Explain why changes in oxygen isotopes (d 18 O) in the ocean reflect changes in

Question

Explain why changes in oxygen isotopes (d18O) in the ocean reflect changes in the amount of ice on land? (3 pts)

Why do isotope ratios in glacier ice change, and what types of climate information does this provide? (3pts)   

The figure bellow shows water isotope records from both Greenland and Antarctica from 70000 years ago to 20000 years ago. Greenland water isotopes are labeled NGRIP 18O (‰) and Antarctic water isotopes are labeled WDC 18O (‰). The 18O notation is just another way of expressing the ratio of O18/O16.

Explanation / Answer

1. Ocean waters are particularly rich in heavy oxygen. During ice ages, water vapour having heavy oxygen rains out of teh atmosphere at lower latitudes because of teh extension of cooler temperatures towards the equator. The water vapour containing lighter oxygen moves towards the poles, condenses and falls onto the ice sheets where it stays. Thus the water in the ocean will be accumulated with heavy oxygen and ice develops at a higher concentration of lighter oxygen. Thus the changes in the concentration of oxygen isotopes like whether it is light oxygen or heavy oxygen tells scientists that light oxygen is trapped in te ice sheet or not. The exact oxygen ratio can show how much ice covered teh earth.

Conversely higher than global concentration of light oxygen in ocean water indicate that global temperatures ahve warmed and subsequently the glaciers or ice in the poles have melted resulting in less global ice cover and less saline water. thus scientists connect lower levels of heavy oxygen with warmer temperatures and melting.

2. Isotope ratios in glacier changes beacuse of the climatic changes. The ratio of oxygen isotopes thus gives record of ancient water temperature. During ice ages glaciers will be having more light oxygen than heavy oxygen. So when temperature increases, these lighter oxygen will be released by the melting of ice therby changing the isotope ratios in glacier ice. So this ratio can direclty give the information about the preaviling temperature whether it was an ice age or not.

3. No Figure provided..

Hope this helps you..

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