TY  - JOUR
A1  - Ramisch, Arne
A1  - Lockot, Gregori
A1  - Haberzettl, Torsten
A1  - Hartmann, Kai
A1  - Kuhn, Gerhard
A1  - Lehmkuhl, Frank
A1  - Schimpf, Stefan
A1  - Schulte, Philipp
A1  - Stauch, Georg
A1  - Wang, Rong
A1  - Wunnemann, Bernd
A1  - Yan, Dada
A1  - Zhang, Yongzhan
A1  - Diekmann, Bernhard
T1  - A persistent northern boundary of Indian Summer Monsoon precipitation over Central Asia during the Holocene
JF  - Scientific reports
N2  - Extra-tropical circulation systems impede poleward moisture advection by the Indian Summer Monsoon. In this context, the Himalayan range is believed to insulate the south Asian circulation from extra-tropical influences and to delineate the northern extent of the Indian Summer Monsoon in central Asia. Paleoclimatic evidence, however, suggests increased moisture availability in the Early Holocene north of the Himalayan range which is attributed to an intensification of the Indian Summer Monsoon. Nevertheless, mechanisms leading to a surpassing of the Himalayan range and the northern maximum extent of summer monsoonal influence remain unknown. Here we show that the Kunlun barrier on the northern Tibetan Plateau [similar to 36 degrees N] delimits Indian Summer Monsoon precipitation during the Holocene. The presence of the barrier relocates the insulation effect 1,000 km further north, allowing a continental low intensity branch of the Indian Summer Monsoon which is persistent throughout the Holocene. Precipitation intensities at its northern extent seem to be driven by differentiated solar heating of the Northern Hemisphere indicating dependency on energy-gradients rather than absolute radiation intensities. The identified spatial constraints of monsoonal precipitation will facilitate the prediction of future monsoonal precipitation patterns in Central Asia under varying climatic conditions.
Y1  - 2016
U6  - https://doi.org/10.1038/srep25791
SN  - 2045-2322
VL  - 6
SP  - 596
EP  - 633
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Wang, Rong
A1  - Biskaborn, Boris
A1  - Ramisch, Arne
A1  - Ren, Jian
A1  - Zhang, Yongzhan
A1  - Gersonde, Rainer
A1  - Diekmann, Bernhard
T1  - Modern modes of provenance and dispersal of terrigenous sediments in the North Pacific and Bering Sea: implications and perspectives for palaeoenvironmental reconstructions
JF  - Geo-marine letters : an international journal of marine geology
N2  - During expedition 202 aboard the RV Sonne in 2009, 39 seafloor surface sediment sites were sampled over a wide sector of the North Pacific and adjoining Bering Sea. The data served to infer land-ocean linkages of terrigenous sediment supply in terms of major sources and modes of sediment transport within an over-regional context. This is based on an integrated approach dealing with grain-size analysis, bulk mineralogy and clay mineralogy in combination with statistical data evaluation (end-member modelling of grain-size data, fuzzy cluster analysis of mineralogical data). The findings on clay mineralogy served to update those of earlier work extracted from the literature. Today, two processes of terrigenous sediment supply prevail in the study area: far-distance aeolian sediment supply to the pelagic North Pacific, and hemipelagic sediment dispersal from nearby land sources via ocean currents along the continental margins and island arcs. Aeolian particles show the finest grain sizes (clay and fine silt), whereas hemipelagic sediments have high abundances of coarse silt. Exposed sites on seamounts and the continental slope are partly swept by strong currents, leading to residual enrichment of fine sand. Four sediment sources can be distinguished on the basis of distinct index minerals revealed by statistical data analysis: dust plumes from central Asia (quartz, illite), altered materials from the volcanic regions of Kamchatka and the Aleutian Arc (smectite), detritus from the Alaskan Cordillera (chlorite, hornblende), and fluvial detritus from far-eastern Siberia and the Alaska mainland (quartz, feldspar, illite). These findings confirm those of former studies but considerably expand the geographic range of this suite of proxies as far south as 39A degrees N in the open North Pacific. The present integrated methodological approach proved useful in identifying the major modern processes of terrigenous sediment supply to the study region. This aspect deserves attention in the selection of sediment core sites for future palaeoenvironmental reconstructions related to aeolian and glacial dynamics, as well as the recognition of palaeo-ocean circulation patterns in general.
Y1  - 2016
U6  - https://doi.org/10.1007/s00367-016-0445-7
SN  - 0276-0460
SN  - 1432-1157
VL  - 36
SP  - 259
EP  - 270
PB  - Springer
CY  - New York
ER  -