Embed Size (px)
Citation preview
C21B-01: Glaciers Response to Climatic Trend and Climate Variability in Mt Everest Region (Nepal) Sudeep Thakuri1,2,3, Franco Salerno1,3, Nicolas Guyennon1, Gaetano Viviano1,3, Claudio Smiraglia2,3 , Carlo D’Agata2,3, Gianni Tartari1,3 1Water Research Institute ̶ CNR, Brugherio; 2Graduate School of Earth, Environment and Biodiversity, University of Milan, Milan; 3Ev-K2-CNR Committee, Bergamo, Italy. (Correspondence: [email protected])
2. Data and Method Multi-temporal satellite imagery (Corona KH-4 1962, Landsat MSS/TM/ETM+ (1975, 1992, 2000, 2011), ALOS/AVNIR-2 2008 and ASTER-DEM with resolution ranging ~ 8 to 60 m), assisting by topo-maps (1950s, 1963 & 1992) and hydro-meteorologial data (temperature, precipitation and river discharge) from stations were used. Time series for temperature and precipitation reconstructed through the monthly quantile mapping and expectation maximization techniques from 6 Automatic weather stations located in the region. The singular spectral analysis (SSA) and monthly sequential Mann-Kendall test (seqMK) were performed for trend analysis.
1. Introduction Mount Everest region in central southern Himalaya, influenced by monsoon-dominated climate system, is characterized by dense debris-covered glaciers (Scherler et al., 2011). Glaciers in response to climate shows dynamic behavior in terms of glacier morphology and mass balance. Little efforts has been put so far on studies on interdisciplinary linkages of hydro-meteorological process and glacier dynamics in the Himalaya.
We present glacier terminus, surface area, snowline altitude (SLA) and debris-cover area change from 1960s to 2011 and climatic trends with the aim of understanding coupled climate-glacier dynamics in the Sagarmatha (Mt Everest) National Park (1148 km2) in Nepal Himalaya (Fig. 2).
Debris-covered ablation zone
Accumulation zone
Fig. 1. Upper part of Ngojumba glacier (~98 km2).
Fig. 4. Evolution of moraine-dammed pro-glacier lake in the terminus, one of the main cause of glacier terminus retreat. A case of Imja lake evolution since 1962 to 2011. The debris-covered ablation zone of the glaciers in these region are characterized by a large number of supraglacier lakes
Fig. 3. Spatio -temporal changes of glacier terminus (A), surface area (B), snowline altitude (C) and debris-covered area (D) from 1962 to 2011. In the upper left panel, boxplot represents variation occurred among glaciers (red points are mean) in each analysed period while in the lower panel, cumulative changes with associated uncertainty. In the right side, the map shows spatial variation of glaciers.
minimum and maximum discharges, with stationarity in overall trend until 2000 and than, increased trend with two separate pre-monsoon and monsoon peaks. Our observations of terminus and surface are lower than most of the previously reported values from the eastern, western Himalaya and Tibetan plateau. These differences in variation of glaciers could be explained by the distribution of debris-cover of glaciers. The glaciers in the central southern Himalaya are heavily debris-covered than other parts of the Himalaya (Scherler et al., 2011).
Fig. 5. SeqMK test and SSA for (A) temperature, (B) precipitation, (C) downstream discharge, and (D) Kathmandu temperature. In (A&B), upper first plot is SSA trend whereas in (C&D), upper first plot is annual trend. For all the variables, middle plot is monthly SeqMK trend and third, for trend of Sen’s slope coeff. The asterisk shows the significance of trend.
Using the Kuhn’s Climate- ELA model (Roger, 2005; Kayastha & Harrison, 2008), we estimated that for observed 182 m upward shift of the snowline, a temperature increase of 1.1 °C or 535 kg m-2 of precipitation decrease or 1.78 MJ m-2 d-1 of solar imbalance increase is required.
The temperature has increased by +0.6°C and the precipitation has decreased by around 100 mm in last two decades (Fig. 5A-B). Both temperature and precipitation trend are statistically significant for pre-monsoon and winter months. The longest and closed time series of temperature and precipitation from Kathmandu station also agree with this observation, indicating increase of temperature by 0.44/decade in 1961-2011 (Fig. 5D), while the precipitation has statistically no significant trend until 1990s, but significantly weakening trend in 1990s to 2011. The stream-flow data (Fig. 5C) indicates significantly widening of annual
-20
-10
0
10
1955 1965 1975 1985 1995 2005 2015
ΔSur
face
(%)
0
50
100
150
200
1955 1965 1975 1985 1995 2005 2015
ΔSLA
(m)
-10
0
10
20
1955 1965 1975 1985 1995 2005 2015
ΔDeb
ris-c
over
(%)
1955 1965 1975 1985 1995 2005 2015-450
-350
-250
-150
-50
ΔTer
min
us (m
)
1962-75 1975-92 1992-00 2000-08 2008-11 1962-11
-60
-40
-20
020
glac
ier t
erm
inus
cha
nge,
m y
r -1
1962-75 1975-92 1992-00 2000-08 2008-11 1962-11
-10
010
2030
40
SLA
shift
, m y
r -1
1962-75 1975-92 1992-00 2000-08 2008-11 1962-11
-4-2
02
46
8
debr
is-c
over
are
a ch
ange
, % y
r -1
1962-75 1975-92 1992-00 2000-08 2008-11 1962-11
-6-4
-20
2
glac
ier s
urfa
ce c
hang
e, %
yr -1
A
B
C
D
a1
a2
a3
b1
b2
c1
c2
d1
d2
b3
d3
ΔTer
min
us(m
a-1)
ΔTer
min
us(m
)ΔS
urfa
ce(%
a-1)
ΔSur
face
(%)
ΔSLA
(m a-1
)ΔS
LA (m
)ΔD
ebris
-cov
er(%
a-1)
ΔDeb
ris-c
over
(%)
c3
4. Conclusion and Perspectives The observed variation of glacier surface and SLA changes could be explained by the increase of temperature and more importantly, by changes of precipitation in recent years but more analysis is still required. We will explore the climate-glacier relationship by further more analysis of the climate variables with the aim of integrating the glaciological, hydrological and climatic data for understanding of future water availability scenario.
Fig. 2. (A) Location of the study site in Nepal; (B) Enlarged 3D visualization of the Sagarmatha (Mt. Everest) region (C) Area-elevation curve showing the glacier area distribution in 2011; (D) Glacier extent change in 1962 and 2011.
China
India Mt Everest (8848m)
AWS-NC Namche
AWS1 & AWS-ABC
AWS-KP
Pheriche AWS2
Gokyo
Thame
Automatic Weather Station (AWS)
ALOS- AVNIR-2, Acquisition 24 Oct 2008; Cloud cover: 0-2% B
A C
D
(b1)
(b2)
(b3)
B
(d1)
(d2)
(d3)
D
A (a1)
(a2)
(a3)
(c1)
(c2)
(c3)
C
3. Results and Discussion The continuous retreatment of glaciers observed since 1960s to 2011 with continuously increased rate. Majority of glaciers are retreating but some glaciers are stationary or even advancing in some analysed periods. The average terminus retreat of glaciers was about 400±34 m (8.2 m a-1) in 1962 to 2011 (Fig. 3A). The glacier surface area had loss of 13.0±3.4 % (0.27 % a-1) from 404.6 km2 to 351.8 km2 in 50 years with the loss by 0.13 % a-1 in 1962-75 to 0.57 % a-1 in recent years (Fig. 3B)
The smaller glaciers with <1 km2 dimension had decreased by 43 % in their surface area showing rapid disappearance of small glacier/ice. The accumulation area decreased by 24.8 %, whist ablation area increased by 17.7 % with about 17.6 % increase in debris-covered area in ablation zone (~ 6 % net increase) from 1962 to 2011 (Fig. 3D).
The SLA, a measure of ELA (Rabatel et al., 2012) and a proxy for the climate change ( McFadden et al., 2011), was continuously moving upward (Fig. 3C) from 5289 m a.s.l. (σ=139) in 1962 to 5471 m a.s.l. (σ=170) in 2011 with the overall vertical shift of 182±8 m (3.7 m a-1). The rate of SLA shift was the highest in recent years with the rate of 10.6±2.9 m a-1 a.s.l. The continuous upward shift of the snowline indicates the negative mass balance.
References: Hooke, R.L. Principles of Glacier Mechanics, Cambridge University Press, p. 429 (2005). Kayastha, R.B. & Harrison, S.P. Annals of Glaciology, 48:93-99 (2008). McFadden, E. M., Ramage, J., and Rodbell, D. T. The Cryosphere, 5(2): 419-430 (2011). Rabatel, A., Bermejo, A., Loarte, E., Soruco, A., Gomez, J., Leonardini, G., Vincent, C., and Sicart, J. E. Journal of Glaciology, 58(212): 1027–
1036 (2012). Scherler, D., Bookhgen, B., and Strecker, M.R. Nature Geoscience, 4(3):156-159 (2011).
