Session: Benchmarking & cross-cutting Group 1 (Isotope modelling, COMPARE)
Author: Max Holloway / email@example.com / British Antarctic Survey
Co-author: Louise Sime, British Antarctic Survey;
Paul Valdes, University of Bristol;
The isotope thermometer method combines the observed strong linear relationship between temperature and the stable water isotopic composition (D and 18O) of surface snow with ice core records to reconstruct temperature changes over glacial-interglacial timescales. This method requires the assumption of stationarity - that the observed relationship has not changed with time. The development of isotope-enabled coupled General Circulation Models (GCMs) allows this assumption to be tested within a modelling framework. Here, we present a suite of time-slice simulations using the isotope-enabled HadCM3 GCM (iHadCM3) covering the last deglaciation, from 21,000 years ago to present. Modelled isotope-temperature relationships are validated against independent isotope and temperature constraints from Antarctica, before testing the application of spatially and time-independent relationships in the reconstruction of past temperature. Simulated isotope-temperature relationships agree well with present-day spatial distributions. However, there is considerable variability between Antarctic regions and between time periods. We identify locations that exhibit relatively constant isotope-temperature relationships across spatial and temporal scales and, therefore, might provide robust paleo-temperature reconstructions from ice cores. Finally, our methodology is applied to an ensemble of transient iHadCM3 forced historical simulations to place our results in the context of the last 150 years and the observational record.