[Lore]

A lot of the Mediterranean countries are virtually bankrupt right now. I doubt there will be much money put into mitigation, rather reaction through relocation.

[KaiserJeep]

If the Nile delta returns from fertile farmland to the salt marsh it formerly was, it will curtail a lot of human crops but provide habitat for lots of birds and amphibians, and spawning places for many species of fish in the Med. There are two sides to every coin.

Maybe the Muslims can divert some of the oil money from sponsoring terrorism to geo-engineering projects.

[Tanada]

there is a considerable area of land surrounding the Mediterranean that would flood if sea levels rose significantly

the Nile delta for example

it may be worth the cost

Like any river delta the Nile is constantly subsiding and being rebuilt by the silt from the river. In a natural system there is always a balance, the more silt that comes down the further out to sea the delta will extend and vice versa. Years ago I read that there were serious problems in Egypt's future because the Aswan High Dam cuts the silt quantity greatly from what it was before it was built by controlling the annual floods. I don't know if any solution was ever found for the problem other than allowing some portion of the silty flow out of the reservoir.

Certainly you could build a dike on the delta, but because the soil is not stable it would require constant repairs to keep it as high as you want it to be, and you would have to pump the river flow over the dike because the river itself would be below sea level. New Orleans is facing this situation in places that are now below sea level, any dike problem even when the river is flowing normally will flood sections of the city. The Nile river valley, at least the lower portion where most people like geologically resembles the Grand Canyon filled with silt. The river during periods when the Mediterranean Sea level was lower during the ice ages carved a deep canyon and lay at the bottom. When the sea levels rose 12,000 years ago to nearly the current level silt coming down the river filled in the canyon keeping the river bed just above sea level. If sea level rises a few feet and we let nature proceed uninterrupted the river bed will rise to compensate just as it did at the start of the Holocene.

IIRC the Nile can still rise quite a few meters before it would be able to leave its canyon watercourse and seek a different channel. Humans are not willingly going to do that, the Aswan Dam and levies and other projects distort the process until we stop doing them.

[KaiserJeep]

Tanada, everything you said is true. Yet parts of the Netherlands have been below sea level for centuries, pumped dry originally by 16th century windmills, and have been producing luxury crops like tulip bulbs for as long. They presently have some pretty impressive civil engineering projects protecting those areas as well.

[Outcast_Searcher]

Below dear reader you will find a startling proposal for one of the largest geo-engineering projects of all time, the damming of the Gibraltar straits to control the direction, volume, and make up of the water exchange between the Med Sea and the Atlantic Ocean. The authors in dead earnest propose that this megaproject must be done to prevent the onset of the next ice age in 2090 due to global warming and the Aswan High Dam in Egypt.

Seems to me removing the Aswan high dam would be a hell of a lot easier, but what do I know?

This reminds me of a Lewis Black (comedian) bit, where a couple/few years back, he laments how cold the previous winter was in the northeastern US. His fix is to build a 5 foot high wall across the US/Canadian border to keep the cold air out of the US.

A hilarious play on the practicality of the proposed wall along the Mexican/US border to "fix" the illegal immigration problem, and since he's a comedian, the practicality/science issues don't come into play.

Sadly for such a "serious" proposal to "cure" global warming, science needs to count, and hopefully peer reviews and sanity will put a stop to such nonsense (however well-meaning it may be).

.....

I was just reminded of the Mel Brooks movie "Blazing Saddles" where the good guys put a toll booth in the middle of the prairie to slow down the bad guys on horseback. Instead of simply riding around the toll booth (on the wide open prairie), the bad guys are going through the toll booth one at a time, and Slim Pickins says "Somebody's got to go back and get a whole shit-load of dimes."

Yeah. One dam will solve everything for the entire planet. Sure. No problem.

[dohboi]

They talk about plans to damn the Gibralter starting at 30:30 here: http://climatestate.com/2013/08/09/eart ... cumentary/

Estimated cost: a cool $275 billion

But they'll have to keep building all these higher. If we continue on our current path (burning everything we can lay our hands on), we end up with about 75 meters of sea level rise in a few centuries, as Hansen points out towards the end of the video.

Or put another way: https://www.youtube.com/watch?v=X3zqE7IpTBg "Why the f*ck aren't we freaking the f*ck out?"

[kiwichick]

@ doh

70 - 75 metres ( 210 - 225 feet) sea level rise

and that is the point

the big losers around the Mediterranean, apart from Egypt, would be Italy and to a lesser degree France.

Further east Rumania , Ukraine and Russia lose large areas

[dohboi]

And it's not just landmass; it's pretty much all the major cities on or near the coasts, including Rome, Istanbul, Izmir, most of Athens, Cairo, Alexandria, Marseille, Montpellier, Venice (of course), but also Pisa, Bologna, most of Naples, Beirut, Tel Aviv...

In other words, most of the places that people think of when they think about what makes the Mediterranean the Mediterranean.

And of course that means tens to hundred of millions of people displaced just in that region, including some of the largest cities in the world:

Istanbul is 5th with over 14 million
Cairo is 11th with ~12m

And elsewhere the seven other biggest cities in the world would all be under water: Shanghai, Karachi, Beijing, Tianjin, Lagos, Guangzhou, and Mumbai--well over 100 million between them.

Dhaka (10th largest city) along with all the rest of Bangladesh also submerged ~160 million.

Yes, all these people won't just stand there waiting for the rising waters to engulf them. But where will they go? There are already huge refugee and immigration problems just about everywhere you look, even though it is right now still a relative trickle.
Izmir and Alexandria at over 4 million each

[Tanada]

They talk about plans to damn the Gibralter starting at 30:30 here: http://climatestate.com/2013/08/09/eart ... cumentary/

Estimated cost: a cool $275 billion

But they'll have to keep building all these higher. If we continue on our current path (burning everything we can lay our hands on), we end up with about 75 meters of sea level rise in a few centuries, as Hansen points out towards the end of the video.

Or put another way: https://www.youtube.com/watch?v=X3zqE7IpTBg "Why the f*ck aren't we freaking the f*ck out?"

It is not just Gibraltar either, if we end up melting all of the permanent ice on the planet and get maximum rise the Sinai Peninsula is no longer a barrier between the Red Sea and Mediterranean. IIRC the ridge they cut through to make the Suez canal sea level is only 24 meters high. If sea level crosses that threshold increase water will pass freely between the seas. A similar threshold separates the Black Sea from the Caspian Basin that is already well below sea level so it too would flood up to the world sea level connecting the Caspian to the rest of the world for the first time in millions of years.

I find the Hubris expressed in all Geo-engineering schemes laughable in the it hurts too much to cry so you have to laugh sense.

[dohboi]

Yup, they'd need to build another giant dam right across where Suez is.

Someone in the video I posted noted that dam building will be the biggest employer in the coming century.

(I notice I misspelled 'dam' as the homophonous swear word above--probably some subliminal indication of how dam...mad I am about the whole thing!? I hope the mod's won't take it as gratuitous bad language--not that I am completely above such things... )

[Lore]

You're right Gas. It's all speculation without much practicality. I believe we're going to see a rasher of these ideas pop up as it becomes a more desperate situation. Some of it by sophisticated engineering firms selling snake oil.

One thing you can be sure of, somebody's always out to make a buck even as humanity grasps at straws to preserve its status quo.

[kiwichick]

the article I read had pipes taking Mediterranean water out and bringing Atlantic water in

I assume you would need docks , like on the Suez Canal, for ships

[Tanada]

The Mediterranean nearly dried up. A cataclysmic flood revived it.

New evidence reignites a longstanding debate about how the sea reconnected with the ocean.

The serene turquoise waters of the Mediterranean Sea hide a sharp-tasting secret: a layer of salt up to two miles thick, lurking deep underneath the basin. The ghostly white minerals are one of the few traces of an ancient Mediterranean Sea that vanished millions of years ago. Some scientists believe that the entire sea evaporated for a time, desiccated like the Sahara to the south.

Even after decades of study, the details surrounding the sea’s vanishing act and the torrents of water that refilled the basin remain an enduring mystery. The refilling of the Mediterranean about five million years ago may have been the biggest flood in our planet’s history. By one estimate, the cascade of water that filled the cavernous basin was about 500 times larger than the flow of the Amazon River.

“It was a sensational thing,” says Daniel García-Castellanos of the Institute of Earth Sciences Jaume Almera in Spain. In a recent analysis published in Earth-Science Reviews, Garcia-Castellanos and his team identified a pocket of sediments that may have been deposited by the megaflood.

Without this cataclysmic reconnection with the Atlantic Ocean, the Mediterranean as we know it today would not exist. Ships couldn’t have crisscrossed the watery highway to fuel the rich cultures that have dotted its shorelines since the early stages of human civilization. And today, the Mediterranean Sea is a vital pump for global water circulation. Evaporation infuses its waters with an extra dose of salt, which spills into the Atlantic and helps drive oceanic conveyor belts that circumnavigate the planet, influencing temperatures, storm patterns, and more.

As modern temperatures continue their steady march upward, and the ice caps dwindle at the poles, it's "pretty blooming important" to figure out what processes led to the planet we see today, says Rachel Flecker, a geologist at the University of Bristol.
The flood of the eon

Today, the Mediterranean Sea’s million cubic miles of water are constantly evaporating, with roughly four feet of water turning to vapor each year. Rains and rivers aren’t enough to sate the system. The only water source keeping the body stable is a steady flow from the neighboring Atlantic Ocean, pouring through a narrow channel between Spain and Morocco, the Strait of Gibraltar.

Many millions of years ago, tectonic shifts deep below the surface may have forced the landscape upward, crimping the vital connection between the Mediterranean and Atlantic. Waters likely continued to flow into the basin, but the shift would have severed the escape route for dense saline currents running along the basin floor to reach the open ocean. Roughly six million years ago, salts began to pile up—enough to give each of the world’s 7.7 billion people nearly 50 Great Pyramids of Giza filled with the stuff.

Some researchers suggest the region nearly dried up before the flood, leaving a cavernous basin dipping more than a mile below current sea level. All that stood between the empty basin and the mighty Atlantic may have been a narrow spit of land where the Gibraltar Strait is today (though the exact width of this former land bridge is still uncertain).

Some 5.3 million years ago, a massive flood breached the divide and reconnected the ocean and the sea. But just as the extent of the Mediterranean’s drying is debated, so too is the size of the flood. With scant evidence available, García-Castellanos and his team wondered just how fast an empty Mediterranean basin could refill. The breach likely started as a trickle over the natural dam connecting modern-day Europe to Africa, according to their models from a 2009 study. But erosion quickly took over. “The process becomes unstoppable very soon,” García-Castellanos says.

As the water mounted, it scoured out a deepening path that allowed still more water to pass. At its peak, the flow may have gushed at 100 million cubic meters per second, filling the sea in two years or less. Such an event would have excavated at least 400 million olympic swimming pools worth of sediment, cutting a channel through the Strait of Gibraltar and carving a canyon that extends into the seafloor.

“This is like water coming out of a firehose,” says Columbia University’s William Ryan, a marine geologist at Columbia University who was part of early work identifying the Mediterranean salt deposits.

The cataclysmic event transformed the entire region, moving not just water but also cutting away chunks of rock, sand, and anything else in the way. “When you have that kind of energy, you don’t move sediment as little grains bouncing along the bottom. Everything is thrown up into a chaotic, highly turbulent state,” says Victor Baker, a geologist with the University of Arizona and an expert in very big floods.
Piecing together a prehistoric mystery

Geologists of the 1800s didn’t think floods of this scale were even possible. They required evidence from modern processes to prove an ancient event could have occurred. “The problem is, big, giant floods are rare,” Baker says. Similar to the catastrophic Chicxulub asteroid impact that forever changed life on Earth, megafloods don’t happen every year—or even every million years.

Scientists first began digging into the history of the Mediterranean as early as the 1950s, when they found salt deposits on the shores hinting at a particularly briny ancient sea. In the 1970s, researchers on board the Glomar Challenger drilled cores from the seafloor, allowing them to finally lay eyes on the salty remains of this tumultuous time in the sea’s history.

Features that resembled the cracked surface of a mudflat when left to bake in the sun were found embedded in the upper layers of salt—a hint that waters may not have always been sloshing above, Ryan says. But exactly how much of the Mediterranean’s water disappeared, and for how long, remains hotly debated.

Over the years, many researchers have dipped their toes into the puzzling waters, and as more evidence accrues, the more perplexing the situation becomes. Throughout the basin, fossils of critters can be found that point to a Mediterranean nearly full of water just before it reconnected to the Atlantic, says Wout Krijgsman, a geologist at Utrecht University in the Netherlands. Perhaps before the flood swept in, the region was not a desert but a shrunken sea.

One of the major questions that García-Castellanos and others have worked to answer is, where did all the sediment go? An estimated 240 cubic miles of sediment would have been strewn across the Mediterranean basin, collecting in pockets where the water flow was low. But the sediments, laid long before people first set foot in the region, are now buried beneath the seafloor.

To spot the ancient clues, researchers use a method akin to a geologic ultrasound, sending seismic vibrations from a boat to the bottom of the Mediterranean and measuring the echoes. A pocket of rocks and sand, possibly deposited by the flood, was discovered just to the east of the boundary that divides the western and eastern basins. And by looking through old seismic data, García-Castellanos and his colleagues think they’ve found another sediment deposit in the form of a rocky tail extending behind a submarine volcano. While the pockets of sediment are intriguing finds, they have not been sampled, so scientists don’t know exactly when they formed, Flecker says.

Yet answers may soon be on the horizon. Flecker and others hope to drill multiple sites throughout the Mediterranean in search of more clues to these key moments in the region’s geologic past.

“Future drilling could have a big impact on telling us on what really happened, how it happened,” Ryan says.

NatGeo Link