Higher 180/160 ratio in oceans indicates a colder climate, while a lower ratio signifies a warmer climate. Oxygen isotopes in foraminifera shells serve as a proxy for past climate conditions.
Higher 180/160 ratio in oceans indicates a colder climate as during colder times, the ratio of oxygen-18 to oxygen-16 in seawater increases due to the storage of oxygen-16 in ice sheets on continents.
Conversely, a lower 180/160 ratio indicates a warmer climate as when the climate warms, glacial ice melts and increases the 180/160 ratio in water.
Oxygen isotopes in foraminifera shells provide a proxy indicator of past climate by reflecting the temperature and evaporation of seawater.
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