Foreword
Preface
Section I Pattern
Chapter 1 Modeling and Analysis of Lake Water Storage Changes on the Tibetan Plateau Using Multi-mission Satellite Data 3
1.1 Research objective 3
1.2 Study area 4
1.3 Materials and methodology 5
1.3.1 ICESat satellite altimetry data 5
1.3.2 Optical satellite images 6
1.3.3 GRACE satellite gravimetry data 6
1.3.4 Monitoring lake water extent changes 7
1.3.5 Modeling lake water storage changes 8
1.4 Water level changes in 30 typical lakes on the TP 10
1.5 Surface area changes in all lakes on the TP 11
1.6 Modeling lake water storage variations on the TP 13
1.7 Mass changes on the TP observed from GRACE satellite gravimetry 18
1.8 Limitations and uncertainty analyses 19
1.9 Summary 20
References 21
Chapter 2 Refined Estimation of Lake Water Level and Storage Changes on the Tibetan Plateau from ICESat/ICESat-2 25
2.1 Research objective 25
2.2 Study lakes on the Tibetan Plateau 26
2.3 Materials and methods 27
2.3.1 ICESat/ICESat-2 data for deriving lake levels from 2003 to 2020 27
2.3.2 Lake area derived from Global Land Analysis and Discovery (GLAD) data 28
2.3.3 Lake mapping and storage variation from 2003 to 2019 28
2.3.4 Classification of the TP lakes as closed and upstream types 29
2.4 Coverage of ICESat/ICESat-2 measurements over the TP lakes 29
2.5 Lake level changes between 2003 and 2020 31
2.6 Lake water storage changes between 2003 and 2020 32
2.7 Uncertainty in estimating lake water storage changes on the TP 33
2.8 Comparison of lake changes during the ICESat era and joint-mission period 34
2.9 Summary 35
References 36
Chapter 3 Heterogeneous Hydrologic Changes of TP Lakes Observed by Multi-mission Altimeters 39
3.1 Research objective 39
3.2 Study lakes on the Tibetan Plateau 40
3.3 Study data and methods 42
3.3.1 CryoSat-2 altimetry data 42
3.3.2 ICESat altimetry data 43
3.3.3 Other sources of radar altimetry data archives 43
3.3.4 In-situ lake level observations and other materials 44
3.3.5 Data processing and estimation of lake level trends 46
3.4 Evaluation of CryoSat-2 altimetry data on the two typical lakes 47
3.5 Heterogeneous changes in water level for the TP lakes based on combined ICESat/CryoSat-2 altimetry data 49
3.6 Heterogeneous water level variations of typical large lakes based on multi-source merged radar altimetry data 52
3.7 Possible cause of the heterogeneous change patterns of the TP lakes 56
3.8 Summary 58
References 59
Chapter 4 Seasonal and Abrupt Changes in Water Level of the Lakes on the Tibetan Plateau 63
4.1 Research objective 63
4.2 Study lakes 64
4.3 Data and methods 64
4.3.1 ICESat altimetry data to extract lake water level data 64
4.3.2 Meteorological data 65
4.3.3 GRACE gravimetric terrestrial water storage data 66
4.3.4 Definition and retrieval of seasonal lake water level variations 67
4.3.5 Cluster analysis onchange patterns of lake level 71
4.3.6 Conceptual model of lake water balances 72
4.4 Comparison of time-series lake level variations during warm and cold seasons 73
4.5 Cluster-based spatial pattern on seasonal and abrupt water level changes 75
4.6 The correlations between abrupt changes in lake level and climatic variables in abnormal years 77
4.7 Comparison of GRACE-observed TWS changes and seasonal and abrupt lake-level variations 80
4.8 Evaluations of cluster-based lake changing patterns 82
4.9 The associations of lake expansions with the precipitation， evaporation and glacial meltwater 83
4.10 Summary 84
References 85
Section II Drivers
Chapter 5 Accelerated Lake Expansion on the Tibetan Plateau in the 2000s: Induced by Glacial Melting or Other Processes? 91
5.1 Research objective 91
5.2 Study area， materials， and methods 92
5.2.1 The TP lakes and climate 92
5.2.2 Optical images for measuring lake area variations 93
5.2.3 Satellite altimetry data for measuring lake water level variations 94
5.2.4 Other materials and data processing 98
5.2.5 Linear model of the water level change rate and the analyzed factors 99
5.3 Comparing the lake variation characteristics in the 2000s and the 1970–2000 99
5.4 Analysis of the relationship between lake changes and the glacier meltwater supply and lake supply coefficient at the plateau scale 102
5.5 Analysis of the interzone difference in the relationship between lake changes and the glacier wastage and supply coefficient 103
5.6 The relationship between lake changes and the precipitation and evapotranspiration variability 106
5.7 Comparative analyses based on typical lake cases 107
5.8 Uncertainty analyses 108
5.9 Summary 110
References 111
Chapter 6 The Climate Cause of Spatio-temporal Heterogeneous Changes in Lake Level on the Tibetan Plateau and Surroundings 115
6.1 Research objective 115
6.2 Study area and materials
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Section I Pattern
Chapter 1 Modeling and Analysis of Lake Water Storage Changes on the Tibetan Plateau Using Multi-mission Satellite Data
1.1 Research objective
The Tibetan Plateau (TP)， known as the “Asian Water Tower” and Earth’s “Third Pole”， is highly relevant to global climate dynamics and the Asian monsoon system (Krause et al.， 2010). There is a large number of alpine lakes on the TP， with the total lake surface area surpassing 44，990 km2 (Jiang and Huang， 2004). As the alpine hydrologic environment has been minimally disturbed by human activities， such as agricultural settlements and irrigation， it has become an important indicator of climate change. In the past few decades， climate change， characterized by rapidly rising temperature and changing precipitation and evapotranspiration patterns， had a substantial impact on the water storage of the inland lakes over the TP. In particular， the rapidly rising temperature has accelerated the retreat of glaciers and permafrost thawing， which have become the predominant inflow sources for many expanding lakes (Yao et al.， 2007; Ye et al.， 2007; Zhu et al.， 2010). Therefore， accurate estimation of the interannual water storage changes in these alpine lakes is not only of great importance to furthering our understanding of their responses to climate change， but also crucial for the effective modeling of the hydrological and ecological processes on the TP (Birkett， 2000; Deniz and Yildiz， 2007; Medina et al.， 2008; Mercier et al.， 2002).
A small number of typical lakes have been investigated in terms of their surface extent using medium- and high-resolution optical satellite images. For instance， Wang et al. (2007) adopted aerial photos and Landsat and CBERS imagery to investigate fluctuations in the typical lakes of the TP between 1969 and 2001. Bian et al. (2009) and Meng et al. (2012) monitored the stable expansion process of the Siling Co in central Xizang， and Kropácek et al. (2012)， Phan et al. (2012)， and Zhang et al. (2011b) reported lake level changes derived from satellite altimetry. These studies indicate that lakes with an inflow of glacial meltwater tends to expand rapidly， whereas those that are supplemented primarily by rainfall runoff are generally stable or even shrinking. However， most studies focused on the qualitative detection and analysis of variations in either lake surface area or water level over the past several decades (Liu et al.， 2009; Wang et al.， 2007; Ye et al.， 2008， 2007)， which is insufficient to accurately express the water balance of lake basins in response to climate change. Furthermore， because of the remoteness and inaccessibility of the lakes on the TP， and the high cost of research in the region， direct hydrologic observations or measurements， including water storage， have been limited to the few lake basins with traditional water observation stations， such as Qinghai Lake (Qinghai Hu)(丁永建和刘凤景， 1995; Li et al.， 2005)， Nam Co (Zhang et al.， 2011b)， Yamzhog Yumco (Bian et al.， 2009)， and Zabuye Salt Lake (齐文和郑绵平， 2006). To date， there have been no estimations of total water storage or mass changes in regional-scale lakes across the plateau owing to a lack of direct and comprehensive observations of water storage.
In this chapter， we analyze the extent of and elevation changes in typical large TP lakes using data derived from optical and satellite altimetry images， respectively. We then establish the statistical relationship (hypsometric curve) between the surface area and water level of each lake to reconstruct time series of water level based on corresponding lake areas derived from optical satellite images over a longer time scale. Furthermore， for the first time， we estimate and analyze the time-series changes in lake water storage by combining multi-temporal area and water level data. Lastly， we use Gravity Recovery and Climate Experiment (GRACE) data to estimate the mass change in terrestrial water storage over the plateau， and to compare the gravimetry estimations with the results of empirically modeled lake water storage changes.
