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| Titel |
Late Holocene environmental reconstruction of Lake Issyk-Kul (Rep. Kyrgyzstan) |
| VerfasserIn |
Santiago Giralt, Armand Hernández, Alberto Sáez, Juan José Pueyo, Núria Cañellas-Boltà, Olga Margalef |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250037950
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| Zusammenfassung |
| Lake Issyk-Kul is an endorheic mountain lake located at 1608 m a.s.l., in the northern Tien
Shan ranges, in the Republic of Kyrgyzstan, Central Asia. It has an area of 6236 km2, a
length of 180 km, a width of 60 km, and a maximum depth of 668 m making it the fifth
deepest lake in the world. The lake is monomictic, brackish (6 g/l), oligotrophic to
ultra-oligotrophic (2 – 3.8 μg/l of phosphorous), and it has high values of dissolved oxygen
(6.5 – 7.5 mg/l at the bottom of the lake).
In August 2000, a gravity 150 cm long core (C142a, 42°34’312” N - 77°20’030” E) was
recovered at 150 m of water depth at the central northern shore of the lake. This core was
characterized using X-Ray Fluorescence (XRF) core scanner (measurements every 300 μm),
X-Ray Diffraction (XRD) every 3 mm, and elemental (TC and TN) and isotopic composition
(δ13C and δ15N) of bulk organic matter every centimeter. The preliminary chronological
framework was constructed with 4 AMS 14C dates. Statistical analyses (clusters, Principal
Component (PCA) and Redundant (RDA) Analyses) were employed to identify and isolate
the environmental forcings that have triggered the input, distribution and deposition of
sediments within the lake.
The core records the last ca. 4,000 cal. yrs BP and, during this time its primary productivity
has steadily increased (higher values of TC and TN). δ13C and δ15N values suggest that the
main primary producer are blue-green algae. The last ca. 100 years, the primary productivity
has experienced a dramatic increase. Furthermore, PCA on XRF data also highlights that
more than the 50% of the total variance is related to changes in primary productivity (the first
eigenvector (EV) is tied by the opposition of the terrigenous - organic matter geochemical
indicators). This EV shows that the primary productivity oscillated at decadal and centennial
frequencies.
The main forcing of these primary productivity fluctuations seems to be temperature changes
linked to both solar activity (11 years Schwabe cycles) and anthropogenic global warming. |
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