Volcanic forcing and climate variations during the last glacial period

Abstract. Measurements of δ¹⁸O in the Greenland Ice Sheet Project 2 (GISP2) ice-core from Summit, Greenland, show repeated temporal variations associated with rapid warming events throughout the last glacial period of the Pleistocene-10–110 kya. The majority of these warming events are preceded in the ice-core record by an increased concentration of insoluble micro-particulate sulfate, indicative of increases in global volcanism. Wavelet analysis of ice-core and marine-sediment records show a repeated 5000–6000 yr periodicity in both volcanic SO₄ and δ¹⁸O ice records, as well as a 5000–8000 yr cycle in the lithic concentration of ice-rafted debris, atmospheric CO₂ concentration, and a database of late Quaternary volcanic eruptions. Increasing concentrations in atmospheric CO₂ and CH₄ initiated during periods of increased volcanism, peaking during a warm transition, reflect a volcanic-atmospheric-deglaciation feedback, regulated by meridional overturning current-shutdown related cooling.