Proxy-model comparison for Late Eocene and early Oligocene conditions around the margins of Antarctica
Abstract
Climate records for Antarctica, beyond the age limit of ice cores, are restricted to the few unglaciated areas with exposed rock outcrops and marine sediment cores recovered from the Antarctic margins. We add a new brGDGT (branched glycerol dialkyl glycerol tetraether) based temperature reconstruction from SHALDRIL-II sediment cores off the coast of the Antarctic Peninsula. These soil-derived biomarkers indicate a mean annual air temperature of 12°C for the late Eocene. In addition, we compile proxy records that constrain environmental conditions during the late Eocene and early Oligocene marking the shift from the Greenhouse to Icehouse world. Existing paleoclimate records around the Antarctic continent from Maud Rise, Prydz Bay, Kerguelen Plateau, and the Antarctic Peninsula indicate regional differences in terrestrial and ocean temperatures. These temperature records derive from a range of proxies including biomarkers, microfossils, clumped isotopes, and weathering approaches to provide information on terrestrial and ocean temperature. We compare the proxy compilation to previous DeepMIP-EOT climate model simulations generated with varied pCO2, paleogeography, and ice sheet extent. The models were divided based on their pCO2 levels with the higher pCO2 (>560 ppm) for the Late Eocene and pCO2 of 560 ppm for the Oligocene. Overall, the models are warm-biased for the Eocene and cold-biased for the Oligocene compared to proxy surface air temperature reconstructions with average model-proxy discrepancies for the Eocene of +1C and -4C for the Oligocene. Air temperature proxy reconstructions for the late Eocene from the Antarctic continental margins ranged from 7 to 22C. The Antarctic Peninsula mean annual air temperature reconstructions from proxies range from 10 to 22C for the late Eocene with the large range attributed to proxy disagreement with higher temperature estimates generated from the brGDGTs. Model ensemble surface air temperature estimates for the late Eocene proximal to proxy sites on the Antarctic Peninsula range from 8 to 16°C (mean 12°C). Outside of the Antarctic Peninsula the proxy-model difference across the remaining sites ranges from -6 to 5°C (mean 2°C). Oligocene proxy-model intercomparisons are complicated by model differences in the prescribed continental ice sheet.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMPP55D0696T