What do variations in oxygen isotopes in ocean sediments signify?

Variations in oxygen isotopes in ocean sediments are significant because they provide insights into historical climate conditions, particularly the changes between glacial and interglacial periods. The ratios of different oxygen isotopes, specifically oxygen-16 and oxygen-18, can indicate past temperatures and ice volume on Earth. During glacial periods, lighter oxygen isotopes are preferentially locked away in ice sheets, resulting in a higher ratio of the heavier isotopes in the ocean sediments. Conversely, during warmer interglacial periods, the melting of ice releases these lighter isotopes back into the ocean. Therefore, by analyzing these isotopic ratios in sediment cores, scientists can reconstruct past climate conditions and understand the timing and intensity of glacial and interglacial cycles, making this option the correct answer.