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| Titel |
Deglacial ice-sheet meltdown: orbital forcing versus CO2 effects |
| VerfasserIn |
Axel Timmermann, Malte Heinemann, Oliver Elison Timm, Fuyuki Saito, Ayako Abe Ouchi |
| 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 |
250089077
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| Publikation (Nr.) |
 EGU/EGU2014-3265.pdf |
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| Zusammenfassung |
| Eighty thousand years of ice-sheet build-up came to a rapid end ~20-10 thousand years
before present (kaBP), when ice sheets receded quickly, and global mean surface
temperatures increased by about 4°C. It still remains unresolved whether insolation
changes due to variations of earth’s tilt and orbit were sufficient to terminate glacial
conditions.
Using a coupled fully three-dimensional climate–ice-sheet model (iLOVE=IcIES+LOVECLIM),
we simulate the transient climate and Northern Hemisphere ice-sheet evolution from
78kaBP to 0kaBP in good agreement with sea level and ice topography reconstructions.
Based on this simulation and a series of deglacial sensitivity experiments with individually
varying orbital parameters and CO2, we find that enhanced calving led to a slow-down of
ice-sheet growth already 5ka to 8ka prior to the Last Glacial Maximum (LGM),
as evidenced by the change in curvature of the simulated and reconstructed ice
volume time series. Increasing obliquity and precession then led to accelerated ice
loss due to ablation and calving, thereby initiating the glacial termination. The
deglacial sensitivity experiments further reveal that the ~100ppmv rise of atmospheric
pCO2 after ~18kaBP was a key contributor to the deglaciation. Without it, the
present-day ice volume would be comparable to that of the LGM and global mean
temperatures would be about 3°C lower than today. We further demonstrate that neither
orbital forcing nor CO2 forcing alone were sufficient to complete the deglaciation. |
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