Can the snowline be used as an indicator of the equilibrium-line and mass balance for glaciers in the outer tropics?

Can the snowline be used as an indicator of the

equilibrium-line and mass balance for glaciers in

the outer tropics?

Dr. Antoine Rabatel, Ing. E. Loarte, Dr. A. Soruco, Ing. J. Gomez

August 28, 2009

Ph : B. Pouyaud

Huaraz, 1 - 4 de julio 2013

Laboratorio Mixto Internacional GREAT – ICE

Servicio de Observacion GLACIOCLIM

Dr. A. Rabatel, LMI Great Ice, 1-4 julio 2013

Context

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1) Context & background

2) Validation of the method for the outer tropical Andes

3) Application to the Cordillera Real - Bolivia

“The World Glacier Inventory contains information for over 100,000 glaciers through out the

world. Parameters within the inventory include: geographic location, area, length, orientation,

elevation, and classification of morphological type and moraines.”

World Glacier Inventory website

Context

2 / 18





“Basic information on specific net balance, cumulative specific balance, accumulation area

ratio and equilibrium line altitude is given for 111 glaciers.”

GMBB #10, WGMS-Zurich, 2009





Context

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0.1 % of the glaciers are monitored at worldscale

Limitation for the study of:

- glacier sensitivity to climate/morphological parameters

- glacier contribution to hydrological systems












Context

2 / 18

Remote-sensing is an efficient tool to realize the

measurement of glaciological parameters at a regional scale

0.1 % of the glaciers are monitored at worldscale

Limitation for the study of:

- glacier sensitivity to climate/morphological parameters

- glacier contribution to hydrological systems












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Background

Equilibrium line, MB = 0

Acc > Ab

Saint Sorlin Glacier (French Alps)

For mid-latitude glaciers : end-of-summer snowline = equilibrium line

Ab > Acc

The snowline is easy to identify on optical satellite images





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Background





4 / 18

Background





Background





BUT !

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5 / 18

Background





BUT !

Validation of the method for the outer tropical Andes

Tropical climate generates a sequence of

accumulation and ablation processes all

year round that differs from that of mid-

latitude glaciers.

6 / 18





Outer tropical Andes (Peru – Bolivia)

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Ph : B. Pouyaud

Monthly mass balance measurements on

the glacier tongue (5250 – 4850 m a.s.l.)

ELAi for each year i

Mass balance gradient

Zongo Glacier (Bolivia, 16 S)Monitored since 1991

IRD-France and UMSA-Bolivia0

z

b





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Ph : B. Pouyaud

Monthly mass balance measurements on

the glacier tongue (up to 4850 m a.s.l.)

ELAi for each year i

Mass balance gradient

Artesonraju Glacier (Peru, 9 S)Monitored since 2000

UGRH - ANA

z

b





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List of the used satellite images

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How to detect the snowline on satellite images?

Test of different combinations of bands and band ratios applied on Landsat-5 image

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Comparison of the highest remote-sensed SLA for each year and the annual ELA

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Comparison of the highest remote-sensed SLA for each year and the annual ELA

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Reconstruction of glacier surface mass balance from the SLA





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z

bSLASLAtb ieq )()(

Snowline altitude for each year i of the study

period, computed from satellite images

Snowline altitude representative of a steady state of

the glacier





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Mass balance gradient derived

from field data, valid at a regional

scalez

bSLASLAtb ieq )()(






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z

bSLASLAtb ieq )()(

n

ieqzb

BSLA

nSLA

1 /

1with:






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Mean mass balance of the glacier over

the study period computed by DEM

difference

z

bSLASLAtb ieq )()(

n

ieqzb

BSLA

nSLA

1 /

1with:






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11 glaciers where is available.

Soruco et al., 2009

)0697(B






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Zongo Glacier (Bolivia, 16 S)



Comparison between mass balance

derived from SLA measurements

and field measurements




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Good consistency between

the glaciers

ENSO is the main forcing of

the interannual variability

El Niño

La Niña






Important difference:

between -3.4 m w.e. and

-21.3 m w.e.

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Application to the Cordillera Real - Bolivia

Morphological parameters are the

main factors controlling the

difference in volume loss between

the studied glaciers

circles = glaciers with a mean elavation > 5150 m a.s.l.

triangles = glaciers with a mean elavation < 5150 m a.s.l.

17 / 18Dr. A. Rabatel, LMI Great Ice, 1-4 julio 2013

Gracias!See also the poster by Ing. Edwin Loarte et al. for an application in the Cordillera Blanca

Rabatel et al., 2005. J. of Glaciology, 51(175), 539-546



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Can the snowline be used as an indicator of the equilibrium-line and mass balance for glaciers in the outer tropics?