first Ar‐Ar radiometric dates from four basaltic lavas that underlie, are intercalated with, and overlie the Barmur Group, and integrate them with existing paleomagnetic records. We show that the Barmur Group has a latest Miocene to early Pliocene age range (c. 6.0–4.4 Ma; C3r–C3n.2n), older than all previous age models. Thus, the Barmur Group does not record the mid‐Piacenzian Warm Period, contra some previous suggestions. Abundant Pacific bivalve molluscs appeared in the Barmur Group during subchrons C3n.4n–C3n.3r at 5.235–4.896 Ma, over 1.3 million years earlier than previously suggested. Appearance of Pacific bivalves in the northern Atlantic occurred shortly after the 5.6–5.4 Ma age previously inferred for first appearance of Arctic bivalves in the Pacific. Thus, our data suggest that first opening of the Bering Strait gateway by the latest Miocene (c. 5.5 Ma) was soon followed by bidirectional trans‐Arctic faunal exchange, and argue against a hypothesized two‐stage faunal exchange process spanning c. 2 million years. Our results also confirm that first opening of the Bering Strait gateway was not directly associated with the growth of large northern hemisphere icesheets, which occurred several million years later. Plain Language Summary: The extent to which global climate change is influenced by the flow of seawater between the world's oceans is an important question in Earth science. Sedimentary rocks from the Tjörnes Peninsula in northern Iceland record the opening of the Bering Strait oceanic gateway, which connects the Pacific and Atlantic Oceans via the Arctic. The signature of this gateway opening event is the sudden appearance in Iceland of bivalve mollusc fossils that previously lived only in the Pacific Ocean. However, the timing of their arrival is uncertain owing to the lack of reliable age measurements. To solve this problem, we applied radioisotope dating methods to a succession of rocks called the Barmur Group from the Tjörnes Peninsula. We found that the sudden appearance of Pacific fossils occurred over a million years earlier than previously thought. Our data show that first opening of the Bering Strait gateway was soon followed by migration of marine faunas in both directions, in contrast to the existing hypothesis that Pacific‐to‐Atlantic migration significantly post‐dated Atlantic‐to‐Pacific migration. Our results also confirm the hypothesis that establishment of the Pacific‐Arctic‐Atlantic oceanic connection did not directly trigger development of large northern hemisphere icecaps, which occurred several million years later. Key Points: New Ar‐Ar dating shows a late Miocene to early Pliocene (6.0–4.4 Ma) age range for the Barmur Group (Tjörnes beds), northern IcelandArrival of Pacific bivalves in Iceland is dated at 5.2–4.9 Ma (chrons C3n.4n–C3n.3r), soon after first Bering Strait opening at 5.6–5.4 MaOpening of the Bering Strait gateway did not directly cause the development of large northern hemisphere icecaps [ABSTRACT FROM AUTHOR]

Recent climate change has been especially pronounced in the High Arctic, however, the responses of aquatic biota, such as diatoms, can be modified by site-specific environmental characteristics. To assess if climate-mediated ice cover changes affect the diatom response to climate, we used paleolimnological techniques to examine shifts in diatom assemblages from ten High Arctic lakes and ponds from Ellesmere Island and nearby Pim Island (Nunavut, Canada). The sites were divided a priori into four groups (“warm”, “cool”, “cold”, and “oasis”) based on local elevation and microclimatic differences that result in differing lengths of the ice-free season, as well as about three decades of personal observations. We characterized the species changes as a shift from Condition 1 (i.e. a generally low diversity, predominantly epipelic and epilithic diatom assemblage) to Condition 2 (i.e. a typically more diverse and ecologically complex assemblage with an increasing proportion of epiphytic species). This shift from Condition 1 to Condition 2 was a consistent pattern recorded across the sites that experienced a change in ice cover with warming. The “warm” sites are amongst the first to lose their ice covers in summer and recorded the earliest and highest magnitude changes. The “cool” sites also exhibited a shift from Condition 1 to Condition 2, but, as predicted, the timing of the response lagged the “warm” sites. Meanwhile some of the “cold” sites, which until recently still retained an ice raft in summer, only exhibited this shift in the upper-most sediments. The warmer “oasis” ponds likely supported aquatic vegetation throughout their records. Consequently, the diatoms of the “oasis” sites were characterized as high-diversity, Condition 2 assemblages throughout the record. Our results support the hypothesis that the length of the ice-free season is the principal driver of diatom assemblage responses to climate in the High Arctic, largely driven by the establishment of new aquatic habitats, resulting in increased diversity and the emergence of novel growth forms and epiphytic species. [ABSTRACT FROM AUTHOR]

Climate change is facilitating rapid changes in the composition and distribution of vegetation at northern latitudes, raising questions about the responses of wildlife that rely on arctic ecosystems. One widely observed change occurring in arctic tundra ecosystems is an increasing dominance of deciduous shrub vegetation. Our goals were to examine the tolerance of arctic-nesting bird species to existing gradients of vegetation along the boreal forest-tundra ecotone, to predict the abundance of species across different heights and densities of shrubs, and to identify species that will be most or least responsive to ongoing expansion of shrubs in tundra ecosystems. We conducted 1,208 point counts on 12 study blocks from 2012–2014 in northwestern Alaska, using repeated surveys to account for imperfect detection of birds. We considered the importance of shrub height, density of low and tall shrubs (i.e. shrubs >0.5 m tall), percent of ground cover attributed to shrubs (including dwarf shrubs <0.5 m tall), and percent of herbaceous plant cover in predicting bird abundance. Among 17 species considered, only gray-cheeked thrush (Catharus minimus) abundance was associated with the highest values of all shrub metrics in its top predictive model. All other species either declined in abundance in response to one or more shrub metrics or reached a threshold where further increases in shrubs did not contribute to greater abundance. In many instances the relationship between avian abundance and shrubs was nonlinear, with predicted abundance peaking at moderate values of the covariate, then declining at high values. In particular, a large number of species were responsive to increasing values of average shrub height with six species having highest abundance at near-zero values of shrub height and abundance of four other species decreasing once heights reached moderate values (≤ 33 cm). Our findings suggest that increases in shrub cover and density will negatively affect abundance of only a few bird species and may potentially be beneficial for many others. As shrub height increases further, however, a considerable number of tundra bird species will likely find habitat increasingly unsuitable. [ABSTRACT FROM AUTHOR]

Information on recent photosynthetic biomass distribution and biogeography of Arctic marine pico-eukaryotes (0.2–3 μm) is needed to better understand consequences of environmental change for Arctic marine ecosystems. We analysed pico-eukaryote biomass and community composition in Fram Strait and large parts of the Central Arctic Ocean (Nansen Basin, Amundsen Basin) using chlorophyll a (Chl a) measurements, automated ribosomal intergenic spacer analysis (ARISA) and 454-pyrosequencing. Samples were collected during summer 2012, the year with the most recent record sea ice minimum. Chl a concentrations were highest in eastern Fram Strait and pico-plankton accounted for 60–90% of Chl a biomass during the observation period. ARISA-patterns and 454-pyrosequencing revealed that pico-eukaryote distribution is closely related to water mass distribution in the euphotic zone of the Arctic Ocean. Phaeocystaceae, Micromonas sp., Dinophyceae and Syndiniales constitute a high proportion of sequence reads, while sequence abundance of autotrophic Phaeocystaceae and mixotrophic Micromonas sp. was inversely correlated. Highest sequence abundances of Phaeocystaceae were observed in the warm Atlantic Waters in Fram Strait, while Micromonas sp. dominated the abundant biosphere in the arctic halocline. Our results are of particular interest considering existing hypotheses that environmental conditions in Nansen Basin might become more similar to the current conditions in Fram Strait. We propose that in response, biodiversity and biomass of pico-eukaryotes in Nansen Basin could resemble those currently observed in Fram Strait in the future. This would significantly alter biogeochemical cycles in a large part of the Central Arctic Ocean. [ABSTRACT FROM AUTHOR]

Knowledge of the polar ionospheric total electron content (TEC) and its future variations is of scientific and engineering relevance. In this study, a new method is developed to predict Arctic mean TEC on the scale of a solar cycle using previous data covering 14 years. The Arctic TEC is derived from global positioning system measurements using the spherical cap harmonic analysis mapping method. The study indicates that the variability of the Arctic TEC results in highly time-varying periodograms, which are utilized for prediction in the proposed method. The TEC time series is divided into two components of periodic oscillations and the average TEC. The newly developed method of TEC prediction is based on an extrapolation method that requires no input of physical observations of the time interval of prediction, and it is performed in both temporally backward and forward directions by summing the extrapolation of the two components. The backward prediction indicates that the Arctic TEC variability includes a 9 years period for the study duration, in addition to the well-established periods. The long-term prediction has an uncertainty of 4.8–5.6 TECU for different period sets. [ABSTRACT FROM AUTHOR]

Development of efficient techniques for monitoring wildlife is a priority in the Arctic, where the impacts of climate change are acute and remoteness and logistical constraints hinder access. We evaluated high resolution satellite imagery as a tool to track the distribution and abundance of polar bears. We examined satellite images of a small island in Foxe Basin, Canada, occupied by a high density of bears during the summer ice-free season. Bears were distinguished from other light-colored spots by comparing images collected on different dates. A sample of ground-truthed points demonstrated that we accurately classified bears. Independent observers reviewed images and a population estimate was obtained using mark–recapture models. This estimate (: 94; 95% Confidence Interval: 92–105) was remarkably similar to an abundance estimate derived from a line transect aerial survey conducted a few days earlier (: 102; 95% CI: 69–152). Our findings suggest that satellite imagery is a promising tool for monitoring polar bears on land, with implications for use with other Arctic wildlife. Large scale applications may require development of automated detection processes to expedite review and analysis. Future research should assess the utility of multi-spectral imagery and examine sites with different environmental characteristics. [ABSTRACT FROM AUTHOR]

Climate change is occurring more rapidly in the Arctic than other places in the world, which is likely to alter the distribution and abundance of migratory birds breeding there. A warming climate can provide benefits to birds by decreasing spring snow cover, but increases in the frequency of summer rainstorms, another product of climate change, may reduce foraging opportunities for insectivorous birds. Cyclic lemming populations in the Arctic also influence bird abundance because Arctic foxes begin consuming bird eggs when lemmings decline. The complex interaction between summer temperature, precipitation, and the lemming cycle hinder our ability to predict how Arctic-breeding birds will respond to climate change. The main objective of this study was to investigate the relationship between annual variation in weather, spring snow cover, lemming abundance and spatiotemporal variation in the abundance of multiple avian guilds in a tundra ecosystem in central Nunavut, Canada: songbirds, shorebirds, gulls, loons, and geese. We spatially stratified our study area based on vegetation productivity, terrain ruggedness, and freshwater abundance, and conducted distance sampling to estimate strata-specific densities of each guild during the summers of 2010–2012. We also monitored temperature, rainfall, spring snow cover, and lemming abundance each year. Spatial variation in bird abundance matched what was expected based on previous ecological knowledge, but weather and lemming abundance also significantly influenced the abundance of some guilds. In particular, songbirds were less abundant during the cool, wet summer with moderate snow cover, and shorebirds and gulls declined with lemming abundance. The abundance of geese did not vary over time, possibly because benefits created by moderate spring snow cover were offset by increased fox predation when lemmings were scarce. Our study provides an example of a simple way to monitor the correlation between weather, spring snow cover, lemming abundance, and spatiotemporal variations in Arctic-breeding birds. [ABSTRACT FROM AUTHOR]

While microbial communities play a key role in the geochemical cycling of nutrients and contaminants in anaerobic freshwater sediments, their structure and activity in polar desert ecosystems are still poorly understood, both across heterogeneous freshwater environments such as lakes and wetlands, and across sediment depths. To address this question, we performed targeted environmental transcriptomics analyses and characterized microbial diversity across three depths from sediment cores collected in a lake and a wetland, located on Cornwallis Island, NU, Canada. Microbial communities were characterized based on 16S rRNA and two functional gene transcripts: mcrA, involved in archaeal methane cycling and glnA, a bacterial housekeeping gene implicated in nitrogen metabolism. We show that methane cycling and overall bacterial metabolic activity are the highest at the surface of lake sediments but deeper within wetland sediments. Bacterial communities are highly diverse and structured as a function of both environment and depth, being more diverse in the wetland and near the surface. Archaea are mostly methanogens, structured by environment and more diverse in the wetland. McrA transcript analyses show that active methane cycling in the lake and wetland corresponds to distinct communities with a higher potential for methane cycling in the wetland. Methanosarcina spp., Methanosaeta spp. and a group of uncultured Archaea are the dominant methanogens in the wetland while Methanoregula spp. predominate in the lake. [ABSTRACT FROM AUTHOR]

A metagenomic analysis was performed on a soil profile from a wet tundra site in northern Alaska. The goal was to link existing biogeochemical knowledge of the system with the organisms and genes responsible for the relevant metabolic pathways. We specifically investigated how the importance of iron (Fe) oxides and humic substances (HS) as terminal electron acceptors in this ecosystem is expressed genetically, and how respiratory and fermentative processes varied with soil depth into the active layer and into the upper permafrost. Overall, the metagenomes reflected a microbial community enriched in a diverse range of anaerobic pathways, with a preponderance of known Fe reducing species at all depths in the profile. The abundance of sequences associated with anaerobic metabolic processes generally increased with depth, while aerobic cytochrome c oxidases decreased. Methanogenesis genes and methanogen genomes followed the pattern of CH4 fluxes : they increased steeply with depth into the active layer, but declined somewhat over the transition zone between the lower active layer and the upper permafrost. The latter was relatively enriched in fermentative and anaerobic respiratory pathways. A survey of decaheme cytochromes (MtrA, MtrC and their homologs) revealed that this is a promising approach to identifying potential reducers of Fe(III) or HS, and indicated a possible role for Acidobacteria as Fe reducers in these soils. Methanogens appear to coexist in the same layers, though in lower abundance, with Fe reducing bacteria and other potential competitors, including acetogens. These observations provide a rich set of hypotheses for further targeted study. [ABSTRACT FROM AUTHOR]

Lower Jurassic and Aalenian deposits are widespread in the Arctic Basin and in northwestern Europe. The succession of Lower Jurassic lithologic units is very similar throughout the Arctic regions. The Lower Toarcian is represented by dark-gray, organic-rich mudstones and often bituminous mudstones developed uniformly over the whole area. All deposits contain rich assemblages of foraminifers, ostracods and palynomorphs, as well as less abundant ammonites and bivalves, providing a mean for correlation of the lithologic units. The established Jurassic zonal subdivisions have been studied in all areas of the Arctic Basin using original material as well as published data. Thus, the Jurassic zonal subdivision of northern Siberia, based on ammonites, bivalves, foraminifers and ostracods, may be considered as the Boreal Zonal Standard. The analysis of biotic and abiotic events as well as the geographic distribution of microbenthos result in the definition of biogeographic realms and provinces based on foraminifer and ostracode data for the Early Jurassic and Aalenian. The differentiation of microbenthos associations is based on the multivariate analysis of characteristic taxa. The configurations of the boundaries between provinces and realms, based on the geographic distribution of the different groups of benthos, changed during geological time. [ABSTRACT FROM AUTHOR]

Very high spatial resolution commercial satellite imagery can inform observation, mapping, and documentation of micro-topographic transitions across large tundra regions. The bridging of fine-scale field studies with pan-Arctic system assessments has until now been constrained by a lack of overlap in spatial resolution and geographical coverage. This likely introduced biases in climate impacts on, and feedback from the Arctic region to the global climate system. The central objective of this exploratory study is to develop an object-based image analysis workflow to automatically extract ice-wedge polygon troughs from very high spatial resolution commercial satellite imagery. We employed a systematic experiment to understand the degree of interoperability of knowledge-based workflows across distinct tundra vegetation units—sedge tundra and tussock tundra—focusing on the same semantic class. In our multi-scale trough modelling workflow, we coupled mathematical morphological filtering with a segmentation process to enhance the quality of image object candidates and classification accuracies. Employment of the master ruleset on sedge tundra reported classification accuracies of correctness of 0.99, completeness of 0.87, and F1 score of 0.92. When the master ruleset was applied to tussock tundra without any adaptations, classification accuracies remained promising while reporting correctness of 0.87, completeness of 0.77, and an F1 score of 0.81. Overall, results suggest that the object-based image analysis-based trough modelling workflow exhibits substantial interoperability across the terrain while producing promising classification accuracies. From an Arctic earth science perspective, the mapped troughs combined with the ArcticDEM can allow hydrological assessments of lateral connectivity of the rapidly changing Arctic tundra landscape, and repeated mapping can allow us to track fine-scale changes across large regions and that has potentially major implications on larger riverine systems. [ABSTRACT FROM AUTHOR]

The article presents a study which determined the threshold or tipping points of that must be reached in order for certain scenarios to play out and identified nine different events that are approaching their tipping points. According to the study, the complete loss of summer Arctic sea ice, a significant reduction of Amazonian rainfall and the intensification of El Nino events are some of the scenarios that are impending if current temperature increases continue. The vanishing of the Greenland ice sheet is one of the other events identified in the study as nearing their tipping points.