Some Parts of Hawaii Are Sinking Faster Than Anticipated
As islands like O’ahu gradually move away from the magmatic hotspot that initially formed them, the weight of the island is causing it to submerge into the ocean at a rate of about 0.6 millimeters annually. However, a recent study has revealed that in certain regions of O’ahu, the sinking rate can be as high as 25 millimeters per year, which is approximately 40 times faster than previously thought.
Researchers attribute this accelerated subsidence to specific areas like the industrial Mapunapuna region, where the land was built on sediment and artificial fill, leading to compaction over time.
Traditionally, Hawaii’s geological history has been characterized by rising land formations. Over a million years ago, the Pacific Island Plate shifted over a volcanic hotspot emerging through the Earth’s surface, resulting in the formation of sea-level volcanic islands, eventually forming the 50th U.S. state. However, a recent study from the University of Hawai’i at Manoa suggests that the island chain may now be undergoing a reversal in its geological trajectory.
Published in the journal Communications Earth & Environment, the study focused on analyzing subsidence on O’ahu, where areas were observed sinking at varying rates. The research highlights that subsidence plays a crucial role in evaluating future flood risks, with some areas experiencing sinking rates that could lead to increased flood exposure sooner than previously projected.
The accelerated subsidence in regions like Mapunapuna could significantly impact flood exposure by 2050, potentially compressing timelines for flood preparedness. Efforts like Climate Ready O’ahu are actively addressing climate concerns on the island, preparing for rising sea levels, soil erosion, and other climate change-related challenges.
By considering the alarming rate of subsidence, decision-makers can better plan for and implement climate adaptation strategies to mitigate potential risks and safeguard the island’s inhabitants.
In a press statement, Chip Fletcher, a co-author and director of the Climate Resilience Collaborative at UH Manoa, emphasized the importance of resilience and long-term urban planning. He highlighted that this research is crucial for the people of Hawai‘i as it ensures that local adaptation strategies are grounded in the most current scientific knowledge.
