However, instead of annual cycles, the oscillations simply represent variations within a single year. They think the amount of snow and ice added each year has been approximately balanced by the ice that is lost by melting and calving of icebergs into the ocean.
Oxygen has three isotopes, each with a different number of neutrons in the nucleus of the atom.
For ice core analysis, the ratio between oxygen-18 and oxygen-16 is used, oxygen-17 being too small for practical purposes.
Some of these parameters vary noticeably between seasons, providing a ‘signature’ for recognising each annual layer of snowfall.
The annual snowfall over Antarctica is normally too small to resolve annual layers down an ice core.
Since the Ice Age ended about 4,000 years ago, the compression of the ice sheet has been much less than uniformitarian scientists believe, but still substantial.