Which term describes the phenomenon characterized by cooler than normal temperatures in the ocean?

The term that describes the phenomenon characterized by cooler than normal temperatures in the ocean is La Niña. This climatic event is part of the El Niño-Southern Oscillation (ENSO) cycle and manifests in the eastern and central Pacific Ocean. During La Niña, the trade winds strengthen and push warm ocean water toward the western Pacific, allowing colder waters to rise to the surface in the eastern Pacific. This combination of factors typically results in a number of significant climate impacts, including wetter conditions in some regions and drier conditions in others.

Understanding La Niña is crucial because it influences various global weather patterns, such as increased rainfall in parts of Asia and drier conditions in the western United States. This phenomenon is important for predicting agricultural yields, managing water resources, and preparing for extreme weather events.

The other terms listed do not accurately describe this cooling phenomenon. For instance, the warm phase refers to conditions associated with El Niño, which is characterized by warmer than normal ocean temperatures. The greenhouse effect relates to the warming of the Earth due to increased greenhouse gases and is unrelated to ocean temperature anomalies. Thus, the unique conditions of La Niña are clearly delineated by its association with cooler ocean temperatures.