DOCTORAL CANDIDATE
Franka Neumann

SUPERVISORS
Dr Emilie Capron, Université Grenoble Alpes (UGA)
Dr. Frédéric Parrenin, Université Grenoble Alpes (UGA)
Dr. Taryn Noble, University of Tasmania (UTAS)
Dr Joel Pedro, University of Tasmania (UTAS)
Dr. Andy Menking, University of Tasmania (UTAS)

Paleoclimatology, Glaciology, Natural Climate Archives, Dating Methods, Interglacials

Past warm periods (referred to as interglacials) are relevant in the context of the current and future global climate change since they represent a natural laboratory to study processes within the Earth system and to understand the impact of a warm climate on its vulnerable components. Two particularly interesting interglacials are the focus of this project:

• Marine Isotope Stage 11 (MIS 11) occurred about 410 thousand years ago and is one of the most prominent past interglacials. At this time global sea level was 6-13 m higher than today. Thus, MIS 11 is a unique period of climate to investigate the impact of climate warming on the polar ice sheets and ocean circulation.

• Marine Isotope Stage 19 (MIS 19) took place about 780 thousand years ago. During this time, the orbital parameters of Earth and therefore the distribution and amount of solar energy received across the globe matched most closely the configuration of our current warm period. So MIS 19 presents an interesting comparison case to Holocene climate.

Numerous paleoclimatic records from natural archives (e.g. polar ice cores, marine sediments and cave speleothems) cover these periods. To interpret these climate records and identify the sequence of changes in different parts of the world, precise dating is essential. However, it is challenging to achieve that far back in time and it results that most climatic records are attached to large dating uncertainties of several millennia. The current lack of global-scale data compilation relying on a robust temporal framework across MIS 11 and MIS 19 prevents refined characterisation on the sequences of climate changes in different parts of the world. It also hinders the identification of the climate mechanisms and feedbacks during these periods.

In this context, the present PhD project aims at constructing global-scale compilations of surface temperature data covering MIS 11 and MIS 19 to provide the spatio-temporal picture of climate variations across these past warm time intervals and help to progress on our understanding of the forcing processes.

An important task will be to produce a common and robust chronology between the selected paleoclimatic records using regionally specific dating strategies. For that purpose, a probabilistic dating model will be used. This tool enables to date jointly numerous climate records from different archives, accounting for various types of chronological constraints and providing also quantitative estimates of the uncertainties attached to the produced age scales. This dating effort will be essential to characterize eventually the amplitudes of the climate warming and its spatial and temporal evolution. More broadly and by linking other climatic records to the temperature patterns, this work will help determine the sequences of events between climate, ocean circulation and polar ice sheets.

The new results will be used to evaluate paleoclimate Earth System Model simulations in order to identify with those physics-based tools the climate forcing and feedbacks at play during interglacials. Overall, these results will provide (i) a better understanding of the impacts of a warm climate on the vulnerable components of the Earth system and (ii) testbeds for evaluating how well Earth System Models simulate warm climates, contributing to improving future climate projections.