How do we know how old the Antarctic Ice Sheet is?

The oldest penetrated Antarctic ice is about 800,000 years old. However, I have read that the Antarctic Ice Sheet has been present for several millions of years. Is there any direct evidence for older ice, or is it simply an inference from dC18 values from somewhere, or something like that? Do global sea-level curves support the older ice story?

-Asked by Joe

Hi Joe,

That is a great question. In fact, there are several ways in which we know when ice first began to accumulate on the Antarctic continent. Firstly, offshore seismic surveys and drilling campaigns of sediments on the continental slope and shelf. These sediments are dated using biostratigraphical methods (such as dinoflagellate cysts), strontium isotopes analysis on pristine shells, and by isotopic analysis of volcanic rocks (see Davies et al., 2012). Some of this evidence comes from the Antarctic Peninsula, summarised here.

This is supported by the deep-sea record of del18O, which is a proxy for global ice volume, and global eustatic sea level change. Together, these indices suggest that glaciation began on Antarctica around 35 million years ago.

 

Davies, B.J., Hambrey, M.J., Smellie, J.L., Carrivick, J.L., Glasser, N.F., 2012. Antarctic Peninsula Ice Sheet evolution during the Cenozoic Era. Quaternary Science Reviews 31, 30-66.

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