Summary
Bubbles of air trapped in ice sheets provide an important record of past atmospheric gas composition. Understanding of climate change and atmospheric composition over the last 400,000 years has been greatly improved using ice core analysis. Ice cores from Law Dome in Antarctica have several attractive properties due to the high snow accumulation rate, low temperatures, low impurity levels and stable glaciology. The cores are generally well dated, have a narrow air age spread, and contain air spanning from recent decades to thousands of years before present. The gas records already produced from Law Dome cores have tracked variations in CO2, (13CO2, and CH4 over the past 1000 years with high precision and age resolution. Holocene climate is considered to be stable compared to the rapid climate changes of the previous ice ages. Published records of methane and carbon dioxide generally show small and slow changes during this period. The age resolution of the Law Dome ice core air, and the high measurement precision for several trace gases, allow subtle changes to be revealed. For example, an abrupt cooling event 8,200 years BP has recently been found in several paleoclimatic records including Greenland ice cores. This project aims to locate the 8,200-year event in the Law Dome "DSS" ice core. Uncertain ice dating through this period means the event must be identified using methane. The event is clear and well dated in the methane record in Greenland ice, and since methane is a globally well-mixed gas, the Antarctic and Greenland methane records may be synchronised. As a result, records such as climate in the DSS ice core may be accurately dated. Furthermore, the global atmospheric CO2 response to the cooling may be found by using the well resolved and preserved CO2 record in Law Dome ice.