Argon argon dating limitations
Drilling a vertical hole through this ice involves a serious effort involving many scientists and technicians, and usually involves a static field camp for a prolonged period of time. Shallow ice cores (100-200 m long) are easier to collect and can cover up to a few hundred years of accumulation, depending on accumulation rates. Stable isotopes of oxygen (Oxygen [The figure above shows changes in ice temperature during the last several glacial-interglacial cycles and comparison to changes in global ice volume. The local temperature changes are from two sites in Antarctica and are derived from deuterium isotopic measurements. They allow us to go back in time and to sample accumulation, air temperature and air chemistry from another time. Slow ice flow at the centre of these ice sheets (near the ice divide) means that the stratigraphy of the snow and ice is preserved.
It is possible to discern past air temperatures from ice cores.
The bottom plot shows global ice volume derived from δ18O measurements on marine microfossils (benthic foraminifera) from a composite of globally distributed marine sediment cores. An example of using stable isotopes to reconstruct past air temperatures is a shallow ice core drilled in East Antarctica.
The presence of a “Little Ice Age”, a cooler period ending ~100 to 150 years ago, is contested in Antarctica.
This section contains 11 annual layers with summer layers (arrowed) sandwiched between darker winter layers.
From the US National Oceanic and Atmospheric Administration, Wikimedia Commons.