From water molecules to climate, making sense of Greenland and Antarctic ice core records

The Research School of Earth Sciences is delighted to announce that the 2017 Jaeger-Hales lecture will be given by Dr Valérie Masson-Delmotte. The Jaeger-Hales Lecture is a prestigious biennial event in the School calendar that honours the foundational contributions of Professors Jaeger and Hales. The lecture is delivered by a highly distinguished scientist in the field of geosciences.

Dr Masson-Delmotte is a senior scientist from Laboratoire des Sciences du Climat et de l'Environnement, Institut Pierre Simon Laplace. She is also co-chair of the Intergovernmental Panel on Climate Change (IPCC) Working Group I, which will assess the physical scientific basis of the climate system and climate change for the 6thassessment cycle. Dr Masson-Delmotte is active in scientific outreach for children and for the general public and has contributed to several books on climate change issues. Her research has been recognized by many prizes, including the European Union Descartes Prize for the EPICA project, 2008; Women scientist Irène Joliot Curie Prize, 2013; Tinker-Muse Prize for science and policy in Antarctica, 2015; and Thomson Highly Cited Researcher since 2014.

The 2017 Jaeger-Hales lecture will be held from 4-5pm at the Finkel Lecture Theatre (building 131). It will be followed by refreshements at the Research School of Earth Sciences (building 142). Please register by 18th July to attend the event.

The abstract of Dr Valérie Masson-Delmotte's lecture follows:

From water molecules to climate, making sense of Greenland and Antarctic ice core records

Ice cores provide a wealth of insights into past climatic and environmental changes. Obtaining information on past polar temperature changes is important to document climate variations beyond scarce instrumental records, and to test our quantitative understanding of past climate variations.
Water stable isotope ratios in ice core records have commonly been used as qualitative proxies for past changes in polar temperature and moisture source characteristics, but extracting quantitative signals is a major challenge. Initially, spatial relationships between surface snow isotopic composition and surface temperature were used to establish a modern "isotopic thermometer". Simulations performed with climate models equipped with water stable isotopes were subsequently used to assess the validity of this "isotopic thermometer calibration" for different climate states (e.g. glacial, interglacial), assuming that the ice core signal is a precipitation weighted deposition record.
I will first present recent findings based on new capability to monitor water vapour isotopic composition in the North Atlantic / Greenland and several Antarctic regions. These new datasets challenge the classical interpretation of ice core records as just precipitation-weighted signals. Moreover, they challenge the ability of atmospheric models equipped with water stable isotopes to fully resolve the initial marine boundary layer isotopic composition spatial patterns. These are key limitations to our quantitative understanding of ice core signals.
I will then illustrate major results obtained from water stable isotope records in Greenland and Antarctic ice cores at three time scales : (i) the documentation of polar climate variability during the last thousand years, and the challenge to separate intrinsic, spontaneous climate variability from the response to natural forcings; (ii) the bipolar structure of abrupt changes during the last climatic cycle, and its implications for the interplay between reorganizations in ocean circulation, sea ice extent and polar climate ; (iii) polar temperature trends during the current and last interglacial period, and their relevance for the assessment of ice sheet vulnerability. Over these three time scales, I will stress why quantifying past changes is relevant for the evaluation of climate models and for the assessment of future risks.