The 2nd Glacier Inventory of China

Transcription

1 The 2nd Glacier Inventory of China LIU Shiyin Guo Wanqin, Xu Junli, Shangguan Donghui, Wei Junfeng, Wu Lizong, Yu Pengchun, Li Jing, Liu Qiao State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Engineering Research Institute, CAS

2 1. Background 5A: Ob River 5J: Yellow River 5K: Yangtze River 5L: Mekong River 5N: Salween River 5O: Ganges River 5Q: Indus River 5X: Central Asia Region 5Y: Eastern Asia Interior Region 5Z: Qinghai-Tibetan Interior Region Glaciers: 46377, km2 and km3 in western China (Shi et al., 2008)

3 Statistics of glacier number, area and volume in different mountains in China: Glaciers in Tianshan, Kunlun, Nyainqentanglha and Himalaya take 68.3% of total glacier area in China

4 Meltwater contribution to the total runoff of different rivers (left panel) and that in surface runoff of 4 west provinces (right panel) (all in %)

5 (% of numbers) distribution of various glacier area classes in China: 95.8% glaciers are smaller than 5.0km2. They only takes about 49% of the total area of glaciers in China

6 Small glaciers may play an important role in the changes of glacier area and the impact on water availability and glacier hazards

7 2. Data and Method for the 2nd GIC ASTER Landsat TM/ETM+ GDEM ASTER Landsat TM/ETM+ Year Numbers Year Number Number (TM) Total 563 Total

8 ASTER scenes used in Second Glacier Inventory of China Totally 563 ASTER imageries were orthorectified.

9 Landsat TM/ETM+ used in Second Glacier Inventory of China Totally 119 Landsat TM/ETM+ imageries were used.

10 ASTER GDEM used in Second Glacier Inventory of China Totally 265 GDEM data were used.

11 Clean-ice glacier outline extraction Band ratio thresholding methods Landsat TM: band 2/band 5, with reference on band 3/band 5 ASTER: band 1/band 4, with reference on band 2/band 4

12 Ice divides extraction Glacier central flow line extraction Glacier attributes calculation method Glacier midflow lines Binary tree search with reference on line length Find glacier label point on primary mid-flow line in firn basin Retrieve point coordinates in lattitude/longitude Extract terminal point of glacier Glacier boundaries ASTER DEM Build polygon topology Retrieve DEM cells in glacier polygon Calculate statistics Glacier code Calculate slope and aspect Median area elevation of glacier Terminal elevation of glacier Glacier length Retrieve half area elevation Glacier area Glacier perimeters Maximum elevation of glacier Average elevation of glacier Glacier slope Glacier orientation

13 Accuracy assessment Accuracy of clean-ice glacier outlines Comparon with field GPS measurements, mean positioning error: ±38 m Comparison with multiexpert judgments, mean positioning accuracy: ±35.2 m Automatically extracted glacier outlines validated with field GPS measurements Assessment for errors from visual interpretation based on different interpreters

14 Area error from satellite images is defined λl is the resolution of image scenes n is the total number of pixels along the outline of a glacier polygon excluding the common ridge line of the mountain. Uncertainty distribution for glaciers in the 4th level watershed

15 3. Result ~85% in area of glaciers were compiled with se cond inventory in western China. The remaining part is mainly located in the so utheast Tibetan Plateau, where very few fine q uality remote sensing imageries are available.

16 Glaciers with the second inventory in China Glacier central flow line extraction Glacier attributes calculation method

17 The present total glacier area in various mountains of China (glaciers without 2nd inventory are substituted with dtat of 1st GIC) Mountains Altai Sawuer Tianshan Pamir Karakoram Kunlun Aktun Qilian Qiangtang Tanggula Gandise Nyainqentanglha Hengduan Himalaya Total Area %

18 Glacier changes in China Basin Code First Glacier Inventory Area (km2) Year Second Glacier Inventory Area (km2) Glacier Change Year Overall(%) 5A J K L N O Q X Y Z Total

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20 Annual mean shrinkage rate: (Sscd/Sfst)(1/n)-1 Sscd and Sfst are areas of the second and first time inventories; n: years between the two time inventories The spatial pattern of glacier area reduction in China: glaciers in central Tibetan Plateat have been generally in smaller area shrinkage

21 Summary Glaciers in ~2010 in China might have a total area of km2 In the last 60 yrs, glaciers in China have lost 18.7% of their area in late 1950s. The spatial pattern glacier areal Shrinkage may be controlled by the physical properties of glaciers.

22 Thank you for your attention!