Vanishing Islands in a Rising Sea

The evacuation of all 2,000 inhabitants of Cataret Island marked the beginning of the end for many low-lying atolls in the Indian and Pacific Oceans.   Rising sea levels have flooded the food and fresh water sources on this small island off Papua, New Guinea, and made it necessary to relocate the inhabitants to nearby Bougainville.

According to IPCC, the Intergovernmental Panel on Climate Change, sea levels worldwide will rise up to 88 cm (34.6 in.) by the end of this century.  Other studies indicate the rise could be lower or much higher than that, depending on the pace of global warming.

            A 3 ft (1 m) sea level rise threatens the existence of many island nations in the Pacific and Indian Oceans.  Many of these coral atolls are only 6 or 7 ft (2m) above sea level.  While a 3 ft (1m) rise in the sea would not totally submerge every one of these islands, many of them would become uninhabitable due to sea water intrusion into the fresh water aquifer, salt water swamping of coconut and taro fields, washing out of roads, hospitals, and public utilities.  Many of these islands are already trying to cope with these destructive changes.  In addition to Cataret, several other low islands are making plans to relocate their populations.  New Zealand has agreed to accept refugees from a small island in the Vanuatu group that is currently undergoing flooding from storms and a rising sea level, and may soon have to be evacuated.

            Among the islands under threat of submersion by the end of this century are the Maldives in the Indian Ocean, hundreds of atolls in the Pacific around New Guinea, the Cook Islands, Fiji Islands, Solomon Islands, and Marshal Islands.  Kiribati, Tuvalu, and Vanuatu all have surrounding atolls that have been partially or completely submerged by rising seas.  Low-lying cities such as Shanghai, only 6 ft (2m) above sea level, and the heavily populated coast of Bangladesh that lies only a few feet above sea level, will also be adversely affected by the steady encroachment of the sea.  Sea water intrusion into Asian rice paddies in fresh water wetlands will threaten the food supply in that part of the world.

            World sea level has risen 8 inches (20cm) in the past century, but global warming has greatly accelerated the process in the past 20 years.  Projected air temperature increases for the 21^st century range from 2.0 to 11.5 degrees F (1.1 to 6.4 degrees C).  NASA satellite imaging shows that the polar ice cap is melting at the rate of 9% per decade.  The Greenland Ice Sheet is disappearing equally fast, and almost all the glaciers of the world are in retreat.

            Rising sea levels are caused by two main factors: (1) melt water from ice caps, ice sheets, and glaciers, and (2) thermal expansion of the sea water (as water gets warmer, it expands and takes up more space).  Both ice melt and thermal expansion are products of global warming.  Scientists estimate that melt water from ice caps, ice sheets, and glaciers contribute approximately 25% to the current increase in ocean volume, while thermal expansion is responsible for 50%.  Exactly what makes up the remaining 25% contribution is not clearly understood.  But to sum up, as air temperature rises due to global warming, ocean temperatures go up, ocean volume increases, and the sea level continues to rise.

            Most of the world’s seacoast cities, ports, and recreation areas will eventually be overtaken by rising sea levels.  New York, New Orleans, Miami, London, Amsterdam, and Venice are among world cities that may be working hard to “hold back the sea” in the not too far distant future.