Antarctic climate and ice-sheet configuration during the early Pliocene interglacial at 4.23 Ma

The geometry of Antarctic ice sheets during warm periods of the geological past is difficult to determine from geological evidence, but is important to know because such reconstructions enable a more complete understanding of how the ice-sheet system responds to changes in climate. Here we investiga...

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Bibliographic Details
Published in:Climate of the past Vol. 13; no. 7; pp. 959 - 975
Main Authors: Golledge, Nicholas R., Thomas, Zoë A., Levy, Richard H., Gasson, Edward G. W., Naish, Timothy R., McKay, Robert M., Kowalewski, Douglas E., Fogwill, Christopher J.
Format: Journal Article
Language:English
Published: Katlenburg-Lindau Copernicus GmbH 27.07.2017
Copernicus Publications
Subjects:
Air temperature
Antarctic climate
Antarctic ice sheet
Atmospheric models
Climate
Climate change
Climate models
Computer simulation
Flotation
Geology
Glaciation
Global sea level
Greenhouse effect
Greenhouse gases
Ice
Ice sheet models
Ice sheets
Interglacial periods
Natural history
Ocean temperature
open climate campaign
Pliocene
Pliocene Epoch
Precipitation
Regional climates
Regional variations
Sea level
Simulation
Southern Hemisphere
Temperature
Topography (geology)
Antarctica
Prydz Bay
ISSN:1814-9332, 1814-9324, 1814-9332
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Summary:The geometry of Antarctic ice sheets during warm periods of the geological past is difficult to determine from geological evidence, but is important to know because such reconstructions enable a more complete understanding of how the ice-sheet system responds to changes in climate. Here we investigate how Antarctica evolved under orbital and greenhouse gas conditions representative of an interglacial in the early Pliocene at 4.23 Ma, when Southern Hemisphere insolation reached a maximum. Using offline-coupled climate and ice-sheet models, together with a new synthesis of high-latitude palaeoenvironmental proxy data to define a likely climate envelope, we simulate a range of ice-sheet geometries and calculate their likely contribution to sea level. In addition, we use these simulations to investigate the processes by which the West and East Antarctic ice sheets respond to environmental forcings and the timescales over which these behaviours manifest. We conclude that the Antarctic ice sheet contributed 8.6 ± 2.8 m to global sea level at this time, under an atmospheric CO2 concentration identical to present (400 ppm). Warmer-than-present ocean temperatures led to the collapse of West Antarctica over centuries, whereas higher air temperatures initiated surface melting in parts of East Antarctica that over one to two millennia led to lowering of the ice-sheet surface, flotation of grounded margins in some areas, and retreat of the ice sheet into the Wilkes Subglacial Basin. The results show that regional variations in climate, ice-sheet geometry, and topography produce long-term sea-level contributions that are non-linear with respect to the applied forcings, and which under certain conditions exhibit threshold behaviour associated with behavioural tipping points.
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ISSN:1814-9332
1814-9324
1814-9332
DOI:10.5194/cp-13-959-2017