Session: Glacial Climates (LGM, Last deglaciation, Ice sheet uncertainties, Glacial-interglacial cycles)
Author: Esther Brady / email@example.com / National Center for Atmospheric Research
Co-author: Bette L. Otto-Bliesner, National Century for Atmospheric Research;
Zhengyu Liu, University of Wisconsin, Madison;
Robert Tomas, NCAR;
Alex Jahn, University of Colorado, Boulder;
Chengfei He, University of Wisconsin, Madison;
Sifan Gu, University of Wisconsin, Madison;
Jiaxu Zhang, University of Wisconsin, Madison;
Jiang Zhu, University of Wisconsin, Madison;
A suite of four transient simulations of the last deglaciation are underway with the isotope-enabled CESM. We are using the CESM implemented with stable water isotope tracers in the atmosphere, land-surface, ocean, runoff, and sea-ice components, and new passive ocean tracers for abiotic 14C and 12C, Protactinium, Thorium, and Neodymium isotopes. These tracers are designed to improve comparison to paleoclimate proxy records and to investigate proxy-climate relationships. The baseline simulation is forced with prescribed changes in insolation, atmospheric greenhouse gas concentrations, continental ice sheet variations, and meltwater fluxes. In addition, three experiments will be performed with different sets of forcings and boundary conditions combined to factor out the relative contributions to the climate evolution of the last deglacial period. The boundary conditions and forcings are taken from the PMIP4 deglacial protocols (Ivanovic et al. 2016.) The ice sheet reconstruction used is ICE-6G (Peltier et al. 2015.) In comparison with our previous transient simulation of the deglacial period using the CCSM3, TraCE-21, run at T31 resolution in the atmosphere and nominally 3 deg. in the ocean, these simulations will be run at a higher resolution (2 deg. in the atmosphere and 1 deg. in the ocean) and with improved physical parameterizations. Preliminary results will highlight both the simulated transient climate response to different forcings in comparison to our TraCE-21, and how the isotopic signals in the water cycle vary in response to climate change globally.
Ivanovic, R. F., L. J. Gregoire, M. Kageyama, D. M. Roche, P. J. Valdes, A. Burke, R. Drummond, W. R. Peltier, and L. Tarasov (2016), Transient climate simulations of the deglaciation 21–9 thousand years before present (version 1)-- PMIP4 Core experiment design and boundary conditions, Geosci. Model Dev., 9, 2563-2587, doi:10.5194/gmd-9-2563-2016.
Peltier, W. R., Argus, D. F., and Drummond, R.: Space geodesy constrains ice age terminal deglaciation: The global ICE-6G_C (VM5a) model, J. Geophys. Res.-Sol. Ea., 120, 450–487, doi:10.1002/2014JB011176, 2015.