New Zealand cities face accelerated sea-level rise due to sinking shorelines

Global sea levels have risen significantly since 1880, with a notable acceleration in the past 30 years. A recent study by New Zealand researchers reveals that many of the country's coastal cities are experiencing sinking shorelines, exacerbating the impact of rising sea levels. The study, led by Dr. Jesse Kearse, used satellite-based mapping to measure vertical land motion in major urban coastal areas between 2018 and 2021. The findings indicate that 77% of New Zealand's urban coastlines are subsiding at a rate of 0.5 mm/yr or more. Some areas, particularly in Christchurch, showed subsidence rates exceeding 3.0 mm/yr. Human activities, such as groundwater extraction and land reclamation, contribute to these localized subsidence hotspots, potentially doubling or tripling the effects of sea-level rise. These findings underscore the importance of considering vertical land motion in assessing sea-level rise impacts and planning future developments in vulnerable coastal areas. The combination of rising sea levels and sinking shorelines poses a significant threat to coastal infrastructure and communities in New Zealand.