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U from dust in the ice matrix can be used to provide an additional core chronology. The thickness of the annual layers in ice cores can be used to derive a precipitation rate (after correcting for thinning by glacier flow). Seasonal differences in the snow properties create layers – just like rings in trees.
If we want to reconstruct past air temperatures, one of the most critical parameters is the age of the ice being analysed.
Fortunately, ice cores preserve annual layers, making it simple to date 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.
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.