New Zealand’s cities are sinking, risk being affected by rising seas: Study

ISTANBUL

New Zealand’s major cities and shorelines are steadily sinking and risk being affected by rising seas, according to a new study, a public broadcaster reported on Monday.

The coastlines near major cities in New Zealand are sinking by a few millimeters each year, with some of the highest rates occurring in the coastal suburbs of Christchurch, said Radio New Zealand News.

Sea level rise is occurring worldwide as the ocean expands due to warming temperatures, while glaciers and polar ice sheets continue to melt, said a researcher at Japan's Kyoto University and Victoria University of Wellington.

Meanwhile, land subsidence occurs on regional or local scales but can potentially amplify the effects of sea-level rise, doubling or tripling its impact in certain areas.

This combined effect of rising seas and sinking land is known as relative sea-level rise.

The researchers used satellite radar images of the Earth's surface to gain insights into which coastal areas are most at risk, requiring detailed and precise measurements of land subsidence.

The study found that estimates of relative sea-level rise for cities of Christchurch, Wellington, Dunedin, and Auckland are near or exceed 7mm per year.

If this trend continues, it would result in approximately 70cm (23.6 inches) of sea-level rise per century, posing a significant threat to most sea defenses.

The study identified hotspots of rapidly sinking regions, which often correspond to areas where the land has been modified, especially along the waterfront.

In the 20th century, large areas of land were reclaimed from the ocean, and this newly created land is still compacting, leading to an unstable foundation for the infrastructure built on top.