HR: 0800h
AN: PP41B-0643    [Abstracts]
TI: Modelling Continental Ice Sheets During the mid-Pliocene Warm Period
AU: * Hill, D J
EM: dahi@bas.ac.uk
AF: Geological Science Division British Antarctic Survey, High Cross Madingley Road, Cambridge, CB3 0ET United Kingdom
AU: Haywood, A M
EM: ahay@bas.ac.uk
AF: Geological Science Division British Antarctic Survey, High Cross Madingley Road, Cambridge, CB3 0ET United Kingdom
AU: Hindmarsh, R C
EM: rcah@bas.ac.uk
AF: Physical Sciences Division British Antarctic Survey, High Cross Madingley Road, Cambridge, CB3 0ET United Kingdom
AU: Valdes, P J
EM: p.j.valdes@bris.ac.uk
AF: Bristol Research Initiative for the Dynamic Global Environment School of Geographical Sciences University of Bristol, University Road, Bristol, BS8 1SS United Kingdom
AB: The mid-Pliocene (~3Myr B.P.) is important for palaeoclimate reconstruction, as it was the last time in Earth history when global temperatures were significantly warmer than modern, over a period longer than any Quaternary interglacial. It is unique in that continental configurations were relatively unchanged from the modern, and geological proxies are superior to preceding warm periods, due to improved geographic distribution, biota-environment correlations and stratigraphy. Therefore, the period may represent the best available analogue for future climate change. General Circulation Models (GCMs) have been successfully run, using the USGS PRISM2 (Pliocene Research, Interpretation and Synoptic Mapping) environmental reconstruction. The most advanced GCMs include fully coupled atmosphere, ocean, sea ice and vegetation models, however the ice sheet extent must be prescribed.
There has been great controversy over the extent of the Pliocene East Antarctic Ice Sheet (EAIS). One group of researchers claim that the Pliocene saw huge changes in East Antarctic ice volume, while the conventional view of a stable EAIS since the Miocene is upheld by others. This potentially huge uncertainty makes it important that the extent of the EAIS during the Pliocene is tested through modelling, particularly when it has been shown that reduction in terrestrial ice sheet coverage may be the major contributing factor to the increased temperatures. PRISM2 specifies a 33% reduction in Antarctic ice volumes, however this is based on palaeo-shoreline and δ¹⁸O records, both of which have large uncertainties. Outputs from fixed ice sheet GCM experiments can be used to drive a 3-D, thermomechanical Ice Sheet Model (ISM). This will test the validity of this supposition and other prescribed Antarctic ice sheets. Presented here are the initial results of our ice sheet modelling studies using the British Antarctic Survey ISM and the Hadley Centre GCM to simulate the equilibrium response of the Antarctic Ice Sheet to the modelled Pliocene climate, based on the PRISM2 data set. These results show that, although EAIS was reduced in extent during the mid-Pliocene, the deglaciation was more limited than PRISM2 prescribed.
These techniques can also be applied to the Greenland Ice Sheet (GIS), whose pre-Quaternary history is poorly constrained, but was specified by PRISM2 to have been 50% smaller. Congruent with ice rafted debris records from the Greenland continental shelf, we find that the mid-Pliocene probably saw a melting of the ice caps that comprised the Pliocene GIS.
DE: 0726 Ice sheets
DE: 0798 Modeling
DE: 1626 Global climate models (3337, 4928)
DE: 9310 Antarctica (4207)
DE: 9315 Arctic region (0718, 4207)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005