Antarctic ice-sheet expansions in the Middle Miocene and Pliocene

• Main Author: Langebroek, Petra
• Other Authors: Schulz, Michael, Tiedemann, Ralf
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2008
• Subjects: Antarctic ice sheet; modeling; CO2; insolation; Middle Miocene; 550; 550 Earth sciences and geology; ddc:550; Antarctic; The Antarctic; Antarc*; Antarctica; Ice Sheet
• Online Access: https://media.suub.uni-bremen.de/handle/elib/2609; https://nbn-resolving.org/urn:nbn:de:gbv:46-diss000112917

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.