title: Was millennial scale climate change during the Last Glacial triggered by explosive volcanism?
abstract: The mechanisms responsible for millennial scale climate change within glacial time intervals are equivocal. Here we show that all eight known radiometrically-dated Tambora-sized or larger NH eruptions over the interval 30 to 80 ka BP are associated with abrupt Greenland cooling (>95% confidence). Additionally, previous research reported a strong statistical correlation between the timing of Southern Hemisphere volcanism and Dansgaard-Oeschger (DO) events (>99% confidence), but did not identify a causative mechanism. Volcanic aerosol-induced asymmetrical hemispheric cooling over the last few hundred years restructured atmospheric circulation in a similar fashion as that associated with Last Glacial millennial-scale shifts (albeit on a smaller scale). We hypothesise that following both recent and Last Glacial NH eruptions, volcanogenic sulphate injections into the stratosphere cooled the NH preferentially, inducing a hemispheric temperature asymmetry that shifted atmospheric circulation cells southward. This resulted in Greenland cooling, Antarctic warming, and a southward shifted ITCZ. However, during the Last Glacial, the initial eruption-induced climate response was prolonged by NH glacier and sea ice expansion, increased NH albedo, AMOC weakening, more NH cooling, and a consequent positive feedback. Conversely, preferential SH cooling following large SH eruptions shifted atmospheric circulation to the north, resulting in the characteristic features of DO events.
authors.affiliation: Department of Earth Sciences, University of Durham, Durham, DH1 3LE, UK.
authors.forename: James U L
authors.initials: JU
authors.lastname: Baldini
authors.affiliation: Department of Earth Sciences, University of Durham, Durham, DH1 3LE, UK.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Brown
authors.affiliation: Department of Earth Sciences, University of Durham, Durham, DH1 3LE, UK.
authors.forename: Jim N
authors.initials: JN
authors.lastname: McElwaine