Most of us probably learned in grade school science class that our Moon’s gravitational pull causes the rise and fall of ocean tides. What you might not know is that the force of that attraction waxes and wanes in conjunction with an 18.6-year lunar cycle. According to a NASA-led study, a new phase in the cycle could bring catastrophic flooding to some U.S. coastal regions starting in the 2030s, a pattern that could last for the entire decade. I always find it crazy how much our weather and things we take for granted in life can depend on the moon and our orbit around the sun. Just a slight tick closer to the sun and we burn up while a shift away from the sun could push us into another ice age…
I think it’s interesting to think about a “moon wobble” creating massive high tides and flooding on the coasts and with the jet stream how does that impact weather across the Midwest and other important crop-growing regions? Will we see way more moisture on the coasts and less in other areas? The weather extremes and how they are impacted by the moon, and our orbits is a huge wild-card.
The study, led by members of the NASA Sea Level Change Science Team from the University of Hawaii, shows that high tides will exceed known flooding thresholds around the country more often beginning in the mid-2030s. This is due to what’s called a “wobble” in the moon’s orbit that takes 18.6 years to complete, aka the Lunar Nodal Cycle. In half this cycle, the Earth’s regular daily tides are suppressed: High tides are lower than normal, and low tides are higher than normal. In the other half of the cycle, the opposite occurs with high tides higher and low tides lower. There’s nothing new or dangerous about the wobble – NASA says skywatchers first documented it in the 1700s. What is new is how one of the wobble’s effects on the Moon’s gravitational pull will combine with rising sea levels.
During the most rapid downward phase of the lunar nodal cycle – which we are in right now – the observed rate of sea-level rise is effectively offset by those “lower high tides.” But the bottom of the cycle around 2025 will see this effect reverse and higher tides will combine with higher sea levels to dramatic effect, particularly in areas where high tides already exceed known flooding thresholds. The study predicts a leap in flood numbers on almost all U.S. mainland coastlines, Hawaii, and Guam. 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.
“Low-lying areas near sea level are increasingly at risk and suffering due to the increased flooding, and it will only get worse,” said NASA Administrator Bill Nelson. The National Oceanic and Atmospheric Administration (NOAA) reported a total of more than 600 such floods in 2019. By the mid-2030s, scientists expect three to four times that amount. What’s more, the floods will sometimes occur in clusters lasting a month or longer, depending on the positions of the Moon, Earth, and the Sun. When all three planetary bodies line up in specific ways with each other, the resulting gravitational pull and the ocean’s corresponding response may leave coastal dwellers coping with floods every day or two.
While the amount of flooding won’t be as much as a hurricane causes, having such frequent flooding can result in heavy economic damage. Phil Thompson, an assistant professor at the University of Hawaii and lead author of the study, points out that because high tide floods involve a small amount of water compared to hurricane storm surges, there’s a tendency to view them as a less significant problem overall. “But if it floods 10 or 15 times a month, a business can’t keep operating with its parking lot underwater. People lose their jobs because they can’t get to work. Seeping cesspools become a public health issue.” Details from the study can be found HERE.
Rising sea levels and coastal flooding make for saltier soils, which could obviously have a big impact on agriculture and farmer livelihoods. Coastal flooding of farmland can lead to immediate, as well as long-term, crop losses. Even after floodwaters recede, salt deposition from seawater establishes a legacy of soil salinity, negatively affecting the growth of many crops with long-term impacts on soil structure. Crop species can have widely varying tolerances to salinity but in general, high salt levels reduce plant nutrient uptake. Farmers along coastal waters may want to start investigating how they can meet these possible challenges sooner rather than later. (Sources: NASA, EESI, NPR)
