October 2022

Melting snow and ice raises sea level

This article is part of our series focused on the causes and consequences of a warming planet.

ice and snowMelting land ice and warming oceans are two significant causes of sea level rise. In this article, we will discuss melting land ice. Next month, we will discuss the warming of the oceans.

Snow and ice floating in water, called sea-ice, covers much of the Arctic Ocean. The Arctic sea-ice has been melting rapidly in recent years, as discussed in last month’s newsletter article. Although melting sea ice impacts the warming of the Earth, its impact on raising sea level is minimal.

To understand this, put an ice cube in a glass and fill the glass with water. Does the glass overflow when the ice cube melts? No, the water level in the glass is unchanged. That’s because the volume of water displaced by the floating ice cube (the amount of the ice cube below water) is equal to the amount of water contained in the ice cube.

Conversely, melting snow and ice on land does raise sea level. For example, if a chunk of the ice covering Greenland breaks off and falls into the ocean, sea level rises.

It is like dropping an ice cube into a glass of water. The water level in the glass will rise by the amount of water the ice cube displaces in the glass, possibly causing the glass to overflow.

Similarly, if a portion of Greenland land ice melts and the water flows into the Arctic, sea level will rise. It is like adding water to the glass of water.

A complete melting of Greenland’s land ice would raise sea level by about 24 feet. A complete melting of Antarctica’s land ice would raise sea level by roughly 200 feet. Although this level of melting would take hundreds or thousands of years, it does show the potential impact of these land ice sheets on sea level.

Glaciers in parts of the world are being impacted. Scientific studies have confirmed that most of the world’s glaciers are retreating. Most of the smaller ones are rapidly disappearing.

For example, in 1850 there were about 150 glaciers in what is now Glacier National Park. Today there are only 25. It is expected that the Park will become glacier-free sometime in the future.

Sea level is expected to rise in the future. Research on Antarctica indicates that significant sea rise may occur in the near future. NASA has stated that we are probably already locked into at least three feet of sea level rise.

Fifteen of the world’s twenty megacities are vulnerable to sea level rise and increased coastal storm surges. More than half of the world’s population lives within 35 miles of the sea. Recent research estimates that over 25% of the world’s population live close enough to coastal areas and at a low enough elevation to be vulnerable to sea level rise, including more intensive storms and flooding.

Rising sea levels, even a small increase, can have devastating effects on our coastal areas. As seawater reaches inland it can flood freshwater wetlands, contaminate soils, cause destructive erosion, seep into freshwater aquifers and destroy wildlife habitat.

See the Ag Decision Maker website for more from this series.

Don Hofstrand, retired extension agricultural business specialist, agdm@iastate.edu
Reviewed by Dr. Eugene Takle, retired professor emeritus Iowa State University


Don Hofstrand

retired extension agricultural business specialist
View more from this author
Reviewed by

Dr. Eugene Takle

retired professor emeritus Iowa State University