Which property of isotopes is important in dating

11-Aug-2020 19:15 by 6 Comments

Which property of isotopes is important in dating

420,000 years of ice core data from Vostok, Antarctica research station. From bottom to top: * Solar variation at 65°N due to en: Milankovitch cycles (connected to 18O). They spent two nights at each site, first collecting radar data and secondly collecting a 15 m shallow ice core. This schematic cross section of an ice sheet shows an ideal drilling site at the centre of the polar plateau near the ice divide, with ice flowing away from the ice divide in all direction. The large Greenland and Antarctic ice sheets have huge, high plateaux where snow accumulates in an ordered fashion. The team were travelling across the West Antarctic Ice Sheet to study snow accumulation.

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. Through analysis of ice cores, scientists learn about glacial-interglacial cycles, changing atmospheric carbon dioxide levels, and climate stability over the last 10,000 years. This picture shows a traversing field camp from December 2010. 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]. 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. Ice cores provide us with lots of information beyond bubbles of gas in the ice. This section contains 11 annual layers with summer layers (arrowed) sandwiched between darker winter layers.

From the US National Oceanic and Atmospheric Administration, Wikimedia Commons.

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.

The bottom plot shows global ice volume derived from δ18O measurements on marine microfossils (benthic foraminifera) from a composite of globally distributed marine sediment cores. An example of using stable isotopes to reconstruct past air temperatures is a shallow ice core drilled in East Antarctica[10].

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