Unit Affiliation: Biology and Paleo Environment, Lamont-Doherty Earth Observatory (LDEO)
Understanding the effects of solar strength, global ice volume and carbon dioxide levels on the global climate system is essential for climate models' ability to reconstruct past and future climate. In particular, studying past ice volume variations are of vital importance to predicting ice sheet stability and sea level change. During the mid-Pleistocene transition (~600,000 to 1,200,000 years ago), the climate's response to solar strength changed dramatically and variations in ice volume and carbon dioxide levels may have contributed to this transition. This project aims to resolve changes in ocean bottom water temperature and circulation to evaluate global ice volume variability as a potential driving factor for the mid-Pleistocene transition. The broader impacts include support for a female postdoctoral scientist, undergraduate research experiences, and educational displays designed for the Lamont-Doherty Earth Observatory Core Repository in New York.
Most climate interpretations for the mid-Pleistocene transition come from oxygen isotope records from benthic foraminifera, which record a combination of temperature and ice volume signals. The Mg/Ca ratio of benthic foraminifera may serve as an independent proxy of ocean bottom water temperature and has been used to separate ocean bottom water temperature and ice volume components in the oxygen isotope records from benthic foraminifera. Currently there are only two high-resolution records of ocean bottom water temperature and seawater oxygen isotope composition (as a proxy for ice volume) during the mid-Pleistocene transition. However, these studies record fundamentally different trends, suggesting different mechanisms for the mid-Pleistocene transition. This project will use coupled Mg/Ca and oxygen-isotope values of benthic foraminifera to evaluate regional and global signals in ocean bottom water temperature and ice volume signals from the North Atlantic. These data will be used to assess any changes in ocean bottom water temperature, the timing of ice volume growth and the magnitude of sea level variation during the mid-Pleistocene transition. This will aid climate modelers in setting boundary conditions for the mid-Pleistocene transition and in identifying the key factors influencing global climate.
OUTCOMES: Ford, H. L., Sosdian, S. M., Rosenthal, Y., & Raymo, M. E.. "Gradual and abrupt changes during the Mid-Pleistocene Transition," Quaternary Science Reviews, v.148, 2016, p. 222. doi:http://doi.org/10.1016/j.quascirev.2016.07.005
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