Southwest Tibet Research Articles

Numerous Tibetan lower-crustal and upper-mantle earthquakes, detected by Sn/Lg ratios, suggest crustal delamination or drip tectonics

Whether intermediate-depth earthquakes beneath Tibet and the Himalaya are in the lower crust or upper mantle should provide insight into rheology, hence composition and temperature, of continental lower crust and upper mantle. Based on the waveguide theory that earthquakes respectively above or below the Moho will excite higher Lg or Sn energy, we develop an Sn/Lg amplitude-ratio analysis using a single permanent station to investigate earthquake depths with respect to the Moho. First, we use synthetics to show the ubiquitous sharp increase of the Sn/Lg ratio for hypocenters beneath the crust. A deep-crustal high-vs layer appropriate for eclogitized Indian lower crust causes a more gradual increase of Sn/Lg ratios for hypocenters within or below the eclogite layer. We measured Sn/Lg ratios of 595 Tibetan earthquakes from 1998 to 2022 with nominal (catalog) hypocentral depths >30 km and magnitudes >3.2 in five regions (west Tibet, southwest Tibet, south Tibet, southeast Tibet, and Qiangtang). As predicted by our normal-mode synthetics, earthquakes in west and south Tibet show Sn/Lg ratios that increase sharply as catalog depths approach the independently determined receiver-function Moho. Numerous earthquakes with high Sn/Lg ratios and nominal depths around the reported Moho are identified between the Karakoram fault and Altyn-Tagh fault (ATF) in west Tibet, which we attribute to an eclogitized Indian lower crust extending north to the ATF. Impingement of this underthrust Indian slab against the Tarim craton and consequent eclogite delamination or dripping may cause the observed below-Moho seismicity which occupies a region 100 km across and 200 km along orogenic strike and extends 30–50 km below published Moho depths. Similarly dense seismicity spans the Moho and occupies a similar volume below the Moho beneath the High Himalaya in south Tibet. The south Tibet Sn/Lg patterns may indicate an eclogitized Indian layer beginning to delaminate or drip south of the Yarlung-Zangpo suture. Our southeast Tibet and southwest Tibet Sn/Lg observations are less clear cut, perhaps due to less appropriate epicentral distances from the available observing stations. The Qiangtang region of Tibet likely has sparse mid-to-lower-crustal earthquakes, but no definitive below-Moho earthquakes. Our work expands the catalog of continental intraplate earthquakes below the Moho by >100 events with mb>3.2, as well as identifying tens of mb>3.2 lower-crustal events, so that Tibet fits neither an ideal crême-brulée nor an ideal jelly-sandwich crustal-strength paradigm. Two clusters of earthquakes that each span the Moho may be best explained by the delamination or dripping of a strong eclogitized lower crust into the upper mantle.

Evaluation of molasses on fermentation profiles of wheat straw ensiled with tall fescue in the southwest Tibet.

Two experiments were carried out to determine the optimal proportion of mixed silage made with wheat straw and tall fescue, and further to evaluate the effects of molasses on fermentation quality. In Experiment 1, wheat straw and tall fescue were mixed at proportions of 10:0 (Control), 8:2 (WT20), 6:4 (WT40) and 4:6 (WT60) on fresh weight (FW) basis. Inclusion of tall fescue significantly (p < 0.05) increased lactic acid, water-soluble carbohydrate contents and ratio of lactic to acetic acid, and significantly (p < 0.05) decreased pH and contents of dry matter, NH3 -N and volatile fatty acids. WT60 had the highest (p < 0.05) lactic acid content, and the lowest (p < 0.05) pH and butyric acid content. In Experiment 2, the mixture of wheat straw and tall fescue (4/6) were treated with 0%, 3%, 4%and 5% molasses on FW basis (defined as control, WTM3, WTM4 and WTM5respectively). Molasses addition significantly (p < 0.05) increased lactic acid and water-soluble carbohydrate contents, and significantly (p < 0.05) decreased pH and ammonia-nitrogen content as compared with control. Acetic acid content slightly (p > 0.05) decreased during ensiling, while trace amounts of propionic and butyric acids were observed. WTM5 had the lowest pH and the highest (p < 0.05) lactic acid, water-soluble carbohydrate contents and ratio of lactic to acetic acid at end of ensiling. In conclusion, the fermentation quality was maximally improved when the addition rate of molasses was 5% in 40% wheat straw ensiled with 60% tall fescue.

Hydrochemical Characteristics of Hot Springs in the Intersection of the Red River Fault Zone and the Xiaojiang Fault Zone, Southwest Tibet Plateau

The coupling relationship between regional seismic activity and the hydrogeochemical field provides an important theoretical basis for regional earthquake precursor exploration. The intersection area of the Red River fault zone (RRF) and the Xiaojiang fault zone (XJF) in southeast Yunnan province has become the focus area of earthquake monitoring and prediction because of its special tectonic position in China. There were 20 hot springs that were sampled and analyzed in the laboratory for major elements, including trace elements, silica, stable isotopes (δ18O and δD), and strontium isotopes, from the years 2015 to 2019. (1) The meteoric water is the main source of recharge for thermal springs in the study area, and recharged elevations ranged from 1.1 to 2 km; (2) the geothermometer method was used to estimate the region of thermal storage temperature, and its temperature ranged between 64.3 to 162.7 °C, whereas the circulation depth ranged from 1.1 to 7.2 km. Hydrochemical types were mainly controlled by aquifer lithology, in which sodium bicarbonate and sulphuric acid water gathered mainly in the RRF, while calcium bicarbonate water gathered mainly in the XJF. According to the silicon–enthalpy equation method, the temperature range and cold water mixing ratio were 97–268 °C and 61–97%, respectively; (3) the circulation depth of the RRF was deeper than that of the XJF, and it was mainly concentrated in the second segment and the fourth segment on the RRF. Most of the hot spring water was immature with a weak water–rock reaction; (4) the hot water intersections of RRF and XJF were obviously controlled by the fault and the cutting depth of granite; (5) the relationship discussed between geothermal anomaly and earthquake activity had a good correspondence with regional seismicity. The intensity of the reaction between underground hot water and the surrounding rock may lead to the change of pore pressure, and the weakening effect of groundwater on fracture may change accordingly, followed by the change in the adjustment of tectonic stress. Eventually, the difference in seismic activity was shown, implying that deep fluid has an important control action on the regional seismicity.

Numerical Simulation and Hazard Analysis of Debris Flows in Guxiang Gully, Tibet, China

Guxiang Gully, located in Bome county in southwest Tibet, China, is a right-bank tributary of the Purlung Tsangpo River. Hanging glaciers are widely distributed upstream of the gully, and a large number of moraines can cause debris flows triggered by run-offs generated by the rainstorm and melting water of glaciers deposited in this gully. The debris flow in the Guxiang Gully can frequently pose a serious threat to the Sichuan–Tibet highway. Due to the lack of field observation data, in this study, the flood discharge method combining the run-off generated by rainstorms and melting water of glaciers was employed to determine the magnitudes of debris flows under once-in-a-century, once-in-two-century, and once-in-three-century flood return periods. Furthermore, a numerical simulation is implemented to determine the maximum flow depth and velocity of the debris flow in each grid cell and the inundated debris flow area in Guxiang Gully with different return periods. Subsequently, each grid cell’s maximum flow depth and velocity are used to assess buried hazards and impact hazards, respectively. The integrated hazard could be calculated by combining the buried hazard and the impact hazard. The result shows that the hazard of the top of the fan and Purlung Tsangpo River affected by the debris flow is highest, and the debris flow is likely to block the Purlung Tsangpo River.

Spatio-temporal variation of climate and its potential productivity in the Southwest Tibet Plateau during 1901-2017

Spatio-temporal variation of climate and its potential productivity in the Southwest Tibet Plateau during 1901-2017

Extracting Terrain Texture Features for Landform Classification Using Wavelet Decomposition

Accurate landform classification is a crucial component of geomorphology. Although extensive classification efforts have been exerted based on the terrain factor, the scale analysis to describe the macro and micro landform features still needs standard measurement. To obtain the appropriate analysis scale of landform structure feature, and then carry out landform classification using the terrain texture, the texture feature is introduced for reflecting landform spatial differentiation and homogeneity. First, applying the ALOS World 3D-30m (AW3D30) DEM and selecting typical landforms of the southwest Tibet Plateau, the discrete wavelet transform (DWT), which acts as the texture feature analysis method, is executed to dissect the multiscale structural features of the terrain texture. Second, through the structural indices of reconstructed texture images, the optimum decomposition scale of DWT is confirmed. Under these circumstances, wavelet coefficients and wavelet energy entropy are extracted as texture features. Finally, the random forest (RF) method is utilized to classify the landform. Results indicate that the texture feature of DWT can achieve higher classification accuracy, which increases by approximately 11.8% compared with the gray co-occurrence matrix (GLCM).

Clumped isotope thermometry of modern and fossil snail shells from the Himalayan-Tibetan Plateau: Implications for paleoclimate and paleoelevation reconstructions

Abstract Carbonate clumped isotope thermometry has been applied to fossil mollusk shells from Tibet to reconstruct the paleoclimate and paleoelevation of the region. However, inferred paleoelevation and climatic conditions from this proxy are inconsistent with paleontological evidence. Here, we report new clumped isotope data from both modern and fossil (5–4 Ma) freshwater mollusk shells with the results of X-ray diffraction (XRD) analyses of fossil shells from the Himalayan-Tibetan Plateau. Although all of the fossil shells analyzed in this study appeared pristine based on visual inspection, XRD data reveal that more than half of these apparently “pristine” fossil shells contain trace amounts of calcite. Clumped isotope temperatures derived from the fossil shells display a large range of variation (&amp;gt;22 °C). Among the fossil shells analyzed, those containing traces of calcite have yielded temperatures that are on average ∼10 °C lower than those with no detectable calcite from the same strata. These observations suggest that clumped isotope alteration can occur in aragonite shells in low-temperature environments and even in shells with no visible signs of alteration that contain only traces of calcite. The temperatures derived from fossil shells with no detectable calcite are on average 4 °C higher than those derived from modern shells, indicating that southwest Tibet was warmer 4–5 Ma than today. After accounting for temperature change due to global cooling, the difference in clumped isotope temperatures between pristine fossil shells and modern shells suggests that the paleoelevation of the southwestern Tibetan Plateau in the Pliocene was similar to its present-day elevation.

Shallow seismic structure beneath the continental China revealed byP-wave polarization, Rayleigh wave ellipticity and receiver function

SUMMARYWe construct a high-resolution shallow 3-D seismic model in the top 10 km of the upper crust in the continental China, with constraints of P polarization, Rayleigh wave ellipticity and receiver function obtained from records of 3848 seismic stations. Our 3-D seismic model has a spatial resolution of 0.6–1.2° in the north–south seismic belt and the trans-north China orogen, and 1–2° in the rest of the continental China (except the Tarim basin and the southwest Tibet). The seismic model exhibits low velocity anomalies of deposits in major sedimentary basins and high velocity anomalies of crustal bedrocks in young orogenic belts and old tectonic blocks. The inferred sediment thickness maps display thick deposits in major sedimentary basins, some compacted sediments in the intermontane basins in young orogenic belts and little sediments in old tectonic blocks. We also discuss compaction effects of the sediments and implications of tectonic history and geological evolution of the major basins in the continental China based on the inferred seismic models. This study provides an effective mean of seismic imaging through joint inversion of various seismic constraints and establishes a framework of seismic data sharing for future studies in the seismological community in a first step of developing a China Seismological Reference Model.

Seismological constraints on the density, thickness and temperature of the lithospheric mantle in southwestern Tibet

We constrain the lithospheric mantle in southwest Tibet to be cold, thick, and dense by considering seismological observations, isostasy, and gravity anomalies. First, virtual deep seismic sounding (VDSS) indicates that the thickness of the crust increases from 50 ± 4 km beneath the Himalaya to 70 ± 4 km in the Lhasa terrane. This implies a ‘residual topography’ (difference between isostatic elevation of crust and true elevation) of −2.4 ± 1.5 km. Taking into account deviations from isostasy, the lithospheric mantle must be dense enough to depress the surface by 0.9 to 4.5 km. Our joint inversion of fundamental-mode Rayleigh wave dispersion and receiver functions suggests that the vertically-polarised shear-wave speed (Vsv) is 4.6 ± 0.1 kms−1 at depths of 120 to 300 km. From the shear-wave speed profile, we estimate the geotherm, which is on average 200°C below the 1350°C adiabat, and suggest that the base of the lithosphere is at a depth of 290 ± 30 km. To match the negative buoyancy, the lithospheric must be denser, on average, than ‘normal’ fertile adiabatic mantle, which rules out a depleted (harzburgite) composition. The density excess can be explained solely by thermal contraction, but we cannot rule out additional density increases due to composition. Our observations are not consistent with a depleted Indian slab underthrusting Tibet in this region, which would result in a lower average density and lower temperatures.

Petrological and Re-Os isotopic constraints on the origin and tectonic setting of the Cuobuzha peridotite, Yarlung Zangbo suture zone, southwest Tibet, China

The upper mantle section of the Cuobuzha ophiolite in the northern subbelt of the Yarlung Zangbo suture zone in southwest Tibet comprises mainly clinopyroxene (cpx)-rich and depleted harzburgites. Spinels in the cpx-harzburgites show lower Cr# values (12.6–15.1) than the spinels in the harzburgites (26.1–34.5), and the cpx-harzburgites display higher heavy rare earth element concentrations than the depleted harzburgites. The harzburgites have subchondritic Os isotopic compositions (0.11624–0.11699), whereas the cpx-harzburgites have suprachondritic 187 Os/ 188 Os ratios (0.12831–0.13125) with higher Re concentrations (0.380–0.575 ppb). Although these geochemical and isotopic signatures suggest that both peridotite types in the ophiolite represent mid-oceanic ridge–type upper mantle units, their melt evolution trends reflect different mantle processes. The cpx-harzburgites formed from low-degree partial melting of a primitive mantle source, and they were subsequently modified by melt-rock interactions in a mid-oceanic ridge environment. The depleted harzburgites, however, were produced by remelting of the cpx-harzburgites, which later interacted with mid-oceanic ridge basalt– or island-arc tholeiite–like melts, possibly in a trench–distal backarc spreading center. Our new isotopic and geochemical data from the Cuobuzha peridotites confirm that the Neo-Tethyan upper mantle had highly heterogeneous Os isotopic compositions as a result of multiple melt production and melt extraction events during its seafloor spreading evolution.

Prevalence and composition of CHD at different altitudes in Tibet: a cross-sectional study.

The prevalence of CHD has been well described worldwide except in Tibet. This study aimed to illustrate the prevalence and composition of CHD in Tibetan children according to altitude. Methods and results In the first part, we prospectively recruited 7088 unselected Tibetan children (4-17 years) from south-west Tibet. The total prevalence of CHD increased from 4.6/1000 below 4200 m to 13.4/1000 above 4700 m, with a female-to-male ratio of 1.3:3.1. The total prevalence and female prevalence of patent ductus arteriosus increased more than 10-fold. Females living above 4700 m had exceptionally high prevalence of patent ductus arteriosus (14.9/1000). The prevalence of atrial septal defect was comparable among different altitudes (3.3-3.8/1000). The prevalence of ventricular septal defect was 1.3/1000 below 4700 m, and no cases were found above this altitude. In the second part, we retrospectively reviewed the clinical data of 383 CHD children in Tibet and 73 children at lower altitudes. The percentage of isolated ventricular septal defect decreased from 54.8 to 3.1%, and the percentage of isolated patent ductus arteriosus increased from 8.2 to 68.4% with elevation. Children living below 4200 m (10.4-13.7%) had a larger proportion of complex CHD than those above this altitude (2.0-3.1%). Of the 20 Tibetan children with complex CHD, 14 (70.0%) lived below 4200 m. A wide variation in CHD prevalence and composition existed in Tibetan children among different altitudes.

Rodingite in the Purang Ophiolite and Its Geological Implication, Southwest Tibet

Rodingite in the Purang Ophiolite and Its Geological Implication, Southwest Tibet

Purang Utramafic Complex and Their Geological Origin, Southwest Tibet

Purang Utramafic Complex and Their Geological Origin, Southwest Tibet

Morphotectonic Study of the Brahmaputra Basin using Geoinformatics

Abstract The Brahmaputra river basin occupies an area of 580,000 km2 lying in Tibet (China), Bhutan, India and Bangladesh. It is bounded on the north by the Nyen-Chen-Tanghla mountains, on the east by the Salween river basin and Patkai range of hills, on the south by Nepal Himalayas and the Naga hills and on the west by the Ganga sub-basin. Brahmaputra river originates at an elevation of about 5150 m in southwest Tibet and flows for about 2900 km through Tibet (China), India and Bangladesh to its mouth in the Bay of Bengal. The Brahmaputra river basin is investigated to examine the influence of active structures by applying an integrated study on morphotectonics, SRTM, and seismic data. The indices for morphotectonic analysis, viz. basin elongation ratio (Re) indicated tectonically active, transverse topographic symmetry (T = 0.018-0.664) indicated asymmetric nature, asymmetric factor (AF=33) suggested tilt, valley floor width to valley height ratio (Vf = 0.0013-2.945) indicated active incision and mountain-front sinuosity (Smf = 1.11-1.68) values indicated active tectonics in the area. Two prominent knicks on the long profile at distances of about 1600 km and 1900 km closely correlate to the two prominent peaks on the SL index. The first one represents the Indus –Tsangpo suture zone after crossing which the Brahmaputra (Tsangpo) enters the Himalayas and the second one represents the zone where the Dihang (Brahmaputra) comes out of the Himalayas after crossing the Main Boundary Thrust. A great or major earthquake in the modern times, in this region may create havoc with huge loss of life and property due to high population density and rapidly developing infrastructure.

Optical Turbulence Characterization by WRF model above Ali, Tibet

Atmospheric optical turbulence modeling and forecast for astronomy is a relatively recent discipline, but has played important roles in site survey, optimization of large telescope observing tables, and in the applications of adaptive optics technique. The numerical approach, by using of meteorological parameters and parameterization of optical turbulence, can provide all the optical turbulence parameters related, such as C2n profile, coherent length, wavefront coherent time, seeing, isoplanatic angle, and so on. This is particularly interesting for searching new sites without the long and expensive site testing campaigns with instruments. Earlier site survey results by the site survey team of National Astronomical Observatories of China imply that the south-west Tibet, Ali, is one of the world best IR and sub-mm site. For searching the best site in Ali area, numerical approach by Weather and Research Forecasting (WRF) model had been used to evaluate the climatology of the optical turbulence. The WRF model is configured over a domain 200km×200km with 1km horizontal resolution and 65 vertical levels from ground to the model top(10millibars) in 2010. The initial and boundary conditions for the model are provided by the 1° × 1° Global Final Analysis data from NCEP. The distribution and seasonal variation of optical turbulence parameters over this area are presented.

The Mule Caravans of Western Yunnan

Mule caravans established a network across physical, political, and ethnic boundaries that integrated Southwest China, Southeast Asia, and Tibet. This article is a first exploration of this little-known mobile network. Based mainly on oral history, it focuses on the mule caravans based in Zhaozhou in western Yunnan from the late Qing to the 1940s, when the first motor roads were constructed. The investigation assembles horse and mule technologies and trade organization in detail in order to reconstruct the role and standing of transporters and their networks in local society, in the regional setting, in a volatile political environment, and in the face of challenging natural conditions.

Cenozoic anatexis and exhumation of Tethyan Sequence rocks in the Xiao Gurla Range, Southwest Tibet

In order to advance our understanding of the suturing process between continental landmasses, a geologic and geochronologic investigation was undertaken just south of the India–Asia suture in southwestern Tibet. The focus of this study, the Xiao Gurla Range, is located near the southeastern terminus of the active, right-lateral strike-slip Karakoram fault in southwestern Tibet. The range exposes metasandstone, phyllite, schist (locally of sillimanite facies), calc-gneiss and marble, paragneiss (± pyroxene), quartzite, metagranite, and variably deformed leucogranite. These metamorphic rocks are exposed in the footwall of a domal, top-to-the-west low-angle normal (detachment) fault, structurally beneath Neogene–Quaternary basin fill and serpentinized ultramafic rocks of the Kiogar-Jungbwa ophiolite. The detachment is interpreted to be the northeastern continuation of the Gurla Mandhata detachment fault system that bounds metamorphic rocks of the Gurla Mandhata Range ~ 60 km to the southwest. U–Pb geochronology on five detrital zircon samples of schist, phyllite, and quartzite yielded maximum depositional ages that range from 644–363 Ma and age probability distributions that are more similar to Tethyan sequence rocks than Lesser Himalayan sequence rocks. A felsic gneiss yielded a metamorphic zircon age of 35.3 ± 0.8 Ma with a significant population of early Paleozoic xenocrystic core ages. The gneiss is interpreted to be the metamorphosed equivalent of the Cambro-Ordovician gneiss that is exposed near the top of the Greater Himalayan sequence. Leucogranitic bodies intruding metasedimentary footwall rocks yielded two distinct U–Pb zircon ages of ~ 23 Ma and ~ 15 Ma. Locally, rocks exposed in the hanging wall of this fault and of the southward-dipping, northward-verging Great Counter thrust to the north consist of serpentinite-bearing mélange and conglomerate of inferred Paleogene age dominated by carbonate clasts. The mélange is intruded by a 44 Ma granite and the stratigraphically highest conglomerate unit yielded detrital zircon U–Pb ages similar to Tethyan sequence rocks. We attribute the middle Eocene magmatism south of the suture to break-off of the Neo-Tethyan oceanic slab. In addition, our observations are consistent with the late Eocene shortening and crustal thickening within the Tethyan Himalayan sequence, early-middle Miocene leucogranite emplacement being related to underthrusting and melting of the Greater and possibly Lesser Himalayan sequences, and late Miocene arc-parallel extension in the hinterland of the southward propagating Himalayan thrust belt.

Thermal analysis of a retrofitted direct-gain solar house without auxiliary heat source in southwest Tibet

Passive solar heating is an ideal choice in remote Tibet because of the laggard economy, poor transport condition, serious lack of conventional fossil energy and rich solar energy. The thermal performance of a model house is studied using a numerical method based on the real building construction and climate data while the effect of high altitude on heat transfer of building envelope is considered. Through analyzing heat loss of different parts, a retrofit scheme based on exterior envelope and south-facing glazing is introduced to decrease the heat loss and increase the direct-solar gain. The sensitive factors such as convective heat transfer coefficient, glazing type and WWR (area ratio of window to wall) are researched in detail. The results show that the direct-gain house can meet the minimum requirement of space heating without an auxiliary heat source in this district. Copyright The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org, Oxford University Press.

Structural complexity resulting from pervasive ductile deformation in the Karakoram Shear Zone, Ladakh, NW India

The NW‐SE trending, ∼800 km long, dextral Karakoram Shear Zone bounds southwest Tibet. We investigate an area immediately NW of the Pangong Lake where midcrustal rocks sections of the shear zone are exposed. Here, the dominant shear zone is characterized by dextral mylonitic rocks sheared at amphibolite facies and partly retrogressed to greenschist facies. These rocks define a kilometric, SE plunging inclined‐to‐recumbent fold in the footwall of a north directed, oblique dextral thrust that exhumed anatectic rocks of the Pangong Range. Argon cooling ages reveal that the Pangong Range cooled from ∼700°C to 300°C between ∼18–15 and ∼10 Ma, contemporaneously with overthrusting. Toward the SE, closer to the Pangong Lake, this kilometric fold is rotated from its NW–SE trend to an E–W trend, and the sense of shear changes to sinistral, with a broadly north directed thrusting component. The documented structures contradict predictions of normal movement in this area derived from considerations of rigid block behavior of the crust and support the interpretation that the system records dextral transpression. Thrusting and exhumation of the deeper and hot rocks exposed in the Pangong Range, folding of the thrust footwall, and the development of a sinistral E–W trending shear zone are all compatible with transpression caused by a northward push by a rigid indenter such as the Ladakh Batholith.

Annual temperature history in Southwest Tibet during the last 400 years recorded by tree rings

AbstractWe present a tree ring‐width record from the southern Tibetan Plateau (TP) which spans from 1612–1998 AD (387 years). The series was developed from Tibetan juniper (Juniperus tibetica Kom) growing at sites near the western distribution limit of the species. Two versions of the chronology, a traditionally standardized chronology (TSC) and a regional curve standardization (RCS)chronology were developed. Linear regression models between ring width and mean annual temperature account for 41% (TSC) and 43% (RCS) of the annual (July–June) temperature variance for the period 1957–1998. According to the TSC reconstruction, warm periods occurred during the 1620s, 1650–1675, 1720s, 1740–1790, 1810s, 1850s–1890s, 1935–1950, and 1957–1964 and since 1980. Cold conditions prevailed during the 1630s–1640s, 1680s–1710s, 1730s, 1820–1840s, 1900s–1920s and the 1970s. Within the last 400 years, the late‐20th century warming is distinctive but still within the range of natural climatic variability of this region. Comparison of our TSC reconstruction with proxy temperature records from other parts of the TP shows that the cold conditions during the 1730s, 1900s–1920s, and 1970s, and the warm periods during the 1770–1800, 1850s–1890s, 1935–1950, and 1957–1964 and since 1980 were synchronously occurring broad‐scale climate anomalies on the whole TP. Differences between the reconstructions are found during the 17th century and around 1760, which were probably caused by local differences in temperature change and different sensitivity in seasonality. The RCS series portrays low‐frequency variations such as warm periods during 1620–1640, 1650–1690, 1715–1790, and 1845–1875, and cold conditions during 1640–1650, 1690–1715, and 1875–1995. These long‐term trends need to be verified by developing other proxy records that target to capture low‐frequency signals in the future. Copyright © 2009 Royal Meteorological Society