What is the effect called when surface temperatures of the ocean are unusually warm in the central Pacific?

The phenomenon where surface temperatures of the ocean are unusually warm in the central Pacific is known as El Niño. This climatic event is characterized by the periodic warming of ocean water in the central and eastern tropical Pacific, which can significantly influence weather patterns around the globe. During El Niño, the usual trade winds weaken, allowing warm water to build up along the western coast of South America, which can lead to a variety of weather impacts including increased rainfall in some regions and droughts in others.

Understanding El Niño is important because it plays a crucial role in global climate variability. Its effects can disrupt normal weather patterns, affecting agriculture, ecosystems, and even economies in different parts of the world. This makes El Niño a key subject of study in oceanography and climate science, highlighting the intricate connection between ocean temperatures and atmospheric conditions.

The other concepts listed refer to different oceanographic or climatic processes. Ocean upwelling refers to the rise of cold, nutrient-rich water from the deep ocean to the surface, typically associated with areas of high productivity, rather than temperature increase. The thermocline is the layer in the ocean where temperature changes rapidly with depth, while the greenhouse effect refers to the warming of Earth's atmosphere due to greenhouse gases, which is a separate concept from ocean