Defining Sea Level
Sea level refers to the average height of the ocean's surface relative to land. It's a fundamental reference point used in geography, cartography, and many scientific disciplines. While often thought of as a constant, sea level is a dynamic quantity influenced by various factors.
How Sea Level is Measured
Measurements typically involve averaging the height of the ocean surface over a period (usually hourly or daily) to account for short-term variations like tides and waves. Tide gauges on coastlines provide long-term local data, while satellite altimetry offers comprehensive global measurements, tracking changes in sea surface height from space.
Global Mean Sea Level vs. Local Sea Level
Global mean sea level (GMSL) is an average across all oceans, representing the total volume of seawater. Local sea level, however, can vary significantly due to regional factors such as ocean currents, land subsidence or uplift, atmospheric pressure, and differences in gravitational pull from Earth's uneven mass distribution.
Importance and Applications
Understanding sea level is crucial for coastal management, maritime navigation, infrastructure planning, and monitoring climate change. Changes in global sea level, primarily driven by thermal expansion of ocean water and melting ice sheets and glaciers, serve as a key indicator of planetary warming and its environmental impacts.