Session: Benchmarking & cross-cutting Group 1 (Isotope modelling, COMPARE)
Author: Jesse Nusbaumer / firstname.lastname@example.org / NASA Goddard Institute for Space Studies
Co-author: Bronwen Konecky, Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado;
Bette Otto-Bliesner, National Center for Atmospheric Research (NCAR);
Allegra LeGrande, NASA Goddard Institute for Space Studies;
Hydrogen and oxygen isotopes in various proxy records are some of the most commonly used datasets for reconstructing past climates, albeit with significant uncertainty inherent to proxy systems. Recently, isotope-enabled climate models have been used to try and reduce this uncertainty. However, climate models have their own uncertainties, and different models can produce different isotopic responses, even with the same external forcings. These discrepancies may arise from differences in model physics and isotope schemes, but may also arise because in models, as well as in nature, statistical relationships between water isotopes and local climate variables are not constant in space or time. This indicates that other, potentially non-local variables or processes may be influencing water isotope ratios, and could explain at least part of the discrepancy between different models.
This study will examine a few of these non-local variables, specifically the evaporative moisture source, in the GISS model. Water tracers will be used to evaluate the relationship between water isotopes and moisture sources and transport pathways for several different climate states, such as the Last Glacial Maximum. These results will then be compared to similar results generated from NCAR’s iCESM model, to determine if they can explain the inter-model isotope differences. Finally, these moisture source and transport changes will be analyzed to determine how changes in the atmospheric circulation impact the atmospheric water cycle, and thus the water isotope ratios themselves.