Ice Core Data
Many materials can appear in an ice core. Layers can be measured in several ways to identify changes in composition. Small meteorites may be embedded in the ice. Volcanic eruptions leave identifiable ash layers. Dust in the core can be linked to increased desert area or wind speed.
Isotopic analysis of the ice in the core can be linked to temperature and global sea level variations. Analysis of the air contained in bubbles in the ice can reveal the palaeocomposition of the atmosphere, in particular CO2 variations. There are great problems relating the dating of the included bubbles to the dating of the ice, since the bubbles only slowly "close off" after the ice has been deposited. Nonetheless, recent work has tended to show that during deglaciations CO2 increases lags temperature increases by 600 +/- 400 years. Beryllium-10 concentrations are linked to cosmic ray intensity which can be a proxy for solar strength.
There may be an association between atmospheric nitrates in ice and solar activity. However, recently it was discovered that sunlight triggers chemical changes within top levels of firn which significantly alter the pore air composition. This raises levels of formaldehyde and NOx. Although the remaining levels of nitrates may indeed be indicators of solar activity, there is ongoing investigation of resulting and related effects of effects upon ice core data.
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