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Antarctic ice-sheet expansions in the Middle Miocene and Pliocene
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Other Titles: | Antarctic ice-sheet expansions in the Middle Miocene and Pliocene | Authors: | Langebroek, Petra | Supervisor: | Schulz, Michael | 1. Expert: | Schulz, Michael | 2. Expert: | Tiedemann, Ralf | Abstract: | The ice sheet-climate model developed in this study describes the Antarctic ice sheet. It is forced by energy and mass balances and includes oxygen isotopes as a passive tracer.Simulating the Middle Miocene climate transition showed that a decrease in atmospheric CO2, crossing a threshold of about 400 ppm, followed by a minimum in summer insolation, initiated a large-scale ice-sheet expansion.Experiments further confirm the validity of the often applied ratio of a 1 permille increase in oxygen-isotope composition for a global sea-level lowering of 100 m. For the mid-Pliocene, the ice-sheet component was forced by temperatures and accumulation rates from a comprehensive climate model. The closure of the Panamanian gateway in the mid-Pliocene was found to induce an intensification of the meridional circulation with a cooling over Antarctica as result. In turn, this cooling forced the Antarctic ice-sheet to expand. From the examples discussed in this study it can be concluded that changes in temperature, due to atmospheric CO2 as well as due to tectonic forcing, have a large impact on the extent of the Antarctic ice sheet. |
Keywords: | Antarctic ice sheet; modeling; CO2; insolation; Middle Miocene | Issue Date: | 12-Dec-2008 | Type: | Dissertation | URN: | urn:nbn:de:gbv:46-diss000112917 | Institution: | Universität Bremen | Faculty: | FB5 Geowissenschaften |
Appears in Collections: | Dissertationen |
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