What drives monsoon climate and droughts over East Asia and the Western Pacific Ocean?

Dr Chuang Xuan, Dr Anya Crocker, Prof Paul Wilson
Rationale: 

The East Asian monsoon (EAM) is a major component of the global climate system and vital to billions of people. What determines the strength of this system? New records of past variability of the monsoonal system are needed to contextualize predictions of future climate change. Critically, existing geological data provide conflicting evidence on the underlying driving mechanisms of floods and droughts, which are still debated. Geochemical records from caves in China reveal climate cycles paced at ~20 thousand-year intervals, suggesting EAM primarily responds to long-term changes in solar radiation, but other records suggest that greenhouse gas- and high-latitude ice sheet forcing are more important. An over-arching problem is a paucity of high-quality records that cover transitions between major climate states.
 

You will study marine sediment cores from regions sensitive to changes of climate conditions in East Asia, including the Japan Sea, the East China Sea, and the North Pacific Ocean. You will build and exploit long, well-dated, and high-resolution records of wind-blown dust from Asia and EAM variabilities. These records will cover key global climate states/transitions including the mid-Pleistocene transition (~1 million years ago, Ma), the late-Pliocene intensification of Northern Hemisphere glaciation (~2.5 Ma), and warmer-than-present periods such as the mid-Pliocene (~3.5 Ma) and mid-Miocene (~16 Ma).

 

Methodology: 

A suite of magnetic, geochemical, and physical property data will be produced for a selection of sediment cores obtained by scientific ocean drilling. Compared with terrestrial archives, marine sediments are typically more continuous, more suited to modern dating methods, and are sensitive to both land and ocean processes. High-resolution age models of the cores will be constructed by combining existing and new data including magnetic and stable isotope stratigraphy, astrochronology, and tephrochronology where possible.

Wind-blown dust content in the cores, a direct record of Asian aridity and wind history, will be reconstructed using a combination of environmental magnetism and X-ray fluorescence (XRF) core scanning. Sediment colour spectrometry, corrected stable isotope data, and sediment magnetic properties will be used to monitor EAM variability. Radiogenic isotopes, grain size distributions, and rock magnetic analyses will also be conducted on selected samples to study sources of dust and geographical extent of aridity over time. The combined records will be compared to other published global and regional climate records to develop a better understanding of the dynamics and causes of Asian aridity and EAM variability associated with major transitions in global climate states.

 

Location: 
University of Southampton
Training: 

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted in the School of Ocean and Earth Science.

Through the project, there will be opportunities to work together with a large group of international scientists collaborating with the supervisory team and gain experience sampling sediment cores at the overseas International Ocean Discovery Program (IODP) Core Repositories (Europe, USA & Japan). Travel to international scientific meetings to present project results is encouraged and supported. Project-specific training includes:

  • Sampling and working with scientific ocean drilling cores and datasets
  • State-of-the-art analytical training in world-class laboratory facilities
  • Stratigraphic correlation and dating of marine sediment cores
  • Palaeomagnetic, and rock and environmental magnetic analyses of sediment samples
  • Stable and radiogenic isotope geochemistry and X-ray fluorescence core scanning
  • Integration and interpretation of multi-proxy datasets from marine sediment cores for palaeoceanographic and palaeoclimate reconstructions
  • Managing and processing large volumes of research data and application of advanced quantitative analysis techniques such as signal correlation and tuning, spectral analysis, and time-series analysis
Eligibility & Funding Details: 

Please see https://inspire-dtp.ac.uk/how-apply for details.

Background Reading: 

Cheng, H., Edwards, R. L., Sinha, A., Spötl, C., Yi, L., Chen, S., Zhang, H. (2016). The Asian monsoon over the past 640,000 years and ice age terminations. Nature, 534(7609), 640-646. doi:10.1038/nature18591

Clemens, S. C., Holbourn, A., Kubota, Y., Lee, K. E., Liu, Z., Chen, G., Nelson, A., and Fox-Kemper, B. (2018). Precession-band variance missing from East Asian monsoon runoff: Nature Communications, v. 9, no. 1, p. 3364.

An Z., Kutzbach, J. E., Prell, W. L., & Porter, S. C. (2001). Evolution of Asian monsoons and phased uplift of the Himalaya–Tibetan plateau since Late Miocene times. Nature, 411(6833), 62-66.