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| Titel |
Reconstruction of cryospheric changes in the Maipo and Juncal river basins, central Andes of Chile: an integrative geomorphological approach |
| VerfasserIn |
Samuel U. Nussbaumer, Juan L. García, Gabriel Gómez, Rodrigo M. Vega, Isabelle Gärtner-Roer, Nadine Salzmann |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250130554
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| Publikation (Nr.) |
 EGU/EGU2016-10824.pdf |
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| Zusammenfassung |
| Water in the central Andes (32–38˚ S), a semi-arid mountainous area with elevations over
6000 m asl., is of great importance and a critical resource especially in the dry summer
months. Ice bodies, such as glaciers and rock glaciers (permafrost) in the high mountains,
provide a substantial part of the fresh-water resources but also for intensive economical use
for the lowlands including Santiago metropolitan region, Chile. However the evolution of
these ice bodies since the last deglaciation (i.e., Holocene, last ∼12,000 years), and in
particular during historical times, and their feedback with climate is fairly unknown.
In view of projected climate change, this is striking because it is also unknown
whether these natural resources could be used as sustainable fresh-water source in the
future.
Within the presented project, we develop and apply an integrative geomorphologic
approach to study glaciers and their long-term evolution in the central Andes of Chile. Apart
from glaciers (with variable debris-coverage), rock glaciers have evolved over time as striking
geomorphological landforms in this area. We combine geomorphologic mapping using
remote-sensing and in-situ data with an innovative surface exposure dating technique to
determine the ages of distinct moraine ridges at three study sites in watersheds of the
Santiago region: Juncal Norte, Loma Larga and Nieves Negras glaciers. First results of the
project are presented, including a detailed geomorphological mapping and first analysis of the
landform dynamics.
At all three sites, we distinguished at least three moraine systems of a Holocene putative
age. These prominent moraine belts show that glaciers were at least 5 km longer than at
present. Deglaciation from these ice marginal positions was gradual and complex in
response to the detrital cover on the glaciers. Differences in ice thickness of the main
glaciers in the respective valleys amount to about 100 m. Due to the partial, extensive
debris coverage, the glaciers diminished in thickness without significant retreat of
the glacier front. Another geomorphological feature identified is the separation
of ice facies, from dynamically flowing ice with an active ice front, to dead ice
covered by debris. In parallel, paraglacial processes affect the morphology of the
moraines.
The central Andes are a climatically very sensitive zone between the southern humid and
northern arid Andes, embracing a key location for uncovering past migration of the southern
westerlies, the main driver of local climate variability. Understanding ice variability in the
semi-arid Andes of Chile during past centuries (i.e., pre-instrumental time) can provide the
urgent climate background context before the 20th/21st-century global warming
and from here to assess local atmosphere-cryosphere linkages. This multifarious,
patrimonial natural heritage and geological archive in the central Andes is nowadays
not only threatened by climatic change but also human activities (e.g., mining). |
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