“Wobble” in the moon’s orbit could cause record flooding by 2030 – study

High-tide floods have wreaked havoc on various coastal cities in the United States. These have inundated streets and homes, caused cesspools to overflow and forced businesses to close. However, a new study has warned that these high tide floods will become more frequent – thanks to the Moon’s gravitational pull and rising sea levels.

According to the National Oceanic and Atmospheric Administration (NOAA), high-tide floods happen when sea levels reach up to two feet above the daily average high tide. The water then starts spilling onto streets or bubbling up from storm drains. The NOAA added: “As sea level rise continues, damaging floods that decades ago happened only during a storm now happen more regularly, such as during a full-moon tide or with a change in prevailing winds or currents.”

The NOAA said that the U.S. experienced more than 600 high tide floods in 2019. But a study published June 2021 in Nature Climate Change warned that these floods will increase in frequency as soon as the 2030s arrive. Majority of the U.S.’s coastline will see three to four times as many high-tide flood days every year for at least a decade, the study added.

The researchers who penned the study warned that these extra flood days will not be spread out evenly over the year – but are likely to cluster together over the span of just a few months. This meant that coastal areas facing just two or three floods monthly may soon experience a dozen or more. They also cautioned that the prolonged coastal flood seasons will cause major disruptions to people’s lives and livelihoods if planning for them does not start immediately.

Lead study author Phil Thompson of the University of Hawaii said in a statement: “It’s the accumulated effect [of the floods] over time that will have an impact. If it floods 10 or 15 times a month, a business can’t keep operating with its parking lot under water. People lose their jobs because they can’t get to work. Seeping cesspools become a public health issue.”

The moon affecting sea levels will play a role in the increased flooding

The study authors noted two important factors that will play a role in more frequent floods come the 2030s – sea level rise and the moon’s orbital cycle. They cited figures by the NOAA that said global average sea levels had risen about 21 to 24 centimeters since 1880. About a third of the increases happened in the last 25 years.

The authors also mentioned the Moon’s contribution to tide levels through its gravitational pull. However, they remarked that the power of its pull is inconsistent from year to year. This is because of a regular “wobble” in the Moon’s orbit that takes 18.6 years to complete. While the wobble was first reported in 1728, the study pointed out its effects on the Moon’s gravitational pull – subsequently affecting sea levels.

The Earth’s regular daily tides are suppressed in half of this cycle – with high tides becoming lower and low tides becoming higher. Meanwhile, the other half of the cycle amplifies tides – resulting in high tides becoming higher and low tides becoming lower. With global sea level rises pushing tides in one direction, the Moon’s 18.6-year cycle either counteracts or exacerbates this effect.

Currently, the Moon is in the tide-amplifying cycle. The study authors warned that higher sea levels, amplified by the lunar cycle, will cause more flooding. They pointed out that both the East and West Coasts, Hawaii and Guam will experience more intense high tide floods. Only Alaska and other far northern coastlines will be spared for another decade or longer due to long-term geological processes, they added.

Study co-author Ben Hamlington of the National Aeronautics and Space Administration (NASA) noted that the findings of their research are a vital resource for coastal urban planners. The scientist at NASA’s Jet Propulsion Laboratory said: “From a planning perspective, it’s important to know when we’ll see an increase. Understanding that all your events are clustered in a particular month, or you might have more severe flooding in the second half of a year than the first – that’s useful information.”

NASA Administrator Bill Nelson remarked: “Low-lying areas near sea level are increasingly at risk and suffering due to the increased flooding, and it will only get worse. The combination of the Moon’s gravitational pull [and] rising sea levels … will continue to exacerbate coastal flooding on our coastlines and across the world.” Thus, the study by Thompson, Hamlington and their colleagues concluded that planning for these floods should begin at the soonest.

Climate.news has more articles about how celestial bodies such as the Moon play a role in flooding.

Sources include:

LiveScience.com

TidesAndCurrents.NOAA.gov

Nature.com

NASA.gov