Changes during these events commonly occur over decades or less. Shifts in the patterns of atmospheric circulation could explain the rapidity and magnitude of these events. Most recently, subtle versions of these rapid climate change events were identified through the reconstruction of atmospheric circulation patterns in the Holocene portion of the Greenland ice record. Major climatic change events are also recorded in the isotopic temperature record of the Vostok core from central East Antarctica, but not as clearly as in cores from Greenland. Both cores also show rapid oscillations in climate during that time period, but with different timing and character.
Ice flow disturbs the climate record by allowing ice from different layers to mix.
The amounts of gases in both cores differ from those of the Vostok, Antarctica core, where the Eemian era ice is undisturbed by ice flow. Much remains to be learned about Eemian climate from these cores. Just as they were needed to confirm the rapid oscillations observed in older cores, a core from a site where the Eemian is farther above the bed and thus is less subject to flow disturbance will provide the best information. Scientists are already looking at sites in North Greenland and Antarctica capable of delivering such records. Measurements of gas-bubble compositions from Antarctic cores provide the best paleorecords of CO 2 concentrations.