What is the relationship between glaciers and sea level?
“Eustacy” refers to a change in global sea level. For much of its multi-billion year history, Earth has experienced hundreds of periods of eustatic rise and eustatic fall of sea level. In simplest terms, there are two primary causes of sea level change:
- change in number of water molecules (“eustatic change”)
- change in water temperature
The reason that sea level rises because of an increase in water temperature is that the size of each individual water molecule increases as temperature increases. This is referred to as “steric change.” The science community believes that steric change accounts for 50% of present day sea level change.
Glaciers play a critical role in controlling the number of molecules contained in the ocean. For any given temperature, sea level is a function of the number of water molecules contained in the ocean. As glaciers grow, the water that contributes to their expansion evaporates from the oceans, falls as snow in the glacier’s accumulation area, and remains locked in the glacier as glacier ice. The longer this happens, the lower sea level becomes. When temperatures increase, glacier melting increases. The newly released meltwater returns to the ocean and sea level rises.
- If all of the glacier ice on Earth were to melt, sea level would rise ~ 80 m (~ 265 ft), flooding every coastal city on the planet.
- If all of Earth’s temperate glaciers melted, sea level would rise ~ 0.3 – 0.6 m (~ 1 - 2 ft).
- If all of Greenland’s glaciers melted, sea level would rise ~ 6 m (~ 20 ft).
- If all of Antarctica’s glaciers melted, sea level would rise ~ 73 m (~ 240 ft).
- If all of Alaska’s glaciers melted, sea level would rise ~ 0.12 m (~ 4.7 in).