Fortunately, ice cores preserve annual layers, making it simple to date the ice.
For example, melt layers are related to summer temperatures.
Snow precipitation over Antarctica is made mostly of HO is related to surface temperature at middle and high latitudes.
The relationship is consistent and linear over Antarctica.
From the US National Oceanic and Atmospheric Administration, Wikimedia Commons.
U from dust in the ice matrix can be used to provide an additional core chronology.