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Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
957
DOI: 10.4408/IJEGE.2011-03.B-104
ANNUAL TEMPERATURE IMPACT ON MORAINE LAKE
OUTBURSTS IN TIBET, CHINA
J
inGJinG
LIU
(*)(**)(***)(****)
, ZUNLAN CHENG
(*)(**)
, C
Huan
TANG
(***)
,
y
onG
LI
(*)(**)
& P
enGCHenG
SU
(*)(**)(****)
(*)
Instit. of Mountain Hazards and Environment, Chinese Academy of Sciences & Ministry of Water Conservancy, Chengdu, 610041
(**)
Key Laboratory of Mountain Hazards and Surface Process, Chinese Academy of Sciences, Chengdu, 610041
(***)
State Key Lab of Geohazard Preventions, Chengdu, 610059
(****)
Graduate School of Chinese Academy of Sciences, Beijing, 100039
change and changes in glaciers and glacier-lakes are
considered as indicator of warming (l
iu
& s
HaRma
,
1988; d
inG
& l
iu
, 1992; z
HanG
, 1992; w
aldeR
&
d
RiedGeR
, 1994; m
ool
, 1995; R
eynolds
, 1995; w
al
-
deR
& C
osta
, 1996; b
isHoP
et alii, 1998; C
laGue
&
e
vans
, 2000; s
Haun
& J
oHn
, 2000; R
udoy
, 2002;
thus may be an important indicator for global climat-
ic change (t
HomPson
et alii, 1989; l
i
& k
anG
, 2006;
a
mes
, 1998). In response to warming, glaciers in Ti-
bet have been retreating since the early 20th century,
and the retreats have been accelerating since the 1980s
(z
HanG
& y
ao
, 1998; l
iu
& k
anG
, 1999; s
Hi
& l
iu
,
2000; s
Hi
et alii, 2000; Shi, 2001; H
e
et alii, 2002a,
2002b; P
u
& y
ao
, 2004; s
Hen
, 2004; y
ao
et alii, 2004).
As a result, lakes dammed by moraines are getting like-
ly to collapse, especially in Tibet. Dam failure usually
brings about devastating flood or even debris flow. For
example, in July, 2009, a flood was induced by glacier-
lake outburst (GLOF) in the Zhemaico Lake and Cilaco
Lake in Tibet, which killed 2 persons, destroyed 53 km
highways, 20 bridges and 3 culverts.
Changes in glaciers and glacier-lakes are considered
as indicator of warming (l
iu
& s
HaRma
, 1988; d
inG
&
l
iu
, 1992; z
HanG
, 1992; w
aldeR
& d
RiedGeR
, 1994;
m
ool
, 1995; R
eynolds
, 1995; w
aldeR
& C
osta
, 1996;
b
isHoP
et alii, 1998; C
laGue
& e
vans
, 2000; s
Haun
&
J
oHn
, 2000; R
udoy
, 2002), but few studies focus on the
relationship between GLOFs and temperature variation.
Many end-moraine lakes were formed when gla-
ciers retreat at the end of the Little Ice Age (C
laGue
,
ABSTRACT
Glacier-lake outburst is common in Tibet. Global
warming is expected to increase the frequency of out-
burst. This paper attempts to find out the relationship
between the outburst and annual temperature varia-
tion based on analysis of 16 outburst events in Tibet.
Multiyear climate data from meteorological stations
in the study area are used. We find that the outbursts
are sensitive to acute change in annual temperature.
Specifically, the outburst probability increases when
average annual temperature rises by more than 0.5°C.
Finally, we put forwards an evaluation of the increas-
ing risk of potential outburst of glacier lake in Tibet.
K
ey
words
: annual temperature, impact on, moraine lake
outbursts, Tibet
INTRODUCTION
Glaciers retreat continuously and glacier lakes
have increased both in number and size over the last
decades because of the global warming. As a result,
lakes dammed by moraines are getting likely to col-
lapse, especially in Tibet. Dam failure usually brings
about devastating flood or even debris flow. For ex-
ample, in July, 2009, flood induced by glacier-lake
outburst (GLOF) happened in the Zhemaico Lake
and Cilaco Lake in Tibet, which killed 2 persons, de-
stroyed 53 km highways, 20 bridges and 3 culverts.
Glaciers in the Tibetan Plateau are of considerable
interest because of their high sensitivity to climatic
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J. LIU, Z. CHENG, C. TANG, Y. LI & P. SU
958
5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
(SEQTP, 1986), which are distributed in two distinct
regions of different climate conditions. The two re-
gions can be further divided into four subregions A,
B, C, and D, as shown in Fig. 1 (SEQTP, 1986): Conti-
nental glaciers, in subregions A and C, grow and melt
slowly, are less active and receive less rainfall; Mari-
time glaciers in B and D regions are mainly influenced
by marine climate, they have high temperature, low
snow line, and intense activity.
Since 1950s, more than 20 outbursts have taken
place in the area. Among them, 19 events in 16 lakes
have been recorded in details. Figure 1 shows the sites
and 14 meteorological stations in vicinity
The outbursts are listed in Table 1, including data
from field surveys. Among them, the Ayaco Lake
and Jialongco Lake have collapsed for several times.
Some events were reported by local inhabitants and
difficult to be located in the map. Their locations are
inferred from the literatures and topographic maps.
2003; H
ambRey
& a
lean
2004). Climate fluctuations
play a role in stimulating the outbursts. Dry weather is
favorable for the outburst in Alps, and more than 95%
of the outbursts there happened in June to September
(t
ufnell
, 1984). Lv (1989) found that humidity and
dry heat are most likely to cause dam failure in Tibet,
while l
i
(1992) thought the major motivating factors
are sustained high temperatures and abnormal
rainfall. All these studies advocate the influence
of climatic changes but few focuses on the relation-
ship between GLOFs and temperature variation. This
paper is devoted to the relationship between lake break
and temperature change in Tibet based on analysis of
16 outburst events in Tibet from 1960-2009.
OUTBURSTS IN TIBET SINCE 1950s
BACkGROUND OF STUDY AREA
Glaciers in Tibet include continental glaciers and
maritime glaciers according to their characteristics
Fig. 1 - Distribution of outburst lakes and nearby me-
teorological stations in Tibet of China (The se-
rial numbers of meteorological stations(▲):(1)
Nielamu; (2) Dingri; (3) Lazi; (4) Jiangzi; (5)
Langkazi; (6) Cona; (7) Longzi; (8) Jiacha; (9)
Linzhi; (10) Jiali; (11) Biru; (12) Bomi; (13) Luo-
long; (14) Suo. The outburst lakes labeled serial
number according to chronological order. Several
information comes from IMDE1999)
Tab 1 - The nineteen out-
bursts of sixteen
lakes in Tibet
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A STUDY OF INFRASONIC SIGNALS OF DEBRIS FLOWS
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
959
Having steep slopes and contain unsolidated sedi-
ment, moraine dams are highly susceptible to failure
(C
laGue
, 2003). Fig.2 shows the forming and outburst
of a moraine lake. The snout of glacier near the lake
may extend into the lake. The dam is typically narrow
and high with poor structural strength. Large volume
of water impounded increases the pressure against
the dam while ice avalanche fall into lake. Limited
freeboard between the dam crest and the lake level re-
duces the height of waves needed to overtop the dam
(R
eynolds
G
eo
-s
CienCes
l
td
., 2003). Having steep
slopes and contain unsolidated sediment, moraine
dams are highly susceptible to failure (C
laGue
, 2003).
The lakes lie in the high altitude and it is difficult
to obtain field data. In this study, weather data is ana-
lyzed to find the possible impact of annual tempera-
ture on outburst.
DATA AND CORRECTION
The data come from 14 weather stations near the
lakes and 12 lakes which have relatively complete
data are taken for case studies, which list in Table 2.
As elevation impacts temperature considerably
(d
odson
, 1997; H
ulme
M, 1995; R
obeson
, 1998), the
recorded temperature is corrected to diminish the el-
evation effect by the following formula (l
i
, 2006)
T
H
=T
0
– k ΔH
(1)
where T
0
is the recorded temperature from the set of
Chinese surface climate data, ΔH is the elevation dif-
ference between the lake and the station, k is the cor-
rection coefficient, as showed in Fig. 4 (l
i
, 2006)
.
And the refinement of inverse distance weighted
FORMATION AND OUTBURST OF MORAINE
LAkES
There are many kinds of glacier lakes, such as
superglacial lake, englacial lake (the water body),
and ice-dammed lake (formed by the valley glacier
blocking the mainstream channel). . And on aspects
about glacier retreat, there are end-moraine lake, ice-
erosion trough valley - moraine lake, cirque lake and
lateral moraine lake. All the 19 outbursts in Tibet oc-
curred in moraine lakes (IMHE, 1999). The moraines
are formed by unsorted soil, rock, and other material
left by the glaciers. Rock debris rolls off the glacier
edges and builds piles of unconsolidated rocks called
"glacier moraine". "Lateral moraines" form along the
side of a glacier and curl into a "terminal moraine"
at the glacier's downvalley end. Terminal moraines
are formed at the farthest limit reached by a glacier
and lateral moraines are formed along the sides of a
glacier (s
Cot
d
aHms
, 2006). lakes considered were
caused by avalanches closely related to temperature
Fig. 2 - Schematic diagram showing the formation and
outburst of moraine-dammed Lake (modified from
c
lAGue
& e
vANS
, 1993, Fig. 8)
Tab. 2 - The data of 12 lakes from different
stations
Fig. 4 - Lapse rate of temperature in Tibet (the number is
the correction coefficient ) (l
i
, 2006)
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J. LIU, Z. CHENG, C. TANG, Y. LI & P. SU
960
5th International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment Padua, Italy - 14-17 June 2011
flections of temperature fluctuation, either from high
to low or from low to high. High temperature may in-
crease the outburst probability because it contributes
to melting and icefall. The annual mean temperature
and the increment of Jilaico and Damenlakeco Lake
were both the maximal till 1964. And in the early
1960s, especially in 1962 and 1963, the regions were
under wet cold weather,. The difference of mean an-
nual temperature was about 1°C between 1963 and
1964, when the climate began to warm. Ayaco Lake
broke successively in the three years. The years of
1965 and 1966 constituted a cold period. The aver-
age annual temperature in 1966 was the lowest. And
it increased to -2.5°C in 1968 and to -1.6°C in 1969,
the maximum till 2002.
The glaciers advanced in the cold period of 1965-
1967 and the ice snout moved forwards or even en-
tered into the lake. While temperature rose rapidly, the
glacier melted and collapsed into the lake and finally
led to the outburst. The annual temperature of Cilaco
Lake and Zhemaico Lake went up rapidly by 1.1°C and
1.3°C in 2009 after a sharp decline in 2008. It can be
concluded that stronger annual temperature fluctuation,
which may be more than about 0.9°C, increases the
possibility of outburst.
This disagrees with the conclusion of the previous
studies (IMHE, 1999) that most outbursts occur after
high temperature year. We observe that outburst oc-
curred when temperature increased by only 0.5°C or
more for seven cases. However, there are five cases like
Zharico Lake where the outbursts occur on a low annual
temperature point.
TEMPERATURE ANOMALY YEAR
Fluctuation of temperature makes some years
abnormal, having a large deviation from the mean
interpolation is
where T is the final value used in study, T
H
is the re-
vised value, D
t
is the horizontal distance between the
lake and the nearby stations.
ANNUAL TEMPERATURE VARIATION
IMPACT ON GLACIER-LAKE OUT-
BURSTS
MEAN ANNUAL TEMPERATURE
We collect annual mean temperature to find its im-
pact on outburst. Figure 5 demonstrates the temperature
variation for the lakes in the years around the outburst
(denoted by black dot). The fluctuations is remarkable in
1960s, 1970s and recent years, but it is gentle in 1980s.
The signed number, e.g., 0.7604, in Fig.5, means
the temperature is increased by 0.7604°C over the
year prior to the outburst. Similarly, -0.9 means the
temperature is decrease by 0.9°C comparing with the
year before the outburst.
It is found that the outbursts occurred at the in-
(2)
Fig. 5a - Variation of annual temperature of 12 lakes be-
tween 1960 and 2009 (● indicates the outburst
years) (a) The outbursts in 1960s and 1970s
Fig. 5b - Variation of annual temperature of 12 lakes be-
tween 1960 and 2009 (● indicates the outburst
years) (b) The outbursts in 1980s
Fig. 5c - Variation of annual temperature of 12 lakes be-
tween 1960 and 2009 (● indicates the outburst
years) (c) The outbursts in 2000s
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A STUDY OF INFRASONIC SIGNALS OF DEBRIS FLOWS
Italian Journal of Engineering Geology and Environment - Book www.ijege.uniroma1.it © 2011 Casa Editrice Università La Sapienza
961
temperature from 14 meteorological stations nearby.
Glacier-lake outburst is the response to volatility in
annual temperature. A great fluctuation of temperature
is more likely to induce the outburst. It is found that
multiyear-data other than one-year data is more relevant
to determine an outburst. In a year of abrupt climate
change, particularly when a cold year turn into a warm
year, the probability of outburst increases rapidly only if
the average temperature rises by more than 0.5°C.
Apparently, glacier-lake outburst is concerned
with many factors, including the features of the
lake and the environment. Temperature as an indica-
tor for glacier change may dominate in influencing
the potential of outburst, but it is not sufficient to
predict a special event. For accurate prediction of
outburst, more data is needed both of the outburst
process and the related information of weather, such
as the daily and monthly variation of the tempera-
ture prior to the outburst.
ACKNOWLEDGEMENT
This study is supported by the Opening Fund
of State Key Laboratory of Geohazard Prevention
and Geoenvironment Protection (Grant No. SKLG-
P2010K003), and the National Natural Science Foun-
dation of China (Grant No. 40771024).
temperature of many years. According to World Mete-
orological Organization (WMO), a year is defined as
anomal when the temperature variation is two times
higher than the standard deviation, or when the return
period is longer than 25 years.
The annual temperature variation C is
C = |T
A
|/ S
D
where T
A
is annual average temperature and SD is
standard deviation.
In the following, we take C ≥2 , 1.5 ≤ C ≤2 and
1≤ C ≤1.5 as the categories for anomaly, close to the
anomaly, and drift slightly higher or lower, respec-
tively. The results are listed in Table 3 for the outburst
years and the preceding years. (+ means high anomaly
and - means low anomaly.)
Glacier-lake outbursts are induced by great change
in temperature. 12 out of the 15 events occurred on
climate change point, especially in the turning years
from cold to warm. The possibility of outburst is thus
only determined by temperature of the current year,
but also by temperature of the preceding years.
CONCLUSIONS AND DISCUSSIONS
This paper explores the influence of annual temper-
ature on glacier-lake outbursts in Tibet, using data from
16 outburst events in southern Tibet and the relevant
Tab 3 - The temperature anomaly
year of outburst and the
preceding years
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