Final answer:
The level of the ocean's surface is called sea level, which acts as a baseline for elevation and depth on Earth. It's distinct from ocean concepts like thermocline, upwelling, and tides. Sea level rise, attributed to climate change, is an important environmental concern.
Step-by-step explanation:
The Level of the Ocean's Surface
The level of the ocean's surface is commonly referred to as sea level. It serves as a baseline for measuring elevation and depth on Earth. The other options provided, such as a thermocline, upwelling, and tides, relate to different aspects of oceanography. A thermocline is a layer within a body of water where the temperature changes rapidly with depth, upwelling is the rising of deep ocean waters due to prevailing winds, and tides are the alternate rising and falling of sea level caused by the gravitational influence of the moon and sun on Earth's oceans.
When we talk about sea level rise, we refer to the increase in the mean level of the ocean's surface, which is a significant concern in the context of climate change. The increase in global temperatures leads to the melting of land ice and thermal expansion of water, both contributing to sea level rise. This rise can lead to coastal erosion, increased flooding, and other environmental impacts.