Oceans & Tides

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Fortinbras
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Re: Oceans & Tides

#26

Post by Fortinbras » Fri Jul 05, 2019 4:39 pm

Maybe someone can explain it to me (in really simple language): I live in Delaware and the local TV has an extensive weather report that includes the high tides of about two dozen fishing places on the state's Atlantic and Chesapeake coastlines. Places on the same shoreline and only about 20 miles apart have high tide times that are separated by two or more hours. It's not even in sequence from north to south, but lots of alternating between early and late. I had thought that the high tide would affect the whole of the Delaware coastline at one and the same time all the way up and down, instead it looks like a very uneven train schedule. Why this phenomenon?

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Sam the Centipede
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Re: Oceans & Tides

#27

Post by Sam the Centipede » Fri Jul 05, 2019 7:37 pm

I don't know about the tided around Delaware but I di know that tides are more complex than the simple tale that high school science books tell about gravity and the sun and the moon. Those gravity cycles give the water its initial momentum but then it sloshes around in great lumps, affected by the shapes of bays, channels, basins, varying seabed levels etc., sometimes with weird resonance and interaction effects. So some places have three high tides each day, for example.

I once saw a pre-digital mechanical tide calculator, a contraption of wires, pulleyx, dials and a pen plotter. It had about 17 different configurable cycles built into it, so the output graph was a summaton of all those cycles of various periods. And that complexity was required in order to be able to produce tide tables for mariners anywhere in the world.

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Addie
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Re: Oceans & Tides

#28

Post by Addie » Sat Jul 06, 2019 2:23 pm

Associated Press
Intensifying downpours threatening America’s biggest estuary

CONOWINGO, Md. (AP) — When the Conowingo Dam opened to fanfare nearly a century ago, the massive wall of concrete and steel began its job harnessing water power in northern Maryland. It also quietly provided a side benefit: trapping sediment and silt before it could flow miles downstream and pollute the Chesapeake Bay, the nation’s largest estuary.

The old hydroelectric dam spanning the lower Susquehanna River is still ably producing power, but its days of effectively trapping sediment in a 14-mile (22.5-kilometer) long reservoir behind its walls are over. Behind the 94-foot (29-meter) high barrier lies a massive inventory of coal-black muck — some 200 million tons (181 million metric tons) of pollutants picked up over decades from farmlands, industrial zones and towns.

How big a threat this sediment stockpile poses to the Chesapeake Bay or whether anything can even be done about it depends on who you talk to. With Maryland pushing to curb pollution in dam discharges, the issue has become a political football as Conowingo’s operator seeks to renew its federal license to operate the dam for 46 more years after its old license expired.

And as negotiations drag on, the lack of agreement about curbing runoff pollutants following the wettest year on record imperils hard-won gains in restoring the Chesapeake Bay.

The iconic estuary famed for its blue crabs and oysters has been gradually rebounding under a federal cleanup program launched in 1983 that put an end to unbridled pollution. But the 200-mile (325-kilometer) long bay is increasingly being ravaged by runoff-triggering downpours, including record-setting rainfall in 2018 and this year’s soggy spring.

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RTH10260
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Re: Oceans & Tides

#29

Post by RTH10260 » Sat Jul 06, 2019 7:04 pm

Suggestion: build a drainage channel - possibly underwater pipeline - from the dam out into open sea, then start washing out the sediments that ought to have gone that way decades ago. Of course may mess up the oceans ecological system and wash up on the coastline unexpected.

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Addie
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Re: Oceans & Tides

#30

Post by Addie » Sun Jul 07, 2019 8:57 pm

CNN
All 21 of Mississippi's beaches are closed because of toxic algae ...

HABs occur when "colonies of algae -- simple plants that live in the sea and freshwater -- grow out of control and produce toxic or harmful effects on people" or wildlife, the National Oceanic and Atmospheric Administration (NOAA) says.

The toxic algae can cause rashes, stomach cramps, nausea, diarrhea and vomiting, the state agency warned.

Though the state says people can still use the sand portion of the beaches, they should avoid water contact or consumption of anything from the waters "until further notice."

The HAB was at least partly caused by the opening of the Bonnet Carre spillway in Louisiana, which has triggered "excessive" freshwater to the coastline, the Jackson Clarion Ledger reported.

Blooms can be caused by a variety of factors, including increases in nutrient levels from fertilizer run-off, low water flows, changes in water temperature or changes in ocean currents, the Centers for Disease Control and Prevention (CDC) says.

HABs aren't rare. In fact, every US coastal and Great Lakes state experiences them, the NOAA says. However, they are popping up with increasing frequency due to climate change and increasing nutrient pollution, according to the NOAA.

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Addie
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Re: Oceans & Tides

#31

Post by Addie » Tue Jul 09, 2019 8:12 pm

The Guardian
'Inside, the fish are black': the pollution tainting Tunisian beaches

Across the Gulf of Tunis, domestic and industrial waste is pouring into the sea, rendering stretches of coastline ‘unusable’ ...


It isn’t just the waters off La Goulette that are causing concern. The entire Gulf of Tunis is drawing activists’ ire, as domestic and industrial waste from the capital’s 600,000 plus residents, in addition to that flowing from the ports and the industrial estates that line the Gulf, makes its way into the waters outside Tunis, impacting fish populations and presenting a clear hazard to human health.

Tunisia’s pollution issues aren’t new. Its heavy industries have been impacting water quality for years. However, since the revolution of 2011, conversation over the environmental impact of its industrial legacy has at least become possible, even if the kind of reversals activists are calling for remain some way off.

Officially around a quarter of Tunisia’s waste water is recycled, intended, among other things, to irrigate the country’s farmlands. The rest (around 247m cubic metres a year), is expelled from the country’s treatment plants directly into the sea and inland waterways. According to environmental regulations, industrial waste water should initially be treated at source, before being transferred for further treatment. However, campaigners question how rigorously this is being enforced. ...

Across Tunisia, industrial and domestic waste water is channelled from broad areas to large treatment plants. Within the Gulf, the outcomes are clear. “We tested both input and output flows between 2016 and 2017 and the results were consistent,” Garbouj, an environmental engineer, says. “We found increased levels of nitrates, manganese particles, phosphate plus faecal coliforms and streptococci – both present within human waste – among other matters. All of these are harmful to health.

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Addie
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Re: Oceans & Tides

#32

Post by Addie » Wed Jul 17, 2019 12:59 pm

Riviera Maya News (May 29)
Sargassum plant set to open in Cancun

Cancun, Q.R. — A sargassum treatment plant is set to open in Cancun this year. The company, Dianco Mexico, already has one plant in Mexico City and plans to open several more along sargasso-infested regions of the Caribbean, starting with Cancun.

During a press conference, Dianco Mexico CEO Héctor Romero Morales said “There is already a solution, to take advantage of all the sargassum that invades the coasts of Quintana Roo and the Caribbean islands. In addition, there is now a place to deposit all the collected sargassum, to take full advantage of it in an ecological way and without waste.”

The company specializes in the scientific study of algae, he explained, saying that they have a patented solution for the sargassum. Romero Morales explained that the new Cancun plant will have the capacity to process up to 600 tons of seaweed daily in three shifts. ...

“All the sargassum, the stuff that accumulates on the coasts, is used to do three things: cellulose, organic fertilizer and biodegradable plastic (bioplastic). We are a Mexican company made up of entrepreneurs, environmentalists and scientists who have been working on this for close to five years,” he explained.


Addie wrote:
Sat Jun 29, 2019 8:22 am
Independent
Climate change blamed as huge mounds of rotten seaweed spoil pristine beaches in Mexico

Piles of sargassum, which smells of rotting eggs and turns sea water brown, covers Rivera Maya coast

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