Paleoclimatologists measure the ratio of oxygen-18 to oxygen-16 in the calcium carbonate shells of benthic foraminifera found in deep-sea sediment cores. Because water molecules containing the lighter oxygen-16 isotope evaporate more readily from the oceans and are subsequently trapped in continental ice sheets during glacial periods, a higher ratio of oxygen-18 to oxygen-16 in these deep-sea shells indicates a larger global ice volume at the time the shells were formed. Furthermore, the analysis of cores from the North Atlantic shows that during the last three glacial periods, the peak oxygen-18 to oxygen-16 ratio was reached approximately 5,000 years before the minimum sea surface temperatures were recorded in the same region. Which of the following statements are most strongly supported by the information above? (Select all that apply)
- During periods of extensive global glaciation, the ocean water from which benthic foraminifera construct their shells contains a lower concentration of oxygen-16 relative to oxygen-18 than it does during interglacial periods.Answer
- In the North Atlantic, the maximum extent of global ice volume during the last three glacial periods occurred before the ocean surface waters reached their coldest temperatures.Answer
- CThe calcium carbonate shells of benthic foraminifera formed during interglacial periods contain a higher total absolute quantity of oxygen-16 than those formed during glacial periods.
- DThe trapping of oxygen-16 in continental ice sheets is the primary cause of the decrease in sea surface temperatures in the North Atlantic during glacial periods.
- EAll deep-sea marine organisms that construct calcium carbonate shells exhibit the exact same oxygen isotope ratios as benthic foraminifera from the corresponding time periods.