Title: What Is Sea Level and How Is It Measured?
Headings: What Is Sea Level and How Is It Measured?
What Is Sea Level and How Is It Measured?
Local Sea Level Varies
Mean Sea Level
Changing Sea Levels
Impacts of Sea Level Rise and Fall

Content: Islands and continents can rise and fall due to tectonics or due to the melting or growing of glaciers and ice sheets. The second is the increase or decrease in the total amount of water in the oceans . This is primarily caused by the increase or decrease in the quantity of global ice on the Earth's landmasses. During the biggest Pleistocene glaciations about 20,000 years ago, mean sea level was about 400 feet (120 meters) lower than mean sea level today. If all of the Earth's ice sheets and glaciers were to melt, sea level could be up to 265 feet (80 meters) above current mean sea level. Temperature causes water to expand or contract, thus increasing or decreasing the volume of the ocean. Impacts of Sea Level Rise and Fall
When sea level rises, river valleys become inundated with seawater and become estuaries or bays. Low-lying plains and islands are flooded and disappear under the sea. These are the primary concerns about climate change and rising mean sea level, which appears to be rising by about one-tenth of an inch (2 mm) each year. If climate change results in higher global temperatures, then glaciers and ice sheets (especially in Antarctica and Greenland) could melt, dramatically increasing sea levels.