Amount Of Winter Precipitation Research Articles

Dendrochronological analysis of conifers in avalanche catchments of the Northwestern Altai (Korgon River basin)

The purpose of the study was to date the powerful snow avalanches occurred in the avalanche catchment area in the river Korgon basin (Northwestern Altai) by the dendrochronological method. The paper presents the results of the analysis of a number of dendrochronological indicators of avalanches: the age of trees, the relation between widths of annual rings from opposite sides of the trunk, the presence of reactive (compressional) wood and traumatic resin canals, the dates of death and formation of wounds in trees, the presence of clearing effects (a sharp increase in growth) in three avalanche catchments, as well as a complex dendrochronological index of the avalanche activity. The dates of releases of the powerful avalanches were established down to 1570. It has been found that against the background of increasing amount of winter precipitation in these catchments, there are different trends in occurrence of the avalanches, which is determined by their morphological properties. In the avalanche areas with steeper slopes, due to repeated unloading of the avalanche centers in winter, the probability of releasing of powerful avalanches decreases. For the same reason, the powerful avalanches do not release during the years of maximum snow accumulation. The trends in the avalanche activity in the region under consideration had been obtained for the first time. The dendrochronological index of the avalanche activity, which is the ratio of the number of the tree growth failures to the number of the examined trees, is a good indicator of a release of a powerful avalanche even at a value of 0.85, provided that the number of examined trees in the lower part of the transit zone and in the zone of accumulation is 25–35 units. The results of this study may be used to predict the territorial differentiation of changes in the avalanche activity due to climate change. In connection with the recreational development of the Altai territory, they may also be of practical importance.

Winter runoff events pose an unquantified continental-scale risk of high wintertime nutrient export

Winters in snow-covered regions have warmed, likely shifting the timing and magnitude of nutrient export, leading to unquantified changes in water quality. Intermittent, seasonal, and permanent snow covers more than half of the global land surface. Warming has reduced the cold conditions that limit winter runoff and nutrient transport, while cold season snowmelt, the amount of winter precipitation falling as rain, and rain-on-snow have increased. We used existing geospatial datasets (rain-on-snow frequency overlain on nitrogen and phosphorous inventories) to identify areas of the contiguous United States (US) where water quality could be threatened by this change. Next, to illustrate the potential export impacts of these events, we examined flow and turbidity data from a large regional rain-on-snow event in the United States’ largest river basin, the Mississippi River Basin. We show that rain-on-snow, a major flood-generating mechanism for large areas of the globe (Berghuijs et al 2019 Water Resour. Res. 55 4582–93; Berghuijs et al 2016 Geophys. Res. Lett. 43 4382–90), affects 53% of the contiguous US and puts 50% of US nitrogen and phosphorus pools (43% of the contiguous US) at risk of export to groundwater and surface water. Further, the 2019 rain-on-snow event in the Mississippi River Basin demonstrates that these events could have large, cascading impacts on winter nutrient transport. We suggest that the assumption of low wintertime discharge and nutrient transport in historically snow-covered regions no longer holds. Critically, however, we lack sufficient data to accurately measure and predict these episodic and potentially large wintertime nutrient export events at regional to continental scales.

Late Holocene increase of winter precipitation in mid-continental North America from a seasonally resolved speleothem record

Abstract Subannual climate reconstructions of the Holocene are rare despite the ability of such records to provide a better understanding of the underlying factors that drive subannual climate variability. We used specialized confocal laser fluorescent microscope imaging and automated secondary ion mass spectrometry microanalysis to resolve a seasonal oxygen isotope (δ18O) record of a late Holocene–aged (2.7–2.1 ka) speleothem from mid-continental North America. We did this by measuring intra-band δ18O variability (Δ18O) within 117 annual bands over a 600 yr span of the late Holocene. We interpret a change in Δ18O values after 2.4 ± 0.1 ka to reflect an increase in the amount of winter precipitation. Our study produced direct measurements of past seasonality, offers new insights into shifting seasonal precipitation patterns that occurred during the late Holocene in central North America, and adds a new tool for understanding the complex precipitation and temperature histories of this region.

Interpreting the nonstationary relationship between El Niño–Southern Oscillation and the winter precipitation over southeast China

AbstractThe amount of winter precipitation over southeast China (SCWP) is significantly affected by the El Niño–Southern Oscillation (ENSO), with generally an enhanced SCWP response to El Niño events. In this paper, we find that this relationship shows remarkable nonstationarities on the multidecadal timescale. Running ENSO–SCWP correlation maintains statistically significant before the mid‐1960s and after the mid‐1990s but not during the interim period, which exhibits an approximate synchronized temporal evolution with the Atlantic Multidecadal Oscillation (AMO). A statistical method for interpreting nonstationary relationships is then applied to quantitatively verify and measure this possible AMO modulation. It is demonstrated that the nonstationary ENSO–SCWP correlation can be expressed to a large extent by the influence of the AMO–ENSO nonlinear effect (AMO*Niño3.4) on the SCWP. This influence intensifies the ENSO–SCWP relationship during the positive AMO phase but weakens it during the negative AMO phase. Therefore, the nonstationarity in the ENSO–SCWP relationship comes predominantly from an AMO modulation via this key nonlinear effect. We further suggest that a positive AMO favours a westward shift of ENSO sea surface temperature (SST) anomaly pattern in the tropical Pacific. Correspondingly, the anomalous western North Pacific (WNP) anticyclone also migrates westward, which gives rise to pronounced moisture transports and vertical motions over the adjacent southeast China, thereby resulting in a significant ENSO–SCWP relationship. In contrast, during the negative AMO phase, the eastward‐shifted ENSO SST and WNP anticyclonic anomalies produce significant atmospheric anomalies primarily to the east of the Chinese mainland, thus having less effect on the SCWP.

Status of Desert Cottontails (Sylvilagus audubonii) in Arizona, 1955-2020

More than 60 years of survey and hunt data indicate declining trends in Arizona's desert cottontail (Sylvilagus audubonii) populations. Survey numbers, hunter participation, harvests, and hunt success for this species after 1990 are considerably less than prior to the 1980s. Summer surveys conducted in the 1950s and repeated in 2019 and 2020 showed that populations were not uniform and related to winter precipitation amounts (r2=0.71, p=0.07). Although one population in 2020 was at an historic low, others were as robust as in the 1950s. Although declines in hunter numbers may be due to sociological factors, the reasons for declining trends in cottontail survey numbers and hunt success are more difficult to evaluate. Precipitation amounts and temperature data suggest that population declines might have been caused by increased mortality due to climate change, increases in predator populations, and/or the presence of disease.

Moss biomonitoring using lead isotope ratios requires careful attention: Evaluation of transboundary pollutants in Japan

Transboundary atmospheric pollution has become a serious threat to ecosystems and human health at the global scale. Lead isotope ratios in mosses are used to evaluate the influence of transboundary atmospheric pollutants owing to the traceability of the origin of these pollutants. However, uncertainties for these ratios remain because uptake of trace metals by mosses depends on the surrounding environment and their absorption processes. This study examined how these factors affect lead isotope ratios in mosses and discussed their usefulness as indicators of transboundary pollutants. Moss samples were collected from thirteen sites across Japan. On the continental side, the moss samples in areas with a high amount of winter precipitation exhibited lead isotope ratios similar to those of transboundary pollutants. These results can be explained by enhanced influence of transboundary pollutants on the mosses through winter precipitation bias, given that transboundary pollutants are primarily carried to Japan during winter and that mosses efficiently take up pollutants through wet deposition. The moss samples on Pb-enriched soil absorbed a large quantity of soil-derived Pb, which was reflected in their Pb isotope ratios. Furthermore, the Pb uptake by mosses can be inhibited by other trace metals that compete with Pb for cation binding sites at the cell wall. This inhibition can alter the contribution of atmospheric Pb deposition to the total Pb content in mosses, thereby affecting the Pb isotope ratios. In conclusion, these results validate the usefulness of Pb isotope ratios in mosses as indicators of transboundary pollutants; however, they also imply the need for meticulous interpretation of moss biomonitoring results. The enhanced influence of transboundary pollutants on mosses due to the winter precipitation bias emphasizes the importance of moss biomonitoring for evaluating ecosystem integrity, as it gives insights on actual changes in the Pb cycling in an ecosystem through Pb accumulation by mosses.

Klimatske promene kao pokretačka snaga inteziviranja poljoprivrednog korišćenja zemljišta

Climate change in Europe will lead to new precipitation patterns over the coming years and the annual temperature will increase significantly. These changes in climate variables and the resulting effects on agricultural productivity must be differentiated regionally. Plant production depends on sufficient rainfall in summer and, in some regions, on the amount of rainfall in winter. In Central Europe, the amount of precipitation in summer will decrease in the coming decades due to climate change, while in some regions, the amount of winter precipitation will increase significantly. Agricultural production is likely to suffer severely as a result of rising summer temperatures and low water retention capacities in the soil. The effects of reduced summer precipitation and increased air temperatures are partially offset by the expected increased CO2 concentration. Therefore, the effects that changed climatic conditions have on crop production are sometimes less drastic in terms of crop yields. The greatest impact of climate change on land use is expected from increasing evapotranspiration and lower amounts of precipitation in the production of leachate. In addition to the expected mean changes, the occurrence of extreme weather conditions is key. Periods of drought in the growing season and heavy flooding as a result of extreme rainfall are to be expected. However, these events are very difficult or even impossible to predict. In addition to the effects that climate change will have on regional crop production, global changes will have a strong impact on world markets for agricultural products. Another consequence of climate change and population growth is a higher demand for agricultural products on world markets. This will lead to dramatic local land use changes and an intensification of agriculture that will transform existing crop production systems. The intensification caused by rising land and lease prices will primarily affect the maximization of the use of fertilizers and pesticides.

Modern Climate Change in the Black Sea Region

Topicality. Climate change in the Black Sea region in recent decades poses certain risks to the econo-mies of countries of region, and may have a significant negative impact on the state of terrestrial and marine ecosystems. The main areas of economic activity in the Black Sea are maritime freight, oil and gas production and transportation, industrial extraction of marine biological resources, recreational and tourist activities in coastal areas, etc. The Black Sea significantly affects the climate of the south-eastern part of the European continent, forming regional climatic features in the area. The development of measures to adapt to climate change requires the collection and analysis of data on the state of the climate system and the current characteristics of their interaction and feedback. Purpose. The purpose of this work is to review and analyze information on regional climate change observed in recent decades to find patterns and possible links with the variability of the hydrological regime of the Black Sea. Results. This paper contains information on the main climatic characteristics of the Black Sea region, such as air temperature, precipitation, atmospheric pressure, wind speed, as well as indicators of cyclonic activity. Conclusions. In recent decades, the Black Sea region has seen an increase in air temperature caused by changes in large-scale atmospheric circulation, in the form of increased recurrence of anticyclonic processes, leading to a decrease in clouds and an increase in shortwave radiation entering the underlying surface. At the same time, since the mid-2000s, the increase in average annual air temperature has increased. The average annual rainfall is maintained in most parts of the region, with the exception of the eastern part of the Black Sea coast of Turkey and the coastal areas of Georgia, where there is an increase in both rainfall and the frequency of extreme rainfall. At the same time, there is some increase in both the intensity and amount of winter precipitation over the Black Sea. Wind speeds in the Black Sea region as a whole show a decrease in their values, with some increase in the western part of the Black Sea, which is also associated with changes in the peculiarities of circulating processes that develop over South-Eastern Europe.

The timing of snowmelt and amount of winter precipitation have limited influence on flowering phenology in a tallgrass prairie

A growing body of work indicates that the timing of flowering of temperate angiosperms has been affected by shifts in climate since the 1970s. Sensitivity in flowering phenology to changing temperatures has been particularly well-documented, but widespread phenological sensitivity to changing precipitation patterns in temperate communities has only been shown in a few studies. The exception is relationships between snowpack and early flowering in alpine environments, whereby the timing of flowering herbs had strong associations with winter precipitation and the snowmelt timing. Based on these results, we hypothesized that populations in temperate latitudes characterized by strong seasonality and winter snowfall would demonstrate associations between timing of snowmelt and flowering phenology. We combined a historical dataset of first flowering dates in a Minnesota tallgrass prairie with climatic data to construct a structural equation model, testing hypotheses on the relationships between winter precipitation, temperature, and flowering phenology. While temperature had a strong effect on flowering phenology, winter precipitation had a significant relationship with only a few species. The species affected by snow were later flowering species, which is inconsistent with our prediction that winter precipitation affects early flowering phenology. These results suggest future changes in precipitation will have differing consequences depending on region.

Relationships between Large-Scale Climate Signals and Winter Precipitation Amounts and Patterns over Iran

Precipitation is one of the most complex weather phenomena; its successful spatiotemporal modeling provides substantial information for designing water management systems. This research aimed to determine the relationship of sixteen large-scale climate signals with weather types (WTs) as well as precipitation amounts over Iran during the winter season (January–March). Daily precipitation data covering the period 1991–2010 were collected from 130 weather stations across the country. In addition, four atmospheric variables affecting the precipitation process over Iran were derived from National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis datasets as predictors. Several nonhomogeneous hidden Markov models (NHMMs) were employed to identify the prevailing WTs governing the spatial distributions of daily precipitation in winter over Iran. A hidden state (i.e., WTs) in NHMMs was dependent on an immediately previous state of WT in the hidden layer and the reanalyzed atmospheric variables at the current time in the predictor layer. Daily WTs over the recording period were decoded using Viterbi’s algorithm. Results showed that the NHMM including the atmospheric variable of mean sea level pressure (Mslp) in the predictor layer had the minimum value (= 0) of Bayesian information criterion difference (BICD) among the other variables and was treated as the best model. The chosen model distinguished the eight spatially coherent WTs for winter that were in accordance with the eight synoptic patterns influencing the study area. Based on the Spearman’s rank method, amounts of winter precipitation at many stations in Iran were significantly correlated with four climate signals, including the atlantic multidecadal oscillation (AMO), East Atlantic/West Russia (EA/WR) pattern, Southern Oscillation Index (SOI), and Trans Polar Index (TPI). However, these station-based relationships could not exhibit well the spatial dependencies of the teleconnections and regional precipitation. It was also found that the unconditional and conditional frequencies of WTs were under the influence of a greater number of large-scale climate signals than the precipitation amounts, were under the influence of a greater number of large-scale climate signals. Moreover, the inherent nature of WTs in keeping spatial dependencies allowed for a better understanding of regional teleconnective relationships. These findings confirmed the advantage of regional rather than local assessments of teleconnective relationships.

The influence of Arctic air masses on climatic conditions of the snow accumulation period in the center of the European territory of Russia

The subject of this article is exmination of the influence of the Arctic air flow on the climatic conditions of the winter period in the center of the European territory of Russia (Moscow). In recent years, the question of the relationship between regional climatic conditions and such global circulation patterns as the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AK) has become increasingly important. Based on the data of long-term observations of temperature and precipitation, the relationship with the AK and NAO was considered. For the winter months of the period 2014-2018, the back trajectories of the movement of air masses were computed for each date of precipitation to identify the sources of precipitation. The amount of winter precipitation that forms the snow cover of Moscow has no connection with either the North Atlantic Oscillation or the Arctic Oscillation. The Moscow region is located at the intersection of the zones of influence of positive and negative phases of both cyclonic patterns (AK and NAO), which determine the weather in the Northern Hemisphere. For the winter months, a correlation between the surface air temperature and NAO (r = 0.72) and AK (r = 0.66) was established. Winter precipitation in the center of the European territory of Russiais mainly associated with the unloading of Atlantic air masses. Arctic air masses relatively rarely invade Moscow region and bring little precipitation (their contribution does not exceed 12% of the total winter precipitation).

Holocene precipitation seasonality in northern Svalbard: Influence of sea ice and regional ocean surface conditions

Arctic precipitation is predicted to increase in the coming century, due to a combination of enhanced northward atmospheric moisture transport and local surface evaporation from ice-free seas. However, large model uncertainties, limited long-term observations, and high spatiotemporal variability limit our understanding of these mechanisms, emphasizing the need for paleoclimate records of precipitation changes. Here we use lipid biomarkers in lake sediments to reconstruct precipitation seasonality in northern Spitsbergen, Svalbard. We measured the hydrogen isotopic ratios (δ2H) of n-alkanoic acids (C20–C30) from sedimentary leaf waxes in lake Austre Nevlingen, Spitsbergen. We interpret δ2H values of mid-chain (C22) and long-chain (C28) n-alkanoic acids to represent δ2H of lake and soil water, respectively. Austre Nevlingen lake water δ2H reflects amount-weighted mean annual precipitation δ2H. In contrast, soil water is mostly recharged by summer rainfall, and therefore reflects δ2H values of summer precipitation. Austre Nevlingen leaf wax δ2H values are 2H-depleted in the Early Holocene, suggesting high winter precipitation amounts. This coincides with high summer insolation, strong Atlantic water advection and reduced spring sea-ice cover in surrounding waters. Winter precipitation continued to dominate until c. 6 cal. kyr BP. After 6 cal. kyr BP, the trend in the biomarker record is not as clear. This could be related to colder conditions causing longer duration of seasonal lake-ice cover, thereby influencing the precipitation seasonality registered by the lake water. The Austre Nevlingen record suggests a close relationship between precipitation seasonality and regional ocean surface conditions, consistent with simulations suggesting that Arctic winter sea-ice loss will lead to increased local evaporation.

Water Use and Soil Moisture Relationships on Western Juniper Trees at Different Growth Stages

An enhanced understanding of plant water uptake is critical for making better-informed management decisions involving vegetative manipulation practices aimed to improve site productivity. This is particularly true in arid and semiarid locations where water is a scarce, yet precious commodity. In this project, we evaluated the interannual and seasonal variability of soil moisture and transpiration in sapling, juvenile, and mature western juniper (Juniperus occidentalis) trees in a semiarid rangeland ecosystem of central Oregon, USA. Transpiration levels were greatest in mature juniper trees in an untreated juniper watershed (Jensen WS), while the lowest transpiration levels were observed in juniper saplings in a treated watershed (Mays WS) where most mature juniper trees were removed in 2005. Significant differences (p ≤ 0.05) in leaf water potential levels observed between predawn and midday readings for all juniper growth stages indicated water is lost over the course of the day. Results showed seasonal precipitation was highly variable over the course of the study (2017 through 2019) and this was reflected in soil water available for tree uptake. This resulted in considerable intra- and inter-annual variation in transpiration. In years with greater winter precipitation amounts (2017 and 2019), juniper transpiration rates were highest during the summer, followed by spring, autumn, and winter. On average, transpiration rates during the summer in the wettest (329 mm) year 2017 were 115 and 2.76 L day−1 for mature and sapling trees, respectively. No data were collected for juvenile trees in 2017. In the drier (245 mm) year 2018, higher transpiration rates were observed in the spring. On average, spring transpiration rates were 72.7, 1.61, and 1.00 L day−1 for mature, juvenile, and sapling trees, respectively. Study results highlight the sensitivity of western juniper woodlands to variations in seasonal precipitation and soil moisture availability.

Stable H and O isotope-based investigation of moisture sources and their role in river and groundwater recharge in the NE Carpathian Mountains, East-Central Europe

ABSTRACTThe region situated between the mountain area and the lowlands in NE Romania (East-Central Europe) is experiencing increased competition for water resources triggered by a growing population, intensification of agriculture, and industrial development. To better understand hydrological cycling processes in the region, a study was conducted using stable isotopes of water and atmospheric trajectory data to characterize regional precipitation and vapour sources derived from the Atlantic Ocean, Mediterranean and Black Seas, as well as recycled continental moisture, and to assess and partition these contributions to recharge of surface and groundwater. Atmospheric moisture in the lowlands is found to be predominantly delivered along easterly trajectories, while mountainous areas appear to be dominated by North Atlantic Ocean sources, with moisture transported along mid-latitude, westerly storm tracks. Large-scale circulation patterns affect moisture delivery, the North Atlantic Oscillation being particularly influential in winter and the East Atlantic pattern in summer. Winter precipitation is the main contributor to river discharge and aquifer recharge. As winter precipitation amounts are projected to decrease over the next decades, and water abstraction is expected to steadily increase, a general reduction in water availability is projected for the region.

Influence of winter precipitation on spring phenology in boreal forests.

Understanding the variations in spring vegetation phenology associated with preseason climate conditions can significantly improve our knowledge on ecosystem dynamics and biosphere-atmosphere interactions. Recent studies have shown that wet winters can delay the start date of the vegetation growing season (SOS) in the high latitudes. However, associated underlying mechanisms remain unclear due to the lack of observation sites as well as complex interactions between various climate and ecosystem variables. In this study, the impact of winter precipitation on year-to-year variations of the SOS in boreal forests from 1982 to 2005 was investigated. Two experiments were performed using the Community Land Model version 4.5. In the control experiment, observed precipitation was used; in the sensitivity experiment, precipitation in the year 1982 was repeated throughout the period. The SOS in the control experiment shows high temporal correlations with the SOS estimated from the satellite-retrieved leaf area index, indicating that the land model is capable of simulating realistic response of vegetation to interannual climate variability. The effects of winter precipitation on the SOS are examined by comparing the two model experiments for wet- and dry winters. After wet winters, the SOS was delayed by 2.7days over 70.1% of the boreal forests than after dry winters; this accounts for 42.5% of the interannual variation in the SOS. The SOS delay is related to the decrease in the growing degree-days (GDD) based on soil temperatures, suggesting that the effects of heat exposure on vegetation growth is strongly modulated by winter precipitation. The GDD decrease is related to both the increase in snowmelt heat flux and reduced absorption of solar radiation, which are proportional to the amount of winter precipitation and the ratio of short plants to tall trees, respectively. Our results provide a physical basis for the winter precipitation-SOS relationship, suggesting that an increase in winter precipitation can alleviate strong advancing trends in spring vegetation growth in conjunction with global warming even for temperature-limited ecosystems.

Filling a Geographical Gap: New Paleoecological Reconstructions From the Desert Southwest, USA

In 1916 the time stamp for quantitative palynology was set with Lennart von Post’s initial paper on pollen analysis and environmental change in the Scandinavian peat bogs. His subsequent work and reviews provided us with a map of the known palynological world into the 1930s. This map had, and to this day still has, many substantial holes of knowledge. In particular, environmental reconstruction in arid lands remain much less known, largely due to the paucity of depositional environments in these areas as well as challenges with preservation in regions either uniformly dry or subjected to strong wet/dry cycles. In over a decade of work we have examined linkages between wetland development and episodes of wet and arid conditions. Desert wetland or cienegas are groundwater fed systems that appear sensitive to changes in groundwater recharge. These systems appear to “grow” during times of wet periods potentially associated with greater El Nino activity, suggesting an important linkage to winter precipitation amounts and frequency. Preservation of pollen is also important, as episodes of aridity can be identified as times of poor pollen preservation and quantities. We assess modern El Nino events, as analogs of past conditions, to provide context on the atmospheric controls for delivery of moisture into the desert southwest during winter. This analysis demonstrates that the anomalous and persistent moisture delivered into the region during El Nino events allow for the growth of cienegas, preservation of pollen and the production of fuels necessary to support an active fire regime. This paper examines sites from the American Deserts from the US/Mexico Border (hereinafter southwestern deserts) and presents findings and new approaches that embody the spirit of investigation initiated by von Post’s original work in paleoenvironmental research.

Watershed- to continental-scale influences on winter stormflow in the Southern Blue Ridge Mountains

Spatial and temporal influences on the winter (December-March) stormflow characteristics of fifteen United States Geological Survey (USGS)-gaged watersheds in the Southern Blue Ridge Mountains are identified: (1) watershed-scale differences in geomorphology; (2) continental-scale teleconnections during periods of wetness/dryness (based on the relative amount of winter precipitation over a consistent 20 year dataset); and (3) land cover in the context of soil parent material (e.g., development on alluvium/colluvium). Multiple regression was used to determine how much variance could be explained in five hydrologic variables describing the flashiness of peak flow (three original metrics), total seasonal flashiness (Richards Baker flashiness index), and the ratio of total winter stormflow to total discharge (the stormflow index). Models were constrained to three uncorrelated (|0.65|) variables to prevent overfitting to the dataset. Average-, dry-, and wet-years were subset using the z-scores for winter precipitation derived from the 4 km monthly PRISM (Parameter-elevation Relationships on Independent Slopes Model) dataset, for the period of 1986–2006. Relief, slope, and landscape connectivity explain the majority of explained variance in all five of the hydrologic variables during all time periods. During dry-, average-, and wet-years, atmospheric circulation patterns (i.e., North Atlantic Oscillation and Pacific/North American Pattern) explain more variance than total seasonal precipitation (PRISM), which is not true in the majority of the all-years models. Land cover explains only a small portion of the variance in regional stormflow and only when sub-divided based on soil parent material. Results provide a framework for connecting watershed-scale characteristics to regional- and continental-scale processes.

Increased climate seasonality during the late glacial in the Gebel Akhdar, Libya

Oxygen isotope analysis (δ18O) of caprine and bovine tooth enamel carbonates from the Haua Fteah cave (Gebel Akhdar massif, northeast Libya) reveals significant differences in palaeoseasonality during the last c. 70 ka. Data indicate different phases of human occupation of the region occurred under notably different climatic conditions. During the last glacial period, prior to the Last Glacial Maximum, a gradual increase in climate aridity occurred. This was followed in the late glacial (c. 16.6–14.7 ka) by considerably more arid conditions and much greater climate seasonality, which was likely produced by changing winter precipitation amounts and a strengthening of arid summer air masses. The high seasonality in the late glacial coincides with a period when human activity at the Haua Fteah greatly intensified. Significant changes in subsistence strategies and the seasonal exploitation of food resources also occurred at this time. The results presented here suggest that changes in the seasonal climate may have affected the seasonal supply of floral and faunal resources available to local human populations at the time, which resulted in changing subsistence practices.

Warming is Driving Decreases in Snow Fractions While Runoff Efficiency Remains Mostly Unchanged in Snow-Covered Areas of the Western United States

Abstract Winter snowfall and accumulation is an important component of the surface water supply in the western United States. In these areas, increasing winter temperatures T associated with global warming can influence the amount of winter precipitation P that falls as snow S. In this study we examine long-term trends in the fraction of winter P that falls as S (Sfrac) for 175 hydrologic units (HUs) in snow-covered areas of the western United States for the period 1951–2014. Because S is a substantial contributor to runoff R across most of the western United States, we also examine long-term trends in water-year runoff efficiency [computed as water-year R/water-year P (Reff)] for the same 175 HUs. In that most S records are short in length, we use model-simulated S and R from a monthly water balance model. Results for Sfrac indicate long-term negative trends for most of the 175 HUs, with negative trends for 139 (~79%) of the HUs being statistically significant at a 95% confidence level (p = 0.05). Additionally, results indicate that the long-term negative trends in Sfrac have been largely driven by increases in T. In contrast, time series of Reff for the 175 HUs indicate a mix of positive and negative long-term trends, with few trends being statistically significant (at p = 0.05). Although there has been a notable shift in the timing of R to earlier in the year for most HUs, there have not been substantial decreases in water-year R for the 175 HUs.

Изменения температуры воздуха и осадков в межгорных котловинах Юго-Восточного и Центрального Алтая

The study of the regional manifestations of climate change in mountain areas is of special significance, because it can refine the planetary picture of climate changes. Multiyear meteorological data (60 year period) on high-mountain and mid-mountain intermountain hollows – the Chuya hollow (Southeastern Altai physical and geographical province), Kanskaya, Uimonskaya and Ursulskaya troughs (Central Altai physical and geographical province) are analyzed. It is shown that the most significant changes in air temperature and precipitation occur in the Chuya hollow. Based on linear trends, it is found that the average annual air temperature increased 3°C over 1955–2016. In the Kanskaya, Uimonskaya and Ursulskaya troughs, this value is 1.8, 1.9 and 2.3°C, respectively. However, at the same time there is a tendency to a slight cold snap of the last decade. Substantial changes in precipitation patterns in all studied areas are not revealed, but some differences are found when considering seasonal patterns based on linear trends. So, everywhere increase in summer precipitation is recorded: on 33 mm at the meteorological station Ust-Koksa, 23 mm at the meteorological station Ust-Kan and 12 mm at the meteorological station Kosh-Agach. The amount of winter precipitation is reduced by values from 2 to 10 mm. These values are not statistically significant and are provided to illustrate emerging trends. Despite the increase in summer precipitation, these changes indicate a significant trend of increasing aridity of the territory, since the observed increase in air temperatures is not accompanied by a corresponding increase in precipitation.