Climatic Boundary Research Articles

What factors determine the mass elevation effect of the Tibetan Plateau?

The mass elevation effect (MEE) of the Tibetan Plateau (TP) has attracted the attention of geographers because of its significant influence on the Asian climate, snow line, timberline, and other important climate-ecological boundaries of the plateau and on global ecological patterns. In recent years, much progress has been made in quantifying the MEE of TP. However, factors that affect the size of MEE have not been examined in depth, and the key factors still remain unclear. Based on quantification of MEE for each mountain basal elevation plot, this study identifies the factors that contribute significantly to MEE of the plateau. Seven factors are considered, including mountain basal elevation, distance from the core zone of MEE, thermal continentality, maximum elevation, height difference, area, and difference of underlying surface (with the yearly max “Normalized Difference Vegetation Index” (NDVI) serving as a quantitative indicator). We also used these seven factors as independent variables to develop a multiple linear regression model for MEE of the plateau. Results show that: (1) the determination coefficient (R2) of the model reaches as high as 0.877, and the contributions of mountain basal elevation, distance from the core zone of MEE, thermal continentality, maximum elevation, topographical height difference, area, and NDVI are 39.77%, 23.02%, 14.48%, 5.78%, 11.41%, 2.92%, and 2.62%, respectively, with mountain basal elevation and the distance from the core of MEE as the most important factors; (2) thermal continentality and MEE are significantly correlated, and maximum elevation only has a coupling relationship with MEE, with height difference and NDVI contributing little to MEE. This study deepens our understanding of MEE and its forming factors in the Tibetan Plateau.

Spatial-temporal analysis of net primary production (NPP) and its relationship with climatic factors in Iran.

Fluctuations of the climate variables have increased in the recent years. These fluctuations are different in each climatic region. Net primary production (NPP) indicating the plant growth and carbon stabilization over period of time is influenced by these fluctuations. Investigation of the variations in the NPP and analysis of its relationship with the climatic and environmental variables can play a key role in determining the effects of fluctuations of climatic variables on the NPP. Therefore, the present study was conducted to investigate the spatiotemporal changes in the NPP and its correlation with precipitation rate and temperature during 2000-2014 based on the annual NPP estimates determined by the moderate resolution imaging spectroradiometer (MODIS) sensor and precipitation and temperature data of the synoptic stations in eight climate regions in Iran. The slope of variations in the NPP was calculated in these climatic regions, and then, the changes in the NPP trend at two confidence levels of 95 and 99% were investigated based on the pixel-based method using the Mann-Kendall test. The sensitivity of NPP to climatic variables of temperature and precipitation was also estimated by calculating the correlation. The results showed the significant spatial distribution of NPP in the whole region under study indicating a declining trend from north to south and from west to east directions. The results also indicated the nonlinear variations in the temporal distribution of NPP. The annual mean NPP was found to follow the climatic boundaries in the climatic regions except for climate region 2, and region with the higher annual mean precipitation had higher annual mean NPP. Analysis of the trend by the Mann-Kendall method revealed that 3.2% of the pixels in the whole region followed a certain trend. Among the pixels, 70% of them followed a negative trend and the remaining 30% followed a positive trend. The greatest number of pixels with a certain trend was found in the Gulf of Oman coast climate region so that 93% of the pixels had a positive trend. The lowest number of pixels with a certain trend was observed in eastern Alborz foothills so that 87% of the pixels showed a negative trend. Slope variations of the NPP in the whole region varied from - 35 to 46 gC m2 year-1. The eastern plateau had the highest negative slope variations among the climate regions, and the highest positive slope variation of 42% was observed in the highlands climate region. In general, the precipitation rate and temperature showed a mean partial coefficient of 0.22 and 0.02, respectively, and the correlation between the NPP and temperature and precipitation was different in each climatic region. The temperature was negatively correlated with the NPP in four climatic regions with higher annual mean temperatures and in other climatic regions; it had a weak positive correlation. Therefore, the sensitivity of NPP to precipitation and temperature was different in each climatic region.

Will the wind associated with the Adriatic storm surges change in future climate?

Flooding of the Adriatic coastline is predominantly caused by storm surges induced by winds from the south-eastern sector. This phenomenon in Venice is known as acqua alta. We present a study of wind fields favouring storm-surge setups in the Adriatic, including their characteristics in the present climate and their expected characteristics in future scenarios. Analysis is based on (i) measured sea levels in Venice and Bakar (1984–2014), (ii) near-surface wind from ERA5 reanalysis, and (iii) simulations of wind fields with three regional climate models (ALADIN52, RCA4, and RegCM4) forced with several global models (CNRM-CM, MPI-ESM-MR/LR, HadGEM2-ES, EC-EARTH, and IPSL-CM5). For future climates, we considered two scenarios (RCP4.5 and RCP8.5) and two future periods (2041–2070 and 2071–2100) with respect to the historical 1971–2000 period. It was found that the probability that the frequency, intensity, annual cycle, and spatial structure of the wind inducing the Adriatic storm surges will change in future climates is small. The result is robust and consistent according to all considered criteria—it does not depend on the analysed regional climate models, boundary conditions, climate scenarios, or future time interval.

Contrasting signatures of introgression in North American box turtle (Terrapene spp.) contact zones.

Hybridization occurs differentially across the genome in a balancing act between selection and migration. With the unprecedented resolution of contemporary sequencing technologies, selection and migration can now be effectively quantified such that researchers can identify genetic elements involved in introgression. Furthermore, genomic patterns can now be associated with ecologically relevant phenotypes, given availability of annotated reference genomes. We do so in North American box turtles (Terrapene) by deciphering how selection affects hybrid zones at the interface of species boundaries and identifying genetic regions potentially under selection that may relate to thermal adaptations. Such genes may impact physiological pathways involved in temperature-dependent sex determination, immune system functioning and hypoxia tolerance. We contrasted these patterns across inter- and intraspecific hybrid zones that differ temporally and biogeographically. We demonstrate hybridization is broadly apparent in Terrapene, but with observed genomic cline patterns corresponding to species boundaries at loci potentially associated with thermal adaptation. These loci display signatures of directional introgression within intraspecific boundaries, despite a genome-wide selective trend against intergrades. In contrast, outlier loci for interspecific comparisons exhibited evidence of being under selection against hybrids. Importantly, adaptations coinciding with species boundaries in Terrapene overlap with climatic boundaries and highlight the vulnerability of these terrestrial ectotherms to anthropogenic pressures.

A meta-analysis of the effects of treatments used to break dormancy in seeds of the megagenus Astragalus (Fabaceae)

AbstractAstragalus is the largest genus of seed plants with 3000 or more species that occurs naturally on several continents. The genus has some use as a forage and medicine and in industry, and many of the species are rare endemics threatened with extinction. The seeds are reported to be dormant at maturity, and various treatments have been used in an attempt to germinate them. Our primary aim was to determine via a meta-analysis the most effective way(s) to break dormancy in seeds of this species-rich genus. Mechanical and chemical (conc. sulphuric acid) scarification were by far the best of 12 treatments for breaking seed dormancy of the 40 species included in our meta-analysis, whereas prechilling, gibberellin and smoke were ineffective. These results along with those of imbibition tests confirm that seeds of the examined Astragalus species have physical dormancy (PY). Further, PY in these 40 species and (its documented occurrence) in 118 species that could not be included in our meta-analysis transcends climatic and geographic boundaries, edaphic conditions, life cycle/life form types and infrageneric phylogeny. Thus, it seems likely that most species of Astragalus have PY. However, in addition to PY, physiological dormancy (PD), that is, combinational dormancy (PY + PD), has been reported in a few species of Astragalus. This study should be useful to both basic and applied scientists who want to germinate seeds of Astragalus.

A Persistent Kuroshio in the Glacial East China Sea and Implications for Coral Paleobiogeography

AbstractThe Kuroshio Current is a major hydrographical feature of the modern East China Sea, but it has been suggested that its flow was diverted to the east of the Ryukyu Arc at the Last Glacial Maximum. Shoaling of the Yonaguni Depression has also been proposed as a cause of Kuroshio Current diversion which, while unlikely to have been significant at the Last Glacial Maximum, may have been an important consideration further back in time. Using an ensemble of high‐resolution ocean simulations with climatic boundary conditions emulating those of the Last Glacial Maximum, we present the first regional state estimates of the glacial East China Sea which are both physically consistent and compatible with sea surface temperature proxy compilations. We find that while the Kuroshio Current transport in the East China Sea is slightly reduced at the Last Glacial Maximum, its path is relatively unchanged, with limited sensitivity to glacioeustatic sea level change, glacial‐interglacial changes in climate, and tectonic shoaling of the Yonaguni Depression. Simulations with the best model‐proxy agreement predict only limited contraction of the reef front at the Last Glacial Maximum, and strong surface currents associated with the glacial Kuroshio may have maintained or even improved long‐distance coral larval dispersal along the Ryukyu Arc, suggesting that conditions may have enabled coral reefs in this region to remain widespread throughout the last glacial. Further field studies investigating whether this is genuinely the case will provide insights into how the coral reef front responds to long‐term environmental change.

Isolation, diversity, and antimicrobial activity of fungal endophytes from Rohdea chinensis (Baker) N.Tanaka (synonym Tupistra chinensis Baker) of Qinling Mountains, China.

Endophytic fungi have been emerged as fruitful resources for producing structurally fascinating and biologically active secondary metabolites. However, endophytic fungi from medicinal plants of Qinling Mountains–the most important natural climatic boundary between the subtropical and warm temperate zones of China with an astonishingly high level of biodiversity–have rarely been explored as potential sources of novel fungal species and active secondary metabolites. In this study, a total of 371 fungal colonies were successfully isolated from 510 tissue segments of the medicinal Tupistra chinensis Baker collected from Qinling Mountains, China. Roots of T. chinensis Baker are used as a folk medicine to ameliorate pharyngitis and treat rheumatic diseases. A total of 100 representative morphotype strains were identified according to ITS rDNA sequence analyses and were grouped into three phyla (Ascomycota, Basidiomycota, Mucoromycota), seven classes (Dothideomycetes, Sordariomycetes, Eurotiomycetes, Microbotryomycetes, Agaricomycetes, Leotiomycetes, Mortierellomycetes), and at least 35 genera. The genera of Collectotrichum (IF, 29.92%), Fusarium (IF, 8.36%), Aspergillus (IF, 8.09%), and Dactylonectria (IF, 5.39%) were most frequently isolated from the tissues of T. chinensis Baker. The Species Richness Index (S, 65) and the Shannon-Wiener Index (H′, 3.7914) indicated that T. chinensis Baker harbored abundant fungal resources. Moreover, five isolates were potential new taxa because of low similarity of ITS sequences ranged from 95.09%∼96.61%. Fifteen out of 100 endophytic fungal ethyl acetate extracts exhibited inhibitory activities against at least one pathogenic bacterium or fungus. Two important lead compounds produced by two stains (F8047 and F8075) with high antimicrobial activities were identified using high performance liquid chromatography (HPLC) and ultra-performance liquid chromatography-quadrupole-time of flight mass spectrometry (UPLC–QTOF MS) analyses. In addition, it was noteworthy that the strain F8001, which may be a potential new species, showed antimicrobial activity and should be investigated further. Overall, these results indicated that the endophytic fungi from T. chinensis Baker could be exploited as a novel source of bioactive compounds.

Bryophytes at the Western Limits of Canada's Great Lakes Forest: Floristic Patterns and Conservation Implications

The Great Lakes–St. Lawrence Forest Region in Canada occupies a narrow band of mixed forest from the Gaspe Peninsula to southeastern Manitoba. The westernmost extent of this forest region in Manitoba is expected to support at least some of the bryophyte species that occur further east within the climatic and vegetation boundaries of the region. However, very few bryophytes have been reported from this area in Manitoba either in the scientific literature or herbaria, necessitating further investigation. This study provides the first assessment of bryophytes from mixed forests and treed swamps within the Great Lakes forest in Manitoba and relates them to physiography and habitat, including the first documented bryophytes for Buffalo Point First Nation on Lake of the Woods. Reported here are 153 bryophyte taxa, including 40 liverworts from 29 genera in 23 families, and 113 mosses from 77 genera in 31 families. Among these, 27 bryophytes (9 liverworts and 18 mosses) are new to Manitoba, and an additional 7 bryophytes (1 liverwort and 6 mosses) that previously had incomplete information or were equivocal are now confirmed for Manitoba. These findings expand substantially the provincial bryophyte flora. A further 35 bryophytes are re-discovered for Manitoba after more than 40 years since they were last reported in the literature. The surveyed flora is characterized as predominantly boreal (61.7% of taxa) in terms of world phytogeographic distributions. However, more than one quarter of taxa (27.9%) are temperate and frequently associated with habitats containing Fraxinus nigra (Black Ash) or Fraxinus pennsylvanica (Green Ash) trees. Many of the temperate taxa reported have widespread distributions in eastern North America but approach their western and/or northern distribution limits in the study area. Herein I identify bryophytes of high conservation value for Great Lakes forest in Manitoba using nested subsets of taxa. Additional documentation of bryophytes in the area is needed to help inform the conservation and management of lands that support a high diversity of Great Lakes-associated bryophytes.

Assessing the performance of a versatile and affordable geotechnical monitoring system for river embankments

River embankments stability is a key aspect in geohazard assessment and underestimating its failure risk may result in unexpected and severe damages. Changes in hydraulic and climatic boundary conditions are responsible for transient water flow within the embankments, consequently the related soil water content and pore-water pressure distributions vary with time. Therefore, it is crucial to investigate their hydraulic and retention behaviour in order to assess in a reliable way the safety margins towards instability mechanisms. To obtain a realistic estimate of key variables in time and space, as a function of external conditions, a combination of field measurements, laboratory testing and suitably calibrated numerical analyses should be used. To achieve this purpose, a full-scale monitoring system was implemented on a cross section of an embankment along the river Secchia (Modena, Italy), mainly measuring the pore-water pressure (including suction) and the water content at different depths. A relatively large variety of different sensors have been installed, to compare their performance in terms of robustness and reliability, and collected data have been interpreted with the help of laboratory and field geotechnical characterisation. The article describes such system and the sensors used, their capabilities and the installation techniques, resulting in quite innovative solutions for the specific application. The spatial variability of the monitored variables is also finally presented and discussed. The proposed integrated monitoring system, which aims at making use of affordable and commercially available sensors that can be therefore installed along extensive river stretches, appears a fundamental starting point to assess potential risks of such geotechnical infrastructures in real-time and to devise well-balanced related mitigation measures.

The role of the Cape’s unique climatic boundaries in sustaining specialised pastoralists in southern Africa during the last 2000 years

ABSTRACTGenetic analyses show that milch pastoralism existed in southern Africa for at least the last 1300 years. This paper addresses the question of how specialised milch pastoralists would have sustained their herds in the arid western half of southern Africa, where archaeological evidence shows their traces. This might be down to what Jared Diamond terms ‘geographic luck’, i.e. that pastoralists, whom we know moved rapidly to the southern and western Cape, discovered the winter rainfall and all year round rainfall areas that are unique in southern Africa and settled there. Good grazing and all year-round rainfall would have been found by moving between these zones and the summer rainfall zone of the neighbouring Northern and Eastern Cape Provinces. These zones fall outside the areas that were later settled by agropastoralist farmers. European mariner sightings of livestock along South Africa’s shores from the end of the fifteenth century AD onward have previously been used to reconstruct the seasonal movements of pastoralists. There is, however, an inherent bias in these data caused by the prevailing wind patterns that determined the timing of mariners’ arrival to the Cape.

Numerical Study to Predict Temperature and Moisture Profiles in Unventilated Grain Silos at Prolonged Time Periods

The experimental acquisition of data for monitoring cereal grain storage in silos for long periods is not practical in most cases; in such situations, mathematical modeling is an excellent alternative to predict temperature and mass transfer behavior. The model was developed in two dimensions using the equations of heat, mass, and momentum transport. The governing equations were solved using discretization of the spatial coordinates by orthogonal collocation with Jacobi polynomials and the resulting algebraic system was solved by employing nonlinear relaxation method that uses less computational resources. For the ambient boundary conditions, it was used as a more accurate equation to represent the diurnal–nocturnal temperature dynamic. This study analyzes the effects of moisture migration and temperature interactions between the interstitial air and the sorghum cereal grain bed defined as a porous medium in a cylindrical cavity, including the variations affected by meteorological conditions over 1 year. The mass–thermal gradients were predicted, and the effects of environmental temperature were analyzed for flow patterns, isotherms and moisture distribution changes, indicating how the environmental fluctuations influence the heat and moisture of the ambient spots in the grain storage. The maximum temperature inside the silo was 42 °C, considering the respiration heat of the grain, and the maximum temperature of the grain without the climatic boundary conditions was reported to be approximately 35 °C in previous studies. The proposed model can be easily extrapolated to be used for other cereal grains or to incorporate additional effects such as solar radiation, shadow sunlight path, wind velocity, equations to predict more precise ambient temperatures, etc. as boundary conditions.

Total ecosystem carbon stocks of mangroves across broad global environmental and physical gradients

AbstractMangroves sequester large quantities of carbon (C) that become significant sources of greenhouse gases when disturbed through land‐use change. Thus, they are of great value to incorporate into climate change adaptation and mitigation strategies. In response, a global network of mangrove plots was established to provide policy‐relevant ecological data relating to interactions of mangrove C stocks with climatic, tidal, plant community, and geomorphic factors. Mangroves from 190 sites were sampled across five continents encompassing large biological, physical, and climatic gradients using consistent methodologies for the quantification of total ecosystem C stocks (TECS). Carbon stock data were collected along with vegetation, physical, and climatic data to explore potential predictive relationships. There was a 28‐fold range in TECS (79–2,208 Mg C/ha) with a mean of 856 ± 32 Mg C/ha. Belowground C comprised an average 85% of the TECS. Mean soil depth was 216 cm, ranging from 22 to >300 cm, with 68 sites (35%) exceeding a depth of 300 cm. TECS were weakly correlated with metrics of forest structure, suggesting that aboveground forest structure alone cannot accurately predict TECS. Similarly, precipitation was not a strong predictor of TECS. Reasonable estimates of TECS were derived via multiple regression analysis using precipitation, soil depth, tree mass, and latitude (R2 = 0.54) as variables. Soil carbon to a 1 m depth averaged 44% of the TECS. Limiting analyses of soil C stocks to the top 1 m of soils result in large underestimates of TECS as well as in the greenhouse gas emissions that would arise from their conversion to other land uses. The current IPCC Tier 1 default TECS value for mangroves is 511 Mg C/ha, which is only 60% of our calculated global mean. This study improves current assessments of mangrove C stocks providing a foundation necessary for C valuation related to climate change mitigation. We estimate mangroves globally store about 11.7 Pg C: an aboveground carbon stock of 1.6 Pg C and a belowground carbon stock of 10.2 Pg C). The differences in the estimates of total ecosystem carbon stocks based on climate, salinity, forest structure, geomorphology, or geopolitical boundaries are not as much of an influence as the choice of soil depth included in the estimate. Choosing to limit soils to a 1 m depth resulted in estimates of <5 Pg whereas those that included the soil profile >1 m depth resulted in global carbon stock estimates that exceeded 11.2 Pg C.

Effect of rainfall intensity on PM10 and PM2.5 scavenging in Guangzhou at night

The Lingnan area is a region where frequent rainfall occurs in mainland China. In addition to the special occurrence period, the nighttime rainfall has obvious seasonal characteristics, which is different from the climatic boundary conditions during the daytime, and has a great influence on the migration and transformation process of atmospheric pollutants. By counting the observations of atmospheric particulate matter (PM2.5, PM10) before and after rainfall in the Pearl River Delta region, the average clearance rate of PM10 and PM2.5 for the whole region was 2.36% and 1.41%, and the average clearance rate of night rainfall was calculated. 6.44%, 4.22%. The results show that the rainfall can effectively remove atmospheric particulate pollutants through wet deposition, and the nighttime rainfall is more effective than the daytime rainfall on the atmospheric particulate matter. Through classification discussion, it is found that the greater the rainfall intensity, the longer the rainfall time, the larger the particle size, and the more obvious the advantage of night rain.

PCSP’s Diagonal Tie Connectors Thermal Bridges Impact on Energy Performance and Operational Cost: Case Study of a High-Rise Residential Building in Estonia

This study analyses the effect of air circulation around diagonal tie connectors in precast sandwich panels on heating energy demand, energy performance value and heating costs of a sample residential building. Dynamic simulations were performed using 4 different climatic boundary conditions: Estonian test reference year, Estonian 48-year weather dataset as well as data from Eastern Germany and Northern Finland. The results show that the effect of the thermal bridge is most noticeable in total room heating energy demand (increase of 10.3%), while the influence on energy performance value was 1.1%. The relative increase of total room heating energy demand was similar (7.0-10.3%) in all studied climatic regions.

Evolution of a deep-water ferromanganese nodule in the South China Sea in response to Pacific deep-water circulation and continental weathering during the Plio-Pleistocene

The South China Sea (SCS) is connected to the West Pacific through a deep channel in the Luzon Strait. Thus the SCS deep water is sensitive to the evolution of Pacific Ocean circulation, which significantly influences the global climate system. Geochemical data (Pb isotope and redox-sensitive elements data) and magnetic data were determined for a Fe–Mn nodule obtained from Jiaolong seamount in the central SCS. These records reflect interactions between changes in ice sheets, deep Pacific circulation, and weathering inputs to the deep SCS during the Pliocene and Quaternary. Our results show that the SCS deep-water environment can be divided into three major Stages (Stages 1–3). Stage 1 (∼4.8–1.4 Ma) was characterized by a well-oxygenated Pacific Deep Water (PDW) and lower dust inputs; then moderate stable deep-water ventilation and greater inputs of Asian dust occurred during Stage 2 (1.4–0.9 Ma). During Stage 3 (<0.9 Ma), a more isolated PDW was accompanied by sluggish Pacific overturning circulation, probably due to the weakened southern-sourced deep-water formation. In general, the progressive intensification of northern hemisphere ice-sheet play an active role in controlling the variation of the deep-water environment in the SCS. Interestingly, the variation in deep-water ventilation lagged behind weathering and erosion around the Middle Pleistocene Transition, which strongly indicates that the ocean and continent environments had different sensitivities to the global paleoclimatic changes at the glacial climate boundary.

Modeling Indoor Relative Humidity and Wood Moisture Content as a Proxy for Wooden Home Fire Risk.

Severe wooden home conflagrations have previously been linked to the combination of very dry indoor climate in inhabited buildings during winter time, resulting in rapid fire development and strong winds spreading the fire to neighboring structures. Knowledge about how ambient conditions increase the fire risk associated with dry indoor conditions is, however, lacking. In the present work, the moisture content of indoor wooden home wall panels was modeled based on ambient temperature and relative humidity recorded at meteorological stations as the climatic boundary conditions. The model comprises an air change rate based on ambient and indoor (22 °C) temperatures, indoor moisture sources and wood panel moisture sorption processes; it was tested on four selected homes in Norway during the winter of 2015/2016. The results were compared to values recorded by indoor relative humidity sensors in the homes, which ranged from naturally ventilated early 1900s homes to a modern home with balanced ventilation. The modeled indoor relative humidity levels during cold weather agreed well with recorded values to within 3% relative humidity (RH) root mean square deviation, and thus provided reliable information about expected wood panel moisture content. This information was used to assess historic single home fire risk represented by an estimated time to flashover during the studied period. Based on the modelling, it can be concluded that three days in Haugesund, Norway, in January 2016 were associated with very high conflagration risk due to dry indoor wooden materials and strong winds. In the future, the presented methodology may possibly be based on weather forecasts to predict increased conflagration risk a few days ahead. This could then enable proactive emergency responses for improved fire disaster risk management.

Long‐Period Astronomical Forcing of Westerlies' Strength in Central Asia During Miocene Climate Cooling

AbstractThe continental expression of global cooling during the Miocene Climate Transition in Central Asia is poorly documented, as the tectonically active setting complicates the correlation of Neogene regional and global climatic developments. This study presents new geochemical data (CaSO4 content, carbonate δ13C and δ18O) from the endorheic alluvial‐lacustrine Aktau succession (Ili Basin, south‐east Kazakhstan) combined with findings from the previously published facies evolution. Time series analysis revealed long‐eccentricity forcing of the paleohydrology throughout the entire succession, split into several facies‐dependent segments. Orbital tuning, constrained by new laser ablation U‐Pb dates and a preexisting magnetostratigraphy, places the succession in a 5.0 Ma long interval in the middle to late Miocene (15.6 to 10.6 Ma). The long‐term water accumulation in the Ili Basin followed the timing of the Miocene Climate Transition, suggesting increased precipitation in the catchment area in response to climate cooling and stronger westerly winds. This was paced by minima of the 2.4 Ma eccentricity cycle, which favored the establishment of a discharge playa (~14.3 Ma) and a perennial lake (12.6 to 11.8 Ma). Furthermore, low obliquity amplitudes (nodes) caused a transient weakening of the westerlies at ~13.7 to 13.5 Ma and at ~12.7 Ma, resulting in negative hydrological budgets and salinization. Flooding of the windward Ili Basin coeval with aridification in the leeward basins suggests that the Tian Shan was a climate boundary already in the middle Miocene. Our results emphasize the impact of climate fluctuations on the westerlies' strength and thus on Central Asian hydrology.

Transient basin as indicator of tectonic expressions in bedrock landscape: Approach based on MATLAB geomorphic tool (Transient-profiler)

The tectonic and erosional processes sculpture the Earth's surface, producing a landscape that preserves the evolutionary history of rock uplift and incision. The bedrock channels act as an efficient gradation agent where the river profile adjusts to changing tectonic, climatic, or topological (e.g., river capture) boundary conditions, and develops a transient basin. A suite of slope-break knickpoints at comparable elevations in the channel profiles of the transient basin act as important markers. We developed a set of comprehensive and interactive MATLAB tools, called a Transient-profiler, to extract the geomorphic indices from the digital elevation model for a basin characterization and landscape evolution period. The paleo-channel reconstruction from the relict reach in the three studied transient drainage basins (Palar, Umiam, and Dibang) suggest a varying surface uplift from 514, 1246, and 1981 m with a respective relief gain of 158%, 230%, and 95%, respectively. We found that the horizontal knickpoint retreat rate is faster in the Himalayan thrust system as compared to the Shillong pop-up system, whereas the vertical knickpoint retreat rate is faster in the latter.

Dynamic climate-driven controls on the deposition of the Kimmeridge Clay Formation in the Cleveland Basin, Yorkshire, UK

Abstract. The Kimmeridge Clay Formation (KCF) is a laterally extensive, total-organic-carbon-rich succession deposited throughout northwest Europe during the Kimmeridgian–Tithonian (Late Jurassic). It has recently been postulated that an expanded Hadley cell, with an intensified but alternating hydrological cycle, heavily influenced sedimentation and total organic carbon (TOC) enrichment by promoting primary productivity and organic matter burial in the UK sectors of the Boreal Seaway. Consistent with such climate boundary conditions, petrographic observations, total organic carbon and carbonate contents, and major and trace element data presented here indicate that the KCF of the Cleveland Basin was deposited in the Laurasian Seaway under the influence of these conditions. Depositional conditions alternated between three states that produced a distinct cyclicity in the lithological and geochemical records: lower-variability mudstone intervals (LVMIs) which comprise clay-rich mudstone and higher-variability mudstone intervals (HVMIs) which comprise TOC-rich sedimentation and carbonate-rich sedimentation. The lower-variability mudstone intervals dominate the studied interval but are punctuated by three ∼ 2–4 m thick intervals of alternating TOC-rich and carbonate-rich sedimentation (HVMIs). During the lower-variability mudstone intervals, conditions were quiescent with oxic to suboxic bottom water conditions. During the higher-variability mudstone intervals, highly dynamic conditions resulted in repeated switching of the redox system in a way similar to the modern deep basins of the Baltic Sea. During carbonate-rich sedimentation, oxic conditions prevailed, most likely due to elevated depositional energies at the seafloor by current–wave action. During TOC-rich sedimentation, intermittent anoxic–euxinic conditions led to an enrichment of redox-sensitive and sulfide-forming trace metals at the seafloor and a preservation of organic matter, and an active Mn–Fe particulate shuttle delivered redox-sensitive and sulfide-forming trace metals to the seafloor. In addition, based on TOC–S–Fe relationships, organic matter sulfurization appears to have increased organic material preservation in about half of the analysed samples throughout the core, while the remaining samples were either dominated by excess Fe input into the system or experienced pyrite oxidation and sulfur loss during oxygenation events. New Hg∕TOC data do not provide evidence of increased volcanism during this time, consistent with previous work. Set in the context of recent climate modelling, our study provides a comprehensive example of the dynamic climate-driven depositional and redox conditions that can control TOC and metal accumulations in a shallow epicontinental sea, and it is therefore key to understanding the formation of similar deposits throughout Earth's history.

Assessing climate boundary shifting under climate change scenarios across Nepal.

This study assesses the climate boundary shifts from the historical time to near/mid future by using a slightly modified Köppen-Geiger (KG) classification scheme and presents comprehensive pictures of historical (1960-1990) and projected near/mid future (1950s: 2040-2060/1970s: 2060-2080) climate classes across Nepal. Ensembles of three selected general circulation models (GCMs) under two Representative Concentration Pathways (RCP 4.5 and RCP 8.5) were used for projected future analysis. During the 1950s, annual average temperature is expected to increase by 2.5°C under RCP 8.5. Similarly, during the 1970s, it is even anticipated to rise by 3.6°C under RCP 8.5. The rate of temperature rise is higher in the non-monsoon period than in monsoon period. During the 1970s, annual precipitation is projected to increase by 8.1% under RCP 8.5. Even though the precipitation is anticipated to increase in the future in annual scale, winter seasons are estimated to be drier by more than 15%. This study shows significant increments of tropical (Am and Aw) and arid (BSk) climate types and reductions of temperate (Cwa and Cwb) and polar (ET and EF). Noticeably, the reduction of the areal coverage of polar frost (EF) is considerably high. In general, about 50% of the country's area is covered by the temperate climate (Cwa and Cwb) in baseline scenario and it is expected to reduce to 45% under RCP 4.5 and 42.5% under RCP 8.5 during the 1950s, and 42% under RCP 4.5 and 39% under RCP 8.5 during the 1970s. Importantly, the degree of climate boundary shifts is quite higher under RCP 8.5 than RCP 4.5, and likewise, the degree is higher during the 1970s than the 1950s. We believe this study to facilitate the identification of regions in which impacts of climate change are notable for crop production, soil management, and disaster risk reduction, requiring a more detailed assessment of adaptation measures. The assessment of climate boundary shifting can serve as valuable information for stakeholders of many disciplines like water, climate, transport, energy, environment, disaster, development, agriculture, and tourism.