Deep sea core 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. Other ways of dating ice cores include geochemisty, layers of ash (tephra), electrical conductivity, and using numerical flow models to understand age-depth relationships. This 19 cm long of GISP2 ice core from 1855 m depth shows annual layers in the ice.



They form bubble-free ice layers, visible in the ice core. 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]. The presence of a “Little Ice Age”, a cooler period ending ~100 to 150 years ago, is contested in Antarctica. This can be related directly to concentrations of carbon dioxide, methane and other greenhouse gasses preserved in the ice.

Snow precipitation over Antarctica is made mostly of HO is related to surface temperature at middle and high latitudes.

The relationship is consistent and linear over Antarctica[9].