Topographical Survey of July 1St Glacier in Qilian Mountains, China

Bulletin of Glaciological Research ,- (,**0) 0-ῌ01 63 ῌJapanese Society of Snowand Ice

Topographical survey of July +st Glacier in Qilian Mountains, China

Koji FUJITA+, Akiko SAKAI+, Yoshihiro MATSUDA+, Chiyuki NARAMA+, Nozomu NAITO,, Satoru YAMAGUCHI-, Kuniharu HIYAMA+, Jiancheng PU., Tandong YAO/ and Masayoshi NAKAWO0 + Graduate School of Environmental Studies, Nagoya University, Nagoya .0.ῌ20*+, Japan , Department of Environmental Information, Hiroshima Institute of Technology, Hiroshima 1-+ῌ/+3-, Japan - Nagaoka Institute of Snowand Ice Studies, National Research Institute for Earth Science and Disaster Prevention, Nagaoka 3.* ῌ*2,+, Japan . Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Science, Lanzhou 1-****, China / Institute of Tibetan Plateau Research, Chinese Academy of Sciences, P. O. Box ,21+, Beijing +***2/, China 0 Research Institute for Humanity and Nature, Kyoto 0*,ῌ*212, Japan

(Received October -, ,**/; Revised manuscript accepted November ., ,**/)

Abstract

In order to evaluate recent glacier shrinkage in the arid region of China, surveys using a global positioning system (GPS) and digital theodolite with laser distance meter were carried out on the July +st glacier in the Qilian Mountains from ,**, to ,**/. Benchmarks and stakes on around the glacier were installed in ,**,. A new ,**, map was carefully superposed on a map created in +31/ using a salient moraine ridge and boundary of the accumulation area, since no ground control point was available in the old +31/ map. A retreat of the glacier termini has been detectable since +3/0 with a notable retreat occurring between ,**, and ,**-. Surface ﬂowvelocities wereobtained by repeated measurements of a stake network. The new map and benchmarks provide basic information for future survey studies.

+.Introduction

Water from glaciers is significant as water reser- voirs, especially in the arid inland regions of China such as the Taklimakan and Gobi Deserts (Kang et al., +333). The Qilian Mountains are located on the north- ern fringe of the Tibetan Plateau (Fig. +) and hold ,2+/ glaciers, occupying about +3-* km, (Tsvetkov et al., +332). Glacier meltwater and more abundant precipitation in the mountains supply a fair amount of water to oases scattered across the huge desert area, where the scant precipitation cannot support human inhabitants Fig. +. Location of July +st glacier in Qilian Moun- (Ding and Kang, +32/; Kang et al., +333; Wang and tains (open circle). Chen, +333). The river discharge into the desert region has been analyzed and estimated in the context of warming on the Tibetan Plateau (Kang et al., +33,; Determining fluctuations in a glacier is significant, +333;Ye et al., +333; ,**-; Liu and Chen, ,***;Liu et therefore, in evaluating its historical and future dis- al., ,**-). They concluded that the glacier shrinkage charge together with its contribution to human lives derived from warming would increase water dis- in a desert area. charge briefly since the glaciers lost their ice body as The July +st Glacier is located in the western redundant water. The amount of additional water and region of the Qilian Mountains (-3ῌ+/῍N, 31ῌ./῍E, Fig. its persistent duration would depend on the scale, ,). A map of the glacier based on aerial photographs dynamics and change in mass balance of the glaciers. was made in +31/ (Xie et al., +32/a; included in Shi, 64 Bulletin of Glaciological Research

+322). The length and area of the glacier in +31/ were theodolite with laser distance meter (SOKIA SET,+**) -.2 km and ,.32 km,, respectively (Liu et al., +33,). have been carried out on/around the July +st glacier Based on that initial map, the thickness using the since June ,**,, as summarized in Table +. Data proc- gravitational method (Su, +32/) and the glacier surface essing of GPS measurements was performed using ﬂow between +310 and +311 (Sun and Huang, +32/) have been measured. In +32/, various studies such as a resurvey around the ablation area (Liu et al., +33,), glacier ﬂow between +32. and +32/ (Song et al., +33,), and internal ice temperature (Xie et al., +32/b) have been carried out. In order to determine the recent condition of the glacier, we started meteorological, hydrological and glaciological observations in ,**,. Preliminary results on meteorology (Sakai et al., ,**0 a), glacial discharge (Sakai et al., ,**0b), and mass balance of the glacier (Matsuda et al., ,**.) were re- ported. Here summarize the preliminary results of a survey in this report.

,.Survey of July +st Glacier

Surveys by the di#erential Global Positioning System (GPS, CMC Co., Ltd. All Star) and a digital

Fig. -. Map of July +st glacier. Crosses denote the benchmarks installed in ,**, (BM-L+ and BM-R). Glacier boundaries in +3/0 and +31/, contour lines and moraine ridge of left bank are traced from a original map surveyed in +31/ (Xie et al., +32/a). Boundary of ,**, is drawn from GPS data. Dots denote stakes installed in ,**, for mass balance Fig. ,. Photograph of July +st glacier from the north and surface ﬂow measurements. Rhombus denotes (, September ,**-). a rock on the glacier.

Table +. Surveys on/around the July +st glacier since ,**,. TS in method denotes a digital theodolite with laser distance survey.

Season Method Observers Markers June +/ῌ,*, ,**, GPS KF Boundaries, stakes, side moraines Aug. -+ῌSep. 1, ,**, GPS YM Stakes Aug. +/ῌSep. +-, ,**- TS AS, WX, NN Stakes, terminus June +.ῌ+0, ,**. TS AS, WX Stakes, terminus July ,1ῌ,3, ,**. GPS KF Glacier, end moraine Aug. -+ῌSep. ,, ,**. TS AS, WX, CN Stakes, terminus Sep. /, ,**. GPS CN End moraine June ,0ῌJuly /, ,**/ GPS KHTerminus, end moraine June ,1, ,**/ TS SY, KHStakes Abbreviations for observers: KF, Koji Fujita; YM, Yoshihiro Matsuda; AS, Akiko Sakai; WX, Wang Xinming; NN, Nozomu Naito; CN, Chiyuki Narama; KH, Kuniharu Hiyama; SY, Satoru Yamaguchi. Fujita et al. 65

Table ,. Locations of benchmarks and a rock on the glacier in the Universal Transverse Mercator (UTM) coordinate and the geodetic coordinate with WGS2. (last line for BM-L+).

Object Northing Easting Altitude Date BM-L+ .-./-2,4,* -3,+*141. .-.24** ῌ BM-R .-./3,04*- -3+2014*1 .-2241/ ῌ Rock .-./1,,412 -3+/+043, ...-42. , Sep. ,**. BM-L+-3῍+/ῌ.4+/1῎ 31῍..ῌ/143,,῎ .-.24** ῌ Units of UTM coordinate and altitude are in meters.

Fig. .. Change in the terminus of July +st glacier since +3/0. Cross denotes the benchmark (BM-L+).

GrafNav and GrafNet software (Waypoint). Relative positions of all points were calculated on a system of coordinates with their origin at the benchmark on the left bank moraine (BM-L+). Benchmarks, stakes, and glacier boundaries are shown in Fig. -. Locations of benchmarks and a rock on the glacier are shown in Table , on the Universal Transverse Mercator coordinate with WGS2.. The position of BM-L+ was obtained as an average of a measurements repeated several times, since absolute positions cannot be relia- bly measured by the GPS system. A rock located in Fig. /. New map of July +st Glacier. All GPS traces on the mid-ablation area (solid rhombus in Figs. - and /) the glacier (gray dotted lines) and the end/side moraines (gray broken lines) are used for drawing serves as a signiﬁcant marker on the glacier, and its contour lines (thin lines). Thick solid and dotted location will provide useful information for future lines denote the boundary of the glacier in ,**, surveys. and +31/, respectively. Measurement errors in the survey were evaluated by comparing the positions of the / benchmarks (considered to be immovable) installed around the glacier. retreat history of the terminus since +3/0 is shown in Standard deviations of di#erences (-, measurements) Fig. .. Retreat distances and rates of the terminus are from the averages were obtained as measurement er- summarized in Table -. Dividing the ablated area by rors. Horizontal and vertical errors were within *.*1 the width around the terminus gives the retreat dis- and *.+, m, respectively. tance. Both the area and width are obtained from a Figure - also shows the boundaries of the glacier detailed map (Fig. .). A remarkable retreat between in +3/0, +31/,and+32/ (Xie et al., +32/a; Liu et al., +33,). ,**, and ,**- was considered to be due to drastic Contour lines are those of +31/ (Xie et al., +32/a). Sur- melting in the summer of ,**,. This phenomenon was veyed data were carefully superposed on the previous suggested by Sakai et al.(,**0a) based on the meteoro- maps by matching the glacier boundaries of the accu- logical data. mulation area and moraine ridge, since no ground A new map of the glacier was drawn based on all control point was available from the previous maps. A the measurement data (Fig. /). Elevation of the glacier 66 Bulletin of Glaciological Research

Table -. Retreat distance and rate of the termini of determined by a single GPS survey will vary widely July +st Glacier since +3/0. with each measurement, the relative elevation from , Year Duration Retreat distance Retreat rate the benchmarks shown in Table should be compara- ῌ+ (yr) (m) (m yr ) ble in future surveys. This map and the benchmark +3/0 locations, therefore, will provide basic information for +3 024- -40 future studies of fluctuations in the glacier. A detailed +31/ map of the area around the end moraine will be ana- +* ,04. ,40 lyzed elsewhere in order to evaluate the shrinkage of +32/ the glacier since the Little Ice Age. +1 ,/43 +4/ Surface flow velocities were obtained by compar- ,**, ing the locations of stakes (Fig. 0). Decreasing surface + ,*4+ ,*4+ speeds since the +31*s are explainable by thinning of ,**- the glacier ice (Sakai et al., ,**0c). Seasonal changes in + *4* *4* the surface flow speed, ice temperature, and thickness ,**. of the glacier will be analyzed elsewhere. + /43 /43 ,**/ Acknowledgments

The authors wish to express their gratitude to all members of the Project for their valuable support in the field observations. The field research was funded by a Grant-in-Aid for Scientific Research (Project No. +.,*3*,*) from the Ministry of Education, Culture, Sports, Science and Technology of Japan. The data analysis was funded by The Sumitomo Foundation. This paper is a contribution to the Oasis Project (His- torical evolution of adaptability in an oasis region to water resource changes) promoted by the Research Institute for Humanity and Nature (RIHN).

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