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They allow us to go back in time and to sample accumulation, air temperature and air chemistry from another time.
The distribution of melt layers through time is a function of the past climate, and has been used, for example, to show increased melting in the Twentieth Century around the NE Antarctic Peninsula.
It is possible to discern past air temperatures from ice cores.
For example, melt layers are related to summer temperatures.
More melt layers indicate warmer summer air temperatures.
Deeper cores require more equipment, and the borehole must be filled with drill fluid to keep it open.
The drill fluid used is normally a petroleum-derived liquid like kerosene.
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.
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.
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 and Antarctica[4, 5].
* 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.
This section contains 11 annual layers with summer layers (arrowed) sandwiched between darker winter layers.Tags: Adult Dating, affair dating, sex dating