ESR 13 – Coupled Atmosphere-Ocean Modelling: Interpreting Antarctic Deep Ice with Water Tracing and Water Isotopes
Early stage researcher: Qinggang Gao (UKRI-BAS, UK)
Supervisors: L. Sime (UKRI-BAS, UK), E. Capron (CNRS-IGE, FR)
Academic secondment: CNRS-IGE (FR), AWI (D), Univ. of Bergen (NW) ; Non-academic secondment: Central Saint Martins – University of Arts London (UK)
Abstract
Antarctica represents a key region in the Earth’s climate system, where anthropogenic impacts may have important consequences for the future of global sea level due to the large volume of fresh water stored in the ice sheet. Several deep ice cores have already been drilled which describe natural climate variability in Antarctica over a large range of timescales, i.e., covering orbital-scale variability down to annual-scale variations.
Water isotopes recorded in these Antarctic ice cores are influenced by sources and trajectories of the water mass from the evaporative source to the polar precipitation site, and permit very significant insight into Antarctic ice sheet and climate change. In parallel, the analyses of air trapped in ice cores provide a direct access of past changes in atmospheric composition, permitting the role of the forcing in atmospheric greenhouse gas concentrations on natural climate change to be examined.
A key challenge for the orbital-scale natural variability is to understand why the periodicity of glacial to interglacial cycles changed from 41 to 100 thousand of years during the so-called Mid-Pleistocene Transition, between 0.8 and 1.2 million years (Myr) ago, while at the same time the orbital forcing given by astronomical parameters keeps the same periodicity. The oldest Antarctic ice core is currently 0.8 Myr which does not enable answering this key question in climate sciences. However, during the H2020 Beyond EPICA Oldest Ice core (BE OI) project, ten European research institutes will unite to drill a 1.5 Myr ice core on the East Antarctic plateau: now is thus the time to address the major scientific questions on the role of ice sheet size and greenhouse gases concentrations on the dynamics of Antarctica and global change.
This project will investigate the different possible influences on past water isotope changes in the East Antarctic plateau over the last 1.5 million years. The successful candidate will use coupled atmosphere-ocean models with explicit isotope diagnostics.
They will (1) examine the impact of MPT Antarctic, and global, ice sheet changes on the Antarctic ice core records of water isotopes, (2) evaluate the differences in the representation of the hydrological cycle across isotope enabled models, (3) evaluate the model simulations using climatic and environmental records from natural archives, and in particular (4) develop our understanding of how multi-model differences impact on our understanding of the water isotope measurements. This will improve our modelling of this key period and our interpretation of the new isotope measurements that will be measured on the future BE OI ice core; improve understanding of how key ice sheet changes impacted on the records of MPT transition; and enable a -European cross-comparison of new water isotope enabled CMIP6-class models.
Key words: coupled atmosphere-ocean models, water isotopes, East Antarctica, multi-model comparisons