Abstract:
Similar orbital configurations and comparable atmospheric greenhouse gas concentrations have led to the suggestion that Marine Isotope Stage 11 (MIS 11) is a suitable, possibly the best, geological analogue for the natural development of Holocene and future climate. Yet the apparently strong climate response during MIS 11 in the absence of strong seasonal insolation changes has long been described as the "the stage 11 problem". Any assessment of MIS 11 as analogue or anomaly must include consideration of the timing, duration, climatic stability, and overall amplitude of warmth and sea-level/ice-volume during this interglacial interval. These important questions are best addressed using multiple paleoclimate archives, with deep-sea sediment records prominent among them. Here we review evidence from a number of widely distributed marine locations indicating that MIS 11 was not likely to have been a "super interglacial" interval characterized by both significantly higher sea-level and global temperatures. We discuss the stability and strength of the meridional overturning circulation as a potential compensator for the limited insolation. We also present our own detailed faunal, ice-rafting, and isotopic records from ODP Sites 980 (55 degrees N, 15 degrees W, 2.2km), 983 (60 degrees N, 24 degrees W, 2.0km), and 984 (61 degrees N, 25 degrees W, 1.6 km) that confirm the relative stability of MIS 11 on millennial timescales, and document that the transition to the more characteristic instability of the Pleistocene occurred dramatically and abruptly following the warm interval. In addition, we consider a variety of tuning techniques and apply a new independent dating approach to deep-sea sediment sequences to show that the regional stable warmth of MIS 11 in the North Atlantic long outlasted the elapsed portion of the Holocene. Finally, we present our newest isotopic results from ODP Site 1242 (8 degrees N, 84 degrees W, 1.4km) in the tropical Pacific, and discuss possible ways to reconcile apparently conflicting evidence in existing records of sea-level, temperature, and variability during MIS 11.