Geological records from the Antarctic margin offer direct evidence of environmental variability at high southern latitudes and provide insight regarding ice sheet sensitivity to past climate change. The early to mid-Miocene (23-14 Mya) is a compelling interval to study as global temperatures and atmospheric CO 2 concentrations were similar to those projected for coming centuries. Importantly, this time interval includes the Miocene Climatic Optimum, a period of global warmth during which average surface temperatures were 3-4 °C higher than today. Miocene sediments in the ANDRILL-2A drill core from the Western Ross Sea, Antarctica, indicate that the Antarctic ice sheet (AIS) was highly variable through this key time interval. A multiproxy dataset derived from the core identifies four distinct environmental motifs based on changes in sedimentary facies, fossil assemblages, geochemistry, and paleotemperature. Four major disconformities in the drill core coincide with regional seismic discontinuities and reflect transient expansion of grounded ice across the Ross Sea. They correlate with major positive shifts in benthic oxygen isotope records and generally coincide with intervals when atmospheric CO 2 concentrations were at or below preindustrial levels (∼280 ppm). Five intervals reflect ice sheet minima and air temperatures warm enough for substantial ice mass loss during episodes of high (∼500 ppm) atmospheric CO 2 . These new drill core data and associated ice sheet modeling experiments indicate that polar climate and the AIS were highly sensitive to relatively small changes in atmospheric CO 2 during the early to mid-Miocene.
|Original language||English (US)|
|Number of pages||6|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Mar 29 2016|
Bibliographical noteFunding Information:
Acknowledgments: We thank three anonymous reviewers. We acknowledge the Antarctic Geological Drilling (ANDRILL) Program, which acquired the unique geological section examined in this study. Scientific research was supported by New Zealand Ministry of Business Innovation and Employment Contracts C05X0410 and C05X1001, the US National Science Foundation (Cooperative Agreement 0342484 to the University of Nebraska-Lincoln), the Italian Antarctic Research Programme, the German Research Foundation, the Alfred Wegener Institute for Polar and Marine Research (Helmholtz Association of German Research Centres), and New Zealand Antarctic Research Institute Grant NZARI 2013-1.
- Climate Optimum
- Ice sheet
- Ross Sea