C.: Determining the natural length of the current interglacial, Nat

• Main Authors: P. C. Tzedakis, J. E. T. Channell, D. A. Hodell, H. F. Kleiven, L. C. Skinner
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: ice core; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.420.1364; http://www.seas.harvard.edu/climate/seminars/pdfs/Tzedakis_etal_2012.pdf

No glacial inception is projected to occur at the current atmospheric CO2 concentrations of 390 ppmv (ref. 1). Indeed, model experiments suggest that in the current orbital configuration—which is characterized by a weak minimum in summer insolation—glacial inception would require CO2 concentrations below preindustrial levels of 280 ppmv (refs 2–4). However, the precise CO2 threshold4–6 as well as the timing of the hypothetical next glaciation7 remain unclear. Past interglacials can be used to draw analogies with the present, provided their duration is known. Here we propose that the minimum age of a glacial inception is constrained by the onset of bipolar-seesaw climate variability, which requires ice-sheets large enough to produce iceberg discharges that disrupt the ocean circulation. We identify the bipolar seesaw in ice-core and North Atlantic marine records by the appearance of a