A New 2000 Year Volcanic Record from a South Pole Ice Core

Explosive volcanic eruptions inject large amounts of dust and gases into the atmosphere. One major component is sulfur dioxide which is rapidly oxidized to form sulfuric acid aerosols. These aerosols reflect incoming sunlight and reduce the amount of solar radiation that reaches the Earth's surface resulting in a cooling of temperature. The precise impact of volcanic eruptions on the climatic system needs to be accounted for in climate models in order to predict future climate change in light of the greenhouse warming. The climate models require high quality records of past volcanic eruptions.;In this work, a 182 m South Pole ice core was analyzed continuously for all major ions from chemical impurities in snow using continuous flow analysis-ion chromatography. The chronology, which is established by annual layer counting, goes back to 176 A.D. High concentrations of sulfate in the dated ice core samples are indicators of volcanic eruptions. Due to a variable non-volcanic background of sulfate, a detection threshold is needed to identify volcanic signals in the sulfate data. Here, the detection threshold is established by using a modified approach to the traditional method of determining the background sulfate concentration. The result of applying the threshold to the sulfate data is a new, detailed volcanic record covering the last 2000 years.;This new record is consistent with previous records covering the most recent 1000 years in the number and dates of large volcanic events with a total of 38 events identified in the most recent 1000 years. Within the first millennium A.D. not covered in previous South Pole records, 34 volcanic events are found. The largest events in the first millennium are found at 758, 662, 629, and 531 A.D., which are similar in magnitude to a few very large eruptions that caused significant cooling in the nineteenth century. This record presents a more detailed history of the first 1000 years than the existing records, providing a more accurate impact of volcanic forcing in climate models.