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The drill fluid used is normally a petroleum-derived liquid like kerosene. It must have a suitable freezing point and viscosity.

ice core dating-81

* 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[2].

They allow us to go back in time and to sample accumulation, air temperature and air chemistry from another time[1].

We apply this method simultaneously to one Greenland (NGRIP) and three Antarctic (EPICA Dome C, EPICA Dronning Maud Land, and Vostok) ices cores, and refine existent chronologies.

Our results show that consistent ice and gas chronologies can be derived for depth intervals that are well-constrained by relevant glaciological data.

This 19 cm long of GISP2 ice core from 1855 m depth shows annual layers in the ice.

This section contains 11 annual layers with summer layers (arrowed) sandwiched between darker winter layers. From top to bottom: * Levels of carbon dioxide (CO2). High rates of snow accumulation provide excellent time resolution, and bubbles in the ice core preserve actual samples of the world’s ancient atmosphere[6]. By looking at past concentrations of greenhouse gasses in layers in ice cores, scientists can calculate how modern amounts of carbon dioxide and methane compare to those of the past, and, essentially, compare past concentrations of greenhouse gasses to temperature. Ice cores have been drilled in ice sheets worldwide, but notably in Greenland[3] and Antarctica[4, 5]. Unfortunately, annual layers become harder to see deeper in the ice core. Other ways of dating ice cores include geochemisty, layers of ash (tephra), electrical conductivity, and using numerical flow models to understand age-depth relationships. Ice cores provide us with lots of information beyond bubbles of gas in the ice.