Central Plateau Research Articles

Modifying physical supply and use tables (PSUTs) in the system of environmental-economic accounting (SEEA) for off-farm irrigation water management

A reliable water accounting framework is crucial for understanding the contribution of water resources in meeting agricultural demands and selecting appropriate operating systems for off-farm water systems, including hydraulic conveyance and distribution structures. This ensures fair, adequate, and dependable irrigation water distribution, especially under water scarcity operational scenarios. This study presents a novel and effective method for modifying PSU tables in the SEEA water accounting framework that is specifically designed for small-scale agricultural water management study areas. The proposed approach entails a comprehensive analysis of the surface water distribution within the water holders using a hydraulic simulation model and a spatial analysis of the groundwater extraction for meeting on-farm water demands. This approach was implemented on Iran's Central Plateau and revealed notable variations in water rights and distribution effectiveness among stakeholders so that, surface water contributed 27–40% less than the legal water rights, leading to aquifer overexploitation. The evaluation indicated that changing crop patterns and upgrading to pressurized irrigation systems led to 4–7.5% overexploitation of groundwater and 3.5–6% water conservation on farm scales. Besides, the spatial assessment verified a considerable overlap of 59% between the farms with modern irrigation systems and those with cultivated area expansion, resulting in sustained overexploitation pressure on the aquifer. The present study has two significant practical implications. Firstly, it specifies the contribution of surface- and groundwater resources in fulfilling the water demands of individual water-holders. Secondly, it provides reliable information to decision-makers about the incentives for modernization, rehabilitation, and renovation projects in an irrigation district.

The gravitational signature of the dynamics of oceanization in the Gulf of Aden

We perform a new gravity analysis in the Gulf of Aden with the aim of finding new constraints on the geodynamic evolution of the area. Our analysis is developed within the frame of the recent GO_CONS_GCF_2_TIM_R6 global gravity model solution (Brockmann et al., 2021) that reflects the Earth's static gravity field as observed by GOCE (Gravity field and steady-state Ocean Circulation Explorer). We analyzed the solution at different harmonic degrees, to account for different depths and dimensions of the sources. Terrain correction has been performed by means of a spherical tesseroidal methodology (Marotta and Barzaghi, 2017) and the obtained corrected Geodetic Residual Gravitation has been compared to the Model Residual Gravitation predicted by means of a 2D visco-plastic finite element thermo-mechanic model that simulates the dynamics of the Gulf of Aden, from rifting to oceanization. In order to perform the comparison between observed and predicted gravitational features, data have been extracted along five profiles crossing the Gulf of Aden at different sectors, from the south-east to the north west. Via the Model Residual Gravitation we reproduce its geodetic counterpart, obtaining a characteristic hat-shaped pattern, with a central plateau portraying the highest values, flanked by two regions where the residual gravitation diminishes, finally reaching the lowest values at the far continental domains. The maximum variations of the residual gravitation values, from ridge to continental domain, range between 280 and 420 mGal and the steepest decrease occurs over distances of 200 km for the thick crust model and of 100–150 km for the thin crust model. Finally, the comparison between Geodetic and Model Residual Gravitation allows to further constrain the dynamics of the Gulf of Aden oceanization occurring by a slow passive rift of a hot 150 km thick lithosphere characterized by an initial 40 km thick crust.

Structure of the crust-uppermost mantle beneath the Ethiopian volcanic province using ambient seismic noise and teleseismic P wave coda autocorrelation

The Ethiopian-Yemen plateaus have been affected by plume-related magmatism for at least 40 My, yet the nature and distribution of intrusive magmas and their relation to subsequent East Africa rifting remain poorly characterized. This paper presents a 3D shear (S) - wave velocity structure of the crust and uppermost mantle beneath the northern sectors of the East African rift and the dynamically-supported Ethiopian Plateau. We apply a Bayesian inversion of group and phase velocity dispersion curves for periods 5–40 s extracted from the ambient noise tomography of data from over 125 broadband seismic stations, and we identify seismic discontinuities using autocorrelation of P-wave coda. The resulting crustal structure affecting much of the Main Ethiopian Rift (MER) indicates a pronounced low S-wave velocity lower crust (∼3.6 km/s) that becomes thinner towards the northeast rising to almost the same depth level (∼20 km) as the base crust beneath the Afar triple junction zone. We also find high velocity features in the crust and uppermost mantle beneath the Afar rift axes, the current locus of strain and volcanism, that may indicate voluminous new basaltic crust. Our Moho-depth map indicates that the entire Afar Depression is underlain by crust thinner than 25 km, whereas the MER and central Ethiopian plateau are underlain by low S-wave velocity crust thicker than 35 km. These patterns suggest active underplating beneath the largely unfaulted plateau, in contrast to the efficient magmatic feeder system supplying a narrow zone of incipient seafloor spreading in the Afar depression. Within the uppermost mantle we report evidence of a localized asthenospheric upwelling beneath the western part of the plateau southeast of Lake Tana, overlying a cooled magma body within the upper crust. A broader low-velocity uppermost mantle underlies the crust beneath the Western Plateau. These observations attest to active mantle upwelling, heating, and melt intrusion at relatively different length scales beneath the plateau in agreement with the ongoing active strains reported away from the rift zones. At 45–60 km depth beneath the rift and its shoulders, we observe a fast lid (4.2–4.4 km/s). Beneath the plateau, upper mantle velocity highs that are at least 5 km below the Moho are observed. These areas have most likely experienced prolonged magma extraction and may mark highly depleted areas.

Changes in climate extremes in Zambia during green and dry Sahara periods and their potential impacts on hominid dispersal

Northern Africa experienced humid periods known as African humid periods or Green Sahara periods during the late Pleistocene and Holocene. The waxing and waning of the African Monsoon over the last several million years raises the question of how the climatic variability in the African Saharan region could have influenced the evolution and dispersion of hominins in Africa. Little is yet known about the changes in climate extremes in central southern Africa associated with these cycles and their potential impacts on human migration. In this study, we use a regional climate model to simulate archetypal Green and Desert Sahara periods under high and low boreal summer insolation and investigate the resulting changes in climate variability and extremes in South Tropical Africa, with a focus on Zambia. Our results indicate drier and warmer conditions under Green Sahara conditions relative to the Dry Sahara periods. In particular, an increase in the length of droughts and higher temperature extremes have been simulated over the Zambian region in the Green Sahara experiment. Our results suggest that during the Dry Sahara periods, Zambia may have offered better environmental conditions for hominin populations than the Central African Plateau (CAP). In contrast, the Green Sahara periods offered opposite conditions, potentially encouraging hominins to disperse through the large river valleys into the CAP and northward into the Sahel and Sahara.

An assessment of natural and anthropogenic influences on atmospheric fluoride deposition in central Tibetan Plateau during 1951–2008 A.D. using the Zangser Kangri ice core

Fluoride contamination poses great threat to ecosystems and human health, and has caused widespread concern. Large gaps in knowledge still exist regarding the distribution, sources of fluoride and the influence of atmospheric transport on its dispersal, particularly at high altitudes because of a lack of data due to geographic constraints. Tibetan ice cores are a natural archive for chemical depositions from the atmosphere, and can be used to reconstruct past variations of atmospheric fluoride in remote environment. In this study, we investigate the trends, sources and controlling factor of atmospheric fluoride during 1951–2008 AD using high-resolution chemical deposition records derived from the Zangser Kangri (ZK) ice core, central Tibetan Plateau (TP). Our data shows that the concentration peaks of F− coincide with those of typical crustal species (e.g., Ca2+, Mg2+), indicating that variation of F− in the ZK ice core is largely driven by dust activities, and dust emission from soil is the primarily natural source of F−. F− sources and transport pathways were further investigated by using the empirical orthogonal function (EOF) analysis, excess (Ex) concentration, in combination with airmass backward trajectory analysis. Ex F− in the ZK ice core record could be attributed to anthropogenic emissions, and its significant increase since 1990 was likely related to increased industrial and agricultural activities in the northwestern Indian peninsula. In addition, the strength of the South Asian monsoon is also a key factor in the transport of anthropogenic fluoride to the ZK glacier. This study provides valuable data for understanding the past atmospheric fluoride budget in the central TP.

Reframing the Three Delays framework: factors influencing referrals to facilities by matrones in rural Haiti

In Haiti, there has been limited research on the experiences of traditional birth attendants/matrones when they decide to refer and accompany pregnant women to the facility for giving birth. Understanding...

Hydrothermal activity and metallogenic environment revealed by seismic wave tomography in Yunnan Province, China

S-wave velocity structures are revealed using double-difference tomography, which shows large-scale low-velocity anomalies around the Xiaojiang and Lijiang−Xiaojinhe fault zones at 10−25 km depth. In contrast, an obvioushigh-speed anomaly exists in the center of Emeishan area, which is consistent with the EmeishanLarge Igneousprovince. Combined with the geological and geophysical data, the low-velocity anomaly might relate to the lower crustal flowof central Tibetan Plateau. The high-velocity anomaly associated with mantle plume in Emeishan would obstruct the crustal flow and limit it around the large deep faults. Meanwhile, the results also show that many mineral resources are mainly concentrated on the major faults and low-velocity zones, indicating that the lower crustal flow and the large deep faults provide conditions for mineral fluids and minerals deposit.

Contribution to the Modeling of the Organic Matter of Moroccan Forest Soils within the Context of Global Change: Case study of the Central Plateau

Contribution to the Modeling of the Organic Matter of Moroccan Forest Soils within the Context of Global Change: Case study of the Central Plateau

Sr-Nd isotopic compositions of aeolian sand in the northern Ulan Buh Desert and Yamalik Desert: Implications for provenance and transport processes

Tracing the provenance of aeolian sand in deserts is essential for comprehending the mechanisms underlying desert formation and sediment transportation processes. There are multiple sand belts that interconnect major deserts within the Alxa Plateau of northern China, as evidenced by satellite images and field research. However, the aeolian sand transport from the Badain Jaran Desert (BJD) to the Yamalik Desert (YD) and Ulan Buh Desert (UBD) through these expanding sand belts is still being underestimated. In this study, we analyzed trace metal contents and Sr-Nd isotopic compositions in the < 125 μm fraction of dune sands in the northern UBD and YD, along with bedrocks from the Langshan Mountains (LM). Based on bivariate plots of Zr vs. Hf, Zr/Hf vs. Hf, Cr/V vs. Y/Ni, and Th/Co vs. Th/Sc, the aeolian sands in the northern UBD and YD have similar sources but are different from those in the southern UBD. Comparison of Sr-Nd isotopes with potential source areas suggests that fine-grained aeolian sands in the YD and northern UBD are mainly sourced from the BJD and the southern Mongolian Gobi. Although the heterogeneity of bedrock samples impeded the precise interpretation of contributions from all potential sources, the εNd(0) signatures in the UBD suggest that up to 25% of the fine-grained sand is derived from the LM, which displays highly negative εNd(0) values. On a larger geographical scale, the northern UBD serves as a transfer intersection for long-distance transportation of sand and dust ultimately sourced from the Central Asian Orogen and northern Tibetan Plateau. This study also demonstrates the essential role of sand belts in facilitating aeolian transport within the Alxa Deserts.

Controls on long-term denudation rate of carbonate terrains in the Eastern Mediterranean

Quantifying denudation rates under different climatic and tectonic settings is fundamental to understanding landscape evolution. Carbonate rocks may respond differently to climatic and tectonic forcings than other rock types because of their tendency to dissolve congruently. Yet, there is little information on the long-term denudation rate of carbonates and their controlling factors in different settings. Here, we present the first long-term denudation rates for carbonates in the south of the Central Anatolian Plateau. We quantified the outcrop denudation rates using in-situ cosmogenic 36Cl measured in 13 rock samples to evaluate spatial variations and potential controls on the style and rate of denudation. 36Cl-derived denudation rates range from 1.92 ± 0.31 to 45.77 ± 3.91 mm/ka. On the plateau, denudation rates are strongly correlated with precipitation and are lower than the theoretical maximum dissolution rates predicted assuming zero evaporation, implying that climate exerts the major control on carbonate denudation. These results indicate that chemical weathering is the prevalent denudation style. The denudation pattern shows spatial variability with a decreasing trend from SW to NE consistent with climate zones. High-to-moderate denudation rates occur in the continental climate, while the lowest denudation rates occur in the arid plateau interior. In the Mediterranean coastal region, measured denudation rates are higher than the predicted maximum dissolution rates, reflecting the mechanical removal of overlying rock or soil. The low denudation rates in the plateau interior indicate a slowly evolving landscape with an arid climate. The physical properties of rocks showed the weakest control on carbonate denudation.In the Central Taurides, significant infiltration of surface runoff resulted in strong subsurface karstification at the expense of surface drainage. This process caused disequilibrium between uplift and denudation and resulted in the preservation of high-elevation topography. Therefore, in the actively uplifting plateau margin, the influence of tectonics on carbonate denudation has been interfered with the impact of precipitation and subsurface karstification.

Petrogenesis of Eocene Lamprophyre Dykes in Northern Qiangtang Terrane, Tibetan Plateau: Implications for the Tethyan Mantle Metasomatism and Tectonic Evolution

Post-collisional (ultra)potassic lamprophyre dykes are the key probes for understanding mantle metasomatism and reconstructing tectonic evolution. In this study, we present new petrological, geochronological, geochemical and zircon Lu-Hf isotopic data for lamprophyre dykes in the northern Qiangtang terrane (central Tibet), aiming to constrain their petrogenesis and geodynamic setting. The studied lamprophyres are minettes with phenocrysts of siderophyllite and phlogopite, which intrude into Triassic granite of 236.9 Ma. These lamprophyres yield zircon U-Pb ages of 39.7–40.9 Ma. They exhibit high contents of K2O (7.61–8.59 wt.%) and ultrapotassic features with high K2O/Na2O (11.43–14.38) ratios. They are characterized by increased values of Mg# (69.1 to 72.1) and high concentrations of compatible elements (e.g., Cr = 277–529 ppm, Ni = 232–322 ppm), which are diagnostic of mantle-derived primitive magma. The studied lamprophyres have a high abundance of rare earth elements (∑REE = 902–1061 ppm) with significantly fractionated REE patterns ((La/Yb)N = 66.3–100.6), and they are enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE), but depleted in high field strength elements (HFSE) (e.g., Nb, Ta and Ti) and heavy rare earth elements (HREE) with enriched zircon Hf isotopes (εHf(t) from −6.40 to 3.80). This indicates their derivation from an enriched mantle source which was metasomatized by subduction-related fluids and sediment-derived melts. A petrogenetic study suggests that the lamprophyres were generated by the partial melting of a phlogopite-bearing lherzolite within the garnet stability field. We propose that the Cenozoic ultrapotassic mafic rocks in the central Tibetan Plateau originated in the lithospheric mantle metasomatized by the subduction-related components, and are the magmatic response to the detachment of the subducted Tethyan slab.

A new purple-flowered Butia (Arecaceae) from the highlands of the Chapada dos Veadeiros (Brazil)

Background and aims – The highlands of the Chapada dos Veadeiros region comprise one of the largest savannah areas in central Brazil. The region includes large areas of the rare and little-known cerrado rupestre, which is home to numerous endemic species. During research on the Arecaceae flora of Chapada dos Veadeiros, a new species of Butia was discovered, and it is described here. Material and methods – The morphology and anatomy are described based on field collections. Following the default methodology, pinnae and flowers were analysed using LM (freehand cross- and longitudinal sections) and SEM. The new species is compared to its morphologically similar species from the Brazilian central plateau, and an identification key and distribution map were established. Key results – At first sight, the new species Butia soffiae resembles B. archeri, but with staminate and pistillate flowers, which are always purple, different in size, and congested in the rachillae. After close inspection, it is morphologically allied to B. buenopolensis, differing mainly by its glaucous peduncular bract – similar size to the inflorescence, herbaceous peduncle, numerous rachillae, purple floral colour, and inconspicuous staminodes. Differences in leaf anatomy, such as the presence of raphides, a cross-sectionally truncated midrib, and the number of accessory bundles on the midrib, also support the description of a new species. Two structures were recorded for the first time for the genus: squamiform trichomes at the base of the pistil and osmophores on the staminodes. The new species is assessed as Critically Endangered based on the restricted area of occurrence and anthropogenic threats. Conclusion – Butia soffiae is the first endemic Butia species described in Chapada dos Veadeiros. The type population is located near Chapada dos Veadeiros National Park, which is the subject of a bill that aims to reduce its area by 73%. The discovery of this new species reinforces the uniqueness of the local flora and the importance of maintaining the park.

Mapping thermokarst lakes in different physical states on the central Tibetan plateau

ABSTRACTMapping and monitoring the spatial–temporal evolution of thermokarst lakes on the Tibetan Plateau can significantly contribute to the estimation of climate change impacts on permafrost degradation. Remote sensing-based methods have been developed to monitor the interannual changes of thermokarst lakes. However, the seasonal changes, which are vital for understanding thermokarst lake dynamics, are commonly overlooked. This paper developed automatic methods which integrated the normalized difference water index (NDWI), modified normalized difference water index (MNDWI), principal component analysis (PCA), and independent component analysis (ICA) with Markov random field (MRF) for rapid mapping of thermokarst lakes in different physical states characterized by season changes. To validate the effectiveness, the proposed methods were applied to map thermokarst lakes on the central Tibetan Plateau, using four Sentinel-2 images representing different evolutionary states. Specifically, the area-to-point regression kriging (ATPRK) method was employed to downscale the 20-m short-wave infrared (SWIR) band to 10 m. Using manually digitized lakes as a reference, the proposed methods achieved an average Kappa coefficient of 0.79, significantly outperforming the water index thresholding method that merely attained 0.44. The results corroborate that the proposed methods can be robustly applied in mapping thermokarst lake dynamics with both interannual and seasonal trends on the Tibetan Plateau.

AI-based estimation of precipitation in the Tibetan Plateau using multi-frame FY-4A satellite data

ABSTRACT The weather system over the Tibetan Plateau can cause disasters around the plateau and its downstream areas. Since there are few surface meteorological observation stations over the Tibetan Plateau, the precipitation here cannot be comprehensively detected. Therefore, satellite precipitation estimation products with high timeliness, accuracy, and full coverage are relied upon. This paper presents an AI-based precipitation estimation method using multi-frame FY-4A meteorological satellite data (FY-4A PRE-M). Firstly, multiple-derived features are constructed according to the brightness temperature of the satellite different channels, and the regional precipitation estimation model is then trained using the light gradient boosting machine (LGBM) algorithm. Based on the research results from precipitation retrieval using the infrared channel radiation features, this model analyzes the possible contribution of the radiation difference between channels at the same time and the radiation change in the same channel at different periods (15, 30, 45 and 60 min) to the precipitation estimation. The algorithm continuously updates the model with the history of available precipitation data. From 1 September 2021 to 31 August 2022, the precipitation estimations using the multi-frame FY-4A satellite data were evaluated through the ground rainfall gauge data based on the spatial – temporal matching. The results show that the multi-frame FY-4A satellite data have advantages in precipitation estimation. The heavy rainfall caused by a Tibetan Plateau shear line is evaluated using this algorithm. The results show that the precipitation estimations of FY-4A PRE-M and IMERG-L are close to the values of rain gauges. The FY-4A PRE-M can well describe the diurnal variations and the distribution of 24 h cumulative precipitation over the Tibetan Plateau, and the heavy rainfall belts in the central and northern Tibetan Plateau are also well monitored.

Spatiotemporal scales of precipitation in the Central Tibetan Plateau identified by in-situ soil moisture observations

The spatiotemporal scale of precipitation is crucial for understanding the local hydrometeorological processes. It also plays a significant role in determining the layout of rain gauges. Convectional rainfalls are typical in the Tibetan Plateau (TP), but the spatiotemporal scales of precipitation events in the TP, particularly at scales less than 10 km, remain unclear, which is mainly due to limited in-situ precipitation observations and the relative coarse spatial resolution of satellite precipitation products. Building upon the strong response of soil moisture changes to precipitation, this study attempts to reveal the spatiotemporal scales of precipitation in the central TP during summertime (June–September) by investigating the inter-station correlation of accumulated positive soil moisture increments obtained from in-situ soil moisture measurements in a mesoscale region of the central TP. The soil moisture-implied spatiotemporal scales are further verified against precipitation from the Integrated Multi-satellitE Retrievals for GPM (IMERG) at spatial scales larger than 10 km. Results show that: 1) the variations of surface soil moisture increase and precipitation are fairly consistent, making positive increments in surface soil moisture an effective surrogate for reflecting the spatiotemporal scales of precipitation in central TP; 2) the spatial extents of precipitation as indicated by the precipitation-induced positive soil moisture increments are positively correlated with the temporal scales; 3) precipitation events with relatively short durations (0–6 h) and spatial extents of less than 16 km (and in particular, 0–3 h for scales less than 10 km) dominate the central TP. This study provides a novel approach for characterizing precipitation scales in regions with scarce in-situ precipitation observations, and is expected to inspire new way of assessing large scale soil moisture and precipitation products.

Species diversity and vegetation structure of woody plants in regenerating Juniperus forest replacing Eucalyptus in the conservation area of Gullele Botanic Garden, Addis Ababa, Ethiopia

The Gullele Botanic Garden (GBG) adjoins the north-western limit of the city of Addis Ababa, capital of Ethiopia. The floristic composition, species diversity and vegetative structure of the woody plant species in the conservation area of the garden are presented from 81 plots (20 m x 20 m). A total of 104 woody plant species (90% indigenous, the rest planted or naturalised) of 83 genera and 47 families were recorded. The dominant families were Fabaceae and Asteraceae. The number of individuals of the most dominant species, Juniperus procera, decreases with increasing DBH and height class, which indicates a good and healthy reproduction potential of the species in the conservation area. No statistically meaningful plant communities could be identified in the conservation area. Many of the species present in the dry forests of the central Ethiopian plateau occur in GBG. The species richness appears to be relatively high in comparison with what other researchers have found in natural forests on the highland plateau; 87 native woody species (of which 11 are planted) in GBG, 57-97 (cumulatively 127) in Wof-Washa, 32-85 (cumulatively 113) in Menagesha and 41-77 (cumulatively 81) in Chilimo, 34-67 (cumulatively 69) in Entoto, though the definitions for woody species have varied between studies. Clustering on the floristic data gives four partly overlapping clusters with the lowest p-values for indicator species, but the distribution of the plots on clusters changes notably if information on Eucalyptus is in- or excluded. Ordination graphs with partly overlapping groups of species are presented. The findings in this paper can serve as a baseline to follow the regeneration of the conservation area towards natural forest. This is needed for future management and sustainable utilization of the forest species at local and national levels.

Comparative Study on Carbon Footprint Assessment of Rice-Wheat Production System

The carbon footprint is a robust tool to guide sustainable food production system. It is widely accepted as an indicator of GHGs emissions and their impact on global warming. An assessment was undertaken to measure the carbon footprint (CF) of rice-wheat production for two different locations i.e., Damoh (L1) and Ludhiana (L2), comes under central plateau and hill region, and Trans-Gangetic plain region of India, respectively. Further, variability in CF among these two climatically diversified regions having different soil type and management practices was analysed and compared. Results showed that, CF per unit area of rice and wheat production was obtained as 0.497 t Ce/ha and 0.481 t Ce/ha, respectively. Key contributors to CF were nitrogen fertilizer and energy use (diesel for tillage, sowing, harvesting and transport, and electricity for irrigation) for both crops in both regions. Nitrogen fertilizer comprised 27% and 31% of CF in rice, and 30% and 42% in wheat, for L1 and L2, respectively. Diesel and electric energy contributed 36% and 18% (rice, L1), 26% and 27% (rice, L2), 32% and 30% (wheat, L1), and 30% and 18% (wheat, L2). As the contributing factors to the CF vary between regions, mitigation strategies that account for regional diversity are likely to yield greater effectiveness than approaches solely focused on the country level.

Paleoenvironmental changes on the central Tibetan Plateau over the last two millennia inferred from sedimentological proxies and brGDGTs in Bamu Co

Understanding multi-centennial climate variations and their impact on lake catchment productivity over the last 2000 years (the Common Era), is crucial for assessing the role of natural climatic factors in driving productivity changes, and for predicting productivity changes under recent global warming scenarios. However, the climate patterns on the Tibetan Plateau (TP), including temperature and hydrological variations, during the Common Era, and their possible links with productivity, are poorly understood. We present a quantitative reconstruction of mean annual air temperature (MAAT), together with grain size and other sedimentary records, from a non-glacial lake sediment archive on the central TP, with the objective of tracking changes in climate and lake catchment productivity over the past two millennia. Our results reveal an overall cooling trend in temperature reconstructed from branched glycerol dialkyl glycerol tetraethers (brGDGTs), with multi-centennial-scale fluctuations superimposed. These fluctuations include relatively warm periods during 200 BCE–400 CE and the Medieval Climate Anomaly (1050–1400 CE), and cold periods centered on ∼500–1000 CE and the Little Ice Age (∼1500–1900 CE). A rapid warming trend since 1900 CE corresponds to the Current Warm Period. The variations in sedimentary grain size reflect lake level changes associated with changes in the summer monsoon. Paleoproductivity inferred from total organic carbon (TOC) shows a similar pattern to the paleoclimate records, suggesting that millennial-scale productivity was influenced by both temperature and the catchment hydrology. In recent decades, human activities exerted a more substantial influence on lake productivity. Additionally, we suggest that the use of brGDGTs for temperature reconstruction necessitates the investigation of the temperature relationship of various fractions of brGDGTs, specifically tetramethyl-brGDGTs; and that careful selection of the temperature calibration equation is needed to minimize inaccuracies in paleotemperature reconstruction.

Pre-earthquake MBT anomalies in the Central and Eastern Qinghai-Tibet Plateau and their association to earthquakes

Thermal anomalies prior to large and hazardous earthquakes have been extensively detected by thermal infrared and microwave remote sensing techniques. However, few of the current research focuses on long-term tracking of the thermal anomalies for decades and their earthquake prediction potential in a seismically active area. Targeting at exploiting the association of thermal anomalies to earthquakes in terms of time, spatial patterns and magnitudes, comprehensive statistical analysis on the pre-earthquake microwave brightness temperature (MBT) anomalies of 103 destructive earthquakes with Ms. ≥ 5.0 in the Central and Eastern Qinghai-Tibet Plateau (90° E – 102° E, 28° N – 38° N) is conducted. To detect robust pre-earthquake thermal anomalies buried by the complex background and frequently variant meteorological noise, we propose a wavelet-based two-step difference (WTSD) approach which incorporates hierarchical clustering and wavelet decomposition, adopting it on the 17 years' microwave data collected by AMSR-E and AMSR-2 sensors. Interestingly, an NE trending MBT increase stripe has been repeatedly occurring prior to 60 of the 103 earthquakes (accounting for 58.25%). Then, we conduct comprehensive statistics on the occurring time, spatial patterns and intensities of the MBT anomalies, and find them closely associated to seismic events with Ms. ≥ 5.0 occurred in the Bayan Har and Qiangtang blocks. And, the MBT anomaly stripe is spatially consistent with the NE trending extensional faults and geothermal fields in this study area. Furthermore, the possible source mechanism of the MBT anomalies is explored with rock loading microwave observation experiments, and possible physical models suggested by predecessors are also discussed. On this basis, we discuss the relationship between the pre-earthquake MBT anomalies and extensional faults, and speculate the MBT anomalies are probably caused by intensified extrusion of the Indian plate to the Eurasian plate and the increased crustal stress, which indicates their significant potential as earthquake precursors in the Central and Eastern Qinghai-Tibet Plateau.

Soil temperature estimation at different depths over the central Tibetan Plateau integrating multiple Digital Earth observations and geo-computing

ABSTRACTSoil temperature (ST) plays a critical role in ecosystems. Monitoring high-resolution ST profiles remains challenging due to the inherent heterogeneity of ST in space, time, and depth. To address this challenge, in this study, we integrate remote sensing techniques and deep learning methods to retrieve spatiotemporal continuous ST from 2011 to 2020 at four depths (5, 10, 20, and 40 cm) over the central Tibetan Plateau (TP). Landsat and MODIS observations were fused to obtain land surface properties at different resolutions. The fused variables were integrated with in-situ ST and soil moisture (SM) measurements to estimate spatiotemporally continuous (0.0005°, 0.0025°, and 0.0125°) ST profile through deep learning-based training models. The deep belief network (DBN) was applied to estimate ST: (a) from layer to layer (LW-DBN), and (b) from land surface properties directly (Direct-DBN). The ten-fold cross-validation indicates that both approaches achieve promising results (R2 > 0.836, MAE < 2.152 °C), and the Direct-DBN outperformed the LW-DBN at all spatial scales and depths. ST retrieval at deeper depths and coarser resolutions tend to have better monitoring accuracy. Further analysis indicates an increment of ST at all four depths over the study period, which provides valuable insights into global warming.