Philipp Schulte

A persistent northern boundary of Indian Summer Monsoon precipitation over Central Asia during the Holocene

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 [~36°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.

Laser diffraction size analysis of loess-paleosol sequences – pretreatment, calculation, interpretation

.............................................................................................................................. ........................ 24 5.1.

Three climatic cycles recorded in a loess-palaeosol sequence at Semlac (Romania) – implications for dust accumulation in the Carpathian Basin and the northern Hemisphere

Semlac is regarded as a key section for the Carpathian Basin because of the good preservation of the fine silt. The site is situated at the Mures River in its lower reaches (Banat region, western Romanian). The more than 10 m thick loess sequence includes four fossil sol-complexes developed in homogenous relatively fine silty loess and dates back to marine isotope stage (MIS) 10. This setting offers possibilities to a) improve the understanding of the type and composition of the lowland loess sequences in the Carpathian Basin for the last interglacial palaeosol complex and beyond, b) reconstruct the temporal evolution of the local loess-palaeosol successions and c) compare the loess of the region to loess-sequences in adjacent areas (Carpathian Basin, Lower Danube) and to dust proxy data in the northern hemisphere. A strikingly sinusoidal course of physical property data in depth and time point to relatively homogenous, quasi-continuous background sedimentation of dust, which are interpreted as resulting from long-range transport. This is in contrast to a commonly observed more glacial-interglacial pattern with sharp boundaries of paleosols

Environmental change indicated by a site-specific grain size ratio - the example of the Semlac loess-paleosol sequence (Romania)

Loess sequences provide important and at least a partial continuous record of Quaternary palaeoenvironmental change. In addition, loess-palaeosol sequences provide valuable information concerning environmental change and climate evolution. It is customary to reconstruct such changes by means of grain sizes ratios. In this study, we calculated an site-specific grain size (GS) ratio (Schulte et al. in review) and compare this ratio with the common U-ratio (Vandenberghe et al.1985) and, in addition, with selected geochemical parameters. As an example we present the Middle to Late Pleistocene loess-paleosol section of Semlac in western Romania (MIS 10 – 1)