Climate Number: One Inch per Year
The extent of the Arctic sea ice, which is usually gauged by its annual minimum extent in September, has been declining by 11.2 percent per decade since 1979. Large-scale effects of this decline impact Earth’s climate, primarily through increased absorption of sunlight by the open oceans. Local effects have also been documented. As ice has melted, the number of open water days along the coasts of the Beaufort and Chukchi Seas around Alaska increased from an average of 45 days in the late 1970’s to about 95 days in recent years. This increased melt means there is less ice protecting and stabilizing the sea cliffs in the region, which has caused increased cliff erosion along these coasts. The sea cliffs are now retreating at a rate of 45 feet per year. Decreased Arctic sea ice has also made the waters in the Chukchi Sea and Pacific-Arctic Ocean choppier. Less ice means that there is a larger area in which waves can develop and a longer ice-free season, allowing for late fall and early winter storms to move over water instead of ice. These developments mean that the average surface wave heights are growing over the Chukchi Sea at a rate of 0.8 inches per year and over the Pacific-Arctic at a rate of one inch per year. In the Chukchi Sea, there were five events in the 2000s when surface wave heights exceeded 13 feet; during the 1990s, only two of these events occurred.
For comparison: Global sea level is rising at about 2.1 millimeters per year, or a little over one-sixteenth of an inch.
Seasons: Winter, Spring, Summer, Fall
Sources: Overeem, I et al. “Sea ice loss enhances wave action at the Arctic coast.” Geophysical Research Letters 38 (2011): L17503 and National Snow and Ice Data Center: Arctic Sea Ice News and Analysis. Accessed Online 28 January 2011 <http://nsidc.org/arcticseaicenews/> and Francis, OP et al. “Ocean wave conditions in the Chukchi Sea from satellite and in situ observations.” Geophysical Research Letters 38 (2011): L24610.