Understanding Sea Level Variations
We usually measure land height relative to sea level. For example, the eastern peak of Mount Elbrus rises to 5,595 meters above sea level. That makes it easy to assume sea level is a fixed, unchanging reference. But is it?
No, it’s not. Seas and oceans don’t sit level — they tilt. For example, the difference in sea level between the central part of the Baltic Sea and the Åland Islands is about 30 centimeters. At the same latitude along the Pacific coast of the Americas, sea level is about half a meter higher than on the Atlantic coast. Moving from south to north along the Atlantic coastline, sea level gradually increases by about 35 centimeters. Even at the ends of the Panama Canal, which is only 80 kilometers long, the average difference in sea level is around 20 centimeters.
What Causes Sea Level Inequality?
Many factors influence uneven ocean water levels. The biggest drivers are wind and temperature differences. If a layer of ocean water 4,000 meters thick is heated by one degree Celsius, the sea surface will rise by about 30 centimeters. Conversely, cooling that layer by one degree causes it to contract by about 33 centimeters.
