Calendar-year dating of the Greenland Ice Sheet Project 2 (GISP2) ice core from the early sixth century using historical, ion, and particulate data

Abstract

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 Greenland Ice Sheet Project 2 (GISP2) ice core during the early sixth 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 mo to 18 mo 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 A.D. 536–537 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 A.D. 533 and lasting until A.D. 539 or 540. These dancing stars have been previously attributed to cosmogenic dust loading of Earth's atmosphere. The time scale cannot be shifted to be either younger or older by 1 yr without destroying the match to historical accounts of dancing stars.