TY  - JOUR
A1  - Wolff, Christian Michael
A1  - Kristen-Jenny, Iris
A1  - Schettler, Georg
A1  - Plessen, Birgit
A1  - Meyer, Hanno
A1  - Dulski, Peter
A1  - Naumann, Rudolf
A1  - Brauer, Achim
A1  - Verschuren, Dirk
A1  - Haug, Gerald H.
T1  - Modern seasonality in Lake Challa (Kenya/Tanzania) and its sedimentary documentation in recent lake sediments
JF  - Limnology and oceanography
N2  - From November 2006 to January 2010, a sediment trap that was cleared monthly was deployed in Lake Challa, a deep stratified freshwater lake on the eastern slope of Mt. Kilimanjaro in southern Kenya. Geochemical data from sediment trap samples were compared with a broad range of limnological and meteorological parameters to characterize the effect of single parameters on productivity and sedimentation processes in the crater basin. During the southern hemisphere summer (November-March), when the water temperature is high and the lake is biologically productive (nondiatom algae), calcite predominated in the sediment trap samples. During the "long rain" season (March-May) a small amount of organic matter and lithogenic material caused by rainfall appeared. This was followed by the cool and windy months of the southern hemisphere winter (June-October) when diatoms were the main component, indicating a diatom bloom initiated by improvement of nutrient availability related to upwelling processes. The sediment trap data support the hypothesis that the light-dark lamination couplets, which are abundant in Lake Challa cores, reflect seasonal delivery to the sediments of diatom-rich particulates during the windy months and diatom-poor material during the wet season. However, interannual and spatial variability in upwelling and productivity patterns, as well as El Nino-Southern Oscillation (ENSO)-related rainfall and drought cycles, exert a strong influence on the magnitude and geochemical composition of particle export to the hypolimnion of Lake Challa.
Y1  - 2014
U6  - https://doi.org/10.4319/lo.2014.59.5.1621
SN  - 0024-3590
SN  - 1939-5590
VL  - 59
IS  - 5
SP  - 1621
EP  - 1636
PB  - Wiley
CY  - Waco
ER  - 
TY  - JOUR
A1  - Lauterbach, Stefan
A1  - Witt, Roman
A1  - Plessen, Birgit
A1  - Dulski, Peter
A1  - Prasad, Sushma
A1  - Mingram, Jens
A1  - Gleixner, Gerd
A1  - Hettler-Riedel, Sabine
A1  - Stebich, Martina
A1  - Schnetger, Bernhard
A1  - Schwalb, Antje
A1  - Schwarz, Anja
T1  - Climatic imprint of the mid-latitude Westerlies in the Central Tian Shan of Kyrgyzstan and teleconnections to North Atlantic climate variability during the last 6000 years
JF  - The Holocene : an interdisciplinary journal focusing on recent environmental change
N2  - In general, a moderate drying trend is observed in mid-latitude arid Central Asia since the Mid-Holocene, attributed to the progressively weakening influence of the mid-latitude Westerlies on regional climate. However, as the spatio-temporal pattern of this development and the underlying climatic mechanisms are yet not fully understood, new high-resolution paleoclimate records from this region are needed. Within this study, a sediment core from Lake Son Kol (Central Kyrgyzstan) was investigated using sedimentological, (bio) geochemical, isotopic, and palynological analyses, aiming at reconstructing regional climate development during the last 6000 years. Biogeochemical data, mainly reflecting summer moisture conditions, indicate predominantly wet conditions until 4950 cal. yr BP, succeeded by a pronounced dry interval between 4950 and 3900 cal. yr BP. In the following, a return to wet conditions and a subsequent moderate drying trend until present times are observed. This is consistent with other regional paleoclimate records and likely reflects the gradual Late Holocene diminishment of the amount of summer moisture provided by the mid-latitude Westerlies. However, climate impact of the Westerlies was apparently not only restricted to the summer season but also significant during winter as indicated by recurrent episodes of enhanced allochthonous input through snowmelt, occurring before 6000 cal. yr BP and at 5100-4350, 3450-2850, and 1900-1500 cal. yr BP. The distinct similar to 1500year periodicity of these episodes of increased winter precipitation in Central Kyrgyzstan resembles similar cyclicities observed in paleoclimate records around the North Atlantic, likely indicating a hemispheric-scale climatic teleconnection and an impact of North Atlantic Oscillation (NAO) variability in Central Asia.
KW  - Central Asia
KW  - climate
KW  - Holocene
KW  - lake sediments
KW  - mid-latitude Westerlies
KW  - NAO
Y1  - 2014
U6  - https://doi.org/10.1177/0959683614534741
SN  - 0959-6836
SN  - 1477-0911
VL  - 24
IS  - 8
SP  - 970
EP  - 984
PB  - Sage Publ.
CY  - London
ER  -