Things can get technical pretty quickly when talking about Arctic ice. In many publications, you’ll come across terms like sea ice, ice sheets, glaciers, permafrost, summer ice, winter ice, multi-year ice, and first-year ice. To help you understand, we’ll focus on sea ice in this post.
The first thing that people often don’t know about sea ice is that melting sea ice does not contribute directly to sea level rise because the ice is already floating in the water. Like an ice cube melting on top of water in a glass, the melting ice doesn’t actually change the water level of the ocean. However, with more melting in the Arctic, there is less ice to reflect solar radiation and the Arctic becomes warmer as a result. When the Arctic is warmer, the Greenland ice sheet melts faster, causing sea level rise. Therefore, melting Arctic ice is a large lever on sea level rise.
What’s an ice sheet?
An ice sheet is just a mass of land-based ice formed from snow and ice that has piled up and compressed over many years. Ice sheets cover at least 20,000 square miles of land, while glaciers are the same thing but do not have a size minimum. So, anything smaller than 20,000 square miles is considered a glacier.
Below is a map of the primary ice sheets on Earth:
Of primary interest for sea level rise are the Greenland and West Antarctic ice sheets, which contain more than 99% of the freshwater ice on Earth. The Antarctic Ice Sheet is 5.4 million square miles (the size of the U.S. + Mexico combined) and the Greenland Ice sheet is 656,000 square miles (3x the size of Texas).
Above is the change in mass of the ice sheets until 2012. Notice that the Greenland ice sheet is melting the fastest, at around 400 Gigatons (billion tons) per year! When compared to West Antarctica’s 175 Gigatons per year, the Greenland Ice Sheet is the area of greatest concern. If the Greenland ice sheet melts, sea levels will rise by 23 feet. Restoring ice in the Arctic is the only way we can slow down or stop this melting and sea level rise that could severely impact populations worldwide.