decade in the tropical Andes of Bolivia, Peru and Ecuador
by the «Institut de Recherche pour le Développement» (IRD)
and its local partners. Observations indicate that glaciers
have retreated dramatically since the recent decades.
(more than 4800 m asl) and are mostly temperate below
6000 m asl. Despite their small size (generally less than
5 km
Their high sensitivity to climate makes them particularly suit-
able to document changes occurring in the low/mid tropos-
phere at the infra- and the multi-decadal time scale as well.
For analysing the link existing between glacier and climate, a
permanent observation network has been installed through-
out the Andean chain involving glaciers from the nearby
equator (the so-called «inner tropics») to the 16°S (the
«outer tropics») (figure 1). Two of these glaciers, Zongo
(Bolivia) and Antizana (Ecuador), are part of the ORE
(Observatoire de Recherche pour l'Environnement) GLACIO-
CLIM network (France), which includes other monitored
glaciers in the Alps and in the Antarctica. We present a short
overview of results concerning Chacaltaya (Bolivia), a typical
small-sized glacier (0.05 km
scale since 1991. Chacaltaya is representative of many glaci-
ers of the central Andes whose recession has been particu-
larly dramatic since the 1980s.
accumulation (amount of solid precipitation which incorpo-
rates the ice mass) and the ablation (melting + sublimation),
which removes mass in liquid and vapour forms. Unlike mid
latitude glaciers where an accumulation and an ablation
season alternatively occur, ablation processes are important
year round in the Tropics, with a clear maximum during the
October-April summer season in Bolivia and Peru. Note that
in the Tropics the summer months include also the wet sea-
son. Due to the fact that ablation and accumulation peak at
the same time, any alteration of the precipitation regime
provokes an enhanced response of glaciers. This explains
why glaciers are very sensitive to the climate variability, par-
ticularly if a deficit of precipitation occurs when temperature
of atmosphere is unusually warm.
the 10-year period 1991-2001. The seasonality is strong
and portrays a period of 7 months from October to April dur-
ing what mass balance is highly variable. These months
account for 98 % of the year mass balance variance. During
sur les dernières décennies montrent un recul impor-
tant de l'ensemble des glaciers. Le réseau d'observation
mis en place depuis une décennie par l'Institut de
Recherche et Développement et ses partenaires andins
(voir carte) permet de mieux comprendre la relation
entre le recul de glaciers et le climat ainsi que
l'influence de l'ENSO (El Niño South Oscillation).
une altitude élevée (plus de 4800 m), et sont en général tem-
pérés en dessous de 6000 m. Bien que de petite taille (moins
où de longues périodes de sécheresse existent (voir encarts 1
et 2). Ces glaciers qui réagissent rapidement aux variations
climatiques sont particulièrement intéressants à étudier pour
retracer l'évolution du climat. Nous présentons ici leur évolu-
tion sur les récentes décennies. Un réseau d'observation per-
manent a été installé en différents points de la chaîne des
Andes, allant de l'équateur aux tropiques (16°S) (figure 1).
cales par l'IRD et ses partenaires. Deux de ces glaciers (Antizana
et Zongo) font partie du réseau GLACIOCLIM, réseau qui com-
prend également des glaciers des Alpes et de l'Antarctique (ORE-
Observatoire de Recherche pour l'Environnement).
South-American partners