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Water isotopes in ice cores and sediments What is one of the main reasons O18/O1

ID: 111320 • Letter: W

Question

Water isotopes in ice cores and sediments

What is one of the main reasons O18/O16 isotope ratios in marine carbonate sediments change? (3pts)

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.

From the graph what happens to Antarctic temperature as inferred from water isotopes after Greenland experiences rapid warming events? These events are indicated by the yellow line and are called Dansgaard-Oeschger Events.( 3pts)  

60 40 500 b 2 10 98 MIS 3 -10DO: 1716 15 14 13 12 7 6 52 51 65 60 50 WD2014 age (kyr )

Explanation / Answer

What is one of the main reasons O18/O16 isotope ratios in marine carbonate sediments change? The reason behind the change in the ratios is the resistance of O18 isotope in evaporation as it has 2 more neutrons and it is heavier than the O16. Since it is heavier, comparitively the O16 evaporates and forms glaciers and the O18 is left behind in the ocean.