CALENDAR-YEAR DATING OF THE GISP2 ICE CORE USING HISTORICAL, ION AND PARTICULATE DATA: IMPLICATIONS FOR COSMIC DUST FLUXES AND CLIMATE DOWNTURNS

We use the occurrence of unusual or out-of-season dust storms and dissolved ion data as proxies for dust to propose a calendar-year chronology for a portion of the GISP2 ice core during the early 6^th century A.D. Our new time scale moves a small sulfate peak to early 537 A.D., which is more consistent with recent findings of a 6-month to 18-month time lag between volcanic eruptions and atmospheric fallout of their sulfate aerosols. Our new time scale is consistent with a small volcanic input to the 536-537 A.D. climate downturn. We use the time range of Ni-rich fragments and cosmic spherules to provide an independent test of the chronology. The time range of Ni-rich fragments and cosmic spherules matches historical observations of “dancing stars” starting in the summer of 533 A.D. and lasting until 539 or 540 A.D. These dancing stars have been previously attributed to cosmogenic dust loading of the Earth’s atmosphere. The time scale cannot be shifted to be either younger or older by one year without destroying the match to historical accounts of dancing stars. Using the volumes of Ni-rich particles, we also look at the minimum volume of cosmic dust loading during the period 533 to 540 A.D. We find that the minimum volume is between 5 and 11 times the average Holocene flux of meteoritic smoke per cm² at high latitudes of the Earth.