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| Titel |
The role of ice shelves in the Holocene evolution of the Antarctic ice sheet |
| VerfasserIn |
Jorge Bernales, Irina Rogozhina, Maik Thomas |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250098480
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| Publikation (Nr.) |
 EGU/EGU2014-14162.pdf |
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| Zusammenfassung |
| Using the continental-scale ice sheet-shelf model SICOPOLIS (Greve, 1997[1]; Sato and
Greve, 2012[2]), we assess the influence of ice shelves on the Holocene evolution
and present-day geometry of the Antarctic ice sheet. We have designed a series of
paleoclimate simulations driven by a time-evolved climate forcing that couples the surface
temperature record from the Vostok ice core with precipitation pattern using an empirical
relation of Dahl-Jensen et al., (1998)[3]. Our numerical experiments show that the
geometry of ice shelves is determined by the evolution of climate and ocean conditions
over time scales of 15 to 25 kyr. This implies that the initial configuration of ice
shelves at the Last Glacial Maximum (LGM, about 21 kyr before present) has a
significant effect on the modelled Early Holocene volume of ice shelves (up to
20%) that gradually diminishes to a negligible level for the present-day ice shelf
configuration. Thus, the present-day geometry of the Antarctic ice shelves can be
attained even if an ice-shelf-free initial condition is chosen at the LGM. However, the
grounded ice volume, thickness and dynamic states are found to be sensitive to
the ice shelf dynamics over a longer history spanning several tens of thousands of
years. A presence of extensive marine ice at the LGM, supported by sediment core
reconstructions (e.g. Naish et al., 2009[4]), has a clear buttressing effect on the
grounded ice that remains significant over a period of 30 to 50 kyr. If ice-shelf-free
conditions are prescribed at the LGM, the modelled Early Holocene and present-day
grounded ice volumes are underestimated by up to 10%, as opposed to simulations
incorporating ice shelf dynamics over longer periods. The use of ice-shelf-free LGM
conditions thus results in 50 to over 200 meters thinner ice sheet across much of East
Antarctica.
References
[1]Greve, R. (1997). Application of a polythermal three-dimensional ice sheet
model to the Greenland ice sheet: response to steady-state and transient climate
scenarios. Journal of Climate, 10(5), 901-918.
[2]Sato, T., and Greve, R. (2012). Sensitivity experiments for the Antarctic
ice sheet with varied sub-ice-shelf melting rates. Annals of Glaciology, 53(60),
221-228.
[3]Dahl-Jensen, D., Mosegaard, K., Gundestrup, N., Clow, G. D., Johnsen, S.
J., Hansen, A. W., and Balling, N. (1998). Past temperatures directly from the
Greenland ice sheet. Science, 282(5387), 268-271.
[4]Naish, T., Powell, R., Levy, R., Wilson, G., Scherer, R., Talarico, F., ... and
Schmitt, D. (2009). Obliquity-paced Pliocene West Antarctic ice sheet oscillations.
Nature, 458(7236), 322-328. |
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