Final answer:
The correct statement about mean sea level is that it is a measurement based on long-term averaging of hourly tidal levels at specific sites. This measure accounts for natural variability and has seen changes over historical and recent times due to natural forces and human-influenced climate change.
Step-by-step explanation:
Sea level:
The sea level is that it is calculated based on average tidal levels recorded hourly at a given site over a period of many years. Mean sea level is a critical reference point used in geography and environmental science, representing the average ocean level of our planet that has been measured over time. Mean sea level is determined by measuring the tidal heights at a specific location over a long period of time, usually several years. By calculating the average of these tidal heights, a consistent value for mean sea level can be determined.
Variability in sea level is influenced by numerous factors, such as gravitational pull from the moon, changes in local topography and bathymetry, and climate variations causing ice melt and thermal expansion of the oceans. Notably, sea level has changed significantly over Earth's history, experiencing both natural and human-influenced variations. In recent decades, sea levels have been rising at a faster rate due to climate change, contributing to concerns about coastal flooding and ecosystem disruption.