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| Titel |
Mid- to Late Holocene climate development in Central Asia as revealed from multi-proxy analyses of sediments from Lake Son Kol (Kyrgyzstan) |
| VerfasserIn |
Stefan Lauterbach, Peter Dulski, Gerd Gleixner, Sabine Hettler-Riedel, Jens Mingram, Birgit Plessen, Sushma Prasad, Antje Schwalb, Anja Schwarz, Martina Stebich, Roman Witt |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250080160
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| Zusammenfassung |
| A mid-Holocene shift from predominantly wet to significantly drier climate conditions,
attributed to the weakening of the Asian summer monsoon (ASM), is documented in
numerous palaeoclimate records from the monsoon-influenced parts of Asia, e.g. the Tibetan
Plateau and north- and southeastern China. In contrast, Holocene climate development in the
arid regions of mid-latitude Central Asia, located north and northwest of the Tibetan Plateau,
is less well-constrained but supposed to have been influenced by a complex interaction
between the mid-latitude Westerlies and the ASM. Hence, well-dated and highly resolved
palaeoclimate records from Central Asia might provide important information about
spatio-temporal changes in the regional interplay between Westerlies and ASM and thus
aid the understanding of global climate teleconnections. As a part of the project
CADY (Central Asian Climate Dynamics), aiming at reconstructing past climatic and
hydrological variability in Central Asia, several sediment cores were recovered
from alpine Lake Son Kol (41Ë 48’N, 75Ë 12’E, 3016 m a. s. l.) in the Central
Tian Shan of Kyrgyzstan. A radiocarbon-dated sediment sequence of 154.5 cm
length, covering approximately the last 6000 years, was investigated by using a
multi-proxy approach, including sedimentological, (bio)geochemical, isotopic and
micropalaeontological analyses. Preliminary proxy data indicate hydrologically
variable but predominantly wet conditions until ca. 5100 cal. a BP, characterized
by the deposition of finely laminated organic-carbonatic sediments. In contrast
to monsoonal Asia, where a distinct trend towards drier conditions is observed
since the mid-Holocene, the hydrologically variable interval at Lake Son Kol was
apparently followed by an only short-term dry episode between ca. 5100 and 4200 cal. a
BP. This is characterized by a higher δD of the C29 n-alkanes, probably reflecting
increased evapotranspiration. Also pollen, diatom and ostracod data point towards drier
climate conditions. Higher δ15N values during this period may also reflect increased
evaporation but could also be related to dust input of NOx, being in agreement with
high amounts of fine-grained minerogenic material. Further periods of higher δ15N
values and contents of fine-grained minerogenic material occurred at 3600–3000
and 2000–1600 cal. a BP. However, as biogeochemical data indicate no further
distinct dry episodes since about 4200 cal. a BP, these intervals most probably reflect
increased dust deposition. Finally, a trend towards wetter climate conditions can be
observed during the last ca. 1500 years, reflected by high ostracod and diatom diversity
and (bio)geochemical data. The absence of a pronounced drying trend since the
mid-Holocene, as observed in monsoonal Asia, is largely consistent with results from
other regional palaeoclimate records and might reflect the predominant influence
of the strengthening mid-latitude Westerlies on regional climate since this time. |
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