The fractionation technique of dating

The bubbles disappear and the ice becomes more transparent.

the fractionation technique of dating-24the fractionation technique of dating-20the fractionation technique of dating-22

An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier.

Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper, and an ice core contains ice formed over a range of years.

The proportions of different oxygen and hydrogen isotopes provide information about ancient temperatures, and the air trapped in tiny bubbles can be analysed to determine the level of atmospheric gases such as carbon dioxide.

Since heat flow in a large ice sheet is very slow, the borehole temperature is another indicator of temperature in the past.

Buried under the snow of following years, the coarse-grained hoar frost compresses into lighter layers than the winter snow.

As a result, alternating bands of lighter and darker ice can be seen in an ice core.

The cuttings (chips of ice cut away by the drill) must be drawn up the hole and disposed of or they will reduce the cutting efficiency of the drill.

The fluid must have a low kinematic viscosity to reduce tripping time (the time taken to pull the drilling equipment out of the hole and return it to the bottom of the hole).

Ice cores have been studied since the early 20th century, and several cores were drilled as a result of the International Geophysical Year (1957–1958).

Depths of over 400 m were reached, a record which was extended in the 1960s to 2164 m at Byrd Station in Antarctica.

These data can be combined to find the climate model that best fits all the available data. Coastal areas are more likely to include material of marine origin, such as sea salt ions.

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