365 Days of Climate Awareness 215 – Sea Level in the Solomon Islands

The Solomon Islands are a nation consisting of six major islands and more than 900 minor islands northeast of Australia and east of Papua New Guinea, on the western margin of the Pacific Ocean. The islands were first settled nearly 30,000 years ago by Australasian migrants, and the current population is 652,000. Its capital is Honiara, on the island of Guadalcanal. The nation has been independent since 1978. However, the global ocean has risen slightly more than 20 cm over the past 140 years, and the Solomons are slowly disappearing.

Map of the Solomons.

In the early 2000’s local Solomon fishermen began noting the disappearance of tiny coral islands in their fishing grounds. These reports led to an aerial photograph study in Australia which found a pattern of tiny coral islands in Melanesia disappearing in the late 20^th and early 21^st centuries. The western Pacific has seen faster sea level rise than other parts of the world. On top of glacial melt, which affects the entire planet more or less equally, relative increase in ocean temperature in that part of the Pacific is due to thermal expansion of the water, as the sea warms locally. Some of the most extreme warming in the global ocean has occurred in the southwest Pacific.

Honiara on Guadalcanal, the Solomons' capital.

Sea level rise is especially rapid in that part of the ocean.

Rising sea level for low-lying islands is not merely an erosional problem. The encroaching salt water contaminates freshwater resources on the island, upsetting the local ecosystem, making it unlivable for humans and other species as well. The monthly mean sea level anomaly is a noisy signal but shows a general upward trend of slightly more than the global average of 3 mm rise per year. Sea level data from the past 27 years shows a local increase in sea level of 15-20 cm, a rate approaching 7 mm annually. While some coralline islands in the western and southwestern Pacific seem to be gaining size, this is not the case in the Solomons.

Sea level, Solomon Islands, 1994-2021.

Shoreline retreat, 1947-2014.

Tomorrow: revisiting Australia’s rain forest.

Be brave, and be well.