David Hodell (University of Cambridge)
Persistent instability of glacial climate and overturning circulation in the North Atlantic for the past 1.5 million years
Nick Shackleton’s pioneering work on piston cores from the Iberian Margin demonstrated that the planktonic d18O signal resembles in great detail the temperature record of Greenland for the last glacial cycle. In the absence of a continuous ice core older than the last interglacial (~124 ka) in Greenland, a long sediment sequence from the Iberian Margin could serve as a surrogate for millennial climate variability (i.e., Dansgaard-Oeschger events) in the North Atlantic during the Quaternary. To this end, we drilled IODP Site U1385 (the “Shackleton site”) on the SW Iberian Margin and recovered a 166.5-m continuous section that extends back to ~1.5 million years BP. We measured stable isotopes of foraminifera continuously at 1- or 2-cm resolution corresponding to a temporal resolution of 100-200 years. The isotope record is used to evaluate how the magnitude, duration and pacing of millennial variability changed as glacial boundary conditions evolved across the Middle Pleistocene Transition (MPT).