One of the major challenges in understanding the evolution of our own species is identifying the role climate change has played in the evolution of hominin species.
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* Solar variation at 65°N due to en: Milankovitch cycles (connected to 18O). Ice core records allow us to generate continuous reconstructions of past climate, going back at least 800,000 years.
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.
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.
The thickness of the annual layers in ice cores can be used to derive a precipitation rate (after correcting for thinning by glacier flow).
Past precipitation rates are an important palaeoenvironmental indicator, often correlated to climate change, and it’s an essential parameter for many past climate studies or numerical glacier simulations.
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.
Deeper cores require more equipment, and the borehole must be filled with drill fluid to keep it open.
Unfortunately, annual layers become harder to see deeper in the ice core.