High Arctic Research Papers - Academia.edu (original) (raw)

2025, The Anthropocene Review

Diatom and chrysophyte assemblages from varved sediments of meromictic Crawford Lake, Ontario record major environmental changes resulting from spatially broadening anthropogenic environmental stressors related to the “Great Acceleration” in the mid-20th century. Biannual assessment of diatom and chrysophyte assemblages over the last ~200 years allowed for rate of change analysis between adjacent samples that increased substantially during the mid-20th century, concurrent with significant generalized additive model trends. Changes in diatom and chrysophyte assemblages were likely driven by multiple anthropogenic stressors including local forestry harvesting, agriculture, and milling activities, acidic deposition from regional industrial processes, and anthropogenic climate warming. Novel siliceous algal assemblages now exist in Crawford Lake, likely related to the complexities of the above mentioned local and regional stressors. The major assemblage changes at the proposed base of t...

2025, Science of The Total Environment

The concentration and possible sources of heavy metal input to a high Arctic mire in Kongsfjord, West Spitsbergen were examined; levels of lead, copper and zinc are highest in the surface humus closest to the carboniferous limestone cliff upon which seabirds nest. The concentrations of iron, manganese, nickel, copper, zinc and lead in two cores of peat increase markedly in the upper 5 cm of consolidated peat, with the highest concentrations found in the uppermost centimetre of peat. There has, therefore, been an increase in heavy metal loading to this High Arctic mire within the last 100 years. This cannot be attributed to the direct input of heavy metals from precipitation or coal dust from the local mines as the concentrations of the same elements in these materials are three orders of magnitude lower. It is only in the vicinity of seabird colonies that this pattern is shown and the concentrations ( pg g-l dry wt.) of lead, copper and zinc in faecal samples of kittiwake and glaucous gull are in the range 17-32,35-65 and 63-260, respectively. The concentrations of these heavy metals in the faeces are close to those found in the surface layers of humus closest to the cliff. This indicates that the seabirds are acting as a vector for the movement of heavy metals between the marine and terrestrial ecosystems.

2025, Biogeochemistry

Natural environmental isotopes of nitrate, sulphate and inorganic carbon are discussed in conjunction with major ion chemistry of subglacial runoff from a High Arctic glacier, Midre Lovénbreen, Svalbard. The chemical composition of meltwaters is observed to switch in accordance with subglacial hydrological evolution and redox status. Changing rapidly from reducing to oxidizing conditions, subglacial waters also depict that 15 N/ 14 N values show microbial denitrification is an active component of nutrient cycling beneath the glacier. 18 O/ 16 O ratios of sulphate are used to elucidate mechanisms of biological and abiological sulphide oxidation. Concentrations of bicarbonate appear to be governed largely by the degree of rock:water contact encountered in the subglacial system, rather than the switch in redox status, although the potential for microbiological activity to influence ambient bicarbonate concentrations is recognised. Glaciers are therefore highlighted as cryospheric ecosystems supporting microbial life which directly impacts upon the release of solute through biogeochemically mediated processes.

2025, Journal of Ecology

1 The response of peat-rich permafrost soils to human-induced climate change may be especially important in modifying the global C-flux. We examined the Holocene developmental record of a High Arctic peat-forming wetland to investigate its sensitivity to past climate change and aid understanding of the likely effects of future climate warming on high-latitude ecosystems. 2 The microhabitat of mosses was quantified in the present-day polygon-complex at Bylot Island (73 ° N, 80 ° W) and used to interpret the radiocarbon-dated macrofossil record of three cores, comprising c. 3500 years of wetland development. Recurrent wet and dry phases in the reconstructed palaeohydrological record indicated pronounced temporal variability. Wet and dry phases were compared between cores and with palaeoclimatic proxy values, measured as percentage melt and δ 18 O in nearby ice cores. 3 Periodic wet and dry phases appear unrelated to past climate over c. 50% of the combined stratigraphic records, and are attributable instead to geomorphological mechanisms. At other times, association of wet and dry phases with significantly lower and higher values of percentage melt and δ 18 O indicate a possible effect of past climate change on polygon hydrology and vegetation, although inconsistencies between cores suggest that local geomorphological processes continued to modify a regional climatic effect. However, during a period incorporating the Little Ice Age ( c. 305-530 cal. years  ), reconstructed moisture and vegetation change is pronounced and consistent among all three cores. 4 The results provide strong evidence for the sensitivity of a High Arctic terrestrial ecosystem to past climate change during the Holocene. The estimated magnitude of changes in soil moisture between wet and dry phases is sufficient to imply recurrent shifts in wetland function, periodically impacted upon by pronounced climatic variability, although controlled principally by autogenic processes. The structure and function of such wetlands may therefore be susceptible to predicted, human-induced climate warming.

2025, Integrative and Comparative Biology

We examined the role of trophic interactions in structuring a high arctic tundra community characterized by a large breeding colony of greater snow geese (Chen caerulescens atlantica). According to the exploitation ecosystem hypothesis of Oksanen et al. (1981), food chains are controlled by top-down interactions. However, because the arctic primary productivity is low, herbivore populations are too small to support functional predator populations and these communities should thus be dominated by the plant/ herbivore trophic-level interaction. Since 1990, we have been monitoring annual abundance and productivity of geese, the impact of goose grazing, predator abundance (mostly arctic foxes, Alopex lagopus) and the abundance of lemmings, the other significant herbivore in this community, on Bylot Island, Nunavut, Canada. Goose grazing consistently removed a significant proportion of the standing crop (ϳ40%) in tundra wetlands every year. Grazing changed plant community composition and reduced the production of grasses and sedges to a low-level equilibrium compared to the situation where the presence of geese had been removed. Lemming cyclic fluctuations were strong and affected fox reproduction. Fox predation on goose eggs was severe and generated marked annual variation in goose productivity. Predation intensity on geese was closely related to the lemming cycle, a consequence of an indirect interaction between lemming and geese via shared predators. We conclude that, contrary to the exploitation ecosystem hypothesis, both the plant/herbivore and predator/prey interactions are significant in this arctic community.

2025, Journal of Geophysical Research: Atmospheres

Arctic regions contain large amounts of stored soil carbon and comprise huge areas of discontinuous vegetation. The potential for feedback effects on possible changing climatic conditions through altered source/sink action for atmospheric CO2 is therefore an important issue in tundra regions. In this study we investigate environmental controls on CO2 evolution rates in Arctic soils through observations along a Eurasian transect of tundra sites and comparative experiments in northern Sweden and northeast Greenland. Among factors potentially controlling decomposition rates in Eurasian wet and mesic tundra temperature and depth of the water table significantly influenced the CO2 efflux, while thaw depth, soil nitrogen, and organic matter concentrations explained very little of the variation in fluxes. The minor importance of the soil N status in controlling decomposition rates was confirmed in experiments in which N and P was added in a factorial manner at a subarctic heath and a high‐...

2025, Journal of Ecology

1 Macrolichens are important for the functioning and biodiversity of cold northern ecosystems and their reindeer-based cultures and economies. 2 We hypothesized that, in climatically milder parts of the Arctic, where ecosystems have relatively dense plant canopies, climate warming and/or increased nutrient availability leads to decline in macrolichen abundance as a function of increased abundance of vascular plants. In more open high-arctic or arctic-alpine plant communities such a relationship should be absent. To test this, we synthesized cross-continental arctic vegetation data from ecosystem manipulation experiments simulating mostly warming and increased nutrient availability, and compared these with similar data from natural environmental gradients. 3 Regressions between abundance or biomass of macrolichens and vascular plants were consistently negative across the subarctic and mid-arctic experimental studies. Such a pattern did not emerge in the coldest high-arctic or arctic-alpine sites. The slopes of the negative regressions increased across 10 sites as the climate became milder (as indicated by a simple climatic index) or the vegetation denser (greater site above-ground biomass). 4 Seven natural vegetation gradients in the lower-altitude sub-and mid-arctic zone confirmed the patterns seen in the experimental studies, showing consistent negative relationships between abundance of macrolichens and vascular plants. 5 We conclude that the data supported the hypothesis. Macrolichens in climatically milder arctic ecosystems may decline if and where global changes cause vascular plants to increase in abundance. 6 However, a refining of our findings is needed, for instance by integrating other abiotic and biotic effects such as reindeer grazing feedback on the balance between vascular plants and lichens.

2025, Chemometrics and Intelligent Laboratory Systems

A receptor model has been developed in which meteorological information in the form of air parcel back trajectories are combined with on the atmospheric constituent concentration data to produce conditional probability fields pointing to areas that are likely to have made significant contributions to samples with higher than average concentrations. This approach, potential source contribution function (PSCF) analysis, has proven quite successful in producing maps that have a good correspondence with areas of known high emissions on a variety of spatial scales from large urban scale problems in the air basin that includes Los Angeles, CA to regional transport of pollutants to southern Ontario to semi-global scale transport to several sites in the high Arctic. However, there are cells having a limited numbers of endpoints because trajectories to that region have low probabilities and there is estimate of the uncertainties in the PSCF values. Thus, we have examined the use of bootstrapping to provide better estimates of the probability values and their uncertainties. This approach has been tested on data from several locations at differing levels of geographical scaie for varying numbers of trajectories selected and trials made. The results of the studies for data from the high Arctic at Ny Alesund on Spitsbergen (78%' N, ll"57' E, 5 m above mean sea level) are presented. The results of these studies for the transport of pollutants to the Arctic basin suggest that in many cases the bootstrapped PSCF maps are clearer and more easily interpreted in terms of known sources.

2025, Journal of Geochemical Exploration

Unique springs discharge from the surface of a high arctic glacier, releasing H2S, and depositing native sulphur, gypsum, and calcite. A rare CaCO3 polymorph, vaterite, is also observed. Physical and chemical conditions of the spring water and surrounding environment, as well as mineralogical and isotopic signatures, argue for biologically mediated redox reactions controlling sulfur. Cell counts and DNA analyses, confirm bacteria are present in the spring system.

2025, Arctic Net

Seabirds can be used as as proxies for marine food web because they are better samplers than humans and range from apex predators at the top of the food web. They are both Apex Predators - and eat fish from the top of the food web, and are also lower on food web- and eat small zooplankton. Their habitat is Nearshore to Pelagic and their foraging behavior ranges from Surface feeders to Plunge-divers to Pursuit divers.

2025, The 27th International Ocean and Polar Engineering Conference

2025, JAWRA Journal of the American Water Resources Association

We examined the effect of instream large wood on denitrification capacity in two contrasting, lower order streams — one that drains an agricultural watershed with no riparian forest and minimal stores of instream large wood and another that drains a forested watershed with an extensive riparian forest and abundant instream large wood. We incubated two types of wood substrates (fresh wood blocks and extant streambed wood) and an artificial stone substrate for nine weeks in each stream. After in situ incubation, we collected the substrates and their attached biofilms and established laboratory‐based mesocosm assays with stream water amended with 15N‐labeled nitrate‐N. Wood substrates at the forested site had significantly higher denitrification than wood substrates from the agricultural site and artificial stone substrates from either site. Nitrate‐N removal rates were markedly higher on woody substrates compared to artificial stones at both sites. Nitrate‐N removal rates were signifi...

2025, 2015 AGU Fall Meeting

Climate-induced changes in vegetation phenology at northern latitudes are still poorly understood. Continued monitoring and research are therefore needed to improve the understanding of abiotic drivers. Here we used 14 years of time lapse imagery and climate data from high-Arctic Northeast Greenland to assess the seasonal response of a dwarf shrub heath, grassland, and fen, to inter-annual variation in snow-cover, soil moisture, and air and soil temperatures. A late snow melt and start of growing season is counterbalanced by a fast greenup and a tendency to higher peak greenness values. Snow water equivalents and soil moisture explained up to 77 % of growing season duration and senescence phase, highlighting that water availability is a prominent driver in the heath site, rather than temperatures. We found a significant advance in the start of spring by 10 days and in the end of fall by 11 days, resulting in an unchanged growing season length. Vegetation greenness, derived from the imagery, was correlated to primary productivity, showing that the imagery holds valuable information on vegetation productivity.

2025, Freshwater Biology

1. Oligotrophic Arctic streams are likely to be sensitive to changes in hydrology and nutrient inputs predicted to occur as a consequence of future climate and land use change. To investigate the potential consequences of nutrient enrichment for low-order Arctic streams, we added ammonium-N and phosphorous to a second-order beaded, tundra stream on Alaska's north slope. We measured responses in nutrient chemistry, chlorophyll a standing crop, and in the breakdown and macroinvertebrate colonisation of leaf litter over a 38-day summer period. 2. During the addition, nutrient concentrations immediately downstream of the dripper averaged 6.4 lM M ammonium-N and 0.45 lM M soluble reactive P. Concentrations upstream of the dripper averaged 0.54 lM M ammonium-N and 0.03 lM M soluble reactive P. Uptake of both nutrients was rapid. Concentrations were reduced on average to 28% (ammonium-N) and 15% (inorganic P) of maximum values within 1500 m. Standing crops of chlorophyll a on standardised samplers were significantly higher by the end of the experiment. Breakdown rates of senescent willow (Salix sp.) and sedge (Carex sp.) litter and associated fungal biomass were also significantly increased by nutrient addition. 3. Fertilisation resulted in four-to sevenfold higher macroinvertebrate abundance and twoto fourfold higher macroinvertebrate biomass in litter bags, as well as an increase in latesummer body mass of larval Nemoura stoneflies. 4. Our results are consistent with those of similar studies of larger streams in the high-Arctic region. Based on our short-term experiment, increased inputs of nutrients into these ecosystems, whether caused by climate change or more local disturbance, are likely to have profound ecological consequences. Longer-term effects of enrichment, and their interaction with other components of future change in climate or land use, are more difficult to assess.

2025, Journal of Glaciology

Uncertainties in estimates of glacier and ice-cap contribution to sea-level rise exist in part due to poor quantification of mass-balance errors, particularly those resulting from extrapolation of sparse measurements. Centre-line data are often assumed to be representative of the glacier as a whole, with little attention paid to extrapolation errors or their effect on mass-balance estimates. Here we present detailed digital elevation model (DEM) measurements of glacier-wide elevation changes over the last $40 years at two glaciers on Svalbard, Norwegian Arctic. Austre Brøggerbreen and Midtre Love ´nbreen are shown to have lost 27.54 AE 0.98 and 9.65 AE 0.76 Â 10 7 m 3 of ice, respectively, between 1966 and 2005, findings that we relate to trends in average summer air temperatures and winter accumulation. These volume losses correspond to geodetic balances of -0.58 AE 0.03 and -0.41 AE 0.03 m w.e. a -1 , respectively. Our analysis revealed high spatial complexity in patterns of elevation change, varying between glaciers, between measurement intervals and within and between elevation bins. Balances from extrapolated centre-line geodetic data were the same (within errors) as those from full-coverage DEM differencing in the majority of comparisons, yet significantly underestimated balance in three instances. Additionally, field mass balance from centre-line ablation stake data underestimated balances from full-coverage geodetic measurements during three of six measurement periods. These findings may support the hypothesis that field measurements underestimate Svalbard glacier mass loss, at least partly as a result of the failure of centre-line measurements to account for glacier-wide variations in ablation. Our results demonstrate the importance of deriving accurate interpolation functions and constraining extrapolation errors from sparse measurements.

2025, Scientific Reports

Land surface temperature (LST) is a preeminent state variable that controls the energy and water exchange between the Earth’s surface and the atmosphere. At the landscape-scale, LST is derived from thermal infrared radiance measured using space-borne radiometers. In contrast, plot-scale LST estimation at flux tower sites is commonly based on the inversion of upwelling longwave radiation captured by tower-mounted radiometers, whereas the role of the downwelling longwave radiation component is often ignored. We found that neglecting the reflected downwelling longwave radiation leads not only to substantial bias in plot-scale LST estimation, but also have important implications for the estimation of surface emissivity on which LST is co-dependent. The present study proposes a novel method for simultaneous estimation of LST and emissivity at the plot-scale and addresses in detail the consequences of omitting down-welling longwave radiation as frequently done in the literature. Our analy...

2025, Polar Biology

Long-term change in benthic community structure may have significant impact on ecosystem functions. Accelerating climate change and increased human activity in the Arctic suggest that benthic communities in this region may be expected to exhibit change over time scales coinciding with these potential stressors. In 2000 and 2001, we resampled the softsediment communities of van Mijenfjord, a semi-closed (silled) fjord system on the west coast of Spitsbergen, following initial surveys in 1980. Multivariate community analyses and biodiversity indices identified distinct regions within the fjord. The communities characteristic of two regions were very similar to those sampled 20 years earlier. Regions corresponded with fjord basins and to community patterns and diversity gradients identified for many other Arctic fjords. Benthic communities in open (unsilled) fjords in the area have recently been shown to respond to decadal scale climatic fluctuation. We suggest that semi-closed fjords may be less susceptible to this type of environmental variability, and that communities are shaped by an interaction of impacts from local topography, glacial runoff, local circulation patterns, and faunal life-history traits. Open and closed fjords may respond to climatic warming trends in different ways, resulting in a subsequent divergence in spatial patterns of resident communities.

2025, Behavioral Ecology

In most monogamous sandpiper species, females share parental care but leave the brood earlier than males, a feature unusual among birds in general. In the purple sandpiper (Calidris maritima), females almost always leave the brood at hatching and never share brood care. Males perform uniparental brood care from hatching until well after fledging. In this paper, we report the results of a mate-removal experiment conducted on the purple sandpiper in high Arctic Svalbard and discuss the implications for the evolution of their mate desertion strategy. By removing males from nests near hatching, we tested 2 hypotheses: 1) Males assume brood care because females, who always have a net benefit from deserting, have a fixed brood desertion strategy, whereas males do not; 2) females desert the brood because they cannot perform uniparental brood care as well as males and/or because they are under physiological stress at hatching due to egg laying and incubation activities hypothesis). We found that when experimentally deserted, most female purple sandpipers assumed brood care. Parental behavior and the growth and survival of the chicks suggested that the attending females were not under physiological stress after hatching and did not seem less able than males to perform brood care. Thus, we found no support for either hypothesis. We suggest that uniparental brood desertion is a consequence of strong selection for uniparental brood care in this species and that the actual sex roles may result from rather marginal differences between the sexes in the fitness consequences of care and desertion.

2025, Space Weather

A rapid signal-fading event produced by diffractive scintillations was observed around 0123 UT on 8 November 2004 by three closely sited (less than 250 m apart) GPS scintillation receivers in northern Norway. The entire duration of the event was about 10 s and was recorded by all three receivers. Intense, short duration events such as these are not clearly observable in the 1-min scintillation index (S4) because they do not necessarily last for the entire minute. In spite of their short duration they can cause a receiver to lose lock because of their intensity. The geomagnetic conditions were disturbed at this time with the interplanetary magnetic field southward for a period of several hours. Magnetometers from the IMAGE network in Scandinavia showed evidence of a 2000 nT substorm. The GPS measurements are compared with all-sky camera (ASC) data to show that the signal fades can be attributed to the GPS ray paths crossing electron density structures associated with the aurora. The ASC images reveal moving auroral structures at the same time as the GPS signals show movement of the ionospheric regions causing fading. The results indicate that at high latitudes low-elevation GPS signals can suffer sudden fading due to E-region auroral events. This is the first time that a direct connection has been established between the loss of lock on a GPS receiver and diffractive fading caused by auroral precipitation.

2025, The ISME Journal

We report the first microbiological characterization of a terrestrial methane seep in a cryoenvironment in the form of an Arctic hypersaline (B24% salinity), subzero (À5 1C), perennial spring, arising through thick permafrost in an area with an average annual air temperature of À15 1C. Bacterial and archaeal 16S rRNA gene clone libraries indicated a relatively low diversity of phylotypes within the spring sediment (Shannon index values of 1.65 and 1.39, respectively). Bacterial phylotypes were related to microorganisms such as Loktanella, Gillisia, Halomonas and Marinobacter spp. previously recovered from cold, saline habitats. A proportion of the bacterial phylotypes were cultured, including Marinobacter and Halomonas, with all isolates capable of growth at the in situ temperature (À5 1C). Archaeal phylotypes were related to signatures from hypersaline deep-sea methane-seep sediments and were dominated by the anaerobic methane group 1a (ANME-1a) clade of anaerobic methane oxidizing archaea. CARD-FISH analyses indicated that cells within the spring sediment consisted of B84.0% bacterial and 3.8% archaeal cells with ANME-1 cells accounting for most of the archaeal cells. The major gas discharging from the spring was methane (B50%) with the low CH 4 /C 2 þ ratio and hydrogen and carbon isotope signatures consistent with a thermogenic origin of the methane. Overall, this hypersaline, subzero environment supports a viable microbial community capable of activity at in situ temperature and where methane may behave as an energy and carbon source for sustaining anaerobic oxidation of methane-based microbial metabolism. This site also provides a model of how a methane seep can form in a cryoenvironment as well as a mechanism for the hypothesized Martian methane plumes.

2025, Open Journal of Applied Sciences

2025, Geomorphology

In ice-cored landform assemblages, the process of resedimentation via sediment-flow is important in determining the morphology and sedimentary facies distribution after the ice core has melted. This paper documents the sediment-flow processes associated with the resedimentation of an ice-cored lateral moraine at Kongsvegen, Svalbard. Decay of the ice-cored lateral moraine is dominated by the development of a sediment-flow fan, which has an 'hour-glass' form in plan. The fan comprises a broad source area on the crest of the lateral moraine separated from the fan surface, composed of tessellated flow lobes, by a narrow ice-floored channel system. The principle sedimentary facies associated with this fan include matrix-supported diamictons, laminated silts and fine sands. The evolution of this fan and the likely end-products after complete deglaciation are discussed, and this paper contributes modern analogue data relevant to the interpretation of the Pleistocene landform and sediment record.

2025, Boreas

Although eskers are frequently described glaciofluvial landforms, they are poorly understood. To assist with the interpretation of Pleistocene examples, modern analogue data are required. This paper documents the morphology, sedimentology and formation of a 650 m long esker system in front of the high‐arctic glacier Vegbreen in Svalbard. The esker is located between the Neoglacial maximum and the present ice front and appears to have formed both as a supraglacial trough‐fill and as a channel/conduit‐fill along the suture formed by two confluent glacier lobes. A range of sedimentary facies is preserved within this ridge system providing evidence for braided rivers, ephemeral lakes, episodic flow regimes and sediment gravity flows. This case study provides an important analogue for glaciofluvial sedimentation between retreating ice lobes.

2025, Polar Record

Evidence from colony surveys and local Inuit knowledge strongly suggest that the Canadian population of ivory gulls (Pagophila eburnea) has declined dramatically. The observations of ivory gulls at sea presented here are consistent with this. Ivory gulls were observed during two cruises on the Russian icebreaker Kapitan Khlebnikov in the eastern Canadian high Arctic in August 1993 and 2002. Ivory gulls were seen 3.5 times more often in 1993 (n = 176) than in 2002 (n = 149), and, corrected for observation effort, four times more ivory gulls were seen in 1993 than in 2002. Ivory gulls are scavengers: they were never observed feeding on fish behind the vessel while ice-breaking, although black-legged kittiwakes (Rissa tridactyla) often were seen feeding in this way. Ivory gulls were observed scavenging around polar-bear (Ursus maritimus) kills in 1993 but not in 2002. By far the largest number of ivory gulls was seen near Grise Fiord in 1993. There, opportunities for them to scavenge w...

2025, Cryobiology

The freeze tolerance and accumulation of cryoprotectants was investigated in three geographically different populations of the enchytraeid Enchytraeus albidus (Oligochaeta). E. albidus is widely distributed from the high Arctic to temperate Western Europe. Our results show that E. albidus is freeze tolerant, with freeze tolerance varying extensively between Greenlandic and European populations. Two populations from sub Arctic (Nuuk) and high Arctic Greenland (Zackenberg) survived freezing at À15 °C, whereas only 30% of a German population survived this temperature. When frozen, E. albidus responded by catabolising glycogen to glucose, which likely acted as a cryoprotectant. The average glucose concentrations were similar in the three populations when worms were frozen at À2 °C, approximately 50 lg glucose mg À1 tissue dry weight (DW). At À14 °C the glucose concentrations increased to between 110 and 170 lg mg À1 DW in worms from Greenland. The average glycogen content of worms from Zackenberg and Nuuk were about 300 lg mg À1 DW, but only 230 lg mg À1 DW in worms from Germany showing that not all glycogen was catabolised during the experiment. Nuclear magnetic resonance spectrometry (NMR) was used to screen for other putative cryoprotectants. Proline, glutamine and alanine were up regulated in frozen worms at À2 °C but only in relatively small concentrations suggesting that they were of little significance for freeze survival. The present study confirms earlier reports that freeze tolerant enchytraeids, like other freeze tolerant oligochaete earthworms, accumulate high concentrations of glucose as a primary cryoprotectant.

2025, FEMS Microbiology Ecology

The impacts of simulated climate change (warming and fertilization treatments) on diazotroph community structure and activity were investigated at Alexandra Fiord, Ellesmere Island, Canada. Open Top Chambers, which increased growing season temperatures by 1-3 °C, were randomly placed in a dwarf-shrub and cushion-plant dominated mesic tundra site in 1995. In 2000 and 2001 20N:20P 2 O 5 :20K 2 O fertilizer was applied at a rate of 5 g m À2 year À1 . Estimates of nitrogen fixation rates were made in the field by acetylene reduction assays (ARA). Higher rates of N fixation were observed 19-35 days post-fertilization but were otherwise unaffected by treatments. However, moss cover was significantly positively associated with ARA rate. NifH gene variants were amplified from bulk soil DNA and analyzed by terminal restriction fragment length polymorphism analysis. Non-metric multidimensional scaling was used to ordinate treatment plots in nifH genotype space. NifH gene communities were more strongly structured by the warming treatment late in the growing season, suggesting that an annual succession in diazotroph community composition occurs.

2024

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2024, Journal of Geophysical Research

2024, Proceedings of the …

A common problem for avalanche-prone areas subject to forecasting and control responsibility is the identification of a set of critical meteorological parameters. While storm snowfall and snowfall intensity are generally accepted as among the most important, the complex interplay between terrain, wind, temperature, solar radiation and other meteorological variables makes identifying the next most important parameters difficult Classification tree methodology is introduced as a potential tool for identifying critical meteorological parameters associated with avalanche and control activities. The application of this methodology is described in the context of exploring a subset of the Mammoth Mountain avalanche and meteorology data base. The meteorological parameters most important to avalanche occurrence in two-years of data were identified from a set of thirteen variables from one observation site. It is shown how this information could be used to provide inputs to forecasting programs and guidance in establishing observation priorities.

2024

2024, 2002 International Snow Science Workshop Penticton British Columbia

Decision tree models of maximum avalanche size class run daily at Mammoth Mountain, California. A classification tree grown on an eight-year subset of all weather and avalanche records shows an absolute accuracy on avalanche control days of from about 60-70% in a given year; accepting overestimates increases this to 70-80%. Errors arise from the rarity of large events, exclusion of the smallest most frequent events, and tree sensitivity to small changes in key predictor variables. A complete 19-year data set yields a pair of decision trees forecasting both maximum size class and maximum crown size over the entire mountain. Tested against a twentieth year, the size class tree may be more accurate for extreme events but performed slightly worse overall than the original tree. Coupling the size class and crown trees identified both class 5 avalanches during the test year. A third set of trees, driven by hourly data from a remote instrument network, distributes maximum class and crown sizes over geographic sub-regions of the mountain. These are striking for both small size and low misclassification rate. Ifa major source of error is chaotic avalanche behavior, decision trees may prove most valuable for providing probability estimates from given sets of initial conditions.

2024, Open Journal of Soil Science

In this study, we determine differences in total biomass of soil microorganisms and community structure (using the most probable number of bacteria (MPN) and the number of fungal genera) in patterned ground features (PGF) and adjacent vegetated soils (AVS) in mesic sites from three High Arctic islands in order to characterize microbial dynamics as affected by cryoturbation, and a broad bioclimatic gradient. We also characterize total biomass of soil microorganisms and the most probable number of bacteria along a topographic gradient within each bioclimatic subzone to evaluate whether differences in topography lead to differences in microbial dynamics at a smaller scale. We found total microbial biomass C, the most probable number of heterotrophic bacteria, and fungal genera vary along this bioclimatic gradient. Microbial biomass C decreased with increasing latitude. Overall, microbial biomass C, MPN and the number of fungal isolates were higher in AVS than in PGFs. The effects which topographic position had on microbial biomass C varied across the bioclimatic gradient as there was no effect of topographic position in Isachsen (subzone A) and Mould Bay (subzone B), when compared to Green Cabin (subzone C, warmer site).There was no effect of topographic position on MPN counts at Mould Bay and Green Cabin. However, in Isachsen, MPN counts were highest in the wet topographic position as compared to the mesic and dry. In conclusion, PGFs seem to decouple the effect climate that might have on the total biomass of soil microorganisms along the bioclimatic gradient; and influence gets ameliorated as latitude increases. Similarly, the effect of topography on the total microbial biomass is significant at the warmest bioclimatic zone of the gradient. Thus, climate and topographic effects on total microbial biomass increase with warmer climate.

2024, Lichenologist

Lichens of the most highly stressful habitats in Sverdrup Pass, Ellesmere Island, Northwest Territories, Canada, were examined for reproductive structures, as were lichens of less extreme sites within the same landform features. The study areas included twenty-two stands in a calcareous erosional mountain system and two microhabitats within the ablation zone of a valley glacier. In the most limited stands in the erosional mountains 83% of the lichens were apotheciate species and 93% of these were represented by specimens bearing apothecia. On stressful rock surfaces in the glacier fellfield most species also produced sexual fruiting bodies.

2024, EGU General Assembly Conference Abstracts

Sunlit snow is increasingly recognized as a chemical reactor that plays an active role in uptake, transformation, and release of atmospheric trace gases. Snow is known to influence boundary layer air on a local scale, and given the large global surface coverage of snow may also be significant on regional and global scales. We present a new detailed one-dimensional snow chemistry module that has been coupled to the 1-D atmospheric boundary layer model MISTRA. The new 1-D snow module, which is dynamically coupled to the overlaying atmospheric model, includes heat transport in the snowpack, molecular diffusion, and wind pumping of gases in the interstitial air. The model includes gas phase chemical reactions both in the interstitial air and the atmosphere. Heterogeneous and multiphase chemistry on atmospheric aerosol is considered explicitly. The chemical interaction of interstitial air with snow grains is simulated assuming chemistry in a liquid-like layer (LLL) on the grain surface. The coupled model, referred to as MISTRA-SNOW, was used to investigate snow as the source of nitrogen oxides (NO x) and gas phase reactive bromine in the atmospheric boundary layer in the remote snow covered Arctic (over the Greenland ice sheet) as well as to investigate the link between halogen cycling and ozone depletion that has been observed in interstitial air. The model is validated using data taken 10 June

2024

We present possible analogs for small valleys on Mars found at the Haughton impact crater site, Devon Island, NWT, Canada. Implications for Early Mars climate are discussed.

2024, Journal of Atmospheric and Oceanic Technology

A multispectral scanning spectrometer was used to obtain measurements of the bidirectional reflectance and brightness temperature of clouds, sea ice, snow, and tundra surfaces at 50 discrete wavelengths between 0.47 and 14.0 m. These observations were obtained from the NASA ER-2 aircraft as part of the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE) Arctic Clouds Experiment, conducted over a 1600 km ϫ 500 km region of the north slope of Alaska and surrounding Beaufort and Chukchi Seas between 18 May and 6 June 1998. Multispectral images in eight distinct bands of the Moderate Resolution Imaging Spectroradiometer (MODIS) Airborne Simulator (MAS) were used to derive a confidence in clear sky (or alternatively the probability of cloud) over five different ecosystems. Based on the results of individual tests run as part of this cloud mask, an algorithm was developed to estimate the phase of the clouds (liquid water, ice, or undetermined phase). Finally, the cloud optical thickness and effective radius were derived for both water and ice clouds that were detected during one flight line on 4 June. This analysis shows that the cloud mask developed for operational use on MODIS, and tested using MAS data in Alaska, is quite capable of distinguishing clouds from bright sea ice surfaces during daytime conditions in the high Arctic. Results of individual tests, however, make it difficult to distinguish ice clouds over snow and sea ice surfaces, so additional tests were added to enhance the confidence in the thermodynamic phase of clouds over the Chukchi Sea. The cloud optical thickness and effective radius retrievals used three distinct bands of the MAS, with a recently developed 1.62-and 2.13-m-band algorithm being used quite successfully over snow and sea ice surfaces. These results are contrasted with a MODIS-based algorithm that relies on spectral reflectance at 0.87 and 2.13 m.

2024, Journal of Atmospheric and Oceanic Technology

A multispectral scanning spectrometer was used to obtain measurements of the reflection function and brightness temperature of clouds, sea ice, snow, and tundra surfaces at 50 discrete wavelengths between 0.47 and 14.0 pm. These observations were obtained from the NASA ER-2 aircraft as part of the FIRE Arctic Clouds Experiment, conducted over a 1600 x 500 km region of the north slope of Alaska and surrounding Beaufort and Chukchi Seas between 18 May and 6 June 1998. Multispectral images of the reflection function and brightness temperature in 11 distinct bands of the MODIS Airborne Simulator (MAS) were used to derive a confidence in clear sky (or alternatively the probability of cloud), shadow, and heavy aerosol over five different ecosystems. Based on the results of individual tests run as part of the cloud mask, an algorithm was developed to estimate the phase of the clouds (water, ice, or undetermined phase). Finally, the cloud optical thickness and effective radius were derived for both water and ice clouds that were detected during one flight line on 4 June. This analysis shows that the cloud mask developed for operational use on MODIS, and tested using MAS data in Alaska, is quite capable of distinguishing clouds from bright sea ice surfaces during daytime conditions in the high Arctic. Results of individual tests, however, make it difficult to distinguish ice clouds over snow and sea ice surfaces, so additional tests were added to enhance the confidence in the thermodynamic phase of clouds over the Beaufort Sea. The cloud optical thickness and effective radius retrievals used 3 distinct bands of the MAS, with the newly developed 1.62 and 2.13 pm bands being used quite successfully over snow and sea ice surfaces. These results are contrasted with a MODIS-based algorithm that relies on spectral reflectance at 0.87 and 2.13 pm.

2024, European geosciences union general assembly

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Assessing proglacial sediment sources evolution of three catchments using the index of connectivity (IC), Plan de l’Aiguille, Chamonix, France. Johan Berthet, Laurent Astrade

2024

Ledeniški psevdokras je skupek procesov, katerih rezultat so značilne površinske oblike in jame v ledenikih. Za ledeniški psevdokras je značilen grbinasti relief z jezeri in kanali v notranjosti ledenika in ob stiku led-kamnina. Procesi, ki ustvarjajo ledeniški psevdokras in kras v karbonatih in evaporitih se razlikujejo, vendar so oblike, ki nastajajo v obeh sistemih, podobne. Procesi v ledu so hitri, zato je ledeniški psevdokras lahko primeren fizični model krasa v apnencu. Po drugi strani lahko s poznavanjem krasa v apnencih bolje razumemo ledeniški psevdokras. Seveda govorimo le o splošni podobnosti med fenomeni, medtem ko se oba tipa "krasa" v podrobnostih razlikujeta. Stopnje razvoja ledeniškega psevdokrasa se ujemajo s stopnjami rasvoja v apnenčastem krasu. Zaradi gibanja ledenika lahko razvojne stopnje ledeniškega psevdokrasa spremljamo vdolž ledenika, od jezika do ablacijske cone. Ledeniški psevdokras je razširjen v ledenikih zmerne klime (temperate glaciers) in v politermalnih ledenikih. ključne besede: ledeniška hidrologija, pokriti ledenik, ledeniški psevdokras, notranji drenažni sistem, podobnost glacialnega in apniškega krasa. *Author uses the term Glacial karst, which denotes features on the glacier surface and inside the glacier that result from the melting of ice. Other terms are used for his phenomena, like glacier pseudokarst (see John Gunn (ed.), Encyclopedia of Caves and Karst, fitzroy Dearborn, 2004) COBISS: 1.01

2024

We already wrote about internal drainage systems of glaciers (Mavlyudov, 2006, 2007a). These works were based both on our own investigations and on studying of glacial caves by other groups of researchers (

2024, Oecologia

Environmental constraints on the growth, photosynthesis and reproductive development of Dryas octopetala at a high Arctic polar semi-desert, Svalbard

2024, Oecologia

Integrative ecophysiological and vegetative responses of Dryas octopetala were measured in response to field perturbations of temperature, precipitation and their interactions in a polar semi-desert in Svalbard, Norway (79~ 12~ Leaf carbon isotope discrimination (A), total leaf nitrogen concentration and leaf development were determined for photosynthetic leaves collected during the last week of August 1991, after one season of manipulations. Individual leaf weight and the total mass of leaf tissue were significantly lower when water was added, irrespective of temperature regime. Leaf carbon isotope discrimination and estimated longterm ci/ca values (the ratio of CO2 concentration in leaf intercellular spaces to that in the atmosphere) were significantly higher under all three field manipulation treatments, and A was significantly reduced when Dryas was grown under drought conditions in a related greenhouse study. Nitrogen concentrations of plants from the field experiment were significantly lower under warmed conditions regardless of water regime. Our results indicate that changes in environmental conditions in high arctic settings will result in alterations of Dryas leaf gas exchange, as expressed by increases in carbon isotope discrimination, which may be accompanied by shifts in leaf nitrogen content and leaf biomass.

2024, Journal of Climate

The impact of Arctic sea ice concentrations, surface albedo, cloud fraction, and cloud ice and liquid water paths on the surface shortwave (SW) radiation budget is analyzed in the twentieth-century simulations of three coupled models participating in the Intergovernmental Panel on Climate Change Fourth Assessment Report. The models are the Goddard Institute for Space Studies Model E-R (GISS-ER), the Met Office Third Hadley Centre Coupled Ocean–Atmosphere GCM (UKMO HadCM3), and the National Center for Atmosphere Research Community Climate System Model, version 3 (NCAR CCSM3). In agreement with observations, the models all have high Arctic mean cloud fractions in summer; however, large differences are found in the cloud ice and liquid water contents. The simulated Arctic clouds of CCSM3 have the highest liquid water content, greatly exceeding the values observed during the Surface Heat Budget of the Arctic Ocean (SHEBA) campaign. Both GISS-ER and HadCM3 lack liquid water and have exce...

2024, Molecular Ecology

Population structure and phylogeography of the pink-footed goose, Anser brachyrhynchus Baillon 1833, was studied using mtDNA control region sequences (221 bp) from 142 individuals. Present breeding areas of the species in Greenland, Iceland, and Svalbard were largely covered by ice during the late Pleistocene. In pairwise comparisons φ φ φ φ ST estimates showed significant differentiation among eastern and western populations, whereas sampling localities within both areas were not differentiated. The mtDNA data indicate that the populations have separated recently (less than 10 000 years ago) and present breeding areas were colonized from one refugial population. The levels of haplotype and nucleotide diversity were approximately five times higher for the eastern population compared to the western population and suggest that the latter was colonized by a subset of eastern birds. Time to the most recent common ancestor of the species is 32 000-46 000 years, i.e. the present mtDNA variation of the pink-footed goose has accumulated during the last 0.1 My. Estimates of the long-term female effective population size (5400-7700 for the eastern population) imply that the refugial population of the pink-footed goose has been large. Tundra habitats were more extensive in cold periods of the late Pleistocene than today and may have sustained population sizes that allowed the accumulation of extant genetic polymorphism. It is not probable that the postulated small refugial areas in the high latitudes had a significant role in maintaining this diversity.

2024, The ISME Journal

Arctic air temperatures are expected to rise significantly over the next century. Experimental warming of arctic tundra has been shown to increase plant productivity and cause community shifts and may also alter microbial community structure. Hence, the objective of this study was to determine whether experimental warming caused shifts in soil microbial communities by measuring changes in the frequency, relative abundance and/or richness of nosZ and nifH genotypes. Five sites at a high arctic coastal lowland were subjected to a 13-year warming experiment using open-top chambers (OTCs). Sites differed by dominant plant community, soil parent material and/or moisture regimen. Six soil cores were collected from each of four replicate OTC and ambient plots at each site and subdivided into upper and lower samples. Differences in frequency and relative abundance of terminal restriction fragments were assessed graphically by two-way cluster analysis and tested statistically with permutational multivariate analysis of variance (ANOVA). Genotypic richness was compared using factorial ANOVA. The genotype frequency, relative abundance and genotype richness of both nosZ and nifH communities differed significantly by site, and by OTC treatment and/or depth at some sites. The site that showed the most pronounced treatment effect was a wet sedge meadow, where community structure and genotype richness of both nosZ and nifH were significantly affected by warming. Although warming was an important factor affecting these communities at some sites at this high arctic lowland, overall, site factors were the main determinants of community structure.

2024, Hydrological Processes

Field campaigns were undertaken in May and June of 1992 and 1997 in order to study spectral re¯ectance characteristics of snow during melt-o. The investigations were performed on snow-covered tundra at Ny-A Ê lesund, Svalbard (798N). Spectral measurements were acquired with spectroradiometers covering wavelengths from 350 to 2500 nm. Supporting measurements such as snow thickness, density, content of liquid water, grain size and shape, strati®cation of snowpack, as well as cloud observations and air temperature, were monitored throughout the ®eld campaigns. Spectral measurements demonstrate that the near-infrared albedo is most aected by the ongoing snow metamorphism while the albedo in the visible wavelength range is more strongly aected by surface pollution. Comparisons of spectral measurements and spectrally integrated measurements emphasize the need for narrow-band to broad-band conversion when applying satellite-derived albedo to surface energy-balance calculations. As an example, Landsat TM Band 4 albedo is shown to produce slightly high albedo values compared to the spectrally integrated albedo (285±2800 nm). Daily albedo measurements from 1981±1997 show that the albedo normally drops from 80% to bare ground levels ($10%) within two to four weeks and the date when the tundra becomes snow-free varies from early June to early July. Thus, the changing spectral characteristics of snow during melt-o combined with a general rapid decrease in albedo call for cautious use of satellite-derived albedo, especially when used as absolute numbers. Our data also illustrate the eect of cloud cover on surface albedo for an event in which the integrated albedo increased by 7% under cloudy conditions compared to clear skies without changes of surface properties. Finally, the re¯ectance of snow increases relative to nadir for measurements facing the sun and at azimuths 908 and 1808