HR: 10:35h
AN: PP22A-02    [Abstracts]
TI: Modelling high latitude climates and ice sheets during the mid-Pliocene warm period
AU: * Hill, D J
EM: dahi@bas.ac.uk
AF: British Antarctic Survey, High Cross Madingley Road, Cambridge, CB3 0ET, United Kingdom
AU: * Hill, D J
EM: dahi@bas.ac.uk
AF: BRIDGE School of Geographical Sciences, University of Bristol University Road, Bristol, BS8 1SS, United Kingdom
AU: Haywood, A M
EM: a.m.haywood@leeds.ac.uk
AF: School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, United Kingdom
AU: Hindmarsh, R C
EM: rcah@bas.ac.uk
AF: British Antarctic Survey, High Cross Madingley Road, Cambridge, CB3 0ET, United Kingdom
AU: Valdes, P J
EM: p.j.valdes@bris.ac.uk
AF: BRIDGE School of Geographical Sciences, University of Bristol University Road, Bristol, BS8 1SS, United Kingdom
AU: Lunt, D J
EM: d.j.lunt@bristol.ac.uk
AF: BRIDGE School of Geographical Sciences, University of Bristol University Road, Bristol, BS8 1SS, United Kingdom
AB: Reduction in the polar ice caps and associated climate feedbacks are implicated in the warming of pre- Quaternary palaeoclimates. General Circulation Model (GCM) simulations of the last such warm period, the mid- Pliocene (3.29-2.97 Ma), suggests global surface temperatures were between 1.4°C and 3.6°C warmer than today. However, the changes are amplified in the high latitudes, where the PRISM (Pliocene Research, Interpretation and Synoptic Mapping) palaeoenvironmental reconstruction specifies a 50% reduction in the Greenland Ice Sheet (GrIS) and a 33% reduction in the Antarctic Ice Sheet. These ice sheets configurations are largely based on poorly constrained sea level estimates and are one of the least well-known boundary conditions for the mid-Pliocene.
Utilizing a suite of mid-Pliocene GCM experiments, evaluated against available palaeoenvironmental information, and a 3-D thermomechanically coupled ice sheet model, the state of the GrIS and East Antarctic Ice Sheet (EAIS) during this interval has been reconstructed. Ensemble models of Greenland, which compare favourably to evidence of ice-rafted debris and mid-Pliocene vegetation, suggest a reduction in the ice sheet to 30 - 40% of the modern ice volume. In East Antarctica increased surface temperatures during the mid-Pliocene lead to significant melt over the Wilkes and Aurora Subglacial Basins and a reduction in the extent of the ice sheet. These ice losses are partially offset by an increase in snowfall over the Antarctic plateau. Marine diatoms in the Transantarctic Mountains have been used as evidence of major East Antarctic deglaciations during the Pliocene. However, our EAIS predictions show that the modelled mid-Pliocene climate is insufficient to cause the hypothesized magnitude of ice sheet retreat.
Finally, the mid-Pliocene has been suggested as a possible palaeoclimate analogue for the climate of the late 21st century. Here we compare predictions of mid-Pliocene ice sheets with observations of modern high latitude cryospheric change and discuss the implications for future ice sheet and climate stability of the high latitudes.
DE: 0726 Ice sheets
DE: 3337 Global climate models (1626, 4928)
DE: 9310 Antarctica (4207)
DE: 9315 Arctic region (0718, 4207)
DE: 9605 Neogene
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting