Digital SAT Reading and Writing Practice Question #501

Isotopic fractionation refers to the physical process wherein lighter isotopes, such as Oxygen-16, evaporate more readily than heavier isotopes like Oxygen-18. Consequently, during periods of global warming, the oceans become relatively enriched in Oxygen-18, and the precipitation subsequently trapped in polar ice cores typically exhibits a proportionally higher concentration of Oxygen-18 than it would in colder periods. However, researchers analyzing a specific Greenland ice core corresponding to the Eemian interglacial period—a time of documented global warmth—found anomalously low levels of Oxygen-18. Climate scientist Dr. Aris Thorne suggests that this anomaly does not contradict the fundamental principles of fractionation; rather, it reflects a highly localized atmospheric dynamic. Which finding, if true, most directly supports Dr. Thorne's hypothesis?