Changes In Amount Of Precipitation Research Articles

Nitrogen addition regulates the effects of variation in precipitation patterns on plant biomass formation and allocation in a Leymus chinensis grassland of northeast China.

Global warming is predicted to change precipitation amount and reduce precipitation frequency, which may alter grassland primary productivity and biomass allocation, especially when interact with other global change factors, such as nitrogen deposition. The interactive effects of changes in precipitation amount and nitrogen addition on productivity and biomass allocation are extensively studied; however, how these effects may be regulated by the predicted reduction in precipitation frequency remain largely unknown. Using a mesocosm experiment, we investigated responses of primary productivity and biomass allocation to the manipulated changes in precipitation amount (PA: 150mm, 300mm, 450mm), precipitation frequency (PF: medium and low), and nitrogen addition (NA: 0 and 10 g N m-2 yr-1) in a Leymus chinensis grassland. We detected significant effects of the PA, PF and NA treatments on both aboveground biomass (AGB) and belowground biomass (BGB); but the interactive effects were only significant between the PA and NA on AGB. Both AGB and BGB increased with an increment in precipitation amount and nitrogen addition; the reduction in PF decreased AGB, but increased BGB. The reduced PF treatment induced an enhancement in the variation of soil moisture, which subsequently affected photosynthesis and biomass formation. Overall, there were mismatches in the above- and belowground biomass responses to changes in precipitation regime. Our results suggest the predicted changes in precipitation regime, including precipitation amount and frequency, is likely to alter primary productivity and biomass allocation, especially when interact with nitrogen deposition. Therefore, predicting the influence of global changes on grassland structure and functions requires the consideration of interactions among multiple global change factors.

Modern changes in climatic characteristics and minimum flow of the rivers in the basin of lake Sevan

Formulation of the problem. Studies and data on modern changes in the winter minimum average monthly flow of the rivers of the Lake Sevan basin and their climatic characteristics have acquired great practical importance and considerable interest due to the increased use of water resources for the purposes of various types of economic activities, in particular, in connection with the development of the economy, hydropower, irrigation, population growth and rising living standards. Especially relevant are the calculations of the minimum flow in relation to solving the problems of water supply for settlements, industrial enterprises. The aim of the work. Assessment of modern changes in the winter minimum average monthly runoff of rivers in the Lake Sevan basin and their climatic characteristics. Methods. The following methods were used in the work: mathematical-statistical, extrapolation, interpolation, spatial analysis, analogy, correlation and cartography. Results. A physical map has been compiled with a network of meteorological stations and hydrological posts in the Lake Sevan basin. Close correlations were obtained between the values of the winter minimum average monthly runoff and the average runoff of the winter period for a hydrological year. These dependences can be used for preliminary estimates of the minimum runoff of the winter low-water period of unstudied rivers in the territory under consideration. In the course of the research, the winter minimum average monthly discharges were calculated by months and for the entire observation period, the average value of the minimum runoff for the winter low water, and the linear trend of the climatic characteristic. Based on the obtained results, a map of the distribution of the modul of the average minimum runoff of the winter low-water period and the coefficients of the linear trend of the winter air temperature were constructed. Examples of curves of long-term changes in precipitation amounts for the autumn and winter periods, the sum of positive temperatures and the number of days with a positive average daily air temperature in the winter period for a series of meteorological stations in the study area are presented. The rivers of the Lake Sevan basin are characterized by an uneven spatio-temporal distribution of winter minimum runoff and climatic characteristics, changes in the winter average monthly minimum runoff, precipitation amounts for the autumn and winter periods are multidirectional, and air temperature changes are only an upward trend. In the area under consideration, there is mainly (by 8 out of 12 stations under study) a tendency to decrease in the values of the minimum average monthly river flow. The conducted studies lead us to the conclusion that the main factor causing changes in the low-water runoff of the rivers in the Lake Sevan basin in winter is the air temperature, or rather, its increase. It follows from this that when calculating and forecasting winter runoff, it is necessary to relate the values of runoff and air temperature.

Subdaily Extreme Precipitation and Its Linkage to Global Warming Over the Tibetan Plateau

AbstractThe spatiotemporal characteristics of subdaily extreme precipitation over the Tibetan Plateau (TP) have undergone significant changes due to global warming. In this study, we employed the high‐resolution Weather Research and Forecasting regional climate model to conduct a series of historical and projection simulations under representative concentration pathways (RCPs), especially RCP4.5 and RCP8.5. The aim was to investigate the past and future climatologies and spatiotemporal evolution of subdaily precipitation extremes using newly proposed subdaily extreme precipitation indices (EPIs). The results show that projected changes in precipitation amount, particularly during wet hours, exhibit spatial disparaties. Notably, there are significant decreases along the southern border of the TP and over the western TP, while obvious increases are observed over the inner TP. The southeastern TP, western TP, and southern border of the TP are expected to experience less frequent, shorter duration, and more intense precipitation on an hourly basis. The TP, as a whole, has demonstrated significantly increasing trends in moderate‐to‐heavy precipitation frequencies, along with consistent decreasing trends in precipitation events with short, medium, and long durations. Furthermore, it is predicted that the relationship between extreme precipitation and temperature will deviate from the Clausius‐Clapeyron (C‐C) relationship toward the double C‐C relationship in the far‐future under RCP8.5, particularly over the southeastern TP. Additionally, there are robust correlations between the intensity‐related EPIs and elevation. This indicates that, at the local scale, the complex topography of the region may play a crucial role in shaping the nonuniform distribution of precipitation extremes by modulating associated upward motion.

Global reorganization of atmospheric circulation during Dansgaard–Oeschger cycles

Ice core records from Greenland provide evidence for multiple abrupt cold-warm-cold events recurring at millennial time scales during the last glacial interval. Although climate variations resembling Dansgaard-Oeschger (DO) oscillations have been identified in climate archives across the globe, our understanding of the climate and ecosystem impacts of the Greenland warming events in lower latitudes remains incomplete. Here, we investigate the influence of DO-cold-to-warm transitions on the global atmospheric circulation pattern. We comprehensively analyze δ18O changes during DO transitions in a globally distributed dataset of speleothems and set those in context with simulations of a comprehensive high-resolution climate model featuring internal millennial-scale variations of similar magnitude. Across the globe, speleothem δ18O signals and model results indicate consistent large-scale changes in precipitation amount, moisture source, or seasonality of precipitation associated with the DO transitions, in agreement with northward shifts of the Hadley circulation. Furthermore, we identify a decreasing trend in the amplitude of DO transitions with increasing distances from the North Atlantic region. This provides quantitative observational evidence for previous suggestions of the North Atlantic region being the focal point for these archetypes of past abrupt climate changes.

Differences in Global Precipitation Regimes between Land and Ocean Areas Based on the GPM IMERG Product

Climate change research has received increasing attention from both researchers and the public, and the analysis of precipitation is one of the most important topics in this field. As a supplement to gauge observations, satellite-derived precipitation data present advantages, as they have high spatiotemporal resolution and good continuity. The Global Precipitation Measurement (GPM) mission is the newest generation of precipitation measurement products designed to conduct quasi-global satellite observations. This study used the latest Integrated Multi-satellitE Retrievals for GPM data collected between 2001 and 2020 to analyze changes in precipitation amount, frequency, and intensity on global land and ocean surfaces. The results showed that precipitation intensity over the ocean was generally higher than on land, and the two were more similar at the hourly scale than at the daily scale, as shown by the JS divergence statistics: 0.0323 and 0.0461, respectively. This may be due to the thermodynamic differences between land and the ocean, which can accumulate over a longer time scale. The average number of annual precipitation hours and days increased by 50 h and 5 days during 2011–2020 compared with the previous decade. The absence of obvious changes in annual precipitation amounts led to a decrease in annual precipitation intensity and the weakening of extreme precipitation on land. The analysis of precipitation regimes in nine mainland regions of the globe showed a significant increasing trend for both hourly and daily precipitation in North Asia, while insignificant changes or even decreasing trends were detected in the other regions. The results of this study elucidated the variations in precipitation between land and ocean areas and can contribute to the understanding of global precipitation.

Yield shortfall of cereals in Ukraine caused by the change in air temperature and precipitation amount

Aim. To determine the trends in precipitation patterns, the precipitation productivity, and the cumulative impact of the change in air temperature and precipitation levels on cereal yield, including corn and spring barley, throughout the vegetation cycle stages. Furthermore, the examination of the alterations in the climate suitability, crop yield shortfall, and their specific characteristics within in the soil-climatic zones of Ukraine during 1981–2010 years Methods. In order to accomplish the outlined aims conventional and more specific research methods were used: 1) An analytical- synthetic approach – to examine the existing state-of-the art research; 2) A statistical approach – to assess the intensity and significance of changes in agroclimatic conditions pertaining to crop cultivation; 3) A comparative analysis – to determine the specificities mentioned under 2) in soil-climatic zones of Ukraine and in different stages of plant development; 4) A climatic approach – to characterize precipitation levels and to evaluate their impact on crop productivity; 5) modelling – to assess the effect of changes in precipitation amounts on the productivity of corn and spring barley, to assess the cumulative impact of the variations in surface temperature and precipitation on climate productivity and yield shortfall of these crops; 6) application of abstract and logical method – to formulate the generalizations and draw conclusions based on the findings. Results. During the years 1981–2010, Ukraine experienced changes in precipitation patterns and increased air temperature throughout the vegetation cycle of corn and spring barley in different soil-climatic zones. These changes had implications for climate suitability and crop productivity. In the Polis- sia region, although there were increases in precipitation during most of the crops` growth cycle, the changes were insignificant and had a minimal impact on crop productivity, except during certain periods. Similarly, the cumulative coefficient of temperature and precipitation productivity showed low probability for changes in climate suitability and yield shortfalls in the entire Polissia region, maintaining avorable cultivation conditions for corn and spring barley. In the Forest-Steppe region, precipitation changes varied. There was an increase in the amount of precipitation in the western Forest-Steppe. The speed of these changes was 10–20 % in 10 years in certain areas, leading to decreased corn and spring barley productivity by 3–6 % over the same duration. The central Forest-Steppe witnessed increases and decreases in precipitation levels during specific crop development stages, negatively impacting productivity. The eastern Forest-Steppe had increased precipitation deficits during the vegetation cycle, resulting in reduced productivity. Overall, the changes in precipitation and the increased air temperature had unfavorable effects on field crop cultivation in the Forest-Steppe, particularly in the central region. Corn yield shortfalls of 3–5 % and spring barley yield shortfalls of 2–3 % were observed over each 10 years. In general, however, for spring barley favorable agroclimatic conditions persisted throughout the Forest-Steppe, and corn cultivation remained favorable in the western and satisfactory in the central and eastern areas. In the Steppe region, changes in precipitation levels were minimal, with fluctuations of 5 % over each 10 years. However, significant variations in moisture levels occurred during specific crop development stages. An increase in precipitation levels during the stage milky ripeness-middle dough phase of corn resulted in 3 % yield decrease over each 10 years. Spring barley benefited from increased precipitation during the tillering stage and decreased precipitation during the stagemilky ripeness and middle dough stages, leading to higher (precipitation) productivity. Overall, the considerable increase in air temperature and changes in moisture conditions in many cases adversely affected corn and spring barley cultivation, especially in the southern Steppe. These changes led to a 7–10 % decrease in corn climate suitability cultivation and 3–4 % decrease in spring barley over each 10 years. Corn cultivation conditions in the southern Steppe were deemed unsatisfactory, while those for spring barley remained satisfactory. Yield shortfalls due to the changes in air temperature and precipitation from 1981 to 2010 were 35–40 % for corn and 22–25 % for spring barley. Conclusions. The changes in precipitation and air temperature in Ukraine have significant implications for field crop productivity throughout the vegetation cycle. Decreases in precipitation levels during crop ripening stages and higher precipitation deficits during certain vegetation stages have resulted in reduced precipitation suitability and lower crop productivity. When combined with increased air temperature, these changes further contribute to decreased climate productivity and increased yield shortfalls for corn and spring barley. The most pronounced effects are observed in the Steppe region, particularly in the southern Steppe, where corn yield shortfalls due to air temperature and precipitation changes from 1981 to 2010 reached 35–40 % of the maximum potential yield under optimal climatic conditions, compared to 22–25 % for spring barley In contrast, the agroclimatic conditions for corn and spring barley cultivation in Polissia remained favorable throughout the observation period (1981–2010), regardless of changes in air temperature and precipitation. In the Forest-Steppe zone, conditions were favorable for barley cultivation and satisfactory for corn in the central and eastern areas. Abnormally high air temperatures coupled with precipitation deficits have resulted in higher yield shortfalls for cereals in significant areas of the country. The combination of increased air temperature and drier conditions underscores the diminishing potential of dryland farming in Ukraine, particularly in the Steppe region.

A speleothem record of seasonality and moisture transport around the 8.2 ka event in Central Europe (Vacska Cave, Hungary)

AbstractA stalagmite was collected in northern Hungary from the Vacska Cave, where monitoring and ventilation-based site selection had been conducted. The stalagmite covers the 10–8 ka (relative to AD 1950) period, including the so-called 8.2 ka event, and showed preceding signs of climate change that were evaluated by petrographic observations, 14C activities, Sr concentrations, and stable isotope compositions of calcite and inclusion-hosted water. Comparisons of speleothem records show that isotope peaks at ca. 8.5 ka are related to a regional climate anomaly, rather than to a continental-scale event. In accordance with regional proxy records, the 8.2 ka event was associated with a series of temperature and precipitation amount changes, starting with cooling and a reduction in the winter-to-summer precipitation ratio, and then becoming a humid and warm phase at 8.15 ka. X-ray diffraction-based crystallinity parameter (FWHM) values provided evidence for diagenetic alteration of the stable oxygen isotope compositions of inclusion waters. Nevertheless, the stable hydrogen isotope compositions of inclusion waters and the oxygen isotope values of the host calcite revealed elevated d-excess values, and therefore increased Mediterranean moisture contribution during the 8.2 ka event, which indirectly indicate the southward displacement of moisture transport from the Atlantic Ocean.

Climate-driven changes in the predictability of seasonal precipitation

Climate-driven changes in precipitation amounts and their seasonal variability are expected in many continental-scale regions during the remainder of the 21st century. However, much less is known about future changes in the predictability of seasonal precipitation, an important earth system property relevant for climate adaptation. Here, on the basis of CMIP6 models that capture the present-day teleconnections between seasonal precipitation and previous-season sea surface temperature (SST), we show that climate change is expected to alter the SST-precipitation relationships and thus our ability to predict seasonal precipitation by 2100. Specifically, in the tropics, seasonal precipitation predictability from SSTs is projected to increase throughout the year, except the northern Amazonia during boreal winter. Concurrently, in the extra-tropics predictability is likely to increase in central Asia during boreal spring and winter. The altered predictability, together with enhanced interannual variability of seasonal precipitation, poses new opportunities and challenges for regional water management.

A downscaling and bias correction method for climate model ensemble simulations of local-scale hourly precipitation

Ensemble simulations of climate models are used to assess the impact of climate change on precipitation, and require downscaling at the local scale. Statistical downscaling methods have been used to estimate daily and monthly precipitation from observed and simulated data. Downscaling of short-term precipitation data is necessary for more accurate prediction of extreme precipitation events and related disasters at the regional level. In this study, we developed and investigated the performance of a downscaling method for climate model simulations of hourly precipitation. Our method was designed to recognize time-varying precipitation systems that can be represented at the same resolution as the numerical model. Downscaling improved the estimation of the spatial distribution of hourly precipitation frequency, monthly average, and 99th percentile values. The climate change in precipitation amount and frequency were shown in almost all areas by using the 50 ensemble averages of estimated precipitation, although the natural variability was too large to compare with observations. The changes in precipitation were consistent with simulations. Therefore, our downscaling method improved the evaluation of the climatic characteristics of extreme precipitation events and more comprehensively represented the influence of local factors, such as topography, which have been difficult to evaluate using previous methods.

Model-simulated hydroclimate in the East Asian summer monsoon region during past and future climate: a pilot study with a moisture source perspective

Abstract. Here we present a pilot study of the sensitivity of summer monsoon precipitation in the Yangtze River Valley (YRV; 110–122∘ E and 27–33∘ N, eastern China) to climatic boundary conditions from the Last Glacial Maximum (LGM), pre-industrial conditions, and the Representative Concentration Pathway 6 emission scenario from two different climate models. Using a quantitative Lagrangian moisture source diagnostic based on backward trajectories, we are able to interpret changes in precipitation amount and seasonality in terms of processes at the source regions and during transport that contribute to YRV precipitation. Thereby, we gain insight into influential processes and characteristics related to precipitation variability and the sensitivity of the summer monsoon hydroclimate in East Asia to boundary-condition changes in models. Comparing 10-year time slices similar to present-day conditions from the NorESM1-M and CAM5.1 models to reanalysis data reveals overall similar moisture source regions, albeit with a tendency for a more local precipitation origin in the climate models. The general characteristics of the moisture sources and moisture transport in the YRV are relatively stable across different climate forcings, both concerning the mean location of source regions, transport distance, and the relative contributions of moisture from land and ocean areas. Changes regarding regional precipitation contributions from the East Asian continent indicate that precipitation recycling responds to different climate forcings. We interpret these findings such that models to first order respond with a scaling rather than reorganisation of the hydroclimate to climatic forcing, while land–atmosphere interactions play an important, but secondary, role. If the model simulations are accurate, the moisture source regions and thus the general processes of precipitation in the YRV could remain relatively stable across different climates. However, some differences in moisture source conditions are larger between the different climate models than between different climatic boundary conditions in the same model. It may therefore be possible that current climate models underestimate the potential for non-linear responses to changing boundary conditions, for example due to precipitation recycling. Although limited by the relatively short analysis period, our findings demonstrate that the diagnosis of moisture sources provides a useful additional perspective for understanding and quantifying precipitation mechanisms and the hydroclimate simulated by models and enables more detailed evaluation of model simulations, for example using paleoclimate records.

The influence of the precipitation recycling process on the shift to heavy precipitation over the Tibetan Plateau in the summer

On the Tibetan Plateau (TP), precipitation intensity has shifted to heavy precipitation due to global warming. However, the influence of the precipitation recycling process on this phenomenon remains unknown. Using the Water Accounting Model-2layers (WAM2layers) model and ERA5 reanalysis, this study investigates the contributions of the precipitation recycling process to precipitation shifts over the TP during 1979–2019. The precipitation shift rate was proposed to quantify this process, and the results reveal that the positive precipitation shift (1.384 mm/41 years) over the TP consists of a positive shift over the western TP (5.666 mm/41 years) and a negative shift (−3.485 mm/41 years) over the eastern TP. Considering the source of moisture, either a local source or a remote source, precipitation was decomposed into internal and external cycles of the precipitation recycling process based on the WAM2layers model. Further analysis indicates that the internal cycle (87.2%) contributes more to the shift than the external cycle (12.8%) over the TP. The contributions of the precipitation recycling ratio (PRR) and precipitation amount to the precipitation shift rate induced by the internal cycle were further investigated. The results indicate that PRR changes contribute more to heavy precipitation over the TP, while precipitation amount changes contribute more to light precipitation. The precipitation recycling process contributes to the shift by increasing atmospheric moisture and increasing (decreasing) the dependency on local evaporation in heavy (light) precipitation. Increased dependence of heavy precipitation on evaporation increases the risk of extreme precipitation, and the government should take preventative actions to mitigate these adverse effects.

Significant effects of precipitation frequency on soil respiration and its components-A global synthesis.

Global warming intensifies the hydrological cycle, which results in changes in precipitation regime (frequency and amount), and will likely have significant impacts on soil respiration (Rs ). Although the responses of Rs to changes in precipitation amount have been extensively studied, there is little consensus on how Rs will be affected by changes in precipitation frequency (PF) across the globe. Here, we synthesized the field observations from 296 published papers to quantify the effects of PF on Rs and its components using meta-analysis. Our results indicated that the effects of PF on Rs decreased with an increase in background mean annual precipitation. When the data were grouped by climate conditions, increased PF showed positive effects on Rs under the arid condition but not under the semi-humid or humid conditions, whereas decreased PF suppressed Rs across all the climate conditions. The positive effects of increased PF mainly resulted from the positive response of heterotrophic respiration under the arid condition while the negative effects of decreased PF were mainly attributed to the reductions in root biomass and respiration. Overall, our global synthesis provided for the first time a comprehensive analysis of the divergent effects of PF on Rs and its components across climate regions. This study also provided a framework for understanding and modeling responses of ecosystem carbon cycling to global precipitation change.

Carbon dioxide fluxes of cyanobacterial crusts and underlying soil under different precipitation patterns in the Ulan Buh Desert, China

Cyanobacterial crusts, sensitive to changes in the moisture content, are widely distributed in the Ulan Buh Desert. Changes in precipitation patterns due to global climate change are expected to influence the carbon emission and photosynthetic carbon fixation of soil in areas covered with cyanobacterial crusts. We assessed how changes in precipitation amount and frequency affect carbon processes of Cyanobacterial Crusts. Taking average precipitation amount and frequency in August during the past 30 years as control, we established nine precipitation patterns (three amounts × three frequencies). The net carbon flux (NCF) and dark respiration rate (DRR) of cyanobacterial crusts and underlying soil were investigated. Precipitation could stimulate NCF and DRR immediately. With increasing water application times, the peak values of NCF, DRR and 12 h cumulative carbon emissions gradually decreased. Both precipitation amount and frequency significantly affected cumulative carbon emissions but without an interactive effect. Under the same frequency, cumulative carbon emissions increased with increasing precipitation amounts. Under the same total precipitation amount, cumulative carbon emissions caused by high-frequency events were the highest, followed by those of low-frequency precipitation and the control. However, such changes, against the background of a changing global climate, will result in increased carbon emissions of cyanobacterial crusts and underlying Soil, suggesting that cyanobacteria should be considered in projections of the future carbon budget.

Assessment of the century-long and current trends in the change in the amount of precipitation in the Nakhichevan Autonomous Republic of Azerbaijan

Some issues of assessing the century-long and current state of the amount of atmospheric precipitation in the territory of the Nakhichevan Autonomous Republic of Azerbaijan are considered. Brief general information about this area is given. To assess the century-long tendency in the amount of atmospheric precipitation in the Nakhichevan hydrometeorological station, used the annual amount of atmospheric precipitation for the period 1891–2015. A graph of the dynamics of the annual amount of atmospheric precipitation, as well as the straight-line and curved-line trends in the series of this element, which characterise the features of the considered dynamics for 1891–2015, is presented. An assessment of possible changes in the annual amount of atmospheric precipitation for different climatic periods (1891–1910, 1911–1940, 1941–1971, 1972–2015) in the Nakhichevan hydrometeorological station is also presented. Taking into account the variability of annual precipitation in a large range, the frequency of occurrence of various gradations of this indicator for 1891–2015 was calculated. Due to the fact that the territory of the region under consideration has a complex relief, the values of the vertical gradients of atmospheric precipitation by months were calculated. Using the equations of relationship, the calculations of the annual amount of atmospheric precipitation for different heights are carried out and a comparison with the corresponding values is carried out. The results of calculations and assessment of the corresponding changes are presented.

Downscaling of climate change scenarios for a high-resolution, site-specific assessment of drought stress risk for two viticultural regions with heterogeneous landscapes

Abstract. Extended periods without precipitation, observed for example in central Europe including Germany during the seasons from 2018 to 2020, can lead to water deficit and yield and quality losses for grape and wine production. Irrigation infrastructure in these regions to possibly overcome negative effects is largely non-existent. Regional climate models project changes in precipitation amounts and patterns, indicating an increase in frequency of the occurrence of comparable situations in the future. In order to assess possible impacts of climate change on the water budget of grapevines, a water balance model was developed, which accounts for the large heterogeneity of vineyards with respect to their soil water storage capacity, evapotranspiration as a function of slope and aspect, and viticultural management practices. The model was fed with data from soil maps (soil type and plant-available water capacity), a digital elevation model, the European Union (EU) vineyard-register, observed weather data, and future weather data simulated by regional climate models and downscaled by a stochastic weather generator. This allowed conducting a risk assessment of the drought stress occurrence for the wine-producing regions Rheingau and Hessische Bergstraße in Germany on the scale of individual vineyard plots. The simulations showed that the risk for drought stress varies substantially between vineyard sites but might increase for steep-slope regions in the future. Possible adaptation measures depend highly on local conditions and are needed to make targeted use of water resources, while an intense interplay of different wine-industry stakeholders, research, knowledge transfer, and local authorities will be required.

Long-term hydroclimate variability in the sub-tropical North Atlantic and anthropogenic impacts on lake ecosystems: A case study from Flores Island, the Azores

Human land use and climate change threaten ecosystems and natural resources, particularly on remote islands such as the Azores Archipelago in the North Atlantic. Since the official Portuguese settlement of the archipelago in the 15th and 16th centuries humans have extensively modified the Azorean landscape, with invasive plants dominating the present-day vegetation and evidence of eutrophication in numerous lakes. To evaluate changes in terrestrial and aquatic ecosystems in the Azores, we developed paleoecological and paleoclimate records from Lake Funda on Flores Island that span the last millennium. Changes in precipitation amount, as recorded by hydrogen isotopes from C30 fatty acids (δ Dwax), suggest that the climate was relatively stable between c. 1000–1400 CE. Recent evidence of early human settlers on the Azorean islands (c. 850–1300 CE) suggests that the introduction of livestock led to an increase in primary productivity in Lake Funda and other lakes in the Azores. More depleted δ Dwax values between c. 1500–1620 CE suggest that wetter climate conditions existed during the establishment of permanent settlements on Flores Island. Landscape changes between c. 1500–1600 CE coincided with an increase in primary productivity and hypoxic conditions in the lake bottom water, signifying the eutrophication of Lake Funda. Despite reforestation efforts in the Azores in the early 20th century and shift towards drier conditions, eutrophication in Lake Funda persisted. Reforestation efforts likely reduced nutrient leaching and soil erosion in the catchment area of Lake Funda and other Azorean lakes, yet eutrophication continues to be widespread. This highlights the lasting impacts of early human settlers on Lake Funda, and the need for more active remediation efforts.

Climate change and water supply: governance and adaptation planning in Florida

Abstract Florida has been described as ‘ground zero’ for climate change in the United States with coastal communities vulnerable to sea-level rise and water supplies under threat from saline-water intrusion, changes in precipitation amounts and patterns, and temperature-driven increases in demands. Water utilities and regional suppliers are responsible for their own water supply plans and adaptation strategies, which are developed largely by a relatively small group of technical specialists (internal and contracted). Water supply planning is prescribed by the state water governance system and local community planning processes. The degree of engagement of large coastal communities and water utilities and regional water suppliers in Florida with climate change research is generally high. Climate change-induced impacts to water supplies and demands over the common 20-year planning horizon are likely to be small relative to increases in demand caused by projected on-going population growth and normal climatic variation. Water utilities in Florida have been incidentally moving toward more climate-resilient supplies (e.g., brackish groundwater desalination) due to the unavailability of additional permittable, inexpensive fresh groundwater rather than climate change concerns. Climate change will narrow the alternatives for future water-supply development.

Nonlinear carbon cycling responses to precipitation variability in a semiarid grassland

Changes in precipitation amount and variability would profoundly affect carbon (C) cycling in arid and semiarid grasslands. However, compared to the effects of precipitation amounts, little is understood about the impacts of precipitation temporal variability on terrestrial C cycling. To explore relationships between precipitation variability and C cycling processes and the underlying mechanisms, we conducted a 3-year field experiment and a 12-year model simulation, in which the constant seasonal precipitation amount was temporally manipulated with four and six levels of precipitation variability, respectively, in a semiarid grassland. Based on the manipulative experiment, we found various nonlinear relationships between C cycling processes and the coefficient of precipitation variability (Pcv), including a trinomial relationship for soil respiration (tipping point: 3 and 4.3), convex relationships for gross and net ecosystem production (peak at 3.5) as well as belowground biomass (peak at 4) and a nonlinear negative relationship for ecosystem respiration (peak at 2.5). Such relationships were regulated by seasonal averaged soil water content (SWC), early-growing season precipitation amount, soil inorganic nitrogen availability (SIN), and both SWC and SIN, respectively. However, these results from the manipulative experiment did not match those from the model simulation, in which ecosystem C cycling processes, dominated only by SWC responses, showed positive linear responses to Pcv. Our results mirror that the nonlinear responses of grassland C cycling to precipitation variability as regulate by SWC and SIN should be incorporated into models to forecast future ecosystem shifts under climate change.

Tales from the Underground: Speleothem Records of Past Hydroclimate

Geochemical records from speleothems have significantly advanced our understanding of natural climate variability over the last ~600,000 years. Speleothems are sensitive recorders of past changes in hydroclimate because they can be precisely dated and contain multiple hydrologically sensitive geochemical proxies. Oxygen isotope records from speleothems tell us about the timing and mechanisms of past changes in precipitation amount, temperature, atmospheric circulation, and/or global monsoon intensity. Variations in speleothem carbon isotope ratios or trace element concentrations reflect changes in local water balance, vegetation, and karst hydrology. Speleothem paleoclimate records represent a window into the past that can provide crucial information for understanding how anthropogenic climate change and natural climate variability will impact future water resources on Earth.

Changes in precipitation amounts and extremes across Xinjiang (northwest China) and their connection to climate indices.

Xinjiang is a major part of China’s arid region and its water resource is extremely scarcity. The change in precipitation amounts and extremes is of significant importance for the reliable management of regional water resources in this region. Thus, this study explored the spatiotemporal changes in extreme precipitation using the Mann–Kendall (M–K) trend analysis, mutation test, and probability distribution functions, based on the observed daily precipitation data from 89 weather stations in Xinjiang, China during 1961–2018. We also examined the correlations between extreme precipitation and climate indices using the cross-wavelet analysis. The results indicated that the climate in Xinjiang is becoming wetter and the intensity and frequency of extreme precipitation has begun to strengthen, with these trends being more obvious after the 1990s. Extreme precipitation trends displayed spatial heterogeneity in Xinjiang. Extreme precipitation was mainly concentrated in mountainous areas, northern Xinjiang, and western Xinjiang. The significant increasing trend of extreme precipitation was also concentrated in the Tianshan Mountains and in northern Xinjiang. In addition, the climate indices, North Atlantic Oscillation, Atlantic Multidecadal Oscillation, Multivariate ENSO Index and Indian Ocean Dipole Index had obvious relationships with extreme precipitation in Xinjiang. The relationships between the extreme precipitation and climate indices were not clearly positive or negative, with many correlations advanced or delayed in phase. At the same time, extreme precipitation displayed periodic changes, with a frequency of approximately 1–3 or 4–7 years. These periodic changes were more obvious after the 1990s; however, the exact mechanisms involved in this require further study.