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| Titel |
The Mercedario ice core – an excellent archive for ENSO reconstruction |
| VerfasserIn |
Theo Jenk, Anita Graesslin-Ciric, Leonhard Tobler, Heinz Gäggeler, Uwe Morgenstern, Gino Casassa, Martin Lüthi, Jochen Schmitt, Anja Eichler, Margit Schwikowski |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250109467
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| Publikation (Nr.) |
 EGU/EGU2015-9374.pdf |
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| Zusammenfassung |
| South America is a key region for the understanding of climate dynamics in the Southern
Hemisphere such as the El Niño-Southern Oscillation (ENSO). A direct ENSO signal can be
expected to be preserved in glaciers located between 28 and 35Ë S, as the amount of winter
precipitation in Central Chile is significantly correlated to the Southern Oscillation
Index.
We will present new results from a 104 m long ice core drilled in 2005 at La Ollada
glacier on Cerro Mercedario located in the Central Argentinean Andes (31Ë 58‘S, 70Ë 07‘W,
6100 m asl.). Measured borehole temperatures, ranging from -16.7 Ë C at 104 m depth to
-18.5 Ë C at 10 m below surface, are the lowest englacial temperatures that have been
measured in Andean glaciers to date which is reflected in the complete absence of melt
features in the core. Another rather unique characteristic of this core is the fact that the
oxygen isotopic ratios of water (δ18O) do not show seasonal variation. The core was dated
using a combination of independent tools such as (1) annual layer counting mainly based on
dust related chemical impurities, (2) nuclear dating with 210Pb, 14C of particulate
carbon (i.e. OC fraction) and tritium, (3) measurements of trace gases (i.e. CH4,
N2O and CFCs) trapped in the ice enclosed air bubbles and (4) 2D glacier flow
modelling. This allowed obtaining an accurate chronology for the last 350 years. The
mean annual accumulation rate of the site was determined with 0.27 ± 0.03 m
w.eq., principally allowing seasonal to sub-seasonal resolution. We will discuss
transport and sources of chemical impurities and the relation between them, δ18O and
tropical eastern Pacific sea surface temperatures (SST). As expected for the site, we
find δ18O and most chemical impurities to be strongly modulated by the ENSO
allowing presentation of a new proxy based ENSO reconstruction back to ~1700 AD. |
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