Winter Precipitation Research Articles

Regional variation in climate change alters the range-wide distribution of colour polymorphism in a wild bird.

According to Gloger's rule, animal colouration is expected to be darker in wetter and warmer climates. Such environmental clines are predicted to occur in colour polymorphic species and to be shaped by selection if colour morphs represent adaptations to different environments. We studied if the distribution of the colour polymorphic tawny owl (Strix aluco) morphs (a pheomelanic brown and a pale grey) across Europe follow the predictions of Gloger's rule and if there is a temporal change in the geographical patterns corresponding to regional variations in climate change. We used data on tawny owl museum skin specimen collections. First, we investigated long-term spatiotemporal variation in the probability of observing the colour morphs in different climate zones. Second, we studied if the probability of observing the colour morphs was associated with general climatic conditions. Third, we studied if weather fluctuations prior to the finding year of an owl explain colour morph in each climate zone. The brown tawny owl morph was historically more common than the grey morph in every studied climate zone. Over time, the brown morph has become rarer in the temperate and Mediterranean zone, whereas it has first become rarer but then again more common in the boreal zone. Based on general climatic conditions, winter and summer temperatures were positively and negatively associated with the proportion of brown morph, respectively. Winter precipitation was negatively associated with the proportion of brown morph. The effects of 5-year means of weather on the probability to observe a brown morph differed between climate zones, indicating region-dependent effect of climate change and weather on tawny owl colouration. To conclude, tawny owl colouration does not explicitly follow Gloger's rule, implying a time and space-dependent complex system shaped by many factors. We provide novel insights into how the geographic distribution of pheomelanin-based colour polymorphism is changing.

Citizen science data reveal regional heterogeneity in phenological response to climate in the large milkweed bug, Oncopeltus fasciatus

AbstractRegional populations of geographically widespread species may respond to different environmental factors across the species' range, generating divergent effects of climate change on life‐history phenology. Using thousands of citizen science observations extracted from iNaturalist and associated with corresponding temperature, precipitation, elevation, and daylength information, we examined the drivers of adult mating and of nymphal phenology, development, and group size for populations of the large milkweed bug, Oncopeltus fasciatus, in different ecoregions. Research‐grade iNaturalist images were correctly identified 98.3% of the time and yielded more than 3000 observations of nymphal groups and 1000 observations of mating adults spanning 18 years. Mating phenology showed distinct regional patterns, ranging from year‐round mating in California to temporally restricted mating in the Great Lakes Northeastern Coast ecoregion. Relative temperature increases of 1°C for a given daylength expanded the mating season by more than a week in western ecoregions. While increases in relative temperature delayed mating phenology in all ecoregions, greater winter precipitation advanced mating in the California ecoregion. In the eastern ecoregions, nymphal phenology was delayed by increases in summer rainfall but was advanced by relative temperature increases, whereas in western regions, relative temperature increases delayed nymphal phenology. Furthermore, accumulated growing degree days (AGDD) was a poor predictor of developmental progression, as we found a positive but weak correlation between AGDD and age structure only for the Appalachian Southeast North America and the Great Lakes Northern Coast ecoregions. These complex phenological responses of O. fasciatus are just one example of how populations may be differentially susceptible to a diversity of climatic effects; using data across a species' whole distribution is critical for exposing regional variations, especially for species with large, continental‐scale ranges. This study demonstrates the potential of photodocumented biodiversity data to aid in the monitoring of life history, host plant–insect interactions, and climate responsiveness.

Probabilistic Forecasting Methods of Winter Mixed-Precipitation Events in New York State Utilizing a Random Forest

Abstract Winter mixed-precipitation events are associated with multiple hazards and create forecast challenges that are due to the difficulty in determining the timing and amount of each precipitation type. In New York State, complex terrain enhances these forecast challenges. Machine learning is a relatively nascent tool that can help improve forecasting by synthesizing large amounts of data and finding underlying relationships. This study uses a random forest machine learning algorithm that generates probabilistic winter precipitation type forecasts. Random forest configuration, testing, and development methods are presented to show how this tool can be applied to operational forecasting. Dataset generation and variation are also explained because of their essential nature in the random forest. Last, the methodology of transitioning a machine learning algorithm from research to operations is discussed. Significance Statement Examining the role that machine learning can play in winter precipitation type forecasting is an area of research that has ample room for exploration, as much of the previous research has focused on applying machine learning to warm-season precipitation and severe weather events. Establishing a framework and methodology to successfully combine machine learning and weather research into effective operational tools is a valuable addition to the machine learning community. Because machine learning is increasingly being applied to meteorology, this work can act as a road map to help develop other meteorological tools based in machine learning.

Hysteretic Behavior of Global to Regional Monsoon Area Under CO2 Ramp‐Up and Ramp‐Down

AbstractWhen projecting future monsoon changes by carbon dioxide (CO2) pathway, most studies have analyzed precipitation responses without considering monsoon area (total area of monsoon domain, MA) variations. However, how MA responds to CO2 removal remains uncertain. This study evaluates MA variations and impacts in idealized CO2 ramp‐up (toward CO2 quadrupling), ramp‐down, and stabilized simulations using the Community Earth System Model version 1. Global MA negatively overshoots (i.e., recovery with decreasing tendency beyond the original MA) during the ramp‐down period due to reduced or rapidly recovered MA in several regional monsoons, including Northern and Southern Africa, South and East Asia, and South America, showing hysteresis when comparing CO2 ramp‐up and ramp‐down periods despite similar global warming levels. These non‐linear regional MA variations come from distinct regional summer and winter precipitation variations, which are found to be mostly associated with Intertropical Convergence Zone movements and El Niño‐like response. Further, regional monsoon precipitation characteristics also vary through CO2 ramp‐up and ramp‐down periods consistently with overall hysteresis. Changes in total monsoon precipitation resemble the distinct responses of MA. Our results suggest that regions characterized by a monsoonal climate may experience reduced seasonal rainfall variations under net‐negative CO2 emissions.

Characteristics of Winter Precipitation over Pakistan and Possible Causes during 1981–2018

Winter (December to March) precipitation is the major source of rainfed agriculture, storage, and perennial water flow in the western river system of Pakistan. Hence, this study uses precipitation data and variables of land–ocean and atmosphere from the Pakistan Meteorological Department and European Centre for Medium-Range Weather Forecasts (ECMWF) and fifth-generation reanalysis data (ERA5), respectively, to investigate the changes in winter precipitation and its sensitivity to different land–ocean and atmosphere variables, which are rarely investigated in Pakistan. Non-parametric techniques, such as the modified Mann–Kendal, Sen slope, kernel density-based probability function (PDF), empirical orthogonal function (EOF), and correlation analysis, were used to assess the changes and modes of variability in winter precipitation. The overall seasonal precipitation showed a significant decreasing trend with a (−0.1 mm d−1 yr−1) in the seasonal mean and monthly precipitation, except in February which showed a significant increase (>0.11 mm d−1 yr−1). The highest decrease in daily precipitation (<−0.1 mm d−1 yr−1) was in the north, with a moderate decrease in the southeast. The extreme precipitation indices exhibited an erratic decreasing tendency, but the maximum daily precipitation index increased; post-2000 precipitation extremes displayed an increase, and the seasonal and monthly precipitation exhibited the highest deviations during the drought period (1995–2000). The leading precipitation mode (EOF1) is sensitive to the local land surface processes and significantly correlated (>0.60) with the central Pacific and Indian Ocean’s basin-wide sea surface temperature, corroborating the influence of ENSO-induced meridional/zonal deviation of Hadley–Walker circulations. The Hadley and Walker cells affect the south-westerlies’ jet stream strength, impacting the water vapor transport and precipitation over Pakistan. These changes in the precipitation magnitude will affect rain-fed agriculture, especially the Rabi cropping pattern and perennial river flow.

Convection-parameterized and convection-permitting modelling of heavy precipitation in decadal simulations of the greater Alpine region with COSMO-CLM

Abstract. Heavy precipitation is a challenging phenomenon with high impact on human lives and infrastructure, and thus a better modelling of its characteristics can improve understanding and simulation at climate timescales. The achievement of convection-permitting modelling (CPM) resolutions (Δx<4 km) has brought relevant advancements in its representation. However, further research is needed on how the very high resolution and switching-off of the convection parameterization affects the representation of processes related to heavy precipitation. In this study, we evaluate reanalysis-driven simulations for the greater Alpine area over the period 2000–2015 and assess the differences in representing heavy precipitation and other model variables in a CPM setup with a grid size of 3 km and a regional climate model (RCM) setup at 25 km resolution using the COSMO-CLM model. We validate our simulations against high-resolution observations (E-OBS (ENSEMBLES observations), HYRAS (Hydrometeorologische Rasterdatensätze), MSWEP (Multi-Source Weighted-Ensemble Precipitation), and UWYO (University of Wyoming)). The study presents a revisited version of the precipitation severity index (PSI) for severe event detection, which is a useful method to detect severe events and is flexible for prioritizing long-lasting events and episodes affecting typically drier areas. Furthermore, we use principal component analysis (PCA) to obtain the main modes of heavy precipitation variance and the associated synoptic weather types (WTs). The PCA showed that four WTs suffice to explain the synoptic situations associated with heavy precipitation in winter, due to stationary fronts and zonal flow regimes. Whereas in summer, five WTs are needed to classify the majority of heavy precipitation events. They are associated with upper-level elongated troughs over western Europe, sometimes evolving into cutoff lows, or with winter-like situations of strong zonal circulation. The results indicate that CPM represents higher precipitation intensities, better rank correlation, better hit rates for extremes detection, and an improved representation of heavy precipitation amount and structure for selected events compared to RCM. However, CPM overestimates grid point precipitation rates, which agrees with findings in past literature. CPM systematically represents more precipitation at the mountain tops. However, the RCMs may show large intensities in other regions. Integrated water vapour and equivalent potential temperature at 850 hPa are systematically larger in RCM compared to CPM in heavy precipitation situations (up to 2 mm and 3 K, respectively) due to wetter mid-level conditions and an intensified latent heat flux over the sea. At the ground level, CPM emits more latent heat than RCM over land (15 W m−2), bringing larger specific humidity north of the Alps (1 g kg−1) and higher CAPE (convective available potential energy) values (100 J kg−1). RCM, on the contrary simulates a wetter surface level over Italy and the Mediterranean Sea. Surface temperatures in RCM are up to 2 ∘C higher in RCM than in CPM. This causes outgoing longwave radiation to be larger in RCM compared to CPM over those areas (10 W m−2). Our analysis emphasizes the improvements of CPM for heavy precipitation modelling and highlights the differences against RCM that should be considered when using COSMO-CLM climate simulations.

Winter heavy precipitation events over Northern Europe modulated by a weaker NAO variability by the end of the 21st century

We use an ensemble of models participating in the Coupled Model Intercomparison Project phase 6 (CMIP6) to analyse the number of days with extreme winter precipitation over Northern Europe and its relationship to the North Atlantic Oscillation (NAO), for the historical period 1950–2014 and two future 21st-century scenarios. Here we find that over Northern Europe, the models project twice more extreme precipitation days by the end of the 21st century under the high-emission scenario compared to the historical period. We also find a weakening of the NAO variability in the second half of the 21st century in the high greenhouse gas emission scenario compared to the historical period, as well as an increasing correlation between extreme winter precipitation events and the NAO index in both future scenarios. Models with a projected decrease in the NAO variability across the 21st century show a positive trend in the number of days with extreme winter precipitation over Northern Europe. These results highlight the role played by NAO in modulating extreme winter precipitation events.

Western disturbances alter the trend of winter precipitation and its extremes over Northwest Himalayas: Kashmir Himalaya.

The perception of spatio-temporal variability of winter precipitation covering dominant water resources and environment over Kashmir Himalaya is a pre-eminent perspective under current social interests. The main objectives of the study are, firstly, to unriddle the whole (1980-2020) and post-2000 trend in the winter season precipitation (WP), frequency of low-pressure systems (Lp-S), and western disturbances (WDs) to understand the footprints of climate change over the region; secondly, to evaluate the spatio-temporal variability of winter precipitation under the dominance of global teleconnection indices, using both station and reanalysis datasets. Modified Mann-Kendell test and a linear regression model were utilized to extract the trend and significance in WP, Lp-S, and WDs. The results reveal that WP shows an insignificant decreasing trend (1980-2020), with an increasing trend post-2000, while a decreasing trend is seen during post-2000 in the frequency of Lp-S and WDs. The contribution of WP to annual precipitation shows decadal variability with a decreasing trend post-2000. The anatomy of winter extreme precipitation days has shown a decreasing trend (1980-2020), with a robust coupled increasing trend with WP post-2000. The dynamics of ten severe WD-based extreme precipitation events show that a cyclonic circulation and trough connects the Arabian Sea and the Himalayas, bringing additional moisture to the study region and resulting in extreme precipitation. The cogency of global teleconnections on the variability of WP shows that a pattern with positive phase of NAO, ENSO, and a negative phase in Siberian high intensifies the WD-based precipitation. The study discovers its applicability for the regional forecast system in predicting the winters.

Future Winter Precipitation Decreases Associated With the North Atlantic Warming Hole and Reduced Convection

AbstractClimate projections in the North Atlantic region suffer from great uncertainties, and projections of precipitation are given with a large spread. Some of this uncertainty is related to projections of the North Atlantic warming hole (NAWH). The Community Earth System Model version 2 (CESM2) projects a relatively strong and extensive NAWH, with future sea surface cooling extending to Northern Scandinavia. This study investigates the relatively large winter precipitation decrease projected by CESM2 in the northeastern North Atlantic region, reinforced in a regional model. Three future scenarios from CESM2 are dynamically downscaled with the Weather Research and Forecast model. A methodology to separate convective and orographic from stratiform precipitation is applied to explore the physical mechanisms. Changes in stratiform precipitation closely relate to storm‐track changes, which varies between the scenarios. Convective precipitation decreases by up to 50% over the Norwegian Sea at the end of the century, which is robust across the scenarios. This is explained by the underlying reduced sea surface temperatures of the NAWH, leading to reduced evaporation and reduced convective activity and intensity. The orographic precipitation maximum over the Scandinavian mountains is shifted upstream, likely affected by increased static stability and flow blocking, which also relates to the NAWH. This shift is possibly also explained by more frequent rain versus snow, as well as reduced cross‐barrier wind speeds. This study contributes to highlight the importance of focusing future research efforts on the NAWH, in order to constrain future climate projections in this region.

Projected change of East-Asian winter precipitation related to strong El Niño under the future emission scenarios

Projected change of East-Asian winter precipitation related to strong El Niño under the future emission scenarios

Recurringly Hypoxic: Bottom Water Oxygen Depletion Is Linked to Temperature and Precipitation in a Great Lakes Estuary

Hypolimnetic hypoxia is expanding globally due to anthropogenic eutrophication and climate warming. Muskegon Lake, a Great Lakes estuary, experiences annually recurring hypoxia, impairing ecological, social, and economic benefits. Using high-frequency, time-series Muskegon Lake Observatory (MLO) data, we quantified the dynamics of hypoxia and developed a hypoxia severity index to estimate the spatiotemporal extent of hypoxia during 2011–2021. We also analyzed United States Geological Survey’s temperature and discharge data on the Muskegon River to explain the annual variability in the hypoxia severity index. Severe hypoxia occurred in warmer years with greater stratification, fewer wind mixing events, warmer winter river temperatures, and less winter and spring precipitation, as in 2012 and 2021. Conversely, milder hypoxia was prevalent in colder years with a later stratification onset, more mixing events, colder river temperatures, and more winter and spring precipitation, as in 2015 and 2019. Thus, knowledge of environmental conditions prior to the onset of stratification may be useful for predicting the potential severity of hypoxia for any year. While consistent multi-year trends in hypoxia were not discernible, our findings suggest that temperature and precipitation are major drivers of hypoxia and that as surface waters warm, it will lead to the further deoxygenation of Earth’s inland waters.

Relationship of seasonal variations in drip waterδ13CDIC,δ18O, and trace elements with surface and physical cave conditions of La Vallina cave, NW Spain

Abstract. Cave-monitoring studies clarify the climatic, surface vegetation, and karst processes affecting the cave system and lay the foundation for interpreting geochemical stalagmite records. Here we report the monitoring of cave air, bedrock chemistry, and drip water δ13CDIC, δ18O, and δD, as well as 16 trace elements, covering a full annual cycle spanning the 16 months between November 2019 and March 2021 in La Vallina cave in the northwestern Iberian Peninsula. While decreased rainfall and increased evapotranspiration in the summer months lead to a strong reduction in drip rates, there is little seasonal variation in δ18O and δD in a given drip, likely reflecting the discrete moderately mixed to well-mixed karst water reservoirs. Small differences in δ18O and δD between drip sites are attributed to variable evaporation intensity and/or transit times. The carbon isotope signature of the dissolved inorganic carbon of drip water (δ13CDIC) is likely driven by seasonal changes in the temperature controlling biological processes (vegetation and microbial soil activity), resulting in minimum δ13CDIC in summer and autumn months. Increased bedrock dissolution due to higher soil pCO2 in summer and autumn results in increased trace element concentrations of congruently dissolved elements. Cave air measurements (pCO2, δ13Cair, and temperature) indicate the seasonal ventilation (winter) and stagnation (summer) of cave air. The opposite effects of reduced cave air pCO2, seasonally variable biological activity, and increased drip rate limit the extent of the seasonal variation in degassing and prior calcite precipitation (PCP) supported by trace elements (Sr/Ca index). Estimated stalagmite growth rates using monitoring data suggest biannual phases of potential calcite precipitation in summer and winter and growth cessation during spring and autumn, depending on cave and drip water conditions and the location within the cave, which has important implications for the proxy interpretation of stalagmite records.

Synchronizing ice-core and U ∕ Th timescales in the Last Glacial Maximum using Hulu Cave 14C and new 10Be measurements from Greenland and Antarctica

Abstract. Between 15 and 27 kyr b2k (thousands of years before 2000 CE) during the last glacial, Greenland experienced a prolonged cold stadial phase, interrupted by two short-lived warm interstadials. Greenland ice-core calcium data show two periods, preceding the interstadials, of anomalously high atmospheric dust loading, the origin of which is not well understood. At approximately the same time as the Greenland dust peaks, the Chinese Hulu Cave speleothems exhibit a climatic signal suggested to be a response to Heinrich Event 2, a period of enhanced ice-rafted debris deposition in the North Atlantic. In the climatic signal of Antarctic ice cores, moreover, a relative warming occurs between 23 and 24.5 kyr b2k that is generally interpreted as a counterpart to a cool climate phase in the Northern Hemisphere. Proposed centennial-scale offsets between the polar ice-core timescales and the speleothem timescale hamper the precise reconstruction of the global sequence of these climatic events. Here, we examine two new 10Be datasets from Greenland and Antarctic ice cores to test the agreement between different timescales, by taking advantage of the globally synchronous cosmogenic radionuclide production rates. Evidence of an event similar to the Maunder Solar Minimum is found in the new 10Be datasets, supported by lower-resolution radionuclide data from Greenland and 14C in the Hulu Cave speleothem, representing a good synchronization candidate at around 22 kyr b2k. By matching the respective 10Be data, we determine the offset between the Greenland ice-core chronology, GICC05, and the Antarctic chronology for the West Antarctic Ice Sheet Divide ice core (WDC), WD2014, to be 125 ± 40 years. Furthermore, via radionuclide wiggle-matching, we determine the offset between the Hulu speleothem and ice-core timescales to be 375 years for GICC05 (75–625 years at 68 % confidence) and 225 years for WD2014 (−25–425 years at 68 % confidence). The rather wide uncertainties are intrinsic to the wiggle-matching algorithm and the limitations set by data resolution. The undercounting of annual layers in GICC05 inferred from the offset is hypothesized to have been caused by a combination of underdetected annual layers, especially during periods with low winter precipitation, and misinterpreted unusual patterns in the annual signal during the extremely cold period often referred to as Heinrich Stadial 1.

Low sensitivity of net primary productivity to climatic factors in three karst provinces in southwest China from 1981 to 2019

Karst areas are sensitive to environmental changes due to their fragile ecological environments. It is imperative to explore the temporal and spatial variations in the characteristics of vegetation net primary productivity (NPP) and evaluate the influence of different driving factors on NPP. Taking three karst provinces in southwest China as the study area, where the historical vegetation changes and the mechanisms influencing these changes remain unclear; therefore, the present study used vegetation NPP data from 1981 to 2019 to analyze the temporal and spatial variations in the characteristics of vegetation NPP using slope trend analyses and the sequential Mann-Kendall test. The influence of each driving factor on vegetation NPP and the interaction between each driving factor were investigated using the optimal parameters-based geographic detector (OPGD) model. The results were as follows: (1) The annual variation of the total NPP in the study area from 1981 to 2019 showed a fluctuating growth trend, with a slow growth rate before 2005 followed by a rapid increase. (2) The annual fluctuations in the seasonal NPP in the study area were generally upward, and the total NPP of vegetation in summer was the highest, but the growth rate of NPP in autumn was the fastest, and the area with the largest increase in NPP in autumn was the largest. (3) NPP was related to natural factors, with slope being the primary influencing factor at the annual scale. However, at the seasonal scale, there were differences in the explanatory power of the influencing factors on vegetation NPP. The highest explanatory power was observed for surface soil moisture in spring, air temperature in summer, and precipitation in autumn and winter. (4) The spatiotemporal evolution of NPP characteristics was affected by the interaction among various natural factors. At the annual and seasonal scales, the interaction between each climatic factor and slope greatly enhanced the explanatory power of individual climatic factors. Taken together, the interaction between slope and precipitation contributes the most to NPP.

Himalayan fir reveals moist phase during Little Ice Age in the Kashmir region of the western Himalayas

The Kashmir region in the western Himalayas is located in a transition zone between areas dominated by the South Asian Summer Monsoon (SASM) and the North Atlantic Oscillation (NAO). Currently being primarily influenced by westerly disturbances (WDs), the area is important to decipher teleconnections between these two important circulation systems for the assessment of past climate variability. We evaluated climate-growth relationships of Abies pindrow (Royle ex D. Don) and reconstructed April to June (AMJ) self-calibrated Palmer drought severity index (scPDSI) for the south Kashmir region during the period 1643–2016 CE. Our reconstructed scPDSI revealed a long wet phase during 1650–1816 CE, indicating the impact of the Little Ice Age (LIA) over the region, followed by prominent drier post-LIA episodes. The mid 18th century (1730–1760 CE) was the wettest period in the past four centuries, whereas the period 1817 to 1865 CE marked the driest phase. These phases are consistent with other precipitation reconstructions from the WD-dominated western and Trans-Himalayan regions, but inconsistant with summer precipitation reconstructions from the SASM-dominated Himalayan regions. A significant positive correlation between our scPDSI reconstruction and the North Atlantic Oscillation (NAO) for the wet phase of the LIA suggests that the NAO remained dominant in modulating the winter and spring precipitation at the study region. During the 19th and 20th centuries, scPDSI was either weakly or negatively correlated with the NAO index, indicating the influence of other atmospheric circulation systems in driving the spring/summer precipitation in the study area. This study, augmented with other moisture records, contributes to analyze the temporal and spatial extent of moisture variability in a regional perspective.

Sap flow responses in pioneer and late-successional tree species in secondary tropical montane forests of Eastern Himalaya, India.

The interactive role of life-history traits and environmental forcing on plant-water relations is crucial for understanding species response to climate change but remains poorly understood in secondary tropical montane forests (TMFs). Comparing contrasting life-history traits (pioneer vs late-successional species) in a biodiverse Eastern Himalayan secondary TMF, we investigated sap flow responses in co-occurring pioneer species, Symplocos racemosa (n=5) and Eurya acuminata (n=5), and late-successional species, Castanopsis hystrix (n=3), using modified Granier's Thermal Dissipation probes. The fast-growing pioneers S. racemosa and E. acuminata) had 2.1- and 1.6-times higher sap flux density than the late-successional C. hystrix, respectively, and exhibited characteristics of long-lived pioneer species. Significant radial and azimuthal variability in sap flow (V) between species was observed and attributed to life history traits and the canopy's access to sunlight. Nocturnal V (1800-0500hr) was 13.8 % of daily V and is attributed to stem recharge for evening V (1800-2300hr) and to endogenous stomatal controls for pre-dawn V (0000-0500hr). Both the shallow-rooted pioneer species exhibited midday depression in V attributed to photosensitivity and diel moisture stress response. In contrast, deep-rooted C. hystrix transpired unaffected across the dry season likely accessing groundwater. Thus, the secondary broadleaved TMFs, with the dominance of shallow-rooted pioneers, are more prone to the negative impacts of drier and warmer winters than primary forests, which are dominated by deep-rooted species. The study provides an empirical understanding of life-history traits and microclimate modulating plant-water use in widely distributed secondary TMFs in Eastern Himalaya and highlights their vulnerability against warmer winters and reduced snowfall due to climate change.

The Influence of DOC on the Migration Forms of Elements and Their Sedimentation from River Waters at an Exploited Diamond Deposit (NW Russia)

The development of mineral deposits causes changes that are comparable to natural exogenous geological processes, and prevail over the latter in local areas of intensive mining activity. In this article, a diamond deposit is selected, developed by quarries of great depth, and a forecast is made of the impact of drainage water discharge on changes in the composition of surface water and bottom sediments during the entire period of development of the deposit. Modeling was performed according to various scenarios, taking into account changes in the total dissolved solids of groundwater from 0.5 to 21.7 g/kg H2O. Thermodynamic calculations were carried out using the HCh software package. The role of dissolved organic carbon in the migration of chemical elements and the effect of DOC on the precipitation of chemical elements from mixed solutions is given. It has been established that fulvic acid completely binds to Fe in the Fe(OH)2FA− complex in all types of natural waters and under all mixing scenarios. With humic acid, such a sharp competitive complex formation does not occur. It is distributed among the various elements more evenly. It was determined that the mass of precipitating iron in the presence of DOC decreases by 18–27%, and its precipitation in winter is more intense. In contrast to Fe, the precipitation of Ca, Mg, and C from solutions with DOC is higher in summer, and there are more of them in the solutions in winter. This study contributes to a better understanding of the behavior of heavy metals in surface waters and sediments under anthropogenic pressures in order to improve the sustainable management of water resources in the face of anthropogenic activities.

The North American Monsoon buffers forests against the ongoing megadrought in the Southwestern United States.

The US Southwest has been entrenched in a two-decade-long megadrought (MD), the most severe since 800 CE, which threatens the long-term vitality and persistence of regional montane forests. Here, we report that in the face of record low winter precipitation and increasing atmospheric aridity, seasonal activity of the North American Monsoon (NAM) climate system brings sufficient precipitation during the height of the summer to alleviate extreme tree water stress. We studied seasonally resolved, tree-ring stable carbon isotope ratios across a 57-year time series (1960-2017) in 17 Ponderosa pine forests distributed across the NAM geographic domain. Our study focused on the isotope dynamics of latewood (LW), which is produced in association with NAM rains. During the MD, populations growing within the core region of the NAM operated at lower intrinsic and higher evaporative water-use efficiencies (WUEi and WUEE , respectively), compared to populations growing in the periphery of the NAM domain, indicating less physiological water stress in those populations with access to NAM moisture. The disparities in water-use efficiencies in periphery populations are due to a higher atmospheric vapor pressure deficit (VPD) and reduced access to summer soil moisture. The buffering advantage of the NAM, however, is weakening. We observed that since the MD, the relationship between WUEi and WUEE in forests within the core NAM domain is shifting toward a drought response similar to forests on the periphery of the NAM. After correcting for past increases in the atmospheric CO2 concentration, we were able to isolate the LW time-series responses to climate alone. This showed that the shift in the relation between WUEi and WUEE was driven by the extreme increases in MD-associated VPD, with little advantageous influence on stomatal conductance from increases in atmospheric CO2 concentration.

The spatiotemporal extent of the Green Sahara during the last glacial period

The Sahara Desert, one of today's most inhospitable environments, has known periods of enhanced precipitation that supported pre-historic humans. However, the Green Sahara timing and moisture sources are not well known due to limited paleoclimate information. Here, we present a multi-proxy (δ18O, δ13C, Δ17O, and trace elements) speleothem-based climate record from Northwest (NW) Africa. Our data document two Green Sahara periods during Marine Isotope Stage (MIS) 5a and the Early to Mid-Holocene. Consistency with paleoclimate records across North Africa highlights the east-west geographical extent of the Green Sahara, whereas millennial-scale North Atlantic cooling (Heinrich) events consistently resulted in drier conditions. We demonstrate that an increase in westerly-originating winter precipitation during MIS5a resulted in favorable environmental conditions. The comparison of paleoclimate data with local archaeological sequences highlights the abrupt climate deterioration and the decline in human density in NW Africa during the MIS5-4 transition, which suggests climate-forced dispersals of populations, with possible implications for pathways into Eurasia.

Chir pine forest and pre-monsoon drought determine spatial, and temporal patterns of forest fires in Uttarakhand Himalaya.

The online version contains supplementary material available at 10.1007/s42965-023-00306-9.