The moon barely prevented coastal erosion within the 2030s, this safety ends

Planet earth is currently experiencing an unprecedented warming trend. Average global temperatures are rising at an accelerated rate in response to greenhouse gas emissions caused by human activity. These rising temperatures, in turn, release additional greenhouse gases (like methane), creating positive feedback loops that threaten to make the problem even worse.

This scientific consensus is based on several lines of evidence, all of which indicate the need for swift action. According to new research led by members of the NASA Sea Level Change Science Team (N-SLCT) at the University of Hawaii at Manao (UHM), a new lunar cycle that will begin in the mid-2030s will begin as early as due to the Sea level rise will amplify climate change. This will mean even more coastal flooding during high tide and coastal storms in the near future.

The study describing its results, titled “Rapid Rises and Extreme Months in Projections of Flood Floods in the United States” was published in Nature Climate Change last month. The research was led by Phil Thompson, an assistant professor at UHM’s Joint Institute for Marine and Atmospheric Research, and included members of UC San Diego’s Scripps Institution of Oceanography, the University of South Florida, NASA JPL, and the National Oceanic and Atmospheric Administration (NOAA).

NOAA projections of coastal flooding in 2021. Source: NOAA

High tide floods (HTFs), also known as “nerbel floods” (or sunny day floods), are already a problem in many coastal cities around the world. These occur when the tides are 0.5 to 0.6 m (1.75 to 2 ft) above the daily high tide average, resulting in flooded shorelines, roads, gullies, and basements in coastal communities. In 2019 alone, more than 600 of these floods occurred, according to reports from NOAA.

Similar reports showed that coastal communities in the US had twice as many HTFs between May 2020 and April 2021 as they did in 2000. In addition, 14 locations along the southeast Atlantic and Gulf coasts have broken or broken their records for the number of HTF days A factor of 4 to 11 over what they saw in 2000, and the number of HTF events is now increasing at 80% of NOAA water level stations along the east and Gulf coasts.

According to this current study, the situation will worsen from the mid-2030s and beyond. At this point, the position and orientation of the Earth, Moon, and Sun will cause the Moon to exert an increased gravitational impact on Earth’s oceans. This will result in floods exceeding known flood thresholds in the United States more often, not to mention floods that can occur in clusters that can last a month or more.

The reason the moon’s gravitational pull will worsen sea level rise has to do with the plane of the lunar orbit, which gradually rotates over the course of 18.6 years. The Earth’s regular daily tides are suppressed during half of this cycle, when the tide is lower and the tide is higher than average. In the other half, the tides are intensified, with the high ones getting higher and the low ones getting lower.

For their study, the research team examined data from 89 tide monitoring sites in every coastal state and area in the United States (except Alaska) and combined them with NOAA’s sea level rise scenarios, flood thresholds and the frequency of their exceedance annually. They also took into account statistical representations for various meteorological cycles (i.e. El Niño events) and astronomical cycles.

As Thompson pointed out in a NASA press release, HTFs are seen as less of a problem when compared to hurricane storm surges, which drive the tides much higher. “It is the cumulative effect over time that will have an impact,” he said. “But if it floods 10 or 15 times a month, a company cannot continue to operate its underwater parking lot. People lose their jobs because they cannot come to work. Leaking cesspools are becoming a public health problem. “

In fact, the study shows that the combination of climate change and the gravitational pull of the moon can cause coastal communities along the U.S. mainland, Hawaii, and Guam to struggle with flooding every day or two. As in Alaska, only the coasts in the far north will be spared for about a decade as the coasts in these areas rise due to long-term geological processes. As NASA Administrator Bill Nelson recently described in a NASA press release:

“Low-lying areas near sea level are becoming increasingly vulnerable and suffering from increased flooding, and it only gets worse. The combination of the gravitational pull of the moon, rising sea levels and climate change will further exacerbate coastal flooding on our coasts and around the world. NASA’s Sea Level Change Team provides important information so that we can plan, protect and prevent the environment and livelihoods affected by floods. “

This model is the first to take into account all known oceanic and astronomical causes of flooding, and the results are projected to 2080. It’s also an improvement on the flooding tool (also developed by Thomson) available on the NASA team’s Sea Level Portal. This tool, available to decision-makers and the general public, will be updated in the near future to reflect the results of this study.

Ben Hamlington, a researcher at NASA’s Jet Propulsion Laboratory (JPL) and a co-author of the paper, is also the head of NASA’s Sea Level Change Team. As he said, the results of the new study will be an important resource for coastal city planners in the coming years as they have to prepare for extreme weather events along with further flooding.

“From a planning point of view, it is important to know when we will see an increase,” he said. “To know that all of your events are concentrated in a given month or that you have more floods in the second half of the year than in the first – that is useful information.”

Further reading: NASA, Nature Climate Change

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