by Torsten Haberzettl, Junbo Wang, Liping Zhu, Gerhard Daut, Volkhard Spieß, Daniel Raul Ariztegui, Natasha Barbolini, Leon J. Clarke, Andrew C.G. Henderson

Almost one third of the world’s population depends on water supplied from rivers originating in the Tibetan Plateau, i.e., mainly monsoonal precipitation. Therefore, how the Asian Monsoon system will develop in the future has socio-economic significance. It is essential to refine future climate change scenarios (e.g., IPCC) and the consequences of a changing climate for ecosystems and human societies by validation against improved knowledge of the timing, duration and intensity of past climatic variability and environmental impact on long geologic time scales and under different boundary conditions. Nam Co, one of the largest and deepest lakes on the Tibetan Plateau, records the temporal development of large-scale atmospheric circulation systems due to its location in the modern monsoon regime. Comprehensive pre-site survey seismic data clearly show an infill of >700 m of well-layered, undisturbed sediments in the central part of the lake, spanning several glacial/interglacial cycles. Short piston-core sediment accumulation rates for the past 24 ka and seismostratigraphic investigations suggest a lake formation of >1 Ma. Nam Co's sedimentary record is an exemplar archive to fill the paleoclimate data gap between two ICDP/IODP transects that will allow comparisons of climate evolution/behaviour on a continental scale. Continuous, high-resolution Nam Co paleoenvironmental records for these long time scales will further allow to study sediment budget changes under varying climatic and tectonic settings and contribute to a better understanding of the Quaternary geomagnetic field, since capturing rates of change and defining dynamic features can only be preserved in the highest resolution records. The high altitude Tibetan Plateau also is unique as it has a high degree of endemism in aquatic organisms that were dependent on persistent water bodies; Nam Co likely served as a dispersal centre, because most other lakes desiccated during dry glacial periods. Therefore, Nam Co is a first-class site to study the links between climate and biological evolution within isolated Tibetan Plateau ecosystems. These studies will also include the unknown geomicrobiological communities and processes in the high altitude lacustrine deep biosphere.

• According to the anticipated long geological record of Nam Co (several glacial-interglacial cycles), drilling and studying this bio-geo-chemical archive with an integrative, interdisciplinary scientific approach will enable us to:
• (1) quantify and qualify the diversity of subsurface life in a high-altitude ecosystem;
• (2) shed light on how aquatic biota, including the deep biosphere, reacted to environmental changes and whether the lake has a high biological buffer capacity to environmental change or tectonic activity;
• (3) provide the first late Quaternary paleomagnetic information from the Tibetan Plateau in a resolution capable of capturing rates of change;
• (4) test the importance of the Siberian flux lobe to reconstructions of the global dipole moment;
• (5) study globally important atmospheric circulation system dynamics, e.g., competing monsoon and Westerly intensity over long time scales;
• (6) determine whether Quaternary climate of the region has been mainly influenced by precession, eccentricity or obliquity;
• (7) study glacial-interglacial cycles including their transitions on the Tibetan Plateau;
• (8) examine paleoenvironmental responses of high-altitude mountain regions to climate variations (e.g., vegetation, glaciers) on long geologic time scales;
• (9) quantify sediment budget changes with respect to climate variations and/or tectonic evolution;
• (10) assign absolute ages to the seismic stratigraphy which will allow to analyse the space-time evolution of faulting over a long period in detail.

Geomicrobiology, Paleoclimate, Paleoenvironment, Paleomagnetism, Tectonics

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