Environment: understanding atmospheric and ocean flows
Environment: understanding atmospheric and ocean flows

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Environment: understanding atmospheric and ocean flows

3.10 Summary of Section 3

The ice cores in Greenland and Antarctica currently provide a direct record of the snowfall going back around 800 000 years. As snow falls, impurities such as lead are trapped in the ice, so ice cores can give direct measurements of past atmospheric concentrations. By using isotope proxies such as oxygen-16 and oxygen-18, ice cores can be used to estimate temperature changes.

Over the time period of the ice cores, the Earth has gone through nine cyclical temperature variations, with a cold period (ice age) approximately every 100 000 years. Trapped gases within the ice cores allow a direct measurement of atmospheric CO2 concentration, and throughout the entire Dome C record you can see that temperature and CO2 are positively correlated.

Milankovitch cycles caused by variations in the Earth’s orbit, amplified by greenhouse gases, are the best current theory for the cause of ice ages, but these do not provide a sufficiently accurate model to predict the near future course of atmospheric change.

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