Rising sea levels induced by climate change and a regular 18-year lunar oscillation will combine to increase the risk of coastal flooding in the 2030s, says space agency.
Nasa has warned that a regularly occurring lunar wobble will increase the risk of coastal flooding from the middle of the next decade.
The 18-year lunar oscillation can either amplify or suppress tides, depending on what half of the cycle the moon is in.
During half of the cycle, high tides are higher, and low tides are lower. During the other half of the cycle, less extreme tides are recorded. The process is exactly the same as monthly spring and neap tides, but on a longer cycle.
The moon will next be in the amplification phase around 2030, says Nasa, meaning it will combine with rising sea levels due to climate change to increase the risk of coastal flooding around the globe.
This is expected to “cause a leap in flood numbers on almost all US mainland coastlines, Hawaii, and Guam”, the agency said.
“Only far northern coastlines, including Alaska’s, will be spared for another decade or longer because these land areas are rising due to long-term geological processes.”