Search

Dependent upon the relatively severe ecological conditions of the forest stands at the highland landscapes, they sometimes experience transformations. Forest stand tree species, which are a bit more tolerant to these conditions, gain advantage over the others, and hence often tend to intrude into the nearby stands, transforming them and influencing their canopy characteristics. At a highland landscape of Western Black Sea Region in Turkey, a sessile oak stand, which had remained young and pure along the 20 years (1986–2006), has then been invaded by the Bornmüllerian fir seeds from the surrounding stands and consequently been transformed into young-mature mixed stand throughout the subsequent 15 years (2006–2021). Therefore, then intruded Bornmüllerian firs have primarily and gradually altered the physiological characteristics of the canopies within this mixed stand. The aim of this study is to monitor and analyse the inter-annual physiological changes of these tree canopies using some canopy parameters following the occurrence of the species mixture. The stand canopy physiological characteristics were monitored and analysed by hemispherical photographs and associated parameters obtained from them. These canopy parameters; Leaf Area Index (LAI), Light Transmission (LT), Gap Fraction (GF), Canopy Openness (CO), were acquired for the Junes of the years, 2015, 2018 and 2021. The mean LAI had increased almost 0.50 m2 m–2 within the stand along the eight years period (2007–2015). However, it could only increase 0.20 m2 m–2 along the subsequent six years monitoring period. On the other hand, the percentage values of the other canopy parameters had accordingly decreased. This situation indicated that the first occurrence of the Bornmüllerian fir canopies together with the canopies of the sessile oaks along those eight years period had led to the sudden rise of the mean LAI. Nevertheless, the gradual and slight increment of the mean LAI along the subsequent six years monitoring period, has been attributed to the normal physiological development of the tree species; Bornmülerian firs in particular. In fact, due to the case with the study parcel, the highland landscape has potentially been experiencing gradual increment in the percentage of eco-physiologically more tolerant Bornmüllerian firs and conversely gradual decline in the percentage of eco-physiologically sensitive sessile oaks, whose sustainability within highland landscape should be supported with the ecological and comprehensive management proposals. [ABSTRACT FROM AUTHOR]

The East China Sea Kuroshio (ECS‐Kuroshio) and the Ryukyu Current are the major poleward heat carriers in the North Pacific. Anomalous changes of ECS‐Kuroshio and Ryukyu Current could exert substantial influence on the climate in mid‐latitude regions. However, owing to limited observations and coarse resolution of climate models, how they might change under anthropogenic warming remains unknown. Here, we find an accelerating ECS‐Kuroshio (1.5 Sv) and a decelerating (−2.2 Sv) Ryukyu Current using in‐situ observation during 1958–2022, equivalent to 7% strengthening and 20% weakening in the 65 years. The trend is also simulated by four high‐resolution climate models, with multi‐model ensemble‐mean acceleration (deceleration) of the ECS‐Kuroshio (Ryukyu Current) of 1.2 ± 0.6 Sv (−6.2 ± 2.5 Sv) over 1950–2050. The weakening subtropical wind field reduces their summed transport o. Enhanced stratification, which induces uplift of current system and weaker topography‐flow interaction, leads to the intensifying ECS‐Kuroshio and disappearing Ryukyu Current. Plain Language Summary: The East China Sea Kuroshio (ECS‐Kuroshio) and the Ryukyu Current are the major components of western boundary current (WBC) system in the North Pacific. They transport large amount of heat poleward, maintaining the mid‐latitude region warm and habitable. In this study, we find that in both observation and high‐resolution numerical models, the ECS‐Kuroshio is intensifying and the Ryukyu Current is rapidly declining. Particularly, in climate models, the Ryukyu Current is predicted to experience a 45% weakening during 1950–2050. Weakening wind field in the North Pacific tends to reduce the total transport of WBC system. The rapid weakening of the Ryukyu Current is credit to the enhanced stratification under global warming, which induces uplift of the Kuroshio east of Taiwan. Hence, less water will be blocked by bottom topography (Ilan Ridge) and bifurcates into the Ryukyu Current. Our finding highlights the needs for comprehensive studies on the local and climate effects of the evolution of the WBC system in the North Pacific. Key Points: The East China Sea Kuroshio is intensifying while the Ryukyu Current is rapidly declining in a warming climateThe change is mainly caused by enhanced stratification which induces uplift of current system and weaker topography‐flow interaction [ABSTRACT FROM AUTHOR]

In the context of a warming climate, glacial debris flows will inevitably increase under the coupled effect of increased temperature and precipitation. However, the extent of future losses is unclear due to the complexity of modelling glacial debris flow processes. This study integrated the degree-day model, the TRIGRS model, and the LS-RAPID model to assess increasing risk in the future period (2071–2100) under the SSP2-4.5 scenario compared to the present. A fatal glacial debris flow in the Tianmo Gully that occurred on September 4, 2007 (hereafter referred to as “the event”) was taken as an example. By the 2090s, compared to the event, the contribution of temperature to the occurrence of glacial debris flows was projected to increase significantly, from 77.05 % to 89.68 % under the SSP2-4.5 scenario. Combining meltwater and precipitation, the study reproduced the propagation of the event and simulated the future extreme debris flow event. Although the section of National Highway 318 (G318) below Tianmo Gully was relocated and reconstructed 150 m away from the historic sedimentary fan, a section of 88.46 m remained at risk of inundation in the future. The maximum height of the debris flow dam in the Parlung Zangbo River could reach up to 34.50 m, doubling the height of the event. Debris removal from the road is estimated to take 1 day, resulting in a projected loss of tourism revenue amounting to RMB 17.82 million. Without relocation, the clearing time would take up to 3 days. The economic benefit of rerouting the section was projected at RMB 13.81 million. The mechanisms of glacial debris flow in Parlung region are similar. Both the concept of model integration and the comparison of the simulation results are of great importance for risk assessments under global warming.

Phenotypic diversity and abundance drive salmon resilience in the face of increasing environmental variability. But what happens when human activities fundamentally alter the habitat complexity that drives this diversity? And how can we restore habitats to recover both diversity and abundance to support salmon persistence in a warming climate? Here, we looked at the impact of a large watershed restoration effort on the abundance and climate resilience of the three remaining core natural spring‐run Chinook Salmon populations in the California Central Valley (Butte, Mill, and Deer Creek). Butte Creek fish, which have floodplain access, had higher overall productivity and faster juvenile growth compared with Mill and Deer Creek populations, and the proportion of floodplain inundation was positively correlated with Butte Creek adult abundance two years later. While Butte Creek exhibited significant increases in abundance post‐restoration (~2000%), it generally exhibited lower phenotypic diversity and only a marginal increase in population stability after restoration based on the coefficient of variation (CV). In particular, Butte Creek salmon tended to exhibit larger drops in escapement following dry years (e.g., return years 2010, 2017) compared with Mill and Deer Creek populations, presumably due to limited inundation of its downstream floodplain. The late‐migrating juvenile strategy (i.e., yearling), which disproportionately supported Mill and Deer Creek populations during droughts, was uncommon among Butte Creek adults (averaging 60% of returns for Mill and Deer Creek vs. 0.3% for Butte Creek). Increased spring‐run stock complex stability was found, post‐restoration, when combining the three spring‐run populations (i.e., lower aggregate CV). However, among‐river pairwise correlations also suggested increased synchronization in population abundances post‐restoration, potentially due to increasing frequency and severity of extreme climatic events (e.g., droughts and ocean warming). This study underscores the importance of restoring a connected mosaic of aquatic habitats across modified landscapes, such as cold water refugia and floodplains, to preserve multiple (across‐population) life history pathways for increasing salmon stock complex stability and abundance. These landscape‐scale process‐based habitat restoration efforts are likely to be crucial for the successful long‐term recovery of vulnerable species in a rapidly changing climate. [ABSTRACT FROM AUTHOR]

Abstract The East China Sea Kuroshio (ECS‐Kuroshio) and the Ryukyu Current are the major poleward heat carriers in the North Pacific. Anomalous changes of ECS‐Kuroshio and Ryukyu Current could exert substantial influence on the climate in mid‐latitude regions. However, owing to limited observations and coarse resolution of climate models, how they might change under anthropogenic warming remains unknown. Here, we find an accelerating ECS‐Kuroshio (1.5 Sv) and a decelerating (−2.2 Sv) Ryukyu Current using in‐situ observation during 1958–2022, equivalent to 7% strengthening and 20% weakening in the 65 years. The trend is also simulated by four high‐resolution climate models, with multi‐model ensemble‐mean acceleration (deceleration) of the ECS‐Kuroshio (Ryukyu Current) of 1.2 ± 0.6 Sv (−6.2 ± 2.5 Sv) over 1950–2050. The weakening subtropical wind field reduces their summed transport o. Enhanced stratification, which induces uplift of current system and weaker topography‐flow interaction, leads to the intensifying ECS‐Kuroshio and disappearing Ryukyu Current.

Predator-prey systems face intensifying pressure from human exploitation and a warming climate with implications for where and how natural resource management can successfully intervene. We hypothesized young salmon migrating to the Pacific Ocean face a seasonally intensifying predator gauntlet when warming water temperature intensifies a multiple predator effect (MPE) from Striped Bass Morone saxatilis and Largemouth Bass Micropterus salmoides. We evaluated this hypothesis using data synthesis and simulation modeling.Contemporary studies based on acoustically tagged fish reaffirmed older observations that Chinook Salmon smolts must transit the Delta before water temperature reaches 20°C or mortality will be nearly 100%. Striped Bass attack rates on tethered smolts were insensitive to distance from shore and water temperature, whereas Largemouth Bass attack rates were highest near shorelines in warm water, supporting the temporal aspect of the hypothesis. Whether the combined effects of the two predators produce an MPE remains unconfirmed due to limitations on quantifying salmon behavior.We used multiple simulation models to try to reconstruct the empirical relationship between smolt survival and water temperature. Simulations reinforced attack rate results, but could not recreate the temperature dependence in smolt survival except at higher than observed temperatures. We propose three hypotheses for why and recommend discerning among them should be a focus of research.We found significant linear relationships between monthly mean inflow to the Delta from each of its two largest tributaries and monthly mean water temperatures along associated salmon migration routes, but these relationships can be nonlinear, with most of the correlation occurring at low inflows when water temperature is largely controlled by air temperature and day length. As the global climate warms, changed circumstances in predator-prey relationships may present important challenges when managing species vulnerable to extinction in addition to presently more abundant species.

The alpine grasslands of the Qinghai-Tibetan Plateau play an important role in multiple ecosystem functions, all of which are key in regulating regional climate influences and providing pristine headwaters for millions of people downstream from this basin. Alpine grasslands act as a carbon sink, storing carbon dioxide and keeping heat-trapping greenhouse gases out of the atmosphere, but it is not clear how this will change in a warming climate in the future. In this paper, the net ecosystem productivity (NEP) of alpine grasslands in Qinghai province, on the Qinghai-Tibetan Plateau, was predicted for the period from 2010 to 2099. Trends and stability were analyzed under two climate scenarios, Representative Concentration Pathway 4.5 (RCP4.5) and 8.5 (RCP8.5) representing the lower and higher emission scenarios for greenhouse gases. The results suggest that grasslands will continue to contribute as a carbon sink, with a positive NEP through this century. Almost the same magnitude (38 Tg C a-1, 1 T g = 1012 g) of contribution was projected under both scenarios. Grasslands are projected to be the major contributor to NEP in Qinghai province, with more than 89% of NEP in the future. The carbon sink function will increase over more than 69% of the grasslands and peak around 2069 (RCP4.5) or 2066 (RCP8.5). Then the carbon sink function will begin to decrease and it will decrease more quickly and become more variable under the RCP8.5 than the RCP4.5. The impacts of temperature and precipitation changes were analyzed and NEP was found to be more sensitive to temperature than precipitation change. The trend of increasing contribution to NEP is driven by a warming climate, while the stability of NEP is mainly influenced by the precipitation, which results in an upward trend before the peak and a decline due to stresses from limits in available water in a continued warming climate.

Borealization is a type of community reorganization where Arctic specialists are replaced by species with more boreal distributions in response to climatic warming. The process of borealization is often exemplified by the northward range expansions and subsequent proliferation of boreal species on the Pacific and Atlantic inflow Arctic shelves (i.e., Bering/Chukchi and Barents seas, respectively). But the circumpolar nearshore distribution of Arctic‐boreal fishes that predates recent warming suggests borealization is possible beyond inflow shelves. To examine this question, we revisited two nearshore lagoons in the eastern Alaska Beaufort Sea (Kaktovik and Jago lagoons, Arctic National Wildlife Refuge, Alaska, USA), a High Arctic interior shelf. We compared summer fish species assemblage, catch rate, and size distribution among three periods that spanned a 30‐year record (baseline conditions, 1988–1991; moderate sea ice decline, 2003–2005; rapid sea ice decline, 2017–2019). Fish assemblages differed among periods in both lagoons, consistent with borealization. Among Arctic specialists, a clear decline in fourhorn sculpin (Myoxocephalus quadricornis, Kanayuq in Iñupiaq) occurred in both lagoons with 86%–90% lower catch rates compared with the baseline period. Among the Arctic‐boreal species, a dramatic 18‐ to 19‐fold increase in saffron cod (Eleginus gracilis, Uugaq) occurred in both lagoons. Fish size (length) distributions demonstrated increases in the proportion of larger fish for most species examined, consistent with increasing survival and addition of age‐classes. These field data illustrate borealization of an Arctic nearshore fish community during a period of rapid warming. Our results agree with predictions that Arctic‐boreal fishes (e.g., saffron cod) are well positioned to exploit the changing Arctic ecosystem. Another Arctic‐boreal species, Dolly Varden (Salvelinus malma, Iqalukpik), appear to have already responded to warming by shifting from Arctic nearshore to shelf waters. More broadly, our findings suggest that areas of borealization could be widespread in the circumpolar nearshore. [ABSTRACT FROM AUTHOR]

Study regionThe Edwards Aquifer Region is located in south-central Texas United States.Study focusThe paper focuses on the development and implementation of a data-inspired heuristic drought identification scheme to (i) quantify the intensity, duration, and frequency of precipitation deficit- and high temperature-driven meteorological droughts (PMet- and TMet-droughts), and (ii) link their propagation to groundwater droughts (GW-droughts) using baseline hydroclimatic measures and prevailing drought conditions derived from historical climate data and regional mitigation strategies.New hydrological insights for the regionBased on the intensity, duration, and timing of PMet- and TMet-droughts in the semi-arid karstic region, we identified three distinct GW-droughts, including persistence-driven, preconditions-driven, and intensity-driven droughts. The analysis revealed that successive heavy precipitation events are needed to end GW-droughts. The scheme also identified TMet-droughts with the longest dry spells, TMet- and PMet-droughts with the highest intensity, and GW-drought with the second-highest intensity on record all occurred over the past 15 years. These findings provide evidence for a warming climate, intensified meteorological droughts, and increasing stress on the aquifer. Among the artificial intelligence models used, Extremely Randomized Trees (ERT) regressor predicted time series of intensity & duration of GW-droughts from hydroclimatic features with high accuracy. The ERT classifier revealed that the duration of PMet droughts and the intensity of TMet droughts are the topmost decisive features in predicting GW-drought intensity in the region.

As climate changes, species’ ranges may shift poleward. However, habitat loss in intervening areas has been hypothesized potentially to impede the movements of these species. Populations near range margins offer opportunities to study how marginal species have reacted to habitat loss. We examined the presence/absence of bird species in landscapes that were historically mainly forested (natural land covers) in Southern Ontario, Canada. We used logistic regression to determine each bird species’ probability of occupancy (pocc) as a function of natural cover in 991 landscapes, each 100-km2. We distinguished three groups of species: i) southerly species whose northern range limits fall in the study area (n=37), ii) northerly species whose southern range limits fall in the study area (n=35), and iii) mid-range species (n=106). We compared pocc for these three groups of species in six different habitat guilds. We found that species near their southern range edges are less likely to occur in landscapes where forest amount is reduced, while species near their northern range edge are more likely to occur in landscapes with reduced forest. This result is independent of habitat guild. Our results are inconsistent with the hypothesis in the climate change literature proposing that loss of natural land cover near poleward range margins would inhibit range expansion in response to climatic warming. Rather, we hypothesize that, at southern range edges, the dual stresses of climatic warming and forest conversion both reduce species’ ability to occupy a landscape. However, near northern (potentially expanding) range edges, partially disturbed landscapes are more readily invaded than undisturbed landscapes.

• Temperature' contribution to glacial debris flow is projected to rise from 77.05 % to 89.68 % under SSP2-4.5 by the 2090s. • The glacial debris flow volume on September 4 was 1.34 × 106 m3, which is projected to reach 3.55 × 106 m3 by the 2090s. • The economic benefit of road relocation below the debris flow gully is projected to be 13.81 million yuan. • Integrated modelling explored the entire process of glacial debris flow, from formation to propagation. In the context of a warming climate, glacial debris flows will inevitably increase under the coupled effect of increased temperature and precipitation. However, the extent of future losses is unclear due to the complexity of modelling glacial debris flow processes. This study integrated the degree-day model, the TRIGRS model, and the LS-RAPID model to assess increasing risk in the future period (2071–2100) under the SSP2-4.5 scenario compared to the present. A fatal glacial debris flow in the Tianmo Gully that occurred on September 4, 2007 (hereafter referred to as "the event") was taken as an example. By the 2090s, compared to the event, the contribution of temperature to the occurrence of glacial debris flows was projected to increase significantly, from 77.05 % to 89.68 % under the SSP2-4.5 scenario. Combining meltwater and precipitation, the study reproduced the propagation of the event and simulated the future extreme debris flow event. Although the section of National Highway 318 (G318) below Tianmo Gully was relocated and reconstructed 150 m away from the historic sedimentary fan, a section of 88.46 m remained at risk of inundation in the future. The maximum height of the debris flow dam in the Parlung Zangbo River could reach up to 34.50 m, doubling the height of the event. Debris removal from the road is estimated to take 1 day, resulting in a projected loss of tourism revenue amounting to RMB 17.82 million. Without relocation, the clearing time would take up to 3 days. The economic benefit of rerouting the section was projected at RMB 13.81 million. The mechanisms of glacial debris flow in Parlung region are similar. Both the concept of model integration and the comparison of the simulation results are of great importance for risk assessments under global warming. [ABSTRACT FROM AUTHOR]

This paper reviews currently available evaluations of the effects of continuously increasing anthropogenic loads on water resources. The increase in the fluxes of elements and compounds into the environment, such as the emission of greenhouse gases and dispersion of nutrients (nitrogen and phosphorus), acidifying gases, and toxic elements and compounds that adversely affect water quality, are considered. The significance of fresh waters as a life support factor for human populations is demonstrated. Examples illustrate how key anthropogenic-induced processes develop in land waters under the effect of anthropogenic loads, as exemplified by the Russian Kola regions. Climate warming and the increasing dispersion of elements are demonstrated to result in the eutrophication of surface waters, even in areas remote from anthropogenically impacted regions. Although the emissions of acidifying gases diminish, the waters are still acidified in acid-vulnerable areas, and the chemical compositions of the waters have been significantly modified over the past decades, indicating that the changes in the chemical composition of the waters are irreversible. A new feature of the waters is distinguished: the toxicity of the habitats for aquatic organisms. The novelty of the work was to highlight the bridge between anthropogenic loads on surface water on a planetary scale and their consequences in certain regions, which reflect changes in water quality. Arguments are presented for establishing a theoretical approach for evaluating critical loads. [ABSTRACT FROM AUTHOR]

Understanding the hydrological processes in the Tibetan Plateau (TP) is increasingly important as the snow resources feed the demand for freshwater for a vast downstream population. Given the limited information available, the task of formulating a hydrological model that characterizes future streamflow at downstream locations is challenging. A flexible conceptual hydrological model is proposed relating snow cover fraction (SCF) and snow water equivalent (SWE) based on remote sensing data, with the aim of characterising flow in the region into the future where temperature profiles will be considerably warmer than they are at present. The model's novelty lies in its ability to simulate dynamically varying SCF, SWE and streamflow using limited available data. Results show the Nash-Sutcliffe efficiency values of modelled SCF, SWE and streamflow are 0.82, 0.66 and 0.75, respectively, in the calibration period (1981 to 1992), whereas they are 0.78, 0.56 and 0.70, respectively, in the validation period (1993 to 2000). [ABSTRACT FROM AUTHOR]

The snowpack is a critical component of the hydrologic cycle in cold regions, the change in which becomes important for proper planning and management of water. The Tibetan Plateau provides significant amount of water to most Asian rivers, and consequently the downstream population is dependent on its availability. Despite its importance, potential change in snowpack in this region due to climate change is poorly understood to date, largely because of remoteness and the orographic complexity of the area. This study inspects the impact of climate change on snowpack change over the Tibetan Plateau considering historical simulations (1981–2004), near future projections (2041–2064), and far future projections (2071–2094) from global climate models (GCMs) and regional climate models (RCMs) of derived temperature, precipitation, and snow water equivalent (SWE). A multivariate nesting bias correction approach (MRNBC) was employed to correct possible biases in GCM and RCM derived temperature, precipitation, and SWE jointly over multiple time scales to preserve interdependencies among the variables while enabling simulation of year‐to‐year persistence, which is of importance in water security assessments. MRNBC reduced the bias in model simulations significantly and improved projections of the snow climatology. The results indicate that the annual maximum spell of snow‐free days will increase over the region whereas the snowy day fraction will decrease in the future compared to the historical period. In addition, annual SWE are noted to be decreasing in both the near future and far future with respect to historical averages. Changes in SWE will result from warming temperatures and also from changes in precipitation, which will lead to more rainfall than snowfall thus affecting snowmelt processes. Plain Language Summary: We present a comprehensive assessment of the impacts expected due to climate change in catchments feeding off the Tibetan Plateau snowpack. Our assessment used a carefully devised approach for correcting biases in the joint dependence across climate model simulated variables, and a conceptual model that is designed to operate under limitations of availability of ground data and spatio‐temporal resolutions possible. There is a clear indication of decrease in the Snow Water Equivalent over the region, due to rise in temperature and also changes in precipitation. This has significant implications for the temporal distribution and reliability of streamflow in the rivers that originate from the Tibetan Plateau, impacting millions of people who live downstream. Key Points: A multivariate nested bias correction is adopted to correct climate model derived snow climatology for the regionBoth global climate model and regional climate model derived snow climatology show significant improvement after bias correctionChange in future snow resources will impact the water security of a large downstream population, along with impacting agriculture and ecosystems in the study region [ABSTRACT FROM AUTHOR]

The deformation and evolution of internal solitary waves (ISWs) beneath an ice keel can enable potential diapycnal mixing and facilitate upper ocean heat transport, despite a poor understanding of the underlying physics and energetics of ISWs in Polar environments. This study aims to understand the dynamic processes and mixing properties during the evolution of ISWs beneath ice keels in the Arctic Ocean using high‐resolution, non‐hydrostatic simulations. Ice keels can destabilize ISWs through overturning events. Consequently, the initial ISW disintegrates and transfers its energy into secondary smaller‐scale waves. During the ISW‐ice interaction, ISW‐induced turbulent mixing can reach O(10−3) W/kg with a magnitude of resultant heat flux of O(10)W/m. Sensitivity experiments demonstrated that the ISW‐ice interaction weakened as the ice keel depth decreased, and consequently, the resultant turbulent mixing and upward heat transfer also decreased. The ice keel depth was critical to the evolution and disintegration of an ISW beneath the ice keel, while the approximate ice keel shape had little effect. Our results provide an important but previously overlooked energy source for upper ocean heat transport in the Arctic Ocean. Plain Language Summary: Internal wave‐driven mixing plays an important role in both ocean general circulation and climate change. Internal waves (IWs) at mid to low latitudes have attracted much attention; however, our understanding of the evolution and physics of IWs in high‐latitude Polar oceans remains limited. This study aims to explore the evolution and energetics of internal solitary waves (ISWs, a kind of high‐frequency IW) in the ice environment of the Arctic Ocean using non‐hydrostatic 2D simulations. The results reveal the destabilization process of an ISW during its interaction with an ice keel (undersea portion of ice cover). During the ISW‐ice interaction in the Arctic Ocean, ISW‐induced turbulent mixing can reach O(10−3) W/kg with a magnitude of resultant heat flux of O(10) W/m. Thus, the ISW‐ice interaction provides an important, but previously overlooked, energy source for upper ocean heat transport in the Arctic Ocean. Key Points: Destabilization and disintegration of internal solitary waves (ISWs) under ice keels can radiate energy into secondary wavesTurbulent mixing and vertical heat flux are significantly enhanced during ISW‐ice interactionsThe ISW‐ice interaction and resultant heat transfer weaken with the shrinking of ice keels [ABSTRACT FROM AUTHOR]

The Indo-Pacific warm pool (IPWP) is a region known for its strong atmospheric convection, which plays a key role in global climate. However, in recent decades, the IPWP has experienced human-induced warming, and it has been observed to have a non-linear relationship between sea surface temperature (SST) and precipitation. Despite the rising SSTs, the increase in precipitation is limited until a specific SST, which is defined as saturation threshold SST (STT). The STT indicates a distinct transition before and after the STT, highlighting the non-linear response of precipitation to SST. Nevertheless, the impact of warmer climates on the SST-precipitation relationship and STT remains uncertain. To investigate future changes in this relationship, we analyzed a joint distribution of SST and precipitation using the historical data and three different Shared Socioeconomic Pathway (SSP) scenarios (SSP2-4.5, SSP3-7.0, and SSP5-8.5). We examined the near future (2041–2060), and far future (2081–2100). Our findings reveal that the STT increases with the shift in mean state due to the involvement of atmospheric stratification. This increase is observed across all three scenarios in both future periods, with the SSP5-8.5 scenario exhibiting the most substantial rise during the far future. The warming climate leads to a more pronounced warming in the upper troposphere than the surface, resulting in tropospheric stabilization. This process contributes to the increase in STT through moist-adiabatic lapse rate adjustment. Additionally, the weakening of vertical motion constrains the increase in precipitation, despite the availability of abundant moisture. This study sheds light on the changing SST-precipitation relationship and provides a possible mechanism for the limited increase in precipitation. Therefore, this study offers a background for a better understanding of the non-monotonic response of precipitation to SST in the context of climate change.

This paper reviews currently available evaluations of the effects of continuously increasing anthropogenic loads on water resources. The increase in the fluxes of elements and compounds into the environment, such as the emission of greenhouse gases and dispersion of nutrients (nitrogen and phosphorus), acidifying gases, and toxic elements and compounds that adversely affect water quality, are considered. The significance of fresh waters as a life support factor for human populations is demonstrated. Examples illustrate how key anthropogenic-induced processes develop in land waters under the effect of anthropogenic loads, as exemplified by the Russian Kola regions. Climate warming and the increasing dispersion of elements are demonstrated to result in the eutrophication of surface waters, even in areas remote from anthropogenically impacted regions. Although the emissions of acidifying gases diminish, the waters are still acidified in acid-vulnerable areas, and the chemical compositions of the waters have been significantly modified over the past decades, indicating that the changes in the chemical composition of the waters are irreversible. A new feature of the waters is distinguished: the toxicity of the habitats for aquatic organisms. The novelty of the work was to highlight the bridge between anthropogenic loads on surface water on a planetary scale and their consequences in certain regions, which reflect changes in water quality. Arguments are presented for establishing a theoretical approach for evaluating critical loads.

Most global climate models, such as CMIP5 models, ignore the falling ice (snow) radiative effects (FIREs). Extended from our previous works, we explore the impacts of FIREs on the geographical distribution changes of sea ice concentration (SIC), sea ice thickness and skin temperature (Ts) under 1% per year increase of atmospheric CO2 concentration. We perform a pair of 140-year experiments including FIREs (SoN) and excluding FIREs (NoS) using CESM1-CAM5. These two simulations are compared with each other and against CMIP5 multi-model mean without FIREs (CMIP5-NoS). The results show that the changes of SIC, thickness and radiation fields in NoS minus SoN largely match the changes between CMIP5-NoS and SoN in winter but less so in summer and annual mean. Both NoS and CMIP5-NoS simulate less downward longwave and net radiative warming (~20 - 30 W m-2), resulting in colder Ts over Arctic and adjacent lands (~5 - 8 K colder) and stronger meridional temperature gradient, leading to more SIC and thicker sea ice (~30 - 40 cm) over the Arctic ocean. The inclusion of FIREs produces stronger changes in geographic patterns and magnitudes of Ts, SIC and thickness from the first to middle 20 years but less from the middle to last 20 years. The SIC and thickness changes in SoN are associated with warmer Ts, increasing downward surface longwave warming and thus net warming relative to NoS and CMIP5-NoS. With FIREs, the model shows faster warming-driven sea ice retreats and thinning over the entire Arctic ocean, resulting in a sea ice-free Arctic ocean 30 years earlier, as well as much warmer Ts (up to 5 K) over the adjacent lands than in NoS case. [ABSTRACT FROM AUTHOR]

Every year cyclonic disturbances (CDs) cause destructions along the coastal areas of the designated world basins. Apart from strong winds generated by CDs, torrential rain causes flood and landslides over the places of landfall. By using high‐quality daily rainfall data, the contribution of rainfall by the North Indian Ocean (NIO) CDs over India is investigated in this study. Eastern Indian states suffer landfalling CDs from the Bay of Bengal and the western coastal states experience the influence from those formed over the Arabian Sea. Among eastern coastal states, the accumulated rainfall is higher over Andhra Pradesh (AP), Tamil Nadu (TN), Odisha and southern West Bengal during pre‐monsoon season. Among western coastal states, Karnataka and Kerala suffer maximum rainfall from CDs. During post‐monsoon season, coastal AP, TN, Odisha, Karnataka and coastal Kerala received higher accumulated rainfall. Gujarat received ~70% and both AP and TN received up to 20–30% of rainfall by CDs during pre‐monsoon months. During post‐monsoon season, Gujarat, Odisha and AP received maximum rainfall contribution up to 50%. In most of the states, the overall rainfall contribution by CDs is observed to have a decreasing trend during both seasons. Owning to the stable average rainfall trend over India along with decreasing CD frequency during the post‐monsoon season, the results indicate an increased amount of rainfall by CDs. CDs contribute a considerable amount of rainfall to central and northern India during the post‐monsoon season, which is helpful for agricultural purpose. [ABSTRACT FROM AUTHOR]

Human activities have substantially altered present-day flow regimes. The Headwater Area of the Yellow River (HAYR, above Huanghe’yan Hydrological Station, with a catchment area of 21,000 km2 and an areal extent of alpine permafrost at ~86%) on the northeastern Qinghai-Tibet Plateau, Southwest China has been undergoing extensive changes in streamflow regimes and groundwater dynamics, permafrost degradation, and ecological deterioration under a warming climate. In general, hydrological gauges provide reliable flow records over many decades and these data are extremely valuable for assessment of changing rates and trends of streamflow. In 1998–2003, the damming of the Yellow River by the First Hydropower Station of the HAYR complicated the examination of the relations between hydroclimatic variables and streamflow dynamics. In this study, the monthly streamflow rate of the Yellow River at Huanghe’yan is reconstructed for the period of 1955–2019 using the double mass curve method, and then the streamflow at Huagnhe’yan is forecasted for the next 20 years (2020–2040) using the Elman neural network time-series method. The dam construction (1998–2000) has caused a reduction of annual streamflow by 53.5–68.4%, and a more substantial reduction of 71.8–94.4% in the drier years (2003–2005), in the HAYR. The recent removal of the First Hydropower Station of the HAYR dam (September 2018) has boosted annual streamflow by 123–210% (2018–2019). Post-correction trends of annual maximum (QMax) and minimum (QMin) streamflow rates and the ratio of the QMax/QMin of the Yellow River in the HAYR (0.18 and 0.03 m3·s−1·yr−1 and −0.04 yr−1, respectively), in comparison with those of precorrection values (−0.11 and −0.004 m3·s−1·yr−1 and 0.001 yr−1, respectively), have more truthfully revealed a relatively large hydrological impact of degrading permafrost. Based on the Elman neural network model predictions, over the next 20 years, the increasing trend of flow in the HAYR would generally accelerate at a rate of 0.42 m3·s−1·yr−1. Rising rates of spring (0.57 m3·s−1·yr−1) and autumn (0.18 m3·s−1·yr−1) discharge would see the benefits from an earlier snow-melt season and delayed arrival of winter conditions. This suggests a longer growing season, which indicates ameliorating phonology, soil nutrient availability, and hydrothermal environments for vegetation in the HAYR. These trends for hydrological and ecological changes in the HAYR may potentially improve ecological safety and water supplies security in the HAYR and downstream Yellow River basins.

Even with ever-increasing societal interest in tornado activities engendering catastrophes of loss of life and property damage, the long-term change in the geographic location and environment of tornado activity centers over the last six decades (1954–2018), and its relationship with climate warming in the U.S., is still unknown or not robustly proved scientifically. Utilizing discriminant analysis, we show a statistically significant geographic shift of U.S. tornado activity center (i.e., Tornado Alley) under warming conditions, and we identify five major areas of tornado activity in the new Tornado Alley that were not identified previously. By contrasting warm versus cold years, we demonstrate that the shift of relative warm centers is coupled with the shifts in low pressure and tornado activity centers. The warm and moist air carried by low-level flow from the Gulf of Mexico combined with upward motion acts to fuel convection over the tornado activity centers. Employing composite analyses using high resolution reanalysis data, we further demonstrate that high tornado activities in the U.S. are associated with stronger cyclonic circulation and baroclinicity than low tornado activities, and the high tornado activities are coupled with stronger low-level wind shear, stronger upward motion, and higher convective available potential energy (CAPE) than low tornado activities. The composite differences between high-event and low-event years of tornado activity are identified for the first time in terms of wind shear, upward motion, CAPE, cyclonic circulation and baroclinicity, although some of these environmental variables favorable for tornado development have been discussed in previous studies.

Copyright of Journal of Central China Normal University is the property of Huazhong Normal University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights • First application of SAS theory to study TTDs at large-scale snow-dominated watershed. • Watersheds release more young water to streamflow discharge in spring snowmelt season. • Watersheds release more young water to streamflow discharge in wet years. • Dry years are more sensitive to climate change. • Precipitation sufficiency is more significant on controlling TTDs than energy budget. Abstract Snowmelt is the principal control on the timing and magnitude of water flow through mountainous watersheds. The effects of precipitation type and quantity on storage and hydrologic connectivity in mountainous systems were explored by combining the observed stable isotope δ 18O in rain, snow, snowmelt, and streamflow with numerically simulated hydrologic boundary fluxes and inverse techniques applied to transient travel time distributions (TTD) using StorAge Selection (SAS) functions. Hydrologic simulations of the East River (ER, 85 km2), a snow-dominated Colorado River headwater basin, for water years 2006–2017 were used to test a diverse set of snow accumulation scenarios. During the snowmelt period, the ER released younger water during high storage periods across seasonal and annual timescales (an "inverse storage effect"). Additionally, more young water was released from storage during wet years than during dry years. However, wet years also appeared to increase hydrologic connectivity, which simultaneously flushed older water from the basin. During years with reduced snowpack, flow paths were inactivated and snowmelt remained in the subsurface to become older water that was potentially reactivated in subsequent wet years. Incremental warming in hydrologic model simulations was used to evaluate TTD sensitivity to precipitation changing from snow to rain. Despite the altered timing of boundary fluxes because of warming, years with basin average precipitation above 3.25 mm d−1 (1200 mm y−1) were resilient to temperature increases up to 10 °C with respect to annual water balance partitioning and streamflow TTD. In contrast, years with less precipitation were sensitive to increased temperatures, showing marked increases in the fraction of inflow lost to evapotranspiration. Younger water was preferentially lost to evapotranspiration, which led to an increase in the mean age of streamflow in drier years. [ABSTRACT FROM AUTHOR]

Land skin temperature (Ts) is directly influenced by surface energy balance, in particular, radiative energy, which can be linked to model’s representation of radiative effects of hydrometeors in the atmosphere. This link is inferred by examining the changes of geographical distribution and seasonal cycle of surface radiation, surface turbulent fluxes and Ts between a pair of 140 years sensitivity experiments under 1% per year increase of atmospheric CO _2 . One is with radiative effects of falling ice (snow) hydrometeors on (SON) and the other off (NOS) using CESM1-CAM5 and the results are compared with CMIP5 models without these effects. For boreal winter, NOS relative to SON simulates less surface downward longwave and net flux (∼10–15 W m ^−2 ), resulting in colder Ts (∼2–3 K colder), over mid- and high latitudes, but more solar radiative flux, resulting in warmer Ts (∼1–3 K), over subtropical and tropical land. These differences between NOS and SON are amplified as the surface and the atmosphere become warmer. The results from CMIP5 ensemble generally match with those of NOS. Temporal correlation analysis indicates that the linkage between Ts and falling ice hydrometeor changes is through one between Ts and downward longwave and net fluxes at high latitudes, but strongly weakened by shortwave changes at low latitudes (and boreal summer). Relative to SON, land skin temperatures in NOS and CMIP5 are underestimated throughout the seasonal cycle but only slightly in summer.

Pacific salmon (Oncorhynchus spp.) play two important roles in the North Pacific ecosystem: as a keystone species and as providers of an ecosystem service that offers human food resources for countries of the North Pacific rim. In a climate that has been rapidly warming since the late 2000 s, the return of Japanese chum salmon (O. keta), most of which reproduce through an artificial hatchery program, has reduced. This study reviews the following issues: 1) the impacts of warming climate on production dynamics and the life history of Pacific salmon; 2) the importance of wild salmon on the sea-terrestrial ecosystem linkage; 3) biological and genetic issues of hatchery-produced salmon such as population dynamics (density-dependent effects) and genetic disturbance (seed transplantation and domestication); and 4) the establishment of ecosystem-based sustainable management for Pacific salmon in the warming climate. [ABSTRACT FROM AUTHOR]

• An ecosystem process model-based NEP was predicted under varying climate scenarios. • Alpine grasslands were projected to play an important part in carbon sink contributions in Qinghai Province in the 21st century. • An earlier peak and faster decreasing NEP projected for a warmer climate scenario (RCP 8.5). • A more stable carbon sink was projected under a less warm, stable precipitation scenario (RCP 4.5). The alpine grasslands of the Qinghai-Tibetan Plateau play an important role in multiple ecosystem functions, all of which are key in regulating regional climate influences and providing pristine headwaters for millions of people downstream from this basin. Alpine grasslands act as a carbon sink, storing carbon dioxide and keeping heat-trapping greenhouse gases out of the atmosphere, but it is not clear how this will change in a warming climate in the future. In this paper, the net ecosystem productivity (NEP) of alpine grasslands in Qinghai province, on the Qinghai-Tibetan Plateau, was predicted for the period from 2010 to 2099. Trends and stability were analyzed under two climate scenarios, Representative Concentration Pathway 4.5 (RCP4.5) and 8.5 (RCP8.5) representing the lower and higher emission scenarios for greenhouse gases. The results suggest that grasslands will continue to contribute as a carbon sink, with a positive NEP through this century. Almost the same magnitude (38 Tg C a-1, 1 T g = 1012 g) of contribution was projected under both scenarios. Grasslands are projected to be the major contributor to NEP in Qinghai province, with more than 89% of NEP in the future. The carbon sink function will increase over more than 69% of the grasslands and peak around 2069 (RCP4.5) or 2066 (RCP8.5). Then the carbon sink function will begin to decrease and it will decrease more quickly and become more variable under the RCP8.5 than the RCP4.5. The impacts of temperature and precipitation changes were analyzed and NEP was found to be more sensitive to temperature than precipitation change. The trend of increasing contribution to NEP is driven by a warming climate, while the stability of NEP is mainly influenced by the precipitation, which results in an upward trend before the peak and a decline due to stresses from limits in available water in a continued warming climate. [ABSTRACT FROM AUTHOR]

Annual monitoring data and centennial and millennial-scale paleolimnological records have revealed an increase in small-celled planktonic diatom species relative to heavier tycho-planktonic and small benthic diatoms in many high-altitude lakes, presumably in response to recent climatic warming. In addition to changes in the composition and structure of lacustrine diatom assemblages, there have also been changes in diatom biodiversity; however, these changes are not regionally consistent. In this study, we chose a temperate mid-latitude lake to explore the response of changes in diatom assemblages and biodiversity to recent climatic warming. The diatom record spans the past ca. 200 years and reveals that since 1966 CE the small-celled Cyclotella ocellata + stelligera has replaced the previously dominant, large-celled phytoplankton Cyclotella schroeteri . These changes are in accordance with the increasing trend in global mean surface temperature. Biodiversity increased remarkably from 1966 CE, but began to decline after 1990 CE, presumably in response to rapid climatic warming. Our findings indicate that the response of diatom biodiversity to climate change was a nonlinear process. [ABSTRACT FROM AUTHOR]

Abstract: The acclimation capacity of leading edge tree populations is crucially important in a warming climate. Theoretical considerations suggest that adaptation through genetic change is needed, but this may be a slow process. Both positive and catastrophic outcomes have been predicted, while empirical studies have lagged behind theory development. Here we present results of a 30‐year study of 55,000 Scots pine (Pinus sylvestris) trees, planted in 15 common gardens in three consecutive years near and beyond the present Scots pine tree line. Our results show that, contrary to earlier predictions, even long‐distance transfers to the North can be successful when soil fertility is high. This suggests that present northern populations have a very high acclimation capacity. We also found that while temperature largely controls Scots pine growth, soil nutrient availability plays an important role—in concert with interpopulation genetic variation—in Scots pine survival and fitness in tree line conditions. These results suggest that rapid range expansions and substantial growth enhancements of Scots pine are possible in fertile sites as seed production and soil nutrient mineralization are both known to increase under a warming climate. Finally, as the ontogenetic pattern of tree mortality was highly site specific and unpredictable, our results emphasize the need for long‐term field trials when searching for the factors that control fitness of trees in the variable edaphic and climatic conditions of the far North. [ABSTRACT FROM AUTHOR]

Pigeon et al. (2016) Staying cool in a changing landscape: the influence of maximum daily ambient temperature on grizzly bear habitat selection. Oecologia 181:1101. doi: analyzed the effect of ambient temperature on the habitat selection of grizzly bears ( Ursus arctos) in Alberta, Canada. They concluded that temperature played a significant role in bear habitat selection and that it was unlikely that human activity introduced biases to the habitat selection of bears. However, Pigeon et al. did not consider variables related to human activities in their analyses. They also misinterpreted previous research that has accounted for temperature in the habitat selection of brown bears. There is much literature published on the negative effects of human disturbance on wildlife in general and on bears in particular. Downplaying the role of human disturbance could have important negative consequences if, in fact, human disturbance were a more important factor than thermoregulation. Indeed, dismissing the importance of human influence, in the face of contradictory evidence, could tempt managers to disregard an important factor that is difficult and often unpopular to deal with in their conservation plans. [ABSTRACT FROM AUTHOR]

Global warming has been commonly accepted to facilitate species' range shifts across latitudes. Cross-latitudinal transplantations support this; many tree species can well adapt to new geographical areas. However, these studies fail to capture species' adaptations to new light environment because the experiments were not designed to explicitly separate species' responses to light and temperature. Here we tested reaction norms of tree seedlings in reciprocal transplantations 1,000 km apart from each other at two latitudes (60°N and 69°N). In contrast to past studies, we exposed our experimental plants to same temperature in both sites (temperature of 60°N growing site is recorded to adjust temperature of 69°N site in real time via Internet connection) while light environment (photoperiod, light quality) remained ambient. Shoot elongation and autumn coloration were studied in seedlings of two deciduous trees ( Betula pendula and Sorbus aucuparia), which were expected to respond differently to day length. Sorbus as a member of Rosaceae family was assumed to be indifferent to photoperiod, while Betula responds strongly to day length. We hypothesized that (1) southern and northern populations of both species perform differently; (2) southern populations perform better in both sites; (3) autumn phenology of southern populations may delay in the northern site; (4) and Sorbus aucuparia is less dependent on light environment. According to the hypotheses, shoot elongation of northern population was inherently low in both species. An evolutionary consequence of this may be a competitive success of southern populations under warming climate. Southern population of B. pendula was delayed in autumn coloration, but not in growth cessation. Sorbus aucuparia was less responsive to light environment. The results suggest that light provides selection pressure in range shifts, but the response is species dependent. [ABSTRACT FROM AUTHOR]

Variation in thermal performance within and between populations provides the potential for adaptive responses to increasing temperatures associated with climate change. Organisms experiencing temperatures above their optimum on a thermal performance curve exhibit rapid declines in function and these supraoptimal temperatures can be a critical physiological component of range limits. The gypsy moth, Lymantria dispar ( L.) (Lepidoptera: Erebidae), is one of the best-documented biological invasions and factors driving its spatial spread are of significant ecological and economic interest. The present study examines gypsy moth sourced from different latitudes across its North American range for sensitivity to high temperature in constant temperature growth chamber experiments. Supraoptimal temperatures result in higher mortality in northern populations compared with populations from the southern range extent (West Virginia and coastal plain of Virginia, U.S.A.). Sublethal effects of high temperature on traits associated with fitness, such as smaller pupal mass, are apparent in northern and West Virginia populations. Overall, the results indicate that populations near the southern limits of the range are less sensitive to high temperatures than northern populations from the established range. However, southern populations are lower performing overall, based on pupal mass and development time, relative to northern populations. This suggests that there may be a trade-off associated with decreased heat sensitivity in gypsy moth. Understanding how species adapt to thermal limits and possible fitness trade-offs of heat tolerance represents an important step toward predicting climatically driven changes in species ranges, which is a particularly critical consideration in conservation and invasion ecology. [ABSTRACT FROM AUTHOR]

Given climate change can potentially influence crop phenology and subsequent yield, an investigation of relevant adaptation measures could increase the understanding and mitigation of these responses in the future. In this study, field observations at 10 stations in the Huang-Huai-Hai Plain of China (HHHP) are used in combination with the Agricultural Production Systems Simulator (APSIM)-Wheat model to determine the effect of thermal time shift on the phenology and potential yield of wheat from 1981-2009. Warming climate speeds up winter wheat development and thereby decreases the duration of the wheat growth period. However, APSIM-Wheat model simulation suggests prolongation of the period from flowering to maturity (Gr) of winter wheat by 0.2-0.8 d∙10yr as the number of days by which maturity advances, which is less than that by which flowering advances. Based on computed thermal time of the two critical growth phases of wheat, total thermal time from floral initiation to flowering (TT_floral_initiation) increasesd in seven out of the 10 investigated stations. Alternatively, total thermal time from the start of grainfilling to maturity (TT_start_ grain_fill) increased in all investigated stations, except Laiyang. It is thus concluded that thermal time shift during the past three decades (1981-2009) prolongs Gr by 0.2-3.0 d∙10yr in the study area. This suggests that an increase in thermal time (TT) of the wheat growth period is critical for mitigating the effect of growth period reduction due to warming climatic condition. Furthermore, climate change reduces potential yield of winter wheat in 80% of the stations by 2.3-58.8 kg∙yr. However, thermal time shift (TTS) increases potential yield of winter wheat in most of the stations by 3.0-51.0 kg∙yr. It is concluded that wheat cultivars with longer growth periods and higher thermal requirements could mitigate the negative effects of warming climate on crop production in the study area. [ABSTRACT FROM AUTHOR]

Marine red beds (MRBs) as a special geological phenomenon have been considered relevant to specific palaeogeographic or paleoclimatic conditions. The Wuchiapingian Yundoutan Formation in Xikou, Shaanxi, Central China is characterized by a huge thick succession of red limestones, which is a unique deposition among marine strata of China during the Wuchiapingian. The lithology, mineralogy, and geochemistry features of the Yundoutan Formation MRBs were analyzed by using techniques of field measurement, polarized optical microscope, field emission scanning electron microscope (FESEM), diffuse absorbance spectroscopy (DAS), X-ray diffraction (XRD), and geochemical analysis, which were used to discuss their origin and palaeogeographic and paleoclimatic responses. The results show that the stain mineral for the MRBs is mainly weakly-crystalline hematite which can not be observed in the FESEM but was detected from the DAS first derivative spectra with featured peaks around 570 nm. The similar trend of Fe with refractory elements and the strong positive correlation between Fe and Al suggest Fe is mainly a terrestrial source. Limestones of the Yundoutan Formation contain different colors including red, light gray, and dark gray. Red limestones have comparable contents of Fe with dark gray limestones, which are larger than that of light gray limestones, but they are depleted in redox-sensitive elements (Cr, Ni, Cu, Zn, Mo, U) and riched in Fe(III) compared with dark gray limestones. Those indicate that the formation of red limestones needs both enough terrestrial Fe and strong oxic conditions. A mechanism proposed for the formation of red limestones was that Fe was transported from the highlands, which were then deposited under a strong oxic environment and transformed into hematite. We suggest the Wuchiapingian MRBs formed in Central China represent a unique paleogeography and palaeoclimate association. During that time, the study area attached to the northern margin of the United North China-Qinling Block received terrestrial materials from its northward highlands, which provided Fe under a warm climate. Meanwhile, the study area located between the South and North China blocks was on the narrow seaway connecting the Palaeotethys and Panthalassa, which produced relatively fast exchanging rates of seawater and thus a high content of oxygen that can easily transform terrestrial-sourced Fe into hematite. The gradual transition among color-different limestones may be driven by the changes in rainfall that influenced river transportation on terrestrial materials or sea-level changes that influenced the redox state of the water-sediment interface. • The pigment of the Wuchiapingian MRBs is mainly weakly-crystalline hematite. • Terrestrial Fe and high content of oxygen are the two key conditions for the Wuchiapingian MRBs. • The gradual transitions between red and light gray limestones may be controlled by variations of terrestrial input. • The Wuchiapingian MRBs may document that the South Qinling belt had already merged with North China Block before the Permian. [ABSTRACT FROM AUTHOR]

Warm periods in Earth’s history tend to cool more slowly than cool periods warm. Here we explore initial differences in how the global ocean takes up and gives up heat and carbon in forced rapid warming and cooling climate scenarios. We force an intermediate-complexity earth system model using two atmospheric CO _2 scenarios. A ramp-up (1% per year increase in atmospheric CO _2 for 150 years) starts from an average global CO _2 concentration of 285 ppm to represent warming of an icehouse climate. A ramp-down (1% per year decrease in atmospheric CO _2 for 150 years) starts from an average global CO _2 concentration of 1257 ppm to represent cooling of a greenhouse climate. Atmospheric CO _2 is then held constant in each simulation and the model is integrated an additional 350 years. The ramp-down simulation shows a weaker response of surface air temperature to changes in radiative forcing relative to the ramp-up scenario. This weaker response is due to a relatively large and fast release of heat from the ocean to the atmosphere. This asymmetry in heat exchange in cooling and warming scenarios exists mainly because of differences in the response of the ocean circulation to forcing. In the ramp-up, increasing stratification and weakening of meridional overturning circulation slows ocean heat and carbon uptake. In the ramp-down, cooling accelerates meridional overturning and deepens vertical mixing, accelerating the release of heat and carbon stored at depth. Though idealized, our experiments offer insight into differences in ocean dynamics in icehouse and greenhouse climate transitions.

Notable dryland expansion from changes in global aridity has been documented in previous studies, particularly with the increase in global mean temperature. Here, we examined the changes in the aridity of the western region of Africa over the past four decades. Using the aridity index (P/PET) as an indicator, the Climate Research Unit (CRU TS) data was used to identify drying and wetting areas of the region. The result showed that intense warming of 0.018 °C per year has occurred which was more evident in the last two decades. The warming in the past two decades caused a significant increase in PET. The first two decades were the driest compared to the last decades, particularly the first decade which also had major drought occurrences across the region. The aridity index increased by 0.86 (x10−3) per year within the past four decades, with the greatest change at the semi-arid zone. Result showed that precipitation exerts dominant control on aridity changes in the region despite a significant increase in PET. This was evident in the expansion of the wet areas between 2000 and 2019 compared to the 1979–1998 period. • Warming within the past four decades decreased across the aridity index. • The region has become wetter in recent decades. • Precipitation exerts dominant control on the aridity condition despite enhanced PET in warming years. • Semi-arid and dry-subhumid area increased by 9% and 7% respectively between 2000 and 2019 relative to 1979–1998. • Regional aridity changes exist within the context of global aridity changes. [ABSTRACT FROM AUTHOR]

Based on assimilated meteorological data for the period January 1979 to December 2010, the origin of wind energy is investigated from both mechanical and thermodynamic perspectives, with special focus on the spatial distribution of sources, historical long-term variations and the efficiency for kinetic energy production. The dry air component of the atmosphere acts as a thermal engine, absorbing heat at higher temperatures, approximately 256 K , releasing heat at lower temperatures, approximately 252 K . The process is responsible for production of wind kinetic energy at a rate of 2.46 W / m 2 sustaining thus the circulation of the atmosphere against frictional dissipation. The results indicate an upward trend in kinetic energy production over the past 32 years, indicating that wind energy resources may be varying in the current warming climate. This analysis provides an analytical framework that can be adopted for future studies addressing the ultimate wind energy potential and the possible perturbations to the atmospheric circulation that could arise as a result of significant exploitation of wind energy. [ABSTRACT FROM AUTHOR]

• Higher latitudes regions will witness a high soil NO 3 – production. • Frequent freeze–thaw process may accelerate the soil NO 3 – production. • Soil NO 3 – may reach 18 mg/l concentration during winter only in future. Winter season is characterized by lowering of air temperature and soil temperature, and deceleration of soil nitrogen cycle. Despite low soil temperature, soil NO 3 – is found on the soil surface and in the streams of temperate and higher latitude regions towards the end of winter season. With the rise in global air temperature, the soil temperature is expected to warm up accordingly. Plausible effects of future soil temperature changes in affecting the production and movement of soil NO 3 – within a vertical profile were studied in the present paper. Four Representative Concentration Pathways (RCP) scenarios were considered to estimate the effects of change in air temperature on soil temperature at different depths within a vertical profile and on the soil nitrate status. Since winter season is known to have low to no soil nitrate utilization (due to microbial inactivity and low utilization by biomass), plausible effects of winter warming in the future decades were studied. The occurrence and movement of soil NO 3 – during winter, raises a concern regarding the future warming climate's response. Long-term records from Hubbard Brook Experimental Forest, New Hampshire, USA, were used for observation, calibration, and validation purposes. Non-linear relationship between air temperature, soil moisture, soil temperature, and soil NO 3 – status at different soil depths, were assessed using support vector regression (SVR) models. Soil temperature and soil NO 3 – status at different soil depths were predicted using SVR models, under the four different RCP scenarios. The projections under different RCP scenarios suggested - significant production of soil NO 3 – during winter (approx. 18 mg/l by the year 2095 under a "business as usual" scenario), and movement of soil NO 3 – towards soil surface before the beginning of plant-growing season. [ABSTRACT FROM AUTHOR]