Collaborative Research: P2C2--The Oligocene-Miocene Boundary: Carbon-Dioxide (CO2) Sensitivity and Ice Sheet Hysteresis

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The project is a study of an extreme, short-lived climate oscillation that occurred at the Oligocene-Miocene boundary about 23 million years ago. The event is characterized by a 150,000-year oscillation in the stable oxygen isotope composition (delta18O) of benthic foraminifera, generally thought to reflect a rapid advance and retreat in the Antarctic ice sheet, as well as a perturbation in the global carbon cycle and evidence of biotic impacts in marine and terrestrial systems. The magnitude of the event and its short duration are unusual and in apparent contradiction to our understanding of ice sheet behavior. The researchers will use proxy measurements of past climate and general circulation model simulations to address four overarching questions: What were the primary drivers of the event: carbon cycle dynamics and atmospheric carbon dioxide (CO2), orbits? What was the magnitude of the event in terms of temperature and ice volume change? Could Northern Hemispheric ice sheets have grown, given near-modern atmospheric CO2 levels at the time, and if so, what is their impact on the benthic delta18O signal? How can a polar-centered, terrestrial ice sheet experience such variability if CO2 levels remained as low as suggested by proxy records? The broader impacts include graduate student mentoring, participation in an important summer school focused on past climate history, and the development of undergraduate education modules for climate history.