HR: 0800h
AN: C41A-0061    [Abstracts]
TI: Identifying the climatic drivers of Southern Hemisphere Ice Ages from glacier modelling in New Zealand
AU: Anderson, B M
EM: brian.anderson@vuw.ac.nz
AF: Antarctic Research Centre, Victoria University of Wellington PO Box 600, Wellington, 6140, New Zealand
AU: * Mackintosh, A N
EM: andrew.mackintosh@vuw.ac.nz
AF: Antarctic Research Centre and School of Geography, Geology and Earth Sciences, Victoria University of Wellington PO Box 600, Wellington, 6140, New Zealand
AU: Huybers, P J
EM: phuybers@fas.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University 20 Oxford Street, Cambridge, MA 02138, United States
AU: Pierrehumbert, R T
EM: rtp1@geosci.uchicago.edu
AF: The Department of the Geophysical Sciences, The University of Chicago 5734 S. Ellis Avenue, Chicago, IL 60637, United States
AB: The timing of glacier advances and retreats during the past 30,000 years is broadly consistent between the Northern and Southern hemispheres. In particular, cosmogenic exposure age dating of moraines indicates that the timing of glacier advance and retreat cycles in New Zealand, Chile and Australia broadly matches that of the Northern Hemisphere. And yet the precession component of the insolation forcing is out-of-phase between the hemispheres. If summer insolation at high Northern latitudes is to pace global glaciation, some strong inter hemispheric connection must exist. Southern Hemisphere glaciers may respond to changes in greenhouse gas concentrations, or to shifts in oceanic and atmospheric circulation. Alternately, Southern Hemisphere glaciation may respond to some other component of the insolation forcing or vary independently and, by chance, coincide with the North. In order to draw distinctions between the various influences on Southern Hemisphere glaciations, we explore how models of Southern Hemisphere glaciers respond to a variety of forcing agents. The model includes ablation calculated using an energy balance model, including full seasonal insolation forcing, and accumulation calculated using a precipitation model including the effects of moisture transport over an orographic barrier. A dynamical ice-sheet model relates the resulting mass balance variations to changing ice extent, which is compared to the geological record. The model is used to quantify the relative importance of changes in precipitation and temperature resulting from local intrinsic variability, as a response to local insolation forcing, or resulting from ocean/atmosphere changes induced non-locally, possibly as a result of Northern Hemisphere climate.
DE: 0720 Glaciers
DE: 0762 Mass balance (1218, 1223)
DE: 0764 Energy balance
DE: 0774 Dynamics
DE: 0798 Modeling
SC: Cryosphere [C]
MN: 2007 Fall Meeting