The Spatially Inhomogeneous Influence of Snow on the Radial Growth of Schrenk Spruce (Picea schrenkiana Fisch. et Mey.) in the Ili-Balkhash Basin, Central Asia

Snow has an important impact on forest ecosystems in mountainous areas. In this study, we developed 14 tree-ring-width chronologies of Schrenk spruce (Picea schrenkiana Fisch. et Mey.) for the Ili-Balkhash Basin (IBB), Central Asia. We analyzed the response of radial growth to temperature, precipitation and snow parameters. The results show that previous winter and current summer precipitation have an important influence on the radial growth of P. schrenkiana. Further, we find spatially inhomogeneous effects of snow on subsequent growing-season tree growth in IBB. The radial growth response of P. schrenkiana to snow shows a weak–strong–weak trend from west to east across the Ili-Balkhash Basin. This spatial difference is mainly related to precipitation, as snow has little effect on tree growth in regions that receive more precipitation. Thus, winter snow has an important influence on the radial growth of trees in regions that receive limited amounts of precipitation.

The control of climate sensitivity on variability and change of summer runoff from two glacierised Himalayan catchments

The response of catchment runoff to climate forcing is determined by its climate sensitivity. We investigate the sensitivity of summer runoff to precipitation and temperature changes in winter-snow dominated Chandra (western Himalaya), and summer-rain dominated upper Dudhkoshi (eastern Himalaya) catchments in order to understand the nature of climate-change impact on the mean summer runoff and its variability. The runoff over the period 1980–2018 is simulated with a semi-distribute hydrologic model, which is calibrated using available discharge and glacier mass loss data. An analysis of the interannual variability of the simulated summer runoff reveals that the runoff from the glacierised parts of the catchments is sensitive to temperature changes, but is insensitive to precipitation changes. The behaviour of the summer runoff from the non-glacierised parts is exactly opposite. Such precipitation-independent runoff from the glacierised parts stabilises the catchment runoff against precipitation variability to some degree. With shrinking glacier cover over the coming decades, the summer runoff from the two catchments is expected become more sensitive to the precipitation forcing and less sensitive to the temperature forcing. Because of these competing effects, the impact of the glacier loss on the interannual variability of summer runoff may not be significant. However, the characteristic ‘peak water’ in the long-term mean summer runoff, which is caused by the excess meltwater released by the shrinking ice reserve, may lead to a detectable signal over the background interannual variability of runoff in these two catchments.

Road Salt Damage to Historical Milestones Indicates Adaptation of Winter Roads to Future Climate Change May Damage Arctic Cultural Heritage

There is no doubt that anthropogenic global warming is accelerating damage to cultural heritage. Adaptation measures are required to reduce the loss of sites, monuments and remains. However, little research has been directed towards understanding potential impacts of climate adaptation measures in other governmental sectors on cultural heritage. We provide a case study demonstrating that winter road salt, used to reduce ice related accidents, damages historical iron milestones. As the climate warms, road salt use will move north into areas where sites have been protected by contiguous winter snow cover. This will expose Artic/sub-Arctic cultural heritage, including Viking graves and Sami sites, to a new anthropogenic source of damage. Research and planning should therefore include the evaluation of secondary impacts when choosing climate adaptation strategies.

Start of the Green Season and Normalized Difference Vegetation Index in Alaska’s Arctic National Parks

Daily Normalized Difference Vegetation Index (NDVI) values from the MODIS Aqua and Terra satellites were compared with on-the-ground camera observations at five locations in northern Alaska. Over half of the spring rise in NDVI was due to the transition from the snow-covered landscape to the snow-free surface prior to the deciduous leaf-out. In the fall after the green season, NDVI fluctuated between an intermediate level representing senesced vegetation and lower values representing clouds and intermittent snow, and then dropped to constant low levels after establishment of the permanent winter snow cover. The NDVI value of snow-free surfaces after fall leaf senescence was estimated from multi-year data using a 90th percentile smoothing spline curve fit to a plot of daily NDVI values vs. ordinal date. This curve typically showed a flat region of intermediate NDVI values in the fall that represent cloud- and snow-free days with senesced vegetation. This “fall plateau” was readily identified in a large systematic sample of MODIS NDVI values across the study area, in typical tundra, shrub, and boreal forest environments. The NDVI level of the fall plateau can be extrapolated to the spring rising leg of the annual NDVI curve to approximate the true start of green season.

Concentration and Physical Characteristics of Black Carbon in Winter Snow of Beijing in 2015

In Beijing, the probability of snowfall is decreasing as a result of global warming. At the same time, Beijing has suffered severe air pollution. In this paper, the concentration and particle size characteristics of BC (Black Carbon) in snow during the winter of 2015 in Beijing were analyzed by the SP2 method. The average concentration of BC in snow meltwater in Beijing is 82 ng/mL, with a minimum value of 62.9 ng/mL and a maximum of 210.6 ng/mL. The BC particle size in snow and ice in the Beijing area is mostly concentrated in the range of 70–400 nm. After log-normal, the BC particle size above 600 nm is still small, which should be closely related to the nature of the local BC emission source. The concentration of BC in snow is highly susceptible to meteorological conditions and local pollution levels. When Beijing is under the control of the east wind or the southeast wind, aerosols in the urban areas can easily accumulate in the northwestern mountains and then settle or participate in the snowfall process, resulting in an increase in BC aerosol accumulation in the snow, thus further changing the optical properties of snow in the Beijing area.

Hydraulic function and conduit structure in the xylem of five oak species

Many plant lineages, including oaks (Quercus spp.), have both vessels and tracheids as hydraulically conductive cells within their xylem. The structure of these co-occurring conduit types and their contribution to plant hydraulic function have been relatively little studied. We hypothesized that vasicentric tracheids contribute to hydraulic function under conditions of low water availability. We predicted that within a species, oaks growing at drier and warmer low elevation sites would have more tracheids and be more embolism resistant compared to those growing at moister and colder higher elevation sites. We also predicted that across species, lower elevation oaks would have increased tracheid abundance within their xylem. Five oak species differed in many xylem traits, including vessel diameter and length, tracheid size and abundance, embolism resistance, and hydraulic conductivity. Tracheids were most abundant in the xylem of the highest elevation species at sites that receive winter snow and freezing temperatures. Vessels were relatively vulnerable to embolism as confirmed with multiple methods, including centrifuge vulnerability curves, micro-CT scans of native stem samples, and single vessel air injection. Theoretical conductivity calculations indicated that tracheids account for 5.7–15.5% of conductivity in hydrated stems, with tracheids likely increasing in importance as large diameter vulnerable vessels embolize. The occurrence of both vessels and vasicentric tracheids in the xylem of oaks may enable them to function within highly seasonal climates. Tracheids, though often overlooked, may be particularly important in maintaining conductivity throughout much of the year when water potentials decline from seasonal maximums and following freeze-thaw events.

Factors Governing Winter Snow Accumulation and Ablation Susceptibility Across the Sierra Nevada, U.S.A.

Seasonal snow water equivalent (SWE) accumulation in California’s Sierra Nevada is primarily governed by a few orographically enhanced snowstorms. However, as air temperatures gradually rise, resulting in a shift from snow to rain, the governing processes determining SWE accumulation versus ablation become ambiguous. Using a network of 28 snow pillow measurements to represent an elevational and latitudinal gradient across the Sierra Nevada, we identify distributions of critical temperatures and corresponding storm and snowpack properties that describe how SWE accumulation varies across the range at an hourly timescale for water years 2010 through 2019. We also describe antecedent and prevailing conditions governing whether SWE accumulates or ablates during warm storms. Results show that atmospheric moisture regulates a temperature dependence of SWE accumulation. Conditions balancing precipitable water and snow formation requirements produce the most seasonal SWE, which was observed in the (low-elevation) northern and (middle-elevation) central Sierra Nevada. The high southern Sierra Nevada conservatively accumulates SWE with colder, drier air, resulting in less midwinter ablation. These differences explain a tendency for deep, low-density snowpacks to accumulate rather than ablate SWE during warm storms (having median temperatures exceeding 1.0°C), reflecting counteracting liquid storage and internal energy deficits. The storm events themselves in these cases are brief with modest moisture supplies or are otherwise followed immediately by ablation.

Ratio of isotopic parameters δ2H-δ18o in Late Pleistocene and Holocene ice wedge

The subject of this research is the ratio of isotopic parameters of deuterium of heavy oxygen in ice wedges. The authors considered such parameter as inclination of the line of the ration of deuterium of heavy oxygen in ice wedges. Proximal to GMLV (or LLMV) position of isotope values for ice wedge and inclination of the line proximate to 8 suggests that the ice wedge was formed from atmospheric precipitation (winter snow). The article provides separate examples of anomalous deuterium ratios of heavy oxygen with very low ration of line inclination, which in combination with the abnormally low dexc values indicate the indicate isotopic fractionation processes in snow before melting and/or melting snow water before filling frost-cutting cracks. Three author determines the three main types of ratios of deuterium m of heavy oxygen content in ice wedge: a) normal ratio δ2H-δ18O (with line inclination of the ratio proximate to GLMV or LLMW). b) ratio of deuterium  of heavy oxygen to deviation from GLMV or LLMW (with signs of change in the primary isotope signal of atmospheric precipitation), c) anomalous ratio of deuterium of heavy oxygen. It is shown that the first two types  are characteristic to most ice wedge under study in the vast part of the Russian cryolithozone from the European North to the east of Chukotka; the third type is obtained for several Holocene ice wedge in Transbaikal and upper Yenisei River. This may be explained by significant isotope transformation of snow cover in the conditions of distinctly continental climate.