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How the moon's 'wobble' worsens coastal flooding | University of Hawaiʻi System News – UH System Current News

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High tide nuisance flooding in Miami, Florida. (Photo credit: B137, CC BY-SA 4.0, via Wikimedia Commons)

This editorial by University of Hawaiʻi at Mānoa Assistant Professor Philip R. Thompson was posted in The Hill on July 20, 2021.

Full moon, new moon. High tide, low tide. These are dependable rhythms of our planet. It is not surprising then, that news of a “wobble” in the moon’s orbit—one with implications for the growing problem of U.S. coastal flooding — has piqued the curiosity of many.

So, what exactly is this “wobble?” The word wobble suggests a breakdown in the regular and predictable motion of the moon and its influence on the tides. This is not the intended meaning, though. What the media has termed the ”wobble” is actually a cycle as regular as the seasons but occurring over decades rather than months. More specifically, the path of the moon’s orbit around Earth is tilted in space and rotates once every 18.6 years with a motion similar to the undulations of a spinning coin just before it falls flat. This motion is more precisely described as lunar nodal precession, and it is most certainly not a new discovery. Astronomers have observed this phenomenon for millennia by documenting gradual changes to the moon’s position in the night sky.

Precession of the moon’s orbit is not merely an astronomical phenomenon—it also affects ocean tides, which is how this esoteric “wobble” is connected to coastal flooding and made it into the headlines. The effect of precession on tides is not the same everywhere: To get an idea of the size of the effect, consider St. Petersburg, Florida, where the height of the highest tides changes over the lunar precession cycle by a little less than two inches. That may not seem like much, but keep in mind that the total amount of global average sea-level rise over the last decade is also a little less than two inches. That means that the “wobble” has roughly the same impact on the height of high tides as the most recent decade of global sea-level rise.

These seemingly small changes can have big consequences because high-tide flooding is a game of inches, where benign high water levels suddenly become impactful as the edge of a storm drain or sea wall is breached. Not to mention that the extent and frequency of such events increases rapidly with every incremental increase in the height of high tides. In St. Petersburg, for example, increasing the height of high tides by four inches (similar to the influence of the “wobble” plus a decade of sea-level rise) can produce an increase from 10 high-tide floods per year to 45 floods per year. That same four inches in Honolulu, Hawaii can produce an increase from 10 to almost 70 high-tide floods per year. Inches matter.

Of course, this is not the sort of extreme flooding that makes good fodder for a Hollywood climate-disaster film. Instead, high-tide flooding can occur on a sunny, otherwise normal day and result in impacts like minor erosion; backed up drainage and sewage systems; and/or standing water in roads, parking lots and basements.

We should be careful, though, not to confuse lack of total destruction for lack of importance. This is often a challenge in communicating the real-world, incremental impacts of ongoing climate change. High-tide flooding may not produce the next Atlantis, but it will cause an insidious accumulation of seemingly minor economic and infrastructural consequences. The impact will become acute as more and more events occur over increasingly narrow windows of time.

Planning for any aspect of climate change requires acknowledging and understanding the interplay between natural cycles and human-induced climate trends. Both exist, and the existence of one does not preclude the other. A decade-long global warming “pause,” for example, does not mean that a century-long warming trend is not happening.

Similarly, my research team has shown that precession of the moon’s orbit will at times act to slow (and perhaps even pause) increasing frequency of high-tide flooding due to sea-level rise. But we also know that the opposite will occur, and many U.S. coastal communities will experience periods of rapid increase in high-tide flooding when the cyclical “wobble” acts to enhance the effects of sea-level rise.

Our work specifically points to the mid-2030s as the onset of one such period of rapid change. Under the NOAA Intermediate scenario for sea-level rise, we project that a majority of coastal locations in the Gulf of Mexico, California and Hawaiʻi will experience at least a quadrupling and as much as a ten-fold increase in the frequency of high-tide floods over a 10-year period beginning in the 2030s. These communities will join the many places along the U.S. East Coast that already experience recurrent flooding at high tide, transforming a regional problem into a national issue.

To make matters worse, the onset of this rapid change will come on the heels of a period during which the cyclical “wobble” will suppress increases in high-tide flooding due to sea-level rise. It is essential that affected communities are not complacent during the period of slow change in order to avoid being caught off guard by the rapid change to follow. Fortunately, we can point to a specific natural cycle to predict and explain what is happening, but continued reminders will be necessary.

In Hawaiʻi, where I live, there is a proverb: I Kahiki ka ua, ako ʻē ka hale, which means “while the rain is far away, thatch the house.” The mid-2030s are not all that far away, and the infrastructure projects needed to mitigate the impacts of increased high-tide flooding will take time and resources.

Now is the time to acknowledge the changes we are observing, to be realistic about what’s to come, and to get to work ensuring that our coastal communities are resilient and thrive in the coming decades.

—Philip R. Thompson, is an assistant professor in the Department of Oceanography at University of Hawaiʻi at Mānoa and director of the UH Sea Level Center. He is the lead author of a recent study that generated headlines by showing how a natural cycle in the moon’s orbit affects future coastal flooding due to sea-level rise.

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NASA, Boeing launch Starliner to the ISS: How to watch test flight live – CNET

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Boeing CST-100 Starliner spacecraft sits atop a ULA Atlas V rocket in July 2021.


Boeing/John Grant

Boeing is set to relaunch its Starliner crew capsule for a second attempt at docking with the International Space Station this Tuesday, Aug. 3 (there won’t be any humans aboard). Boeing’s first try in late 2019 failed to reach the ISS but landed safely back on Earth. 

The mission was originally scheduled to take off Friday, but it’s now aiming for Tuesday after an unexpected issue last Thursday with an ISS module firing its thrusters shortly after docking with the station. 

“The International Space Station team will use the time to continue working checkouts of the newly arrived Roscosmos Nauka multipurpose laboratory module (MLM) and to ensure the station will be ready for Starliner’s arrival,” said NASA in a statement.

Software defects and a communications link problem led to a premature end to the original Boeing test flight in 2019, though the CST-100 Starliner capsule landed safely back on Earth. The upcoming Orbital Flight Test-2 (OFT-2) mission is a chance for Boeing to thoroughly vet its hardware and software before a crew of three American astronauts flies on Starliner.

Both Boeing and SpaceX are part of NASA’s Commercial Crew Program, which is all about sending astronauts to the ISS from American soil. SpaceX has now delivered 10 astronauts to the ISS, and Boeing would like to catch up. First, it’ll need to show that its Starliner can safely reach the ISS and return to Earth.

NASA will livestream the launch, which is scheduled to occur at 10:20 a.m. PT (1:20 p.m. ET) on Tuesday Aug. 3. Coverage is expected to begin at 9:30 a.m. PT. 

Starliner will lift off on a United Launch Alliance (ULA) Atlas V rocket. The capsule will be packed with around 400 pounds of crew supplies and cargo. If all goes well, it’ll dock with the space station about 24 hours later, on Wednesday Aug. 4. Docking will also be covered live by NASA’s NASA TV.

ULA shared some scenic photos from the launch site on Monday as it prepares for liftoff. 

Starliner will spend between five and 10 days at the ISS before bringing research samples back to Earth. Boeing will aim to bring the spacecraft back for a gentle parachute landing in the desert of New Mexico.

“OFT-2 will provide valuable data that will help NASA certify Boeing’s crew transportation system to carry astronauts to and from the space station,” NASA said in a statement July 22 after successfully concluding a flight readiness review.

The mission is a key step for NASA’s plans to run regular crewed launches from the US, ending its reliance on Russian Soyuz spacecraft. If all goes well, the first crewed mission, Boe-CFT, could launch in the next six months.

Follow CNET’s 2021 Space Calendar to stay up to date with all the latest space news this year. You can even add it to your own Google Calendar.    

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Meteor Shower 2021: Why There Are Only A Few Precious Hours In 2021 When You Can Reliably See ‘Shooting Stars’ – Forbes

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Have you ever seen a “shooting star?” If you haven’t, you’ll no doubt have read articles imploring you to go outside and experience a “shower” of meteors. 

There’s no such thing as a “meteor shower.” 

Meteoroids don’t behave like that. “Shooting stars” are caused by Earth’s atmosphere colliding with clumps of dust left along its orbital path by a passing comet. They look like streaks and they last around a second, depending on the “shower” in question.

“Shooting stars” are sudden events that can happen anywhere in the night sky, but they’re sporadic. They rarely happen together. For instance, you might see one out of the corner of your eye and, five minutes later, see another one in a completely different part of the sky. Many of them you will miss. There are never two or three—or more—“raining down” at the same time, as composite photographs would suggest.

Besides, when you read that a “meteor shower” like the Lyrids, Orionids or Geminids could have “up to 150 shooting stars per hour,” what it really means that it might be possible to see that many (the so-called zenithal hourly rate or ZHR) in perfect conditions. That scenario is, in practice, impossible to achieve—you would need to be observing the entire night sky constantly, for many hours either side of the absolute “peak” of activity, and in super-dark skies. 

However, the biggest factor that determines what you’re likely to see—and one many meteor shower-promoters fail to point out—is the effect of Moon and moonlight.

If there’s a first quarter Moon or anything brighter, particularly a full Moon, in the sky during the peak night(s) of a meteor shower, you can forget seeing anything other than the very brightest of “shooting stars.” And they’re very rare. 

If the Moon is big and bright then, in effect, you’ll be observing from under a heavily light-polluted night sky even if you’ve gone to a dark sky destination. 

So which meteor showers are the ones to go for in 2021? There are going to be three meteor showers in 2021 that will occur under near-ideal conditions. 

The bad news?

The first (and by far the best) one isn’t until August 2021.

The good news?

It’s the Perseids, arguably the most famous and easiest meteor shower to observe in the northern hemisphere … largely because it occurs in the middle of summer when it’s easiest to be outdoors at night. 

The best three meteor showers in 2021, these will be best observed after midnight, with the exception of the Draconids, which can be observed right after dark. 

1. Perseid meteor shower 2021

When: Thursday/Friday, August 12/13, 2021

Moon phase: 23%-lit crescent Moon

ZHR: 110

2. Draconid meteor shower 2021

When: Friday/Saturday, October 8/9, 2021

Moon phase: 10%-lit crescent Moon

ZHR: 10

3. South Taurid meteor shower 2021

When: Thursday/Friday, November 4/5, 2021

Moon phase: 0.1%-lit crescent Moon

ZHR: 10

Wishing you clear skies and wide eyes.

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Lake Huron sinkhole surprise: The rise of oxygen on early Earth linked to changing planetary rotation rate – Phys.org

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A scuba diver observes the purple, white and green microbes covering rocks in Lake Huron’s Middle Island Sinkhole. Credit: Phil Hartmeyer, NOAA Thunder Bay National Marine Sanctuary.

The rise of oxygen levels early in Earth’s history paved the way for the spectacular diversity of animal life. But for decades, scientists have struggled to explain the factors that controlled this gradual and stepwise process, which unfolded over nearly 2 billion years.

Now an international research team is proposing that increasing on the early Earth—the spinning of the young planet gradually slowed over time, making the days longer—may have boosted the amount of oxygen released by photosynthetic cyanobacteria, thereby shaping the timing of Earth’s oxygenation.

Their conclusion was inspired by a study of present-day microbial communities growing under extreme conditions at the bottom of a submerged Lake Huron sinkhole, 80 feet below the water’s surface. The water in the Middle Island Sinkhole is rich in sulfur and low in oxygen, and the brightly colored bacteria that thrive there are considered good analogs for the single-celled organisms that formed mat-like colonies billions of years ago, carpeting both land and seafloor surfaces.

The researchers show that longer day length increases the amount of oxygen released by photosynthetic microbial mats. That finding, in turn, points to a previously unconsidered link between Earth’s oxygenation history and its . While the Earth now spins on its axis once every 24 hours, day length was possibly as brief as 6 hours during the planet’s infancy.

The team’s findings are scheduled for publication Aug. 2 in the journal Nature Geoscience.

Lead authors are Judith Klatt of the Max Planck Institute for Marine Microbiology and Arjun Chennu of the Leibniz Centre for Tropical Marine Research. Klatt is a former postdoctoral researcher in the lab of University of Michigan geomicrobiologist Gregory Dick, who is one of the study’s two corresponding authors. The other co-authors are from U-M and Grand Valley State University.

“An enduring question in the Earth sciences has been how did Earth’s atmosphere get its oxygen, and what factors controlled when this oxygenation took place,” Dick said from the deck of the R/V Storm, a 50-foot NOAA research vessel that carried a team of scientists and scuba divers on a sample-collection trip from the town of Alpena, Michigan, to the Middle Island Sinkhole, several miles offshore.

“Our research suggests that the rate at which the Earth is spinning—in other words, its day length—may have had an important effect on the pattern and timing of Earth’s oxygenation,” said Dick, a professor in the U-M Department of Earth and Environmental Sciences.

The researchers simulated the gradual slowing of Earth’s rotation rate and showed that longer days would have boosted the amount of oxygen released by early cyanobacterial mats in a manner that helps explain the planet’s two great oxygenation events.

[embedded content]

The project began when co-author Brian Arbic, a physical oceanographer in the U-M Department of Earth and Environmental Sciences, heard a public lecture about Klatt’s work and noted that day length changes could play a role, over geological time, in the photosynthesis story that Dick’s lab was developing.

Cyanobacteria get a bad rap these days because they are the main culprits behind the unsightly and toxic algal blooms that plague Lake Erie and other water bodies around the world.

But these microbes, formerly known as blue-green algae, have been around for billions of years and were the first organisms to figure out how to capture energy from sunlight and use it to produce organic compounds through photosynthesis—releasing oxygen as a byproduct.

Masses of these simple organisms living in primeval seas are credited with releasing oxygen that later allowed for the emergence of multicellular animals. The planet was slowly transformed from one with vanishingly small amounts of oxygen to present-day atmospheric levels of around 21%.

At the Middle Island Sinkhole in Lake Huron, purple oxygen-producing cyanobacteria compete with white sulfur-oxidizing bacteria that use sulfur, not sunlight, as their main energy source.

In a microbial dance repeated daily at the bottom of the Middle Island Sinkhole, filmy sheets of purple and white microbes jockey for position as the day progresses and as environmental conditions slowly shift. The white sulfur-eating bacteria physically cover the purple cyanobacteria in the morning and evening, blocking their access to sunlight and preventing them from carrying out oxygen-producing photosynthesis.

But when sunlight levels increase to a critical threshold, the sulfur-oxidizing bacteria migrate back down below the photosynthetic cyanobacteria, enabling them to start producing oxygen.

New theory: Earth's longer days kick-started oxygen growth
This June 19, 2019 photo provided by NOAA Thunder Bay National Marine Sanctuary shows purple microbial mats in the Middle Island Sinkhole in Lake Huron, Mich. Small hills and “fingers” like this one in the mats are caused by gases like methane and hydrogen sulfide bubbling up beneath them. Feel like days are just getting longer? They are and it’s a good thing because we wouldn’t have much to breathe if they weren’t, according to a new explanation for how Earth’s oxygen rich atmosphere may have developed because of Earth’s rotation slowing. Scientists provided evidence for this new hypothesis by lab testing gooey smelly purple bacteria from a deep sinkhole in Lake Huron. Credit: Phil Hartmeyer/NOAA Thunder Bay National Marine Sanctuary

The vertical migration of sulfur-oxidizing bacteria has been observed before. What’s new is that the authors of the Nature Geoscience study are the first to link these microbial movements, and the resultant rates of oxygen production, to changing day length throughout Earth’s history.

“Two groups of microbes in the Middle Island Sinkhole mats compete for the uppermost position, with sulfur-oxidizing bacteria sometimes shading the photosynthetically active cyanobacteria,” Klatt said while processing a core sample from Middle Island Sinkhole microbial mats in an Alpena laboratory. “It’s possible that a similar type of competition between microbes contributed to the delay in oxygen production on the early Earth.”

A key to understanding the proposed link between changing day length and Earth’s oxygenation is that longer days extend the afternoon high-light period, allowing photosynthetic cyanobacteria to crank out more oxygen.

“The idea is that with a shorter day length and shorter window for high-light conditions in the afternoon, those white sulfur-eating bacteria would be on top of the photosynthetic bacteria for larger portions of the day, limiting oxygen production,” Dick said as the boat rocked on choppy waters, moored a couple hundred yards from Middle Island.

The present-day Lake Huron microbes are believed to be good analogs for ancient organisms in part because the extreme environment at the bottom of the Middle Island Sinkhole likely resembles the harsh conditions that prevailed in the shallow seas of early Earth.

Lake Huron is underlain by 400-million-year-old limestone, dolomite and gypsum bedrock that formed from the saltwater seas that once covered the continent. Over time, the movement of groundwater dissolved some of that bedrock, forming caves and cracks that later collapsed to create both on-land and submerged sinkholes near Alpena.

Cold, oxygen-poor, sulfur-rich groundwater seeps into the bottom of the 300-foot-diameter Middle Island Sinkhole today, driving away most plants and animals but creating an ideal home for certain specialized microbes.

Dick’s team, in collaboration with co-author Bopaiah Biddanda of the Annis Water Resources Institute at Grand Valley State University, has been studying the microbial mats on the floor of Middle Island Sinkhole for several years, using a variety of techniques. With the help of scuba divers from NOAA’s Thunder Bay National Marine Sanctuary—which is best known for its shipwrecks but is also home to the Middle Island Sinkhole and several others like it—the researchers deployed instruments to the lake floor to study the chemistry and biology there.

They also brought mat samples to the lab to conduct experiments under controlled conditions.

Klatt hypothesized that the link between day length and oxygen release can be generalized to any given mat ecosystem, based on the physics of oxygen transport. She teamed up with Chennu to conduct detailed modeling studies to relate microbial mat processes to Earth-scale patterns over geological timescales.

The modeling studies revealed that day length does, in fact, shape oxygen release from the mats.

“Simply speaking, there is just less time for the oxygen to leave the mat in shorter days,” Klatt said.

This led the researchers to posit a possible link between longer day lengths and increasing atmospheric oxygen levels. The models show that this proposed mechanism might help explain the distinctive stepwise pattern of Earth’s oxygenation, as well as the persistence of low-oxygen periods through most of the planet’s history.

Throughout most of Earth’s history, atmospheric oxygen was only sparsely available and is believed to have increased in two broad steps. The Great Oxidation Event occurred about 2.4 billion years ago and has generally been credited to the earliest photosynthesizing cyanobacteria. Nearly 2 billion years later a second surge in , known as the Neoproterozoic Oxygenation Event, occurred.

Earth’s rotation rate has been slowly decreasing since the planet formed about 4.6 billion years ago due to the relentless tug of the moon’s gravity, which creates tidal friction.


Explore further

Researchers find oxygen spike coincided with ancient global extinction


More information:
Possible link between Earth’s rotation rate and oxygenation, Nature Geoscience (2021). DOI: 10.1038/s41561-021-00784-3 , www.nature.com/articles/s41561-021-00784-3

Citation:
Lake Huron sinkhole surprise: The rise of oxygen on early Earth linked to changing planetary rotation rate (2021, August 2)
retrieved 2 August 2021
from https://phys.org/news/2021-08-lake-huron-sinkhole-oxygen-early.html

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