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Climate change has already increased the frequency and severity of hurricanes and other extreme weather events around the world. – But there’s a smaller, less splashing threat on the horizon that could wreak havoc on America’s shores.
High tide flooding, also known as ‘nuisance flooding’, occurs in coastal areas when the tides reach about 0.6 meters above the daily average high tide and begin to flood streets or seep into them. storm sewers. True to their nickname, these floods are more of a nuisance than outright calamity, flooding streets and homes, forcing businesses to shut down and sump pits overflowing – but the longer they last, the more damage they can cause.
The United States experienced more than 600 of these floods in 2019, according to the National Oceanic and Atmospheric Administration (NOAA). But now, a new study by NASA warns that harmful flooding will become much more frequent in the United States as early as the 2030s, with the majority of the American coastline expected to experience three to four times as many flood days at high tide. every year for at least a decade.
The study, published on June 21 in the journal Nature Climate Change, warns that these additional flood days will not be distributed evenly over the year, but are likely to aggregate over a period of only a few months; coastal areas that currently only experience two or three floods per month may soon face a dozen or more.
These extended seasons of coastal flooding will cause major disruption to lives and livelihoods if communities do not start planning for them now, the researchers warned.
“It’s the effect that has built up over time that will have an impact,” said Phil Thompson, lead author of the study, assistant professor at the University of Hawaii. said in a press release. “If there are 10 or 15 floods a month, a business cannot continue to operate with its parking lot underwater. People lose their jobs because they cannot get to work. become a public health problem. “
Several factors are responsible for this expected increase in flood days.
On the one hand, there is the rise in sea level. As global warming warms the atmosphere, glacial ice is melt at a record rate, dumping huge amounts of meltwater into the ocean. As a result, the global average sea level has risen by about 8 to 9 inches (21 to 24 centimeters) since 1880, of which about a third has been in the past 25 years, according to NOAA. By the year 2100, sea level could rise from 12 inches (0.3 m) to 8.2 feet (2.5 m) above what it was in 2000, depending on the way which humans restrict greenhouse gas emissions in the decades to come.
While sea level rise alone will increase the frequency of flooding at high tide, they will have some help from the cosmos – in particular, the moon.
The moon influences the tides, but the moon’s power of attraction is not equal from year to year; the moon actually has an “oscillation” in its orbit, slightly changing its position relative to Earth on a rhythmic cycle of 18.6 years. During half of the cycle, the moon suppresses the tides on Earth, resulting in lower high tides and higher low tides. For the other half of the cycle, the tides are amplified, with higher high tides and lower low tides, according to NASA.
We are currently in the tidal amplification part of the cycle; the next cycle of tidal amplification begins in the mid-1930s; – and by then, global sea level will have risen enough to make those higher-than-normal tides particularly troublesome, the researchers found.
Thanks to the combined effect of sea level rise and the lunar cycle, high tide flooding will increase rapidly across the U.S. coast, the team wrote. In just over a decade, high tide flooding will turn “from a regional problem to a national problem with a majority of the US coastline affected,” the authors wrote. Other elements of the climate cycle, such as El Niño events, will cause these flood days to cluster in parts of the year, resulting in months of relentless coastal flooding.
As scary as this pattern may sound, it’s also important to understand it for planning purposes, the authors wrote.
“Understanding that all of your events are grouped together in a particular month, or that you might have more severe flooding in the second half of the year than the first – this is useful information,” said the co-author of the NASA’s Jet Propulsion Laboratory Ben Hamlington study. declaration.
Extreme weather events can get all the attention of the national media as they strike America’s shores, but high tide flooding will soon be impossible to ignore. Best to start planning now, before it’s too late, the authors concluded.
Originally posted on Live Science.
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