The moon may look like a peaceful neighbour, but scientists are warning that it may be trying to kill us.
Thank the moon’s 18.6-year “wobble” cycle, which has been observed for some 300 years.
When it wobbles one way, the high tides are lower. When it wobbles the other, however, the high tides are even higher, which could be especially destructive as sea levels rise.
“We’re going to have sort of a double-whammy,” National Oceanic and Atmospheric Administration (NOAA) oceanographer William Sweet, one of the study’s authors, told The Washington Post. “It means that coastal communities – unless they adapt and fortify – are likely to expect even greater flooding than they might otherwise.”
NOAA reported 600 floods caused by high tides along the East Coast and Gulf Coast in 2019 alone. The coming wobble could worsen that, leading to “dramatic increases in flood numbers” in coastal cities around the nation.
“We’re getting closer and closer to the flooding thresholds or tipping point in these coastal locations,” NASA Sea Level Change Team leader Ben Hamlington told NPR. “The same variability in the past that didn’t cause flooding is now going to cause flooding.”
There could even be “clusters” of floods, sometimes lasting a month or more, NASA said.
Just one region may escape the threat – for now.
“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,” NASA said.
Tidal floods involve less water than those caused by major weather events, such as storms, and are often taken less seriously as a result.
“But if it floods 10 or 15 times a month, a business can’t keep operating with its parking lot underwater,” Phil Thompson, an assistant professor at the University of Hawaii and the lead author of the new study, said in a news release. “People lose their jobs because they can’t get to work. Seeping cesspools become a public health issue.”
In response, NASA has created a “Sea Level Portal” to project what could happen in the future, which includes tools to anticipate flooding.