changing with the tides

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As we’ve just seen, the Earth's two tidal bulges are aligned with the positions of the moon and the sun. Over time, the positions of these celestial bodies change relative to the Earth’s equator. The changes in their relative positions have a direct effect on daily tidal heights and tidal current intensity. It was the muddy water that caught Stefan Talke’s eye. In the mid-2000s Talke was a postdoctoral scholar at Utrecht University, studying the river Ems that empties into the North Sea between Germany and the Netherlands. Decades earlier, engineers had begun dredging parts of the Ems so that newly built ships could navigate it from a shipyard upriver.

Tides - Met Office Tides - Met Office

Researchers are also using computer models to analyze how changing tides and rising sea levels might affect other types of coastal flooding. A hurricane’s storm surge, for instance, often responds to the changing landscape much as tides do. In a 2016 study, Talke and Ramin Familkhalili of Portland State analyzed how storm surge might change in the Cape Fear River estuary along with the changing tides. While a tidal bore is a tidal wave, a tsunami is not. Tsunami is taken from the Japanese words for “harbor wave.” Tsunamis are caused not by tides, but by underwater earthquakes and volcanoes. Tsunamis are associated with tides because their reach surpasses the tidal range of an area. Tides are really all about gravity, and when we're talking about the daily tides, it's the moon's gravity that's causing them. The Sun causes tides just like the moon does, although they are somewhat smaller. When the earth, moon, and Sun line up—which happens at times of full moon or new moon—the lunar and solar tides reinforce each other, leading to more extreme tides, called spring tides. When lunar and solar tides act against each other, the result is unusually small tides, called neap tides. There is a new moon or a full moon about every two weeks, so that's how often we see large spring tides. Tides are greatly influenced by the gravitational pull from the moon and sun. The moon's elliptic orbit means that twice a month, the moon, sun and Earth are in direct alignment and create a combined gravitational force.

Tides of history

Another tidal energy generator uses a type of dam called a barrage (2). A barrage is a low dam where water can spill over the top or through turbines in the dam. Barrages can be constructed across tidal rivers and estuaries. Turbines inside the barrage can harness the power of tides the same way a dam can harness the power of a river. Barrages are more complex designs than single turbines. Changing tides affect coastal residents in many ways. Someone who wants to sail a tall ship under a short bridge has to wait for just the right tidal conditions while anyone who wants to build a riverfront home in an estuary has to know exactly where the high-tide mark is. Engineers designing a tidal-energy system need to know how much energy they can extract from the water flows. And that’s where the study of changing tides can help people prepare for a changing world. If the moon's gravity is pulling the oceans toward it, how can the ocean also bulge on the side of Earth away from the moon? It does seem a little weird. It's all because the tidal force is a differential force—meaning that it comes from differences in gravity over Earth's surface. Here's how it works: Twice a month, when the Earth, Sun, and Moon line up, their gravitational power combines to make exceptionally high tides, called spring tides, as well as very low tides where the water has been displaced. When the Sun is at a right angle to the Moon, moderate tides, called neap tides, result. From our view on Earth, these tides coincide with certain lunar phases since they occur when the Moon reaches specific positions in its orbit.

Tides? | NOAA SciJinks – All About Weather What Causes Tides? | NOAA SciJinks – All About Weather

changing with the tides is one of those poetry collections that speaks to those who have always seen softness and strength as synonymous. Shelby's ability to write about emotional trauma with such delicacy is truly remarkable. Her sensitivity comes through in every word—making the reader feel like Shelby isn't only sharing her own personal experiences but is being mindful of the reader's comfort. I highly recommend this book to anyone who is coping with anxiety or looking for some healing words without having to read something heavy. Thank you, Shelby, for striking such a graceful balance with your poetry.” —Marya Layth, author of Driftwood To keep with the ocean aesthetic (and because this is just what I envision when I think of the book as a whole), I have the image of waves. I had always assumed tides were constant,” says Talke, now an oceanographer at California Polytechnic State University in San Luis Obispo. “That’s why we have tide tables.” He was amazed to discover, he says, that not only could tides undergo long-term changes, but that they could change by so much. The Moon and Earth exert a gravitational pull on each other. On Earth, the Moon’s gravitational pull causes the oceans to bulge out on both the side closest to the Moon and the side farthest from the Moon. These bulges create high tides. The low points are where low tides occur.

When the sun, moon and Earth are all lined up, the sun’s tidal force works with the moon’s tidal force. The combined pull can cause the highest and lowest tides, called spring tides. Spring tides happen whenever there is a new moon or a full moon and have nothing to do with the season of spring. (The term comes from the German word springen, which means “to jump.”) Rising and ebbing tides happen as Earth’s landmasses rotate through the tidal bulges created by the Moon’s gravitational pull. Our observer sees the tides rise when passing through the bulges, and fall when passing through the low points. Of course, in reality the Earth isn’t a smooth ball, so tides are also affected by the presence of continents, the shape of the Earth, the depth of the ocean in different locations, and more. The timing and heights of the tide near you will be affected by those additional elements. Perhaps most importantly, engineers can analyze changing tides to better plan for future sea level rise. One recent study looked at the low-lying Pearl River Delta in southern China, which is home to more than 60 million people. Michela De Dominicis, an oceanographer at the National Oceanography Centre in Liverpool, UK, and her colleagues calculated how much tidal ranges would shift for a variety of future scenarios of sea level rise.

Tides - Moon: NASA Science Tides - Moon: NASA Science

Engineers have known for at least a century that tides can change locally. In 1899, builders predicted that tides would increase in the Ems River upstream from a weir they planned to construct. (After the weir was built, the tides did increase about as much as they were expecting.) But only recently have scientists collected modern, precise tide gauge data from around the world, showing just how widespread tidal changes have become. “It wasn’t really until about 10 years ago that we started to appreciate that it’s occurring on a much wider level,” says Haigh. Twice a month, when the sun, the moon and Earth are nearly in alignment, Earth experiences “spring” tides. During these periods high tides are a little higher than usual and low tides are a little lower than usual. Seven days after spring tides, when the sun and the moon are at right angles to each other, their gravitational tugs partly cancel each other out, resulting in moderate “neap” tides. First, I must thank the author and the publisher for sending me a copy to review. I am so happy that I was one of the chosen few. Especially with this book, I feel like I needed to read it when it got to me. I needed to hear what it had to say. Perhaps most importantly, engineers can analyse changing tides to better plan for future sea level rise. One recent study looked at the low-lying Pearl River Delta in southern China, which is home to more than 60 million people. Michela De Dominicis, an oceanographer at the National Oceanography Centre in Liverpool, UK, and her colleagues calculated how much tidal ranges would shift for a variety of future scenarios of sea level rise. This article originally appeared in Knowable Magazine, and is republished under a Creative Commons licence.

That explains the first high tide each day, but what about the second high tide?

These two bulges explain why in one day there are two high tides and two low tides, as the Earth's surface rotates through each of the bulges once a day. Does anything else affect tides?

Changing with the Tides by Shelby Leigh | Goodreads Changing with the Tides by Shelby Leigh | Goodreads

Intertidal zones are marked by vertical zonation. Different organisms live in different zones in the tidal range, depending on how much water reaches them. This zonation can often be seen vertically, with dry plants near the top of the tidal zone and seaweeds near the bottom. The tidal range along the Thames River has quadrupled since the time of the Romans, as engineers narrowed and deepened the river for navigation. Those tides rhythmically submerged and revealed the Rising Tide sculpture, underwater artist Jason deCaires Taylor’s 2015 installation at Vauxhall in London. Arrows represent the tidal force. It's what's left over after removing the moon's average gravitational pull on the whole planet from the moon's specific gravitational pull at each location on Earth. On the side of Earth that is directly facing the moon, the moon's gravitational pull is the strongest. The water on that side is pulled strongly in the direction of the moon.An illustration of the tidal force, viewed from Earth's North Pole. Water bulges toward the moon because of gravitational pull. Note: The moon is not actually this close to Earth. Engineers have known for at least a century that tides can change locally. In 1899, builders predicted that tides would increase in the river Ems upstream from a weir they planned to construct. (After the weir was built, the tides did increase about as much as they were expecting.) The low-tide zone (4) is only dry at the lowest tide. Nudibranchs, a type of sea slug, live in tide pools in the low-tide zone. Like the sea star, this animal is a carnivore. Nudibranchs eat sponges, barnacles and other nudibranchs. Nudibranchs can also eat sea anemones, because they are immune to its poisonous tentacles. Arrows represent the force of the moon's gravitational pull on Earth. To get the tidal force—the force that causes the tides—we subtract this average gravitational pull on Earth from the gravitational pull at each location on Earth. High tide (left) and low tide (right) in the Bay of Fundy in Canada. Image credit: Wikimedia Commons, Tttrung. Photo by Samuel Wantman.