3.3.2: Sea Ice
In addition to land-based glaciers and ice sheets, the Arctic and Antarctic regions also contain sea ice, which is ice that forms over the open ocean and which often experiences large seasonal changes. Sea ice in Antarctica is relatively stable and experiencing minimal loss ( Fig 3.3.2.1 ).
Sea ice in the Arctic Ocean is experiencing significant melting ( Fig 3.3.2.2 ). Ice is very reflective and absorbs very little of the sun’s energy; however, liquid water absorbs more than it reflects. Consequently, melting of sea ice leads to a feedback loop in which more open water leads to warmer surface water, which melts more ice and leads to more open water and more melting of sea ice.
The extent of sea ice loss in the Arctic Ocean is most clearly visible in the comparison between the record minimum year of 2012, and an average historical year, such as 1984 (Fig 3.3.2.3). Melting of sea ice in the Arctic Ocean is so severe that scientists predict the Arctic Ocean could be ice free in September by the year 2050.