Coral atolls hold on despite sea-level rise

Ray Lilley in the Associated Press: Some South Pacific coral atolls have held their own or even grown in size over the past 60 years despite rising sea levels, research showed Thursday. Some scientists worry that many of the tiny, low-lying islands throughout the South Pacific will eventually disappear under rising sea levels.

But two researchers who measured 27 islands where local sea levels have risen 4.8 inches (120 millimeters) — an average of 0.08 inch (2 millimeters) a year — over the past 60 years, found just four had diminished in size. The reason: Coral islands respond to changes in weather patterns and climate, with coral debris eroded from encircling reefs pushed up onto the islands' coasts by winds and waves.

Professor Paul Kench of Auckland University's environment school and coastal process expert Arthur Webb of the Fiji-based South Pacific Applied Geoscience Commission, used historical aerial photographs and high-resolution satellite images to study changes in the land area of the islands. While four had gotten smaller, the other 23 had either stayed the same or grown bigger, according to the research published in the scientific journal Global and Planetary Change.

The shape-shifting islands changed their size through what the pair describe as ocean shoreline displacement toward their lagoons, lagoon shoreline growth or extensions to the ends of elongated islands. Kench said it had been assumed that islands would "sit there and drown" as sea levels rise. But as the sea rises, the islands respond. "They're not all growing, they're changing. They've always changed ... but the consistency (with which) some of them have grown is a little surprising," he told The Associated Press on Thursday….

A triangular atoll in the Western Pacific, from NOAA