The School of Geography, Politics and Sociology

Student Profiles

Sonja Felder

Project title: Mid-Pleistocene transition in the Asian monsoon

Supervisors: Dr Andrew Henderson, Professor Thomas Wagner and Professor Melanie Leng (British Geological Survey)

My PhD project (through IAPETUS, a Doctoral Training Partnership between the University of Newcastle and the British Geological Survey) focusses on investigating the possible link between the East Asian Summer Monsoon (EASM) and the changes in the climate cyclicity during the Mid-Pleistocene Transition (MPT). This PhD will provide valuable information on the past changes of the EASM. And the more we understand about past changes, the better we can predict future changes. This is vital research as one-third of the world’s population rely on freshwater resources impacted by fluctuations in the EASM.

In earth’s history there have always been natural climate changes. The climate switches between cold periods with large ice caps on the Poles, so called “glacials” and warm periods with small or no ice caps on the Poles, so called “interglacials”. Currently, as we enjoy warm summers (well, not necessarily in the UK) we live in an interglacial period.

The changes between glacial and interglacial periods are cyclical. These cyclical climate changes happen because of changes in the earth’s position in the universe, changes in so called “orbital parameters”. These are, for example, how close the earth is to the sun during summer (precession) or how strongly the earth is tilted towards the sun (obliquity). About one million years ago there was a major switch in the timing of the cyclicity from 41,000 year cycles to 100,000 year cycles; this period is called Mid-Pleistocene Transition (MPT). What caused the MPT is one question I will be trying to tackle.

Specifically I will be analysing cores of marine sediments which were collected from the Japan Sea by the Integrated Ocean Drilling Program (IODP), a major international scientific ocean drilling programme (IODP Exp. 346 “Asian monsoon”). The Japan Sea is nowadays strongly influenced by the EASM: the rain/ freshwater is transported across the continent to the coast via river systems, such as the Yangtze or the Yellow river. When reaching the ocean the freshwater lowers the salinity of the ocean surface waters. It is then transported by ocean currents into the Japan Sea, lowering the salinity drastically, as the Japan Sea has little connection to the world´s oceans.

The effect of the EASM on the Japan Sea salinity is especially strong during glacial periods. - So during my PhD project I will need to think about both the effects of EASM changes in the oceans and on the continents. To investigate these two systems I will apply a multi-proxy approach, applying various methods, one of which is to measure the chemistry of foraminifera shells. Their chemistry is dependent on parameters such as temperature and salinity of the ocean water, and will therefore give valuable information about past changes in the EASM.