Deepest Lake Drilling on the Tibetan Plateau Successfully Completed

Analysis of lake sediment cores from Nam Co will illuminate paleoenvironmental changes on continental-scale, enabling predictions of future climate changes and its consequences.

An international research team from Germany, China, Switzerland, and the United Kingdom successfully completed over two months of drilling in Nam Co, one of the largest and deepest lakes on the Tibetan Plateau. As a remote location where monsoon systems meet westerly winds, it is an ideal site for studying long-term climate changes. Moreover, given that nearly one-third of the world's population relies on water from the Tibetan Plateau, understanding the region’s hydrological development is highly important. By learning how past climate variations have impacted the environment in both long- and short- geological timescales, researchers can better define the parameters and consequences of future climate change.

At an altitude of over 4700 meters, Nam Co is a physically challenging place for research. To get accustomed to the thin air, researchers spent a few days at the Institute of Tibetan Plateau Research in Lhasa before the start of drilling. But the challenges didn’t end there.

“My tasks in the campaign involved shore laboratory work, like pore water sampling and subsampling core catchers,” says Olga Schmitz, PhD candidate in the Domestication and Anthropogenic Evolution research group at the Max Planck Institute of Geoanthropology and Palaeontology working group of the Friedrich Schiller University (FSU) Jena. “Later I changed to 12-hour night shifts of sediment sampling on a floating drilling platform. As the monsoon was becoming stronger and nights more difficult for drillers, one time we had such a strong swell that the transport boat could not pick us up for more than 10 hours, making our shift 20 hours long, instead of 12. Other than being quite challenging at times, the fieldwork was an incredible life experience with stunning nature around.”

Altogether the team collected almost 1000 meters of sediment samples, with the longest continuous borehole reaching a depth of 510 meters – the deepest lake core which has ever been drilled on the Tibetan Plateau. The sediment cores now available from these drillings will be sliced, meticulously studied and analyzed by international scientists from the NamCore project within the International Continental Scientific Drilling Program (ICDP) in the coming years.

"The deep coring is a great opportunity to decipher the changes of palaeoclimate on the Tibetan Plateau for the last hundreds of thousands of years and to understand the evolution of high-altitude ecosystems and its highly adapted endemic species during the Ice Age," says Prof. Dr. Peter Frenzel, micropalaeontologist from FSU Jena.

In Jena, micropaleontological investigations will be conducted by Schmitz and Frenzel and mineralogical analyses by Dr. Gerhard Daut, all three from FSU Jena. Their goal is to gain new insights into past climate conditions by examining the distributions of ostracods, very small crustaceans with a calcitic shell, which live in almost all aquatic environments. Frenzel and Daut have worked in the Tibetan Plateau for many years, with repeating expeditions.  

“These ostracod microfossils, found in the sediment of the cores, are valuable proxies helping us to reconstruct past environments based on their abundances, species compositions, diversity, isotopic signatures and morphology of their shells, such as salinity, water level, temperature, anthropogenic impacts. Even in geoarcheology there are many applications with ostracods, like provenance studies,” says Schmitz.

“40 years ago, scientists developed the theory that Tibet was completely covered by an ice cap during the last glacial period. This was still partly valid when we started working there 20 years ago. But, there were only very few studies and there was still not even an idea of the water depth of lake Nam Co. Nowadays theories dealing with the Tibetan Plateau are completely different, with almost no glaciers but dry lake basins at the glacial peaks and megalakes that were established at the onset of the monsoons. Now, 20 years later, I think there are several hundred publications of the Nam Co area, dealing with different aspects ranging from modern limnology to all types of paleolimnological aspects, and studies on the biosphere, atmosphere, glacial influence, permafrost, tectonic, field based and remote sensing studies, human impact and much, much more. The ICDP drilling is so far just the top of the iceberg,” says Daut, geoscientist from FSU Jena.

The analysis of ostracods in Germany will start with material from core catchers – “left over” sediment material from between core liners. This will allow a first look into the faunal composition and paleoecological indications, providing the basis for Schmitz’s postdoctoral research proposal. In a few months the first core liners will be opened in Beijing, providing material for further ostracod analysis. Other groups will study methane, sedimentary DNA, Optically Stimulated Luminescence, pore water composition and more.

“Dating will help us to contextualize results and developments over time while the sheer amount of sediment samples provides enough material to keep many scientists busy for years,” says Schmitz.

One of the main reasons for the ICDP’s operations in Nam Co is the lake’s central location on the Tibetan Plateau. It will fill a gap in long-term paleoclimate data, allowing continental-scale paleo-climate comparisons. The lake has also likely been a dispersal center for endemic organisms, while other lakes dried up during glacial periods. In this way, Nam Co offers a unique opportunity to study the link between geological and biological evolution in isolated ecosystems.

Because of its potential for interdisciplinary studies, the project involves numerous research institutes and universities, with five principal investigators and Prof. Torsten Haberzettl from the University of Greifswald as the leading principal investigator. The drilling spots were previously determined based on seismic surveys funded by the German Research Foundation (DFG) while the drilling itself was funded by ICDP, with additional funds from the DFG, the Swiss National Science Foundation, the UK funding organization NERC and Chinese cooperation partners from the Institute of Tibetan Plateau Research (Chinese Academy of Sciences) totaling 3.2 million USD.