scholarly journals InSAR time series analysis of seasonal surface displacement dynamics on the Tibetan Plateau

2020 ◽  
Vol 14 (5) ◽  
pp. 1633-1650 ◽  
Author(s):  
Eike Reinosch ◽  
Johannes Buckel ◽  
Jie Dong ◽  
Markus Gerke ◽  
Jussi Baade ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Surface Displacement ◽  
Slope Instability ◽  
The Tibetan Plateau ◽  
Permafrost Degradation ◽  
Linear Pattern ◽  
Spatial Coverage ◽  
Rock Glaciers ◽  
Gravity Driven ◽  
Displacement Patterns

Abstract. Climate change and the associated rise in air temperature have affected the Tibetan Plateau to a significantly stronger degree than the global average over the past decades. This has caused deglaciation, increased precipitation and permafrost degradation. The latter in particular is associated with increased slope instability and an increase in mass-wasting processes, which pose a danger to infrastructure in the vicinity. Interferometric synthetic aperture radar (InSAR) analysis is well suited to study the displacement patterns driven by permafrost processes, as they are on the order of millimeters to decimeters. The Nyainqêntanglha range on the Tibetan Plateau lacks high vegetation and features relatively thin snow cover in winter, allowing for continuous monitoring of those displacements throughout the year. The short revisit time of the Sentinel-1 constellation further reduces the risk of temporal decorrelation, making it possible to produce surface displacement models with good spatial coverage. We created three different surface displacement models to study heave and subsidence in the valleys, seasonally accelerated sliding and linear creep on the slopes. Flat regions at Nam Co are mostly stable on a multiannual scale but some experience subsidence. We observe a clear cycle of heave and subsidence in the valleys, where freezing of the active layer followed by subsequent thawing cause a vertical oscillation of the ground of up to a few centimeters, especially near streams and other water bodies. Most slopes of the area are unstable, with velocities of 8 to 17 mm yr−1. During the summer months surface displacement velocities more than double on most unstable slopes due to freeze–thaw processes driven by higher temperatures and increased precipitation. Specific landforms, most of which have been identified as rock glaciers, protalus ramparts or frozen moraines, reach velocities of up to 18 cm yr−1. Their movement shows little seasonal variation but a linear pattern indicating that their displacement is predominantly gravity-driven.

scholarly journals InSAR time series analysis of seasonal surface displacement dynamics on the Tibetan Plateau

2019 ◽  
Author(s):  
Eike Reinosch ◽  
Johannes Buckel ◽  
Jie Dong ◽  
Markus Gerke ◽  
Jussi Baade ◽  
...  
Keyword(s):  
Time Series ◽  
Tibetan Plateau ◽  
Time Series Analysis ◽  
Surface Displacement ◽  
The Tibetan Plateau ◽  
Permafrost Degradation ◽  
Nam Co ◽  
Freeze Thaw ◽  
Series Analysis ◽  
Spatial Coverage

Abstract. Climate change and the associated rise in air temperature have affected the Tibetan Plateau to a significantly stronger degree than the global average over the past decades. This has caused deglaciation, permafrost degradation and increased precipitation, heavily changing the water balance of this region. Surface displacement processes are likely to change as the ground continues to warm up and as such it is vital to understand both seasonal and interannual processes dynamics. The Nam Co area is well suited to studying these processes via Interferometric Synthetic Aperture Radar (InSAR) time series analysis, due to its lack of higher vegetation and relatively thin snow cover. The short revisit time of the Sentinel-1 system further reduces the risk of temporal decorrelation, making it possible to produce surface displacement models with good spatial coverage. We created three different surface displacement models to study freeze-thaw processes, seasonal sliding and linear creep. Most slopes of the area are unstable, with velocities of 8 to 17 mm yr−1, and some landforms reach velocities of up to 18 cm yr−1. The monsoonal climate accelerates those movements during the summer months through high temperatures and heavy rainfall. The fastest moving landforms, some of which have been identified as rock glaciers, do not follow this seasonal pattern of accelerated velocity in summer, instead they follow a linear sliding pattern. It is unclear if this linearity is connected to the ice content in those landforms. Flat regions at Nam Co are mostly stable on a multiannual scale but some experience subsidence, which could be caused by permafrost degradation. We observe a very clear seasonal freeze-thaw cycle in the valleys, where thawing and subsequent freezing of the active layer cause a vertical oscillation of the ground of up to a few centimeters, especially near streams and other water bodies.

scholarly journals Moisture and Temperature Covariability over the Southeastern Tibetan Plateau during the Past Nine Centuries

2020 ◽  
Vol 33 (15) ◽  
pp. 6583-6598
Author(s):  
Jianglin Wang ◽  
Bao Yang ◽  
Fredrik Charpentier Ljungqvist
Keyword(s):  
Tibetan Plateau ◽  
Climate Model ◽  
Severity Index ◽  
Early Summer ◽  
Convective Precipitation ◽  
Drought Severity ◽  
The Tibetan Plateau ◽  
Low Frequencies ◽  
The Past ◽  
Spatial Coverage

AbstractAccurate projections of moisture variability across the Tibetan Plateau (TP) are crucial for managing regional water resources, ecosystems, and agriculture in densely populated downstream regions. Our understanding of how moisture conditions respond to increasing temperatures over the TP is still limited, due to the short length of instrumental data and the limited spatial coverage of high-resolution paleoclimate proxy records in this region. This study presents a new, early-summer (May–June) self-calibrating Palmer drought severity index (scPDSI) reconstruction for the southeastern TP (SETP) covering 1135–2010 CE using 14 tree-ring records based on 1669 individual width sample series. The new reconstruction reveals that the SETP experienced the longest period of pluvial conditions in 1154–75 CE, and the longest droughts during the periods 1262–80 and 1958–76 CE. The scPDSI reconstruction shows stable and significant in-phase relationships with temperature at both high and low frequencies throughout the past 900 years. This supports the hypothesis that climatic warming may increase moisture by enhancing moisture recycling and convective precipitation over the SETP; it is also consistent with climate model projections of wetter conditions by the late twenty-first century in response to global warming.

Inventory of active rock glaciers in the western Nyainqêntanglha Range, Tibetan Plateau

2021 ◽  
Author(s):  
Eike Reinosch ◽  
Markus Gerke ◽  
Björn Riedel ◽  
Antje Schwalb ◽  
Qinghua Ye ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
High Reliability ◽  
Surface Velocity ◽  
Windward Side ◽  
Mountain Range ◽  
The Tibetan Plateau ◽  
Automated Classification ◽  
Rock Glacier ◽  
North West ◽  
Rock Glaciers

<p>The western Nyainqêntanglha Range on the Tibetan Plateau (TP) reaches an elevation of 7162 m and is characterized by an extensive periglacial environment. Here, we present the first rock glacier inventory of the central TP containing 1433 rock glaciers over an area of 4622 km². The rock glaciers are identified based on their surface velocity. The surface velocity is derived from Sentinel-1 satellite data of 2016 to 2019 via InSAR time series analysis. 16.4 % of the inventoried rock glaciers are classified as active with a surface velocity above 10 cmyr<sup>-1</sup> and 80.0 % are classified as transitional with 1 to 10 cmyr<sup>-1</sup>. The western Nyainqêntanglha Range forms a climate divide between the dry continental climate brought by the Westerlies from the north-west and the Indian Summer Monsoon to the south. 89.7 % of all active rock glaciers and 74 % of the free ice glacial area are located on the southern side. The higher moisture availability on the southern (windward) side of the mountain range is likely the cause of a higher rock glacier occurrence and the greater activity.</p><p>Manually identifying and outlining rock glaciers is time consuming and subjective. To ensure a high reliability and comparability of our inventory, we therefore combined a manual approach with an automated classification. Three analysts worked in tandem to generate the manual outlines according to the guidelines of the IPA action group on ‘Rock glacier inventories and kinematics’. A subset of these outlines acted as training areas for a pixel-based maximum likelihood classification. Both the manual and the automated classification were performed based on DEM parameters (elevation, slope etc.), optical datasets (Sentinel-2 and NDVI) and surface velocity (generated with InSAR). 87.8 % of all manually outlined rock glaciers were identified successfully at a true positive rate of 69.5 %. 18 additional rock glaciers were added to the inventory based on the automated classification. This combined approach is therefore beneficial to generate a complete inventory. The automated classification can, however, not replace the expertise of an analyst as it greatly overestimates the actual rock glacier area.</p>

Review on global change status and its impacts on the Tibetan Plateau environment

2019 ◽  
Vol 12 (6) ◽  
pp. 917-930 ◽  
Author(s):  
Aamir Latif ◽  
Sana Ilyas ◽  
Yangjian Zhang ◽  
Yuqin Xin ◽  
Lin Zhou ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Global Change ◽  
Warming Trend ◽  
The Tibetan Plateau ◽  
Permafrost Degradation ◽  
Lake Area ◽  
Environmental Consequences ◽  
Belt And Road ◽  
Significant Temperature ◽  
Research Gap

Abstract The Tibetan Plateau (TP) holds fundamental ecological and environmental significances to China and Asia. The TP also lies in the core zone of the belt and road initiative. To protect the TP environment, a comprehensive screening on current ecological research status is entailed. The teased out research gap can also be utilized as guidelines for the recently launched major research programs, i.e. the second TP scientific expedition and silk and belt road research plan. The findings showed that the TP has experienced significant temperature increase at a rate of 0.2°C per decade since 1960s. The most robust warming trend was found in the northern plateau. Precipitation also exhibited an increasing trend but with high spatial heterogeneity. Changing climates have caused a series of environmental consequences, including lake area changes, glacier shrinkage, permafrost degradation and exacerbated desertification. The rising temperature is the main reason behind the glaciers shrinkage, snow melting, permafrost degradation and lake area changes on the TP and neighboring regions. The projected loss of glacial area on the plateau is estimated to be around 43% by 2070 and 75% by the end of the century. Vegetation was responsive to the changed environments, varied climates and intensified human activities by changing phenology and productivity. Future global change study should be more oriented toward integrating various research methods and tools, and synthesizing diverse subjects of water, vegetation, atmosphere and soil.

scholarly journals Growth of a high-elevation large inland lake, associated with climate change and permafrost degradation in Tibet

2009 ◽  
Vol 6 (4) ◽  
pp. 5445-5469 ◽  
Author(s):  
J. Liu ◽  
S. Kang ◽  
T. Gong ◽  
A. Lu
Keyword(s):  
Tibetan Plateau ◽  
High Elevation ◽  
Annual Runoff ◽  
Annual Precipitation ◽  
The Tibetan Plateau ◽  
Permafrost Degradation ◽  
Lake Area ◽  
Pan Evaporation ◽  
Inland Lake ◽  
Precipitation Increase

Abstract. This study analyzed satellite images and long term climate variables from a high-elevation meteorological station (4730 m) and streamflow records to examine hydrological response of Nam Co Lake (4718 m), the largest lake on the Tibetan Plateau, over the last 50 years. The results show the lake area extended by 51.8 km2 (2.7% of the total area) when compared with the area in 1976. This change is associated with an annual precipitation increase of 65 mm (18.6%), annual and winter mean temperature increases of 0.9°C and 2.1°C respectively, an annual runoff increase of 20% and an annual pan evaporation decrease of about 2%, during the past 20 years. The year of the change point in annual precipitation, air temperature, annual pan evaporation and runoff occurred in 1971, 1983, 1997 and 1997, respectively. The timing of the lake growth corresponds with the abrupt increase in annual precipitation and runoff since the mid-1990s. This study suggests a strong positive water balance in the largest inland lake on the Tibetan Plateau.

scholarly journals Regional Lithological Mapping Using ASTER-TIR Data: Preliminary Case Study for the Tibetan Plateau and the Surrounding Area

2016 ◽  
Author(s):  
Yoshiki Ninomiya ◽  
Bihong Fu
Keyword(s):  
Tibetan Plateau ◽  
Structural Information ◽  
Target Area ◽  
The Tibetan Plateau ◽  
Lithological Mapping ◽  
Aster Data ◽  
Central Tibetan Plateau ◽  
Spatial Coverage ◽  
Geological Information ◽  
Characteristic Features

The mineralogical indices, e.g., Quartz Index (QI), Carbonate Index (CI), Mafic Index (MI) for ASTER multispectral thermal infrared (TIR) data have been applied to various geological materials. The indices are proved to be robust in extracting geological information at the local scale. Considering the relatively narrow spatial coverage of each ASTER scene compared to LANDSAT, many scenes are needed when mosaicking the images to be mapped at regional scales. We develop a system to search ASTER data for a target area given the vast and expanding ASTER data archive. The data is then conditioned, prioritized, and the indices are calculated before finally mosaicking the imagery. The maps of the indices covering the very wide region of the central Tibetan Plateau are produced with this system. The characteristic features of the indices relating to their geology in the study area are analyzed and discussed. Many interesting lithological and structural information that are not currently well understood in the central Tibetan Plateau, the highest and most extensive plateau in the world, with an average elevation of over 4,500 meters above sea level, for example, distributions of the mafic-ultramafic rocks along the suture zones, the quarzitic and marine sedimentology accreted to the Eurasian continent and sulfate layers related to the Tethys and neo-Tethys geological setting can be retrieved from the processed ASTER images.

scholarly journals Summer Temperature over the Tibetan Plateau Modulated by Atlantic Multidecadal Variability

2019 ◽  
Vol 32 (13) ◽  
pp. 4055-4067 ◽  
Author(s):  
Chunming Shi ◽  
Cheng Sun ◽  
Guocan Wu ◽  
Xiuchen Wu ◽  
Deliang Chen ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
General Circulation ◽  
Ring Width ◽  
Circulation Model ◽  
The Tibetan Plateau ◽  
Positive Temperature ◽  
Permafrost Degradation ◽  
Atlantic Multidecadal Variability ◽  
Multidecadal Variability ◽  
Instrumental Records

Abstract Rapid warming has led to an aggregated environmental degradation over the Tibetan Plateau (TP) in the last few decades, including accelerated glacier retreat, early snowmelt, permafrost degradation, and forest fire occurrence. Attribution of this warming in recent decades has mainly been focused on anthropogenic forcing. Yet, linkages to the Atlantic multidecadal variability (AMV), an essential part of the climate system causing decadal to centennial fluctuations of temperature, remains poorly understood for the TP, especially at long time scales. Using well-replicated tree-ring width records, we reconstructed 358 years of summer minimum temperature (MinT) of the whole TP. This reconstruction matches the recent warming signal recorded since the 1980s, and captures 63% of the variance in 1950–2005 instrumental records. A teleconnection from the North Atlantic to the TP is further identified based in observations and simulations with an atmospheric general circulation model (AGCM). We propose that half of the multidecadal variability of TP summer MinT can be explained by the AMV over the past three and a half centuries. Both observations and AGCM simulations indicate that the AMV warm phase induces a zonal dipole response in sea level pressure across the Atlantic–Eurasia region, with anomalously high surface pressure and corresponding downward atmospheric motion over the TP. We propose that the descending motion during warm AMV phases causes negative rainfall and positive temperature anomalies over the TP. Our findings highlight that the AMV plays a role in the multidecadal temperature variability over the TP.

scholarly journals Detecting Long-Term Trends in Precipitable Water over the Tibetan Plateau by Synthesis of Station and MODIS Observations*

2015 ◽  
Vol 28 (4) ◽  
pp. 1707-1722 ◽  
Author(s):  
Ning Lu ◽  
Kevin E. Trenberth ◽  
Jun Qin ◽  
Kun Yang ◽  
Ling Yao
Keyword(s):  
Tibetan Plateau ◽  
Bayesian Estimation ◽  
Precipitable Water ◽  
The Tibetan Plateau ◽  
Estimation Model ◽  
Spatial Coverage ◽  
Moderate Resolution ◽  
Long Term Trends ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract Long-term trends in precipitable water (PW) are an important component of climate change assessments for the Tibetan Plateau (TP). PW products from Moderate Resolution Imaging Spectroradiometer (MODIS) are able to provide good spatial coverage of PW over the TP but limited in time coverage, while the meteorological stations in the TP can estimate long-term PW but unevenly distributed. To detect the decadal trend in PW over the TP, Bayesian inference theory is used to construct long-term and spatially continuous PW data for the TP based on the station and MODIS observations. The prior information on the monthly-mean PW from MODIS and the 63 stations over the TP for 2000–06 is used to get the posterior probability knowledge that is utilized to build a Bayesian estimation model. This model is then operated to estimate continuous monthly-mean PW for 1970–2011 and its performance is evaluated using the monthly MODIS PW anomalies (2007–11) and annual GPS PW anomalies (1995–2011), with RMSEs below 0.65 mm, to demonstrate that the model estimation can reproduce the PW variability over the TP in both space and time. Annual PW series show a significant increasing trend of 0.19 mm decade−1 for the TP during the 42 years. The most significant PW increase of 0.47 mm decade−1 occurs for 1986–99 and an insignificant decrease occurs for 2000–11. From the comparison of the PW data from JRA-55, ERA-40, ERA-Interim, MERRA, NCEP-2, and ISCCP, it is found that none of them are able to show the actual long-term trends and variability in PW for the TP as the Bayesian estimation.

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