The curious relationship between volcanic fallout layers and millennial climate changes recorded in polar ice

For more than three decades investigators have noticed an apparent link between volcanic eruptions and stages of glaciation during the last ice age. We have pursued a remarkable association between the onset of millennial cold phases and volcanic or volcano-like explosive fallout layers deposited in polar regions, by deploying a high-resolution optical dust logger in deep boreholes in both Antarctica and Greenland. The sub-centimeter records this produces allow us to simultaneously identify both volcanic ash horizons and changes in dust deposition mediated by climate, in order to study their relationship at an unprecedented level of detail. This compiled evidence offers support for speculation that volcanic eruptions or impact explosions induced climate transitions, or conversely, that climate changes triggered volcanic activity, or both. We have synthesized ice core data with our optical profiles, including the latest images taken in deep South Pole ice during the construction of IceCube. We will present a gallery of those deposition events over the last 90 ka that are most suggestive of a cause and effect dependence, because of the global reach of the fallout, the prominence of the events in the records, and their phasing relative to millennial climate shifts.