Carbon Dioxide and Tectonic Controls on Antarctic Climate and Ice-Sheet Evolution in the Mid-Miocene: a model-data integration
Abstract
Geologic proxy data and model simulations imply a dynamic Antarctic ice sheet, with major variations in volume and extent, during the Mid-Miocene (17-13.8 Ma). This time period has direct relevance for understanding ice sheet response to future climate change as atmospheric CO 2 concentrations and global temperatures were similar to those projected in the near future. We combine available geologic data with new model simulations to investigate the evolution and behavior of the East Antarctic Ice Sheet (EAIS) across Wilkes Land and the Transantarctic Mountains (TAM). This study produces an ensemble of model simulations varying CO 2 concentrations, TAM uplift scenarios, and glacial/interglacial astronomical orbits. Paleo-environmental proxy data are used to identify the range of model boundary conditions consistent with the geologic record. Specifically, sedimentological and palynological data provide the primary constraints on ice extent and temperature variability, respectively, across glacial-interglacial cycles of the Miocene Climate Optimum (17-15 Ma) and Mid-Miocene Climate Transition (MMCT; 14.8-13.8Ma).
Our results imply a threshold for marine-based ice sheet formation in the Mid-Miocene of around 450 ppm, and identify the Wilkes Land Basin as a region particularly vulnerable to warming. Previous studies reproduce a Miocene EAIS that is highly sensitive to CO2; we extend our analysis to a large range of CO2 concentrations and observe a relatively insensitive EAIS at higher CO2. We hypothesize that Mid-Miocene TAM elevations were 500-300 m lower than present day, with lower elevations supporting more wet-based ice. Our model results are consistent with a TAM uplift scenario driven by valley incision and isostatic rebound across the Mid-Miocene. The attainment of approximately modern TAM elevations by the end of the MMCT could have driven the shift from wet-based to cold-based glaciation inferred by terrestrial geologic records in the TAM. The presence of localised tundra under 280 ppm CO 2 and a glacial orbit suggest that despite extinction at high elevations, vegetation could have existed in coastal lowlands post-MMCT, corroborating geologic data from DVDP-10 and -11 cores that indicate plants persisted at lower elevations of the TAM until the Early Pliocene.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMPP007..08C
- Keywords:
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- 4912 Biogeochemical cycles;
- processes;
- and modeling;
- PALEOCEANOGRAPHY;
- 4930 Greenhouse gases;
- PALEOCEANOGRAPHY;
- 4950 Paleoecology;
- PALEOCEANOGRAPHY;
- 4954 Sea surface temperature;
- PALEOCEANOGRAPHY