Stable hydrogen and oxygen isotope ratios (δD and δ¹⁸O) of archived plant tissues can be used in paleoenvironmental reconstructions, assuming a well-grounded understanding of the environmental drivers of stable isotope variation in plant waters. Previous plant water calibration studies have focused on lower latitudes, but given the importance of arctic climate reconstructions, it is necessary to understand the drivers of isotope fractionation in plants that are unique to high latitudes. Here, we present δD and δ¹⁸O values of plant waters from the Kangerlussuaq area in West Greenland. We use the evaporation line created by the xylem waters to estimate the hydrogen and oxygen isotope values of local meteoric source water and find values that are lower than modeled estimates. We also apply the modified Craig-Gordon leaf water model, using local climate parameters and xylem water values to model leaf water values. We find that measured plant water values are generally in good agreement with model estimates, and discrepancies are likely explained by plant microclimates that are warmer and drier than average air measurements. This study extends stable isotope calibrations to arctic regions and provides a new estimate of average precipitation water isotopes values, which in turn inform plant proxy-based paleoclimate studies in the Arctic.

Climate change has been reported to affect shrub growth positively at several sites at high northern latitudes, including several arctic environments. The observed growth rates are, however, not uniform in space and time, and the mechanistic drivers of these patterns remain poorly understood. Here we investigated spatio-temporal interactions between climatic conditions, xylem anatomical traits, and annual growth of 21 Betula nana L. individuals from western Greenland for the period 2001–2011. Structural equation modeling showed that summer precipitation and winter temperature are affecting annual growth positively. Furthermore, vessel lumen area and vessel grouping, which are related to water conductivity and hydraulic connectivity of the xylem, respectively, positively influenced annual growth. To optimize growth B. nana was thus able to adjust its water transporting system. Annual variation in vessel lumen area seemed to be driven mostly by spring and summer temperatures, whereas annual variation in vessel grouping was driven by winter temperature. Linear models did not reveal a pattern in the spatial variation of xylem anatomical traits across the sampled climatic gradient. However, growth was positively correlated with local variation in insolation. Our results suggest that B. nana can adjust its hydraulic capacity to annual fluctuations in climatic conditions in order to optimize its total radial stem growth rate.

Process analysis and hazard prediction are essential for the prevention and mitigation of debris-flow hazards in mountainous areas. Many villages and ongoing infrastructure projects in China are vulnerable to large debris flows during heavy rainfall or glacier lake outbursts. Without emergency management planning, such contingencies can lead to extensive loss of life and egregious property damage. In the eastern Qinghai-Tibet Plateau area, debris-flow disasters are a common phenomenon. Taking Ridi Gully in the Sichuan Province of China as a case study, we analyzed the process of debris-flow events by running a dynamic erosion model. Because of the dynamic nature of the process, we needed to take into account many variables. Some of these variables include strong erosion in the origin area, scouring and downward erosion in debris-flow path, and siltation in accumulation area. Subsequently, we analyzed the elements underlying the hazard formation conditions and proposed a systematic and quantitative method of debris-flow hazard prediction based on kinetic energy and flow depth. Finally, we predicted the hazard and damage potential induced by the debris flow triggered by a 100-year and 200-year return period precipitation in Ridi Gully. The simulation results indicate that debris flow will cause great damage to the Sichuan-Tibet railway (or highway) and the residential area on the alluvial fan. This strongly suggests that, given the high level of debris-flow hazard predicted, the proposed method may serve as pertinent and timely support in planning measures to prevent or reduce the debris-flow hazard, both in the eastern Qinghai-Tibet Plateau area and beyond.

A comprehensive mid-20th century inventory of glaciers and perennial snowfields (G&PS) was compiled for the American West, west of the 100° meridian. The inventory was derived from U.S. Geological Survey 1:24,000 topographic maps based on aerial photographs acquired during 35 years, 1955–1990, of which the first 20 years or more was a cool period with little glacier change. The mapped features were filtered for those greater than 0.01 km². Results show that 5036 G&PS (672 km², 14 km³) populate eight states, of which about 1276 (554 km², 12 km³) are glaciers. Uncertainty is estimated at ±9% for area and ±20% for volume. Two populations of G&PS were identified based on air temperature and precipitation. The larger is found in a maritime climate of the Pacific Northwest, characterized by warm winter air temperatures and high winter precipitation (~2100 mm). The other population is continental in climate, characterized by cold winter air temperatures, relatively low winter precipitation (~880 mm), and located at higher elevations elsewhere. The G&PS in the Pacific Northwest, especially in the Olympic Mountains, are particularly vulnerable to warming winter air temperatures that will change the phase of winter precipitation from snow to rain, further accelerating glacier shrinkage in the future. Comparison with a recent inventory suggests that the total G&PS area in the American West may have decreased by as much as 39% since the mid-20th century.

Glaciers in the Arctic are losing mass at an increasing rate. Here we use surface topography derived from Structure from Motion (SfM) and ice volume from ground penetrating radar (GPR) to describe the 2014 state of Aqqutikitsoq glacier (2.85 km²) on Greenland's west coast. A photogrammetrically derived 1985 digital elevation model (DEM) was subtracted from a 2014 DEM obtained using land-based SfM to calculate geodetic glacier mass balance. Furthermore, a detailed 2014 ground penetrating radar survey was performed to assess ice volume. From 1985 to 2014, the glacier has lost 49.8 ± 9.4 10⁶ m³ of ice, corresponding to roughly a quarter of its 1985 volume (148.6 ± 47.6 10⁶ m³) and a thinning rate of 0.60 ± 0.11 m a^-1. The computations are challenged by a relatively large fraction of the 1985 DEM (∼50% of the glacier surface) being deemed unreliable owing to low contrast (snow cover) in the 1985 aerial photography. To address this issue, surface elevation in low contrast areas was measured manually at point locations and interpolated using a universal kriging approach. We conclude that ground-based SfM is well suited to establish high-quality DEMs of smaller glaciers. Provided favorable topography, the approach constitutes a viable alternative where the use of drones is not possible. Our investigations constitute the first glacier on Greenland's west coast where ice volume was determined and volume change calculated. The glacier's thinning rate is comparable to, for example, the Swiss Alps and underlines that arctic glaciers are subject to fast changes.

Glaciers are reservoirs of atmospherically deposited trace elements that are released during melt. Weathering in glacial environments also contributes solutes to proglacial streams. To investigate the relative importance of atmospheric deposition and weathering on trace element chemistry of glacial streams, we sampled supraglacial and proglacial meltwater at two glacierized catchments in Grand Teton National Park, Wyoming, which is located downwind of agricultural/industrial emissions and dust sources. Concentrations of major ions (Mg² , K , Na , Ca² , SO₄^2-), alkalinity, conductivity, and a subset of trace elements (U, Mo, Sr, Rb, Li, Ba) were low in supraglacial meltwater but increased in proglacial streams because of water-rock interactions. In contrast, concentrations of the trace metals Mn, Co, Zn, Pb, Cd, and Hg had relatively high concentrations in supraglacial meltwater and decreased downstream. These metals are not abundant in the local bedrock and thus are likely sourced from atmospheric deposition. Stable isotopes indicated different water sources in July (snowmelt-dominated) and August (ice melt-dominated), but water chemistry was similar during both months, indicating similar composition of recent snowfall and older ice. These findings have implications for evaluating the relative impacts of atmospheric deposition and weathering in glacier- and snow-dominated catchments.

Patterns of soil bacterial richness using operational taxonomic units (OTUs) and abundance of bacterial groups (phylum or class) were studied in relation to plant richness and soil characteristics in the alpine at Niwot Ridge, Colorado, U.S.A. The study used a landscape gradient and snow fence in addition to plots amended with nitrogen (N). Bacterial richness was not correlated with total soil carbon (C) or total soil N, but showed strong positive correlations with pH and corresponding correlations with metallic cation concentrations. Bacterial richness showed a strong negative correlation (r = -0.86) with soil acidity and declined 30% over the pH gradient of 6.0–4.5. Plant richness correlated with acidity (r = -0.70) and declined 50% over this gradient. Bacterial OTU richness was sensitive to acidity but not to N amendments. However, abundance of five bacterial groups responded positively to N, four responded negatively, and three groups exhibited no changes. In plots with additional snow, snow additions reduced OTU richness. However, when snow was included in an ANCOVA model with N and soil acidity, OTUs were not affected, suggesting that snow effects were largely captured by soil acidity changes. Bacterial richness was correlated with forb richness and cover, but causal relationships remain unresolved.

Active layer detachments (ALDs) are permafrost disturbances associated with climate change and increased seasonal warming. Such perturbations result from thawing of the upper permafrost and downslope movement of the overlying thawed material, including the active layer. ALDs have the potential to impact soil microbial community composition and function in arctic soil ecosystems. Here we report an initial investigation of an ALD located at Cape Bounty on Melville Island in the Canadian High Arctic. We examined soil nutrient content as well as microbial community structure using denaturing gradient gel electrophoresis and sequencing. Soil from the disturbed site showed changes in microbial communities with strikingly different fungal community composition compared to soils from an adjacent undisturbed site. These community changes were correlated with enhanced levels of dissolved organic carbon, microbial carbon, total dissolved nitrogen, and microbial nitrogen. The Nitrososphaerales—an order of ammonia-oxidizing Archaea—were more abundant in the disturbed soil and may have been responsible for the altered nitrogen cycling that resulted in higher levels of total dissolved nitrogen there. The fungal communities at both sites were dominated by orders within the Ascomycota, a phylum of mainly hyphal fungi. Intriguingly however, they were more numerous in the undisturbed soil compared to the disturbed soil, suggesting that certain Ascomycota could not reestablish within six years of the ALD, and more generally that fungal hyphal networks may help to stabilize tundra surface soils against erosional losses.

Periglacial processes are active under current climatic conditions on the more exposed peaks and ridges of Tasmania's high country. Non-sorted steps, stripes, and solifluction lobes with vegetated risers and bare treads have formed on many of the mountains capped in fissile sedimentary rocks. Any disturbance to the balance between vegetation and bare ground can result in biogeomorphic feedbacks leading to an increase or decrease in periglacial activity and thereby threaten the survival of fjaeldmark. We tested the hypotheses that vegetation helps create risers by capturing material moved by needle ice, water, and wind, and that the balance between vegetation and bare ground in fjaeldmark is dynamic in Tasmania at the decadal time scale. Repeat photo plots and temperature data loggers were employed to monitor the dynamism of two non-sorted lobes on Mount Rufus over a seven-month period. Diurnal freeze/thaw cycles resulted in needle ice formation on the bare treads and promoted downslope movement of the surface layer through frost creep. Vegetation was observed to reduce geomorphic activity and to capture soil and clasts transported downslope, thereby steepening the risers. Aerial photographic analysis showed a 0.065% per annum increase in vegetation cover in fjaeldmark since the mid-20th century. Mountains that had a high number of days with snow cover were especially prone to increases in vegetation cover. Decline in vegetation cover occurred on some mountains burned during the past century. The smallest changes occurred on the most exposed peaks and ridges.

Arctic ground squirrels (Urocitellus parryii) rely primarily on dietary protein derived from plants to fuel gluconeogenesis during hibernation, yet fungal sporocarps may be an important, yet overlooked, protein source. Fungivory levels depend on sporocarp productivity, which varies with the dominant plant species and is higher on acidic than on non-acidic soils. To test whether these factors altered fungal consumption, we used stable isotopes to investigate arctic ground squirrel diets at two sites in northern Alaska, Toolik (primarily moist acidic tundra) and Atigun (primarily moist non-acidic tundra). Radiocarbon estimates can also indicate fungivory levels because ectomycorrhizal fungi assimilate soil-derived organic nitrogen whose ¹⁴C levels are higher than current photosynthesis. We measured radiocarbon in hair and δ¹³C and δ¹⁵N in hair, feces, ectomycorrhizal sporocarps, graminoids, and dicots. Feces were higher in δ¹³C and δ¹⁵N at Toolik than at Atigun, and fecal δ¹⁵N increased in August at Toolik, coincident with sporocarp production and fungal spores in feces. Mixing models indicated that graminoids contributed 64%, dicots 35%, and sporocarps 1% to Atigun hair protein, whereas graminoids contributed 37%, dicots 16%, and sporocarps 47% to Toolik hair protein. Acidic soils appeared to correlate with higher sporocarp production and fungivory at Toolik than at Atigun. Atigun hair resembled atmospheric CO2 in ¹⁴C, whereas Toolik hair had higher ¹⁴C, consistent with greater fungal consumption at Toolik. Late-season sporocarps may be a key protein source for some squirrels and may provide an integrated signal of the soil organic nitrogen assimilated by ectomycorrhizal fungi.