Warm-wet Climate Research Articles

Palaeo-environmental significance of evaporative calcite crusts in the Untersee Oasis, East Antarctica

Abstract Secondary carbonate precipitates on the surface of clasts have rarely been reported from Antarctica. Here, we infer the origin, age and palaeo-environmental significance of the calcite crusts in the Untersee Oasis, East Antarctica. The distribution of calcite crusts, which are up to 1 mm thick, is limited to locations with residual snow patches, and they have some of the highest δ18O (up to +17.4‰ Vienna Standard Mean Ocean Water (VSMOW)) and δ13C (up to +14.6‰ Vienna Pee Dee Belemnite (VPDB)) compositions of any carbonate deposits in terrestrial polar environments. Their δ18O and δ13C values are substantially enriched with respect to the isotopic values expected from equilibrium precipitation from the δ18O and δ13CDIC (DIC = dissolved inorganic carbon) of snow meltwater. The formation of the calcite crusts is ascribed to the evaporation of residual snow meltwater and the low relative humidity and strong winds, favouring a kinetic isotope effect. The 14C age distribution of the calcite crusts (1550 cal yr bp to modern) provides a minimum age for ice retreat and drainage of the palaeo-lake in Aurkjosen Cirque. However, in this polar desert environment in which surface melting is limited, the calcite crusts require sufficient snow accumulation and air temperatures warm enough to generate meltwater, and their age distribution corresponds to the late Holocene warm-wet climate period.

Climate change affects plant aboveground biomass by regulating the growth periods in alpine grasslands of the Tibetan Plateau, China

Climate change significantly affects plant biomass and phenological occurrence time in alpine grasslands of Tibetan Plateau. The changes in phenological periods are closely related to the length of vegetative and reproductive growth periods, which may further affect aboveground biomass accumulation. In this study, based on fixed-point observations of plant biomass and phenology as well as the corresponding climatic data from 1997 to 2020 in the alpine grasslands of Tibetan Plateau, we used statistical methods such as ordinary linear regression and piecewise structural equation model to explore the characteristics of interannual climate change in the study area, the variation trends of plant biomass and phenological periods, and the correlations between biomass and phenological and climatic factors. The results showed that mean annual temperature and annual precipitation in the study area increased significantly from 1997 to 2020, suggesting a clear "warm-wet" trend. Aboveground biomass and relative biomass of Stipa sareptana var. krylovii (the dominant species) decreased significantly. However, absolute and relative biomass of subdominant species (Kobresia humilis) increased significantly, indicating that the dominance of K. humilis increased. The warm-wet climates enhanced aboveground biomass accumulation of K. humilis by extending the period of reproductive growth. Mean annual temperature and annual precipitation decreased aboveground biomass of S. sareptana by shortening the length of vegetative growth period. In a word, the warmer and wetter climate significantly affected aboveground biomass accumulation by regulating the changes in the phenological period, and the interspecific difference in their response resulted in a larger change in community composition. This study area may show a trend from alpine grassland to alpine meadow, and thus further works are urgently needed.

Onset of aridification in mid-latitude Asia at 41 Ma linked to the proto-Paratethys Sea retreat

The initial aridification of mid-latitude Asia is thought to be one of the most prominent Cenozoic environmental changes in Asia. However, precisely dated, fine-grained sediments documenting initial aridity beyond central Asia are extremely rare. Here, we reconstruct the history of Middle-Late Eocene (47.8–37.8 Ma) hydroclimate change in northeast China using continuous palynological records from a lacustrine sedimentary sequence in the Fushun Basin. Our results indicate that the onset of aridification occurred concurrently with increased climatic variability at 41.2 Ma, as expressed by a sharp increase in xerophytic Ephedra and mountainous coniferous forest at the expense of an abrupt decrease in broadleaved forest, along with frequent alternations between semi-desert and swamp forest vegetation after 41.2 Ma. The climate changed markedly from a stable, warm-wet climate during the Middle Eocene to a cooler, drier climate with pronounced warm-dry and cold-wet oscillations during the Late Eocene. This finding challenges the previously prevailing idea that the East Asian monsoon was significantly enhanced in northeast China after 41–40 Ma. A comprehensive comparison of records from eastern and central Asia demonstrates that the onset of aridification and enhanced climate variability after 41 Ma were widespread across mid-latitude Asia. This may be explained by reduced moisture transport by the westerlies and strengthening of high- and low-latitude forcing linked to the coeval retreat of the proto-Paratethys Sea.

Grassland productivity increase was dominated by climate in Qinghai-Tibet Plateau from 1982 to 2020

Grassland areas occupy 60% of the Qinghai-Tibetan Plateau (QTP) and play a critical role in enhancing the ecological barrier functions of the QTP. Grassland ecosystems, and net primary productivity (NPP) in general, have dramatically changed in time and space since the 1980s, with climate warming and the intensification of human activities. Current research widely believes that climate and human activities are the common driving factors of grassland ecosystem changes on the QTP. However, there is still controversy over their dominant driving factors and their contribution rates, especially during different research periods. Therefore, this study calculated the relative contributions of climate change, human activities (except LUCC) and LUCC to actual NPP (aNPP) changes during the two periods from 1982 to 2000 to 2001–2020. This study simulated three kinds of NPPs, that is, actual NPP, potential NPP, and human-appropriated NPP, using climate productivity, the light use efficiency model, and the residual method, respectively. Moreover, the study area was divided into two parts, and then the contributions of the three factors were calculated objectively. The results showed that (1) the actual NPP (aNPP) of the QTP increased dramatically from 1982 to 2000 but did not change obviously from 2001 to 2020. (2) Comprehensive evaluation showed that climate was the dominant factor for the aNPP net increase, and its contribution rate dramatically increased from 36.3% during 1982–2000 to 224.2% during 2001–2020. Human activities changed from a positive contribution (53.3%) to a negative contribution (−124.8%) to the aNPP net increase. The contribution rate of LUCC to the aNPP increase significantly decreased from 10.4% to 0.6%. Therefore, finer grassland restoration measures and government policies must be implemented to increase NPP against the background of favorable warm-wet climate conditions for increasing grassland NPP in the QTP. These results benefit the scientific management of grassland resources and ecological barrier building on the QTP.

Red clays indicate sub-aerial exposure of the Rio Grande Rise during the Eocene volcanic episode

Autonomous underwater vehicle (AUV) mapping of the western Rio Grande Rise (RGR), South Atlantic, and subsequent exploration and photography of horizontal lava flows exposed in near vertical, faulted escarpments, showed occurrences of red clays/weathered volcanic tops trapped between successive alkaline lava flows. These red clays indicate a hiatus in successive volcanic eruptions. Here, we report detailed mineralogical, geochemical, and rock magnetic characteristics of one such distinct red clay dredged from ~ 650 m water depth in the western RGR. The mineral constituents of the red clay are kaolinite, magnetite, oxidized magnetite (/maghemite), hematite, and goethite, with biogenic calcite and halite occupying voids or precipitated on the surface of the red clay. The chemical index of alteration (CIA) has a value of 93, showing that red clay is a product of extreme chemical weathering of the lava flows. The alkaline volcanic rocks recovered from nearby show an age of ~ 44 Ma, indicating an Eocene age for the volcanism. We show that the red clays are a product of sub-aerial chemical weathering of these Eocene volcanic rocks, in a warm-wet climate, before the thermal subsidence of the RGR to its modern-day bathymetric depth.

Paleo-lake evolution influenced by tectonic processes and climate changes in the Hetao Basin during the late Quaternary

Exploration of paleo-lake evolution is crucial for the understanding of climatic and tectonic roles in earth surface. Previous studies mainly focused on the climatic effect on river-lake transitions and lake evolutions through lacustrine deposits, but with limited consideration of tectonic drivers, especially for the tectonic rift lakes in the Hetao area.Based on the analyses of lacustrine and fluvial piedmont terraces and a 400-m core from the northern Hetao Basin, along with the optically stimulated luminescence and detrital zircon U-Pb dating, we adopted an integrated “tectonics-climate-surface processes” approach to explore the climatic and tectonic effects on the lake evolution of the Hetao rift basin. Results show that lacustrine deposition on the piedmont terrace T1 (60–47 ka), underlying the T3 fluvial (80–60 ka), has an erosion contact with pluvial deposits at 55 ka, implying the paleo-lake formation at ∼ 80–60 ka and shrinkage at ∼ 55–47 ka. Lake formation was forced by basin depression under the tensile stress of tectonic movement, and was recharged by the Yellow River due to obstruction of the outlet at Tuoketuo caused by uplift.Lake shrinkage was due to the combined effect of basin lifting and warm-wet climate conditions that promoted outflow. A substantial decrease in the erosion base level and rapid water drainage induced by river cutting caused erosion of lacustrine deposits in the basin. The limited sedimentary space of the lake basin in early MIS 2 should be considered a factor in lake disappearance in addition to the dry climate. This study highlights that tectonic effects may be more important than climatic effects in the evolution of rift lakes near the young fold mountain belts.

Effect of depositional evolution on phosphorus enrichment in aquifer sediments of alluvial-lacustrine plain

Groundwater with high geogenic phosphorus (P) is increasingly concerned as a potential risk to surface water eutrophication. Although hydrogeochemical processes responsible for P mobilization in groundwater systems have been studied, the burial characteristics of P and the effect of depositional evolution on P enrichment in aquifer sediments remain unclear. In this study, aquifer sediments were collected from the Dongting Lake Plain (DTP) within the central Yangtze River Basin, a high P groundwater area, and the effect of depositional evolution on P enrichment was elucidated by comprehensively analyzing the lithology, grain size, geochronology, and geochemistry of the sediments, coupled with groundwater chemistry and sediment incubation experiments. The results showed that the contents of total organic carbon (TOC), iron (Fe), and P (the relative content of bioavailable phosphorus (BAP)) were higher in lacustrine sediments deposited under a warm-wet climate, but lower in fluvial sediments deposited under a cold-dry climate. During depositional evolution, the sedimentary facies mainly controlled the content of organic phosphorus (OP), while the paleo-climate controlled the content of both OP and Fe-bound inorganic P (FeP), which jointly affected total P content in aquifer sediments. Under the interaction of groundwater and sediment, the reductive dissolution of P-rich Fe (oxyhydr)oxides and the mineralization of OP in sediment continuously release P into groundwater. Notably, the rapid accumulation of alluvial sediments after the Last Glacial Maximum in the DTP and rapid evolution of Dongting Lake during the Holocene led to a large amount of organic matter (OM) and P buried in sediments, providing materials for P release in aquifers, which seriously threatens groundwater quality. This exploration can provide a new understanding of the enrichment of geogenic P in groundwater from the perspective of depositional evolution.

Outdoor egg production using local forages in the warm wet tropical climate

This review discusses the findings of existing research surrounding the nutritional impact of leaf meals as incorporated in chicken diets, the importance of forages in sustainable poultry production and the capacity of hens to digest high fibre diets. The potentials of conventional and/or outdoor production systems for developing countries, the effects of outdoor production systems on the welfare of laying hens, and methods used in measuring forage intakes and the feed items obtained by hens from the outdoor area are also discussed. This review highlights those factors ranging from utilization to behaviors of free - range hens and the recommendations for better range utilization by egg- laying birds (hens), particularly in the warm wet climate.

Integrating glacio-hydrological and power grid models to assess the climate-resiliency of high mountain hydropower in Nepal

Climate change significantly impacts hydrological systems resulting in hydropower generation uncertainties. In this study, a high-resolution glacio-hydrological model is coupled with an hourly-resolution power grid model to evaluate the climate change influences on hydropower generation across Nepal. Four climate future scenarios namely Cold-Dry, Warm-Dry, Cold-Wet, and Warm-Wet are developed to compare the changes in water availability and optimal power system with historical climate. The total flow increases for the wet scenarios (+11.4% under Cold-Wet for the Koshi basin), compared to the dry scenarios (−24.6% under Warm-Dry for the Karnali basin) for all the major river basins in Nepal. The results illustrate the distribution and magnitude of changes in total water availability and power generation are not proportional for dry and wet scenarios as a ∼20% reduction of water availability in the dry scenarios only results in a ∼2–3% decrease in electricity generation. The capacity requirements of hydro storage decrease by 7.2 GW for Cold-Wet and 6.8 GW for Warm-Wet scenarios compared to historical climate indicating higher capacity requirements in dry scenarios. Larger impacts observed at higher altitudes suggest more attentive adaptation strategies in developing climate-resilient hydropower systems. Results suggest that Nepal should not be entirely focused on exploiting its hydropower potential but rather diversifying the generation mix including solar PV and hydrogen technology. For the least-cost power system expansion, the Warm-Wet climate appears to be the most desirable and a cost savings of about 3.76 billion USD in hydropower development can be realized if better adaptation strategies are employed.

Long-term drying trends since the mid-Holocene in the Qaidam Basin

This study was conducted to improve our understanding of climate changes and landscape evolution in the transitional area between the westerly-dominated regions and monsoonal regions, with the aim of contributing to solving the increasing debate over the “westerlies model” or “monsoon model” in the northeastern Tibetan Plateau. This research mainly focuses on glycerol dialkyl glycerol tetraethers (GDGTs) in a well-dated sediment core that covers the last ∼ 14.1 ka from Hurleg Lake in the Qaidam Basin, combined with grain size and organic element characteristics, to explore the climate and landscape evolution under the influence of potential forcing. Based on the variations in core sedimentary facies and careful calibrations selection, this study reveals that Hurleg Lake experienced a warm–dry climate in the last deglaciation (14.1–11.2 cal ka BP), a cold–wet climate in the early Holocene (11.2–9.3 cal ka BP), a warm–wet climate in the mid-Holocene (9.3–3.5 cal ka BP), and a cool–dry climate in the late Holocene (after 3.5 cal ka BP). Our study suggests that the moisture evolution in the Hurleg Lake area was controlled by the Asian summer monsoon (ASM) and exhibits a typical “monsoon model”, and the modern climate is drier than that in the mid-Holocene. The weakening of ASM since the mid-Holocene has caused the ASM boundary to retreat southeastward to the modern one. Therefore, long-term declines in temperature and precipitation may lead to vegetation deterioration, glacier advancement, and aeolian activity exacerbation, which in turn influence regional ecological landscape.

日尺度下水热因子变化对青藏高原高寒草原生产力的影响特征

PDF HTML阅读 XML下载 导出引用 引用提醒 日尺度下水热因子变化对青藏高原高寒草原生产力的影响特征 DOI: 10.5846/stxb202112103509 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(41701606,U21A2021);中央高校基本科研业务费(2452020009);陕西省自然科学基础研究计划(2021JM-093) Effects of daily variation of hydro-thermal factors on alpine grassland productivity on the Qinghai-Tibet Plateau Author: Affiliation: Fund Project: National Natural Science Foundation of China (41701606、U21A2021)；the Fundamental Research Funds for the Central Universities (2452020009)、Natural Science Basic Research Program of Shaanxi Province(2021JM-093) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:温度和降水变化显著影响高寒生态系统植被生长和系统功能。草地生产力作为草地系统功能强弱的重要体现,对气候变化,特别是温度和降水变化十分敏感。探究高寒草原生产力如何响应气候变化,对预测未来气候变化情景下高寒草地系统功能变化意义重大。前期研究大都从年或季节尺度探究气候变化对草地生产力的影响特征,缺乏更精细时间尺度的关联分析。本研究基于 1997-2020 年青藏高原高寒草原长期植被观测数据及相应气候资料,应用简单线性回归及偏最小二乘回归法(Partial Least Squares regression, PLS)探究了研究区草地地上净初级生产力对日尺度温度和降水变化响应特征。结果表明:(1)近24 a来研究区年平均气温和降水量分别以0.03℃/a和4.36 mm/a的速率显著升高;(2)近24 a来研究区草地生产力显著升高(增幅为5.24 g m-2 a-1),且与年平均温度和降水量呈显著正相关关系;(3)日尺度分析表明,不同阶段温度和降水变化对草地生产力的影响不同,其中5-8月和9-10月的温度及5-7月和9-11月的降水是影响研究区草地生产力的气候因子关键作用期,尤以生长季温度(5-8月)和降水(5-7月)变化影响更高,这表明生长季气候变化是该高寒草地生产力变化的主要驱动因素。总之,本研究指出近24 a生长季温度和降水量显著增加对高寒草原生产力具有重要促进作用,这意味着青藏高原暖湿化对高寒草原生态系统功能(草地生产力)影响不仅依赖于温度和降水变化的幅度,同时亦与温度和降水变化的方向和是否同步密切相关。 Abstract:Changes in temperature and precipitation significantly affect plant growth and system function in the alpine ecosystem. As an important reflection of grassland system function, grassland productivity is very sensitive to climate change, especially to temperature and precipitation. Therefore, it is significant to explore how grassland productivity responds to climate change for predicting system function in the alpine steppe under the background of future climate change. Previous studies often investigated the effects of climate change on grassland productivity at annual or seasonal scales, but there was a lack of correlation analysis at finer time scales. Based on the long-term productivity records and corresponding climatic data from 1997 to 2020, we used simple linear regression and partial least squares regression to reveal the responses of grassland productivity to temperature and precipitation on a daily scale. The results showed that: (1) the annual mean temperature and precipitation in the study area increased significantly in the past 24 years, with a rate of 0.03 ℃/a and 4.36 mm/a, respectively. (2) Meanwhile, grassland productivity increased significantly, with a rate of 5.24 g m-2 a-1, and had significantly positive responses to annual mean temperature and precipitation variation. (3) The results of the daily analysis showed that the effects of temperature and precipitation during different periods on grassland productivity were different. In specific, the temperature from May to August and September to October and precipitation from May to July and September to November were key periods to explain the impacts of climate change on grassland productivity, especially temperature (May to August) and precipitation (May to July) variations during the growing season had the higher impacts on grassland productivity, suggesting climate change in the growing season was the main driving factor for variation in grassland productivity. Overall, the present study indicated that increasing temperature and precipitation during the growing season in the past 24 years significantly promoted grassland productivity of the alpine steppe. The effects of warm-wet climate on alpine grassland ecosystem function (e.g., grassland productivity) were closely dependent on the magnitude, direction, and synchronization of altered temperature and precipitation. 参考文献 相似文献 引证文献

Holocene spatiotemporal millet agricultural patterns in northern China: a dataset of archaeobotanical macroremains

Abstract. Millet agriculture, i.e., broomcorn millet (Panicum miliaceum) and foxtail millet (Setaria italica), initially originated in northern China and provided the basis for the emergence of the first state in the Central Plains. However, owing to the lack of a comprehensive archaeobotanical dataset, when, where, and how these two millet types evolved across different regions and periods remains unclear. Here, we presented a dataset of archaeobotanical macroremains (n=538) spanning the Neolithic and Bronze ages in northern China and suggested a significant spatiotemporal divergence of millet agriculture in the subhumid mid-lower Yellow River (MLY) and semiarid agro-pastoral ecotone (APE). The key timing of the diffusion and transition of millet agriculture occurred around 6000 cal. a BP, coinciding with the Holocene Optimum (8000–6000 cal. a BP) and Miaodigou Age (6200–5500 cal. a BP). It spread westward and northward from the MLY to APE and underwent a dramatic transition from low-yield broomcorn millet to high-yield foxtail millet. The combined influence of warm-wet climate, population pressure, and field management may have promoted the intensification, diffusion, and transition of millet agriculture around 6000 cal. a BP. Thereafter, the cropping patterns in the MLY were predominated by foxtail millet (∼ 80 %), while those in APE focused on both foxtail (∼ 60 %) and broomcorn millet under a persistent drying trend since the mid-Holocene. This study provided the first quantitative spatiotemporal cropping patterns during the Neolithic and Bronze ages in northern China, which can be used for evaluating prehistoric human subsistence, discussing past human–environment interaction, and providing a valuable perspective of agricultural sustainability for the future. The dataset is publicly available at https://doi.org/10.5281/zenodo.6669730 (He et al., 2022).

Reconstruction and application of the temperature-vegetation-precipitation drought index in mainland China based on remote sensing datasets and a spatial distance model

In recent years, remote sensing drought monitoring indices have been gradually developed and have been widely used for global or regional drought monitoring due to their strong drought-monitoring capabilities and easy implementation advantages. However, some defects of remote sensing drought indices stand to be improved due to certain errors in the inversion of surface characteristics by remote sensing datasets. The temperature-vegetation-precipitation drought index (TVPDI) was taken as the research object, and the leaf area index (LAI), the difference between the land surface temperature (LST) and monthly average temperature, and Global Precipitation Measurement (GPM) precipitation data were selected instead of the normalized difference vegetation index (NDVI), LST and tropical rainfall measuring mission (TRMM) data to improve TVPDI. The improved remote sensing drought index was named the improved temperature-vegetation-precipitation drought index (iTVPDI). The drought-monitoring accuracy of iTVPDI was verified by the gross primary productivity (GPP), soil moisture, and crop yield per unit. The drought-monitoring ability of iTVPDI was verified with traditional drought indices, including the standardized precipitation index (SPI), standardized precipitation evapotranspiration index (SPEI), Palmer drought severity index (PDSI), temperature-vegetation drought index (TVDI), drought severity index (DSI) and crop water stress index (CWSI). The drought-monitoring accuracy of iTVPDI was verified by selecting sample areas. iTVPDI was applied to monitor drought in mainland China over the 2001–2020 period and obtained four main results. First, the correlation analyses of iTVPDI and TVPDI with GPP, crop yield per unit area, and soil moisture showed that iTVPDI had a stronger monitoring ability in Northeast, North, and Southwest China; the R2 value obtained with soil moisture was 0.62 (p < 0.05), and this value was higher than that of TVPDI. Then, the correlation analyses of iTVPDI and TVPDI with SPI, SPEI, PDSI, CWSI, DSI and TVDI showed that the correlation coefficients of iTVPDI and TVPDI with these six indicators were basically consistent, which indicated that the drought-monitoring capability of iTVPDI was consistent with that of TVPDI. In local areas such as the Qinghai-Tibet Plateau in China, the monitoring ability of iTVPDI was stronger than that of TVPDI. Third, through the sample area analysis, iTVPDI was found to moderate the NDVI-characterized vegetation factors in TVPDI in low-vegetation-cover areas affected by soil disturbances and in high-vegetation-cover areas affected by oversaturation. Finally, the results obtained from the application of iTVPDI in mainland China showed that during the warm-dry to warm-wet climate transition between 2001 and 2021, in 2010 and 2018, and in other special drought years, iTVPDI had the best response.

Warm–Wet Climate Trend Enhances Net Primary Production of the Main Ecosystems in China during 2000–2021

A significant greening trend has been reported globally in recent decades. The greening indicates the improvement in net primary production (NPP) in vegetation. Adopting statistics-based regression models, we investigated the dynamics of NPP and its climatic drivers in main ecosystems (forest land, grass land, and unused land) over China during the period 2000–2021. The results confirmed an increasing NPP covering approximately 86% area in the main ecosystems. NPP exhibited an increase rate of 6.11 g C m−2 yr−1 in forest land, 4.77 g C m−2 yr−1 in grass land, and 1.25 g C m−2 yr−1 in unused land, respectively. Over the same period, warm–wet climate trend was observed covering approximately 90% of the main ecosystems. The warm–wet climate has had a positive effect rather than negative effect on NPP in the main ecosystems, judging by their significant positive correlation. Our results suggested that the increase in annual precipitation exerted much more important effect on the increasing NPP. The warm–wet climate trend contributes to the upward trend in NPP, even if variability in NPP might involve the influence of solar radiation, atmospheric aerosols, CO2 fertilization, nitrogen deposition, human intervention, etc.

Fast valley landscape response to climate change in the Lower Jinsha River, Southeastern Tibetan Plateau: Field investigations and numerical modeling

The Jinsha River, the upper reaches of the Yangtze River, winds and incises through the eastern margin of the Tibetan Plateau, where Asian monsoon climate prevails. Along the Jinsha River, extensive and thick Quaternary valley fillings and multiple river terraces have been developed. However, their specific relations to climate change and tectonics remain elusive. In this study, we conducted field investigation, chronological studies and numerical modeling in its lower reaches. Our study indicates that the extensive valley fillings in the Wudongde-Menggu segment were formed in cold-arid climate with Optically Stimulated Luminescence (OSL) ages of ~23–19 ka B.P., coinciding with the timing of the Last Glacial Maximum (LGM). We suggest that the post-LGM warming and humidifying, by restrained sediment supply while enhanced discharge, switched the valley from prevailing aggradation into incision. Multiple subsequent fill-cut terraces, postdating the LGM, were formed and nested in the valley fillings. OSL data indicate that sediments of three terraces (T1–T3) were formed at ~10 ka B.P., ~11.5–12.5 ka B.P. and ~13.5 ka B.P., respectively. Our study suggests that these terraces are sensitive records of millennial and sub-millennial cold-arid climate perturbations superimposed over the post-LGM deglaciation. Our modeling highlights a high sensitivity of valley aggradation and incision to cold-arid and warm-wet climate change, as well as a fast valley landscape response in the Jinsha River characterized by high sediment transport influx. We propose that valley landscape and terraces serve as a timely record for climate change in certain rivers with short response time threshold characterized by high sediment transport influx.

Will the arid and semi-arid regions of Northwest China become warmer and wetter based on CMIP6 models?

Abstract Whether there is a transition underway, from a warm-dry climate to a warm-wet climate in Northwest China remains a controversial and scientifically significant issue. Will this trend continue in the future? Another hot issue is whether the climate in Northwest China will continue to be warm and humid over the next few decades. In this paper, eight CMIP6 models were employed to investigate temperature and precipitation changes under five principal Shared Socioeconomic Pathway (SSP) scenarios (from 2015 to 2099) to project the future warming and humidification in Northwest China using the SPEI (standardized precipitation evapotranspiration index) method. The results revealed that (1) the simulated temperature and precipitation of eight CMIP6 models were consistent with that of observed data during 1961–2014, which showed an increase of approximately 28.2 mm, while simulated data revealed an increase of approximately 9.4 mm. The annual precipitation gradually decreased from Eastern Inner Mongolia and the Southern Northwest Mongolia region (&amp;gt;700 mm) to the Central Northwest Mongolia region (&amp;lt;100 mm) from 1961 to 2014; (2) the MME significantly overestimated the temperature and slightly underestimated the precipitation in Northwest Mongolia. The temperature difference between the simulated and observed data was approximately 0.4 °C. The observed data showed an increase of approximately 0.9 °C from 1961 to 2014, whereas the simulated data revealed an increase of approximately 0.7 °C; (3) in the SSP5-8.5 scenario, the percentage of precipitation anomalies at 1.5, 2, 3, and 4 °C were 166.64, 190.58, 226.44, and 274.56%, respectively; thus, alleviating the drought situation while facilitating the warm-dry to warm-wet climate transition; (4) the water balance between rising temperatures and increased evapotranspiration resulting from increased precipitation suggested that not all sites will be wet in the future. There was still a drying trend in some areas, where drought was more severe under the high emissions scenario than the low emissions scenario.

Reconstruction of Climate Changes Based δ18Ocarb on the Northeastern Tibetan Plateau: A 16.1-cal kyr BP Record From Hurleg Lake

Hydroclimate evolution history and changes in the Tibetan Plateau play significant roles in depicting paleoclimate and evaluating climatic conditions in the coming future. However, the interaction of the westerlies and the Asian monsoon complicates our understanding of the mechanism of climate variation over the Tibetan Plateau. In this study, we assessed the paleoclimate of Hurleg Lake, which was previously located in the convergence area of the East Asian monsoon and westerly wind. We first reconstructed the climatic conditions based on fined-grained authigenic carbonate δ18O (δ18Ocarb), plant-derived proxies of C/N, and n-alkane-derived δ13C31. In the Hurleg Lake, δ18Ocarb was controlled by δ18O changes of the lake water and evaporation. The climate evolution since ∼16.1 cal kyr BP can be classified into three stages. The Lateglacial (16.1–11.0 cal kyr BP) was characterized by a warm-wet climate in the beginning, followed by a cold-dry climate since 12.0 cal kyr BP. Typical warm and cold phases occurred during 14.8–12.0 cal kyr BP and 12.0–11.1 cal kyr BP, which may correspond to the Bølling/Allerød (B/A) and Younger Dryas periods, respectively. The early to mid-Holocene was generally characterized by a warm-wet climate; however, notable cold-dry intervals occurred at ∼8.3 cal kyr BP. The Late Holocene (after 4.8 cal kyr BP) displayed a significantly cold-wet climate. Finally, we examined the possible mechanisms responsible for the climate variability in the study area. The results showed that the long-term warm trend in the Lateglacial and colder trend after early Holocene was controlled by insolation. The Asian summer monsoon and the westerlies played a significant role in determining moisture sources during the Lateglacial. The East Asian monsoon contributed greatly to the moisture variation from the early to mid-Holocene, whereas the westerly winds dominated during the late Holocene. Combined, our findings highlight the complex changes in hydroclimate conditions since the last glacial in the Tibetan Plateau and provide crucial implications for comprehending the hydroclimate pattern in the transition zone of westerlies and Asian monsoon.

Pliocene climate in Indonesia: a review

Pliocene climate is known as global cooling. However, some study was showing a warm condition during Pliocene. During Pliocene in the tropics, the warm condition mechanisms are still in debate, whether it occurs due to the permanent El Niño or not. Indonesia is the prominent site to study climate from past to present. Several Pliocene climate studies have resulted from records surrounding Indonesia, but not many were found from inside the Indonesian sea. Pliocene records based on Pollen analysis content in Sajau Formation, Northeast Kalimantan, shows that the presence convinces the warm wet climate condition during the late Pliocene of arboreal pollen domination. However, the causing mechanism of warm wet Pliocene climate has remained a question.

Plant-microbe interactions regulate the aboveground community nitrogen accumulation rate in different environmental conditions on the Tibetan Plateau

Experimental studies have well illustrated that plant and microbe interactions play an important role in the absorption of nitrogen (N) under different environmental conditions. However, it remains to be seen what role plant–microbe interactions play in regulating plant N accumulation rates (NAR) over broad climatic and geographic scales. Here, a transect survey was conducted in alpine grassland on the Tibetan Plateau to measure aboveground net primary production and plant N concentration corresponding with phenology indexes, the NAR patterns were measured by “changepoint” analysis. Meanwhile, matrix correlation analysis and variation partitioning analysis were performed to explore the dynamic of NAR in response to environment factors. Finally, structural equation model was employed to express the path coefficients of environmental factors on NAR. A significantly (P＜0.05) lower NAR (8.9 mg/m2/day) in cold-dry climates than that in warm-wet climates (31.1 mg/m2/day) were detected. Our results further demonstrated a cooperative interaction between microbes and plants stimulated NAR in weakly resource-limited environments but a competitive effect of microbes on plants-constrained NAR in strongly resource-limited environments. The NAR was strongly governed by coupled water-heat availability and microbial biomass via their effects on plant diversity. Our findings highlighted that plant–microbe interactions offered an important framework to better understand the generalizable mechanisms of plant N accumulation in different environmental conditions. The knowledge of ecological N accumulation mechanisms obtained here not only emphasized the importance of incorporating plant phenology and dynamics of plant N into the ecological N cycle model but also promoted our understanding of resource utilization between plants and soil microbes under ongoing global climate change.

New characteristics about the climate humidification trendin Northwest China

<p indent="0mm">At the beginning of 21st century, a study suggested that Northwest China’s climate is becoming warmer and more humid. However, there were doubts about this conclusion because the humidification changes on a small scale only last for a short period, and also suspicions about the development, duration, and impact of the warming-wetting trend in this region. This paper sets out several factors, such as the area, intensity of humidification, and comprehensiveness of the wetness index, to characterize the wetting degree. Furthermore, by using measured climate data, CRU data, climate scenario predictions, and ecological and hydrological data, we systematically analyze temporal and spatial evolution of the warming-wetting trend in Northwest China. Studies have shown that Northwest China has experienced two warming periods during the last century, i.e., the 1940s, and the period from the 1960s to the present (the current warming period). The latter is more substantial. The precipitation in the west and east part of Northwest China has a seesaw change process in many periods. However, humidification has simultaneously occurred in both regions since the beginning of this century. The current precipitation in the west part of Northwest China has far exceeded any period over the past <sc>100 a.</sc> In contrast, the east part’s recent rainfall is still currently lower than that of the 1950s and 1960s. Since 1961, Northwest China’s west region has experienced consistent humidification, which has been more pronounced since 1987. Simultaneously, the east part was drying from 1961 to 1997, and has become humid since 1997. The temperature, precipitation, and aridity index changes in the west part show the same patterns. In most periods, the west part was either cold-dry or warm-wet. In comparison, such consistency of the temperature, precipitation, and aridity changes does not exist in the east region. Before this century, warm-wet climates rarely occurred in the east region, having become more frequent. This is probably due to the different dominant temperatures and precipitation processes in the west and east regions. From a spatial point of view, the temperature increases in the whole of Northwest China, and the precipitation increases in the west region and decreases in the east region. The area with increasing rainfall has become larger during the past three climatic periods, and currently covers the whole of Northwest China. The precipitation, aridity index, and comprehensive humidity index in Northwest China have a non-linear increasing trend. The expanding humidity trend has been significant since the beginning of this century. The current warming and humidification have not changed the basic climate pattern in Northwest China. However, if the current trend continues, they would change the climate pattern in the future. Such climate change may result from the simultaneous enhancement of the westerly circulation and the East Asian summer monsoon circulations in this century. The climate warming and humidification in Northwest China significantly impacted extreme weather events, water resources, ecological environment, and agriculture during this century. This research will provide a basis for decision-making on issues such as implementing the Western development strategy in the new era, the ecological protection and high-quality development of the Yellow River Basin, environmental construction planning, and water resources management policies in Northwest China.