In fact the clearest dating is obtained when several seasonal signals are examined and compared.Many cores however come from regions where the yearly snowfall accumulation is too small for the annual layers to be distinguished, and other methods of dating must be used.These all have independent methods of dating, and so the timing of a major climate shift or volcanic eruption can be used to synchronise the age scales.
However, the layers in ice cores are not generally visible in the ice.
They only become apparent when the core is analysed for a chemical signal that varies with the seasons, which most signals do, to some extent.
This region currently drains 22% of the Antarctic ice sheet and has undergone large-scale sustained retreat since the Last Glacial Maximum.
It is important to constrain and understand this deglaciation if we are to predict the future of the ongoing retreat in other parts of the West Antarctic Ice Sheet and its future contribution to sea level rise.
It was one of the earliest techniques to be developed, during the 1940s.
Radiocarbon dating works because an isotope of carbon, C, is constantly formed in the atmosphere by interaction of carbon isotopes with solar radiation and free neutrons.
Here, 7 protons and 7 neutrons (N) plus one neutron form an isotope of carbon, with 8 neutrons and 6 protons.
This project aims to exploit the peculiar way in which ice flows to provide new constraints on the retreat of the grounding line – the line that separates grounded ice from floating ice in marine ice sheets – over the last few thousand years through the area currently occupied by the Ronne Ice Shelf in West Antarctica (Figure 1).
From: Wikimedia Commons We can indirectly date glacial sediments by looking at the organic materials above and below glacial sediments. Marine geological constraints for the grounding-line position of the Antarctic Ice Sheet on the southern Weddell Sea shelf at the Last Glacial Maximum.
Radiocarbon dating provides the age of organic remains that overly glacial sediments.
We are now combining these data with radar observations of structures that form within the ice rises due to the peculiar way in which ice deforms in these locations.