from Nikolay Koldunov @oceanographer / image
One year in life of ocean eddies.
This is 3km resolution Southern Ocean setup of @AWI_Media FESOM model. HR video
Saturday, July 23, 2022
Friday, July 22, 2022
High-tech seafloor mapping is finding surprising structures everywhere
REEF TOWER
SOUTH PACIFIC, 50 MILES EAST OF CAPE YORK PENINSULA, AUSTRALIA
SOUTH PACIFIC, 50 MILES EAST OF CAPE YORK PENINSULA, AUSTRALIA
Scientists at James Cook University in Australia were charting
underwater habitats just beyond the northern end of the Great Barrier
Reef using multibeam sonar when they came on a freestanding coral reef
tower 1,640 feet tall—taller than the Empire State Building.
The base of
the wedge, shaped like a shark fin, is almost a mile across, and the
tip is only 130 feet below the sea surface.
Subsequent dives by a
remotely operated vehicle showed the tower was teeming with fish and
exhibited no signs of the coral bleaching that has tormented the Great
Barrier Reef.
Credit: Maceij Frolow
From Scientific American by Mark Fischetti
Giant coral towers, vast reefs and other formations are captivating explorers
Oceanographers are fond of saying that we know more about the moon's surface than we do about Earth's seafloor.
It's true.
As of 2017, only 6 percent of the global seabed had been mapped, typically by ships with sonar instruments sailing back and forth in straight lines across a local section of sea.
MILLION MOUNDS CORAL PROVINCENORTH ATLANTIC, 100 MILES EAST OF GEORGIA, U.S.
Investigators at the National Oceanic and Atmospheric Administration have finished mapping the “million mounds” deep-sea province.
Investigators at the National Oceanic and Atmospheric Administration have finished mapping the “million mounds” deep-sea province.
Thousands of coral mounds, each 30 to 300 feet high, blanket 11,000 square miles of ocean floor, making it the largest deep-sea coral ecosystem ever discovered.
At a depth of 2,000 to 2,600 feet, the seafloor receives no sunlight, so the white corals don’t house symbiotic algae that give shallow reefs their color.
When old corals in the mounds die, their skeletons provide the foundation for new corals; some mounds have been growing for thousands of years.
Credit: Maceij Frolow
But since then, nations have become eager to chart the seafloor within their own “exclusive economic zones,” which reach 200 nautical miles from their shores, in part to look for critical minerals they can scrape up using big mining machines.
The other push is Seabed 2030—an effort to map Earth's entire seafloor by 2030, run jointly by the Nippon Foundation and the nonprofit General Bathymetric Chart of the Oceans.
RYDER GLACIER SILLGeologists at Stockholm University were puzzled about why the front edge of Ryder Glacier, at the Sherard Osborn Fjord, was losing less ice than the faces of other Greenland glaciers.
Using multibeam sonar on an icebreaker in the fjord, they discovered two parallel sills of bedrock (red), separated by a basin, that cross the fjord.
The inner sill, about 3.8 miles across and 1,600 to 1,900 feet high, blocks relatively warm Atlantic Ocean water from reaching the glacier and melting its underside, slowing the glacier’s demise.
Credit: Maceij Frolow
Localization with the GeoGarage platfrom (DGA nautical raster chart)
The goal is to collect and stitch together mapping done by governments, industries and research institutions everywhere.
Public release of previously private bathymetric data is helping to widen the areas plotted.
And uncrewed, remotely operated vehicles fitted with sonar that can zoom around underwater for days at a time are speeding the pace of mapping.
By June 2022 an impressive 21 percent of the world's seafloor had been charted.
The more experts map, the more surprises they find—such as the three unexpected, unusual formations revealed here.
Links :
Thursday, July 21, 2022
What humans can learn from the sea cucumber’s toxic arsenal
While ordinary vegetable cucumbers cost $3 per kilo, sea cucumbers can cost over $3,000 per kilo. These animals are prized as a delicacy in Asia, and are used by pharmaceutical companies to treat diseases like cancer.
Unfortunately, over-harvesting now threatens many sea cucumber populations.
From Wired by Maggie Chen
Sea cucumbers are squishy and soft.
They also employ lethal strategies to protect themselves.
A SEA CUCUMBER, lying innocently on a bed of sand, looks kind of like a blob, and feels almost plushy.
But although the creatures seem squishy and defenseless, they have evolved fascinating strategies to keep themselves safe.
Anne Osbourn, a biologist at the John Innes Center in England, recently published a paper in Nature Chemical Biology that uncovered chemical compounds through which sea cucumbers protect themselves from attack—and themselves from being destroyed by their own poison.
Her team believes that understanding how to synthesize these valuable compounds can allow for the design and mass production of molecules that might be useful for human health.
Despite their unassuming demeanor, sea cucumbers are equipped with clever chemical tricks.
When threatened by predators, one of the strategies these animals can use is to expel their thread-like internal organs—known as Cuvierian tubules—through their anus.
These tubules immobilize the predator in a sticky, toxic embrace.
The toxicity comes from saponins: chemical compounds that are known for their antioxidant and anti-inflammatory properties.
Saponins are commonly found in plants as an antimicrobial defense mechanism, and they are used to fend off pathogens such as fungi.
Their antifungal activity comes from their ability to bind with cholesterol—a key component of the cell membrane—and poke holes in it, causing cell death.
But saponins are much less common in animals.
Having originally studied these compounds in plants, Osbourn was intrigued to find that they existed in sea cucumbers—specifically a variety of saponins that are built from terpenoids, organic ring-like scaffolds.
(These triterpenoid saponins differ chemically from other classes, due to the attachment of methyl groups at specific carbon positions. And, as Osbourn puts it, “They look a bit like chicken wire.”)
To figure out exactly which saponins the sea cucumber makes, the scientists extracted chemical compounds from stores of dried sea cucumber as well as from the tissues of live sea cucumbers (P.
parvimensis and A.
japonicus) at various stages of development.
Reconstituting a dried sea cucumber was relatively simple: “You just put one sea cucumber in a petri dish, put some water, come back a day later, and it becomes a real sea cucumber,” says coauthor Ramesha Thimmappa, formerly a postdoctoral scholar in Osbourn’s lab.
“It swells!”
Then, the scientists used liquid chromatography mass spectrometry, where individual compounds in the extracts are separated into charged particles and shot into a mass spectrometer.
The instrument measures the speed at which the particles travel to determine each one’s weight, which can then be used to identify each compound’s molecular composition.
Sea cucumbers are squishy and soft.
They also employ lethal strategies to protect themselves.
A SEA CUCUMBER, lying innocently on a bed of sand, looks kind of like a blob, and feels almost plushy.
But although the creatures seem squishy and defenseless, they have evolved fascinating strategies to keep themselves safe.
Anne Osbourn, a biologist at the John Innes Center in England, recently published a paper in Nature Chemical Biology that uncovered chemical compounds through which sea cucumbers protect themselves from attack—and themselves from being destroyed by their own poison.
Her team believes that understanding how to synthesize these valuable compounds can allow for the design and mass production of molecules that might be useful for human health.
Despite their unassuming demeanor, sea cucumbers are equipped with clever chemical tricks.
When threatened by predators, one of the strategies these animals can use is to expel their thread-like internal organs—known as Cuvierian tubules—through their anus.
These tubules immobilize the predator in a sticky, toxic embrace.
The toxicity comes from saponins: chemical compounds that are known for their antioxidant and anti-inflammatory properties.
Saponins are commonly found in plants as an antimicrobial defense mechanism, and they are used to fend off pathogens such as fungi.
Their antifungal activity comes from their ability to bind with cholesterol—a key component of the cell membrane—and poke holes in it, causing cell death.
But saponins are much less common in animals.
Having originally studied these compounds in plants, Osbourn was intrigued to find that they existed in sea cucumbers—specifically a variety of saponins that are built from terpenoids, organic ring-like scaffolds.
(These triterpenoid saponins differ chemically from other classes, due to the attachment of methyl groups at specific carbon positions. And, as Osbourn puts it, “They look a bit like chicken wire.”)
To figure out exactly which saponins the sea cucumber makes, the scientists extracted chemical compounds from stores of dried sea cucumber as well as from the tissues of live sea cucumbers (P.
parvimensis and A.
japonicus) at various stages of development.
Reconstituting a dried sea cucumber was relatively simple: “You just put one sea cucumber in a petri dish, put some water, come back a day later, and it becomes a real sea cucumber,” says coauthor Ramesha Thimmappa, formerly a postdoctoral scholar in Osbourn’s lab.
“It swells!”
Then, the scientists used liquid chromatography mass spectrometry, where individual compounds in the extracts are separated into charged particles and shot into a mass spectrometer.
The instrument measures the speed at which the particles travel to determine each one’s weight, which can then be used to identify each compound’s molecular composition.
They discovered several saponin compounds, some of which, Osbourn says, “tend to be in the outer walls of the sea cucumber: in the tentacles, the body wall, the feet. In the outer tissues, it’s the right place to provide protection.”
They found others that were primarily present in the early growth stages of the sea cucumbers.
“We think that they may protect the eggs against predators—fish and various other grazing creatures,” she says.
But this chemical defense creates a big problem for sea cucumbers: They need to avoid killing themselves with their own toxins.
And that means their own cells can’t contain cholesterol, the target that the saponins bind to and pierce.
Instead, they have evolved two kinds of cholesterol alternatives: lathosterol and 9(11) sterols, which probably fulfill the same function of maintaining cell membrane stability.
The scientists believe that the sea cucumbers’ ability to make saponins—and these saponin-resistant sterols—evolved concurrently.
“We think it’s a self-defense strategy,” Osbourn says.
“If you can produce these toxic compounds, you have to be able to not poison yourself.”
“We think that they may protect the eggs against predators—fish and various other grazing creatures,” she says.
But this chemical defense creates a big problem for sea cucumbers: They need to avoid killing themselves with their own toxins.
And that means their own cells can’t contain cholesterol, the target that the saponins bind to and pierce.
Instead, they have evolved two kinds of cholesterol alternatives: lathosterol and 9(11) sterols, which probably fulfill the same function of maintaining cell membrane stability.
The scientists believe that the sea cucumbers’ ability to make saponins—and these saponin-resistant sterols—evolved concurrently.
“We think it’s a self-defense strategy,” Osbourn says.
“If you can produce these toxic compounds, you have to be able to not poison yourself.”
As it turns out, these unique evolutionary capabilities hinged upon a single point.
Sea cucumbers are part of the echinoderm family, along with sea stars and sea urchins.
They all share a common ancestor, but sea urchins don’t have the same saponin defense superpowers.
So to figure out how the sea cucumbers had diverged genetically from the rest of the group, Osbourn and Thimmappa (now an assistant professor of genome engineering at Amity University) compared their genomes to those of their echinoderm counterparts.
Specifically, the researchers were interested in studying lanosterol synthase, a highly evolutionarily conserved enzyme that is critical for sterol and saponin biosynthesis.
It folds their precursor molecules into intricate origami-like shapes.
The team discovered that sea cucumbers just don’t have it.
Instead, they have two enzymes that are from the same family but are drastically different in biological function: One gives rise to the saponins found in juvenile sea cucumbers, the other creates their cholesterol alternative and also generates saponins found in their outer walls.
One change from the traditional lanosterol synthase sequence in the amino acid chain was all it took to create these two sea cucumber-specific enzymes with completely different functions—an evolutionary adaptation that was “simple, but very elegant,” says Thimmappa.
This work of characterizing and determining the functions of single chemical compounds in sea cucumbers is “super cool,” says Leah Dann, a PhD student at the University of Queensland who studies island conservation and was unaffiliated with the study.
For sea cucumbers, which don’t have adaptive immunity (the ability to generate antibodies that can prevent future diseases), these saponins might help protect against harmful microbes or fungi.
And, since they don’t have a spiny outer shell, these chemical defenses may explain why many organisms leave them alone.
“They look so yummy,” Dann says.
“But most fish will not touch them.”
“They explained why sea cucumbers have triterpenoid saponins,” says Lina Sun, a professor at the Institute of Oceanology at the Chinese Academy of Sciences.
(Sun is unaffiliated with the study, and her comments have been translated from Chinese.) Discovering and characterizing the two synthase pathways that generate these saponins and special sterols is “very important,” she adds.
From this work, Sun is interested to see how, in other echinoderm species, the genes associated with saponin biosynthesis might differ from those in sea cucumbers.
A compound that attacks cholesterol has some intriguing implications for human health care.
“Sea cucumbers are highly valued both for food and for health,” Osbourn says.
“Sea cucumber extracts, which are rich in saponins, are very valuable.”
Sea cucumbers are part of the echinoderm family, along with sea stars and sea urchins.
They all share a common ancestor, but sea urchins don’t have the same saponin defense superpowers.
So to figure out how the sea cucumbers had diverged genetically from the rest of the group, Osbourn and Thimmappa (now an assistant professor of genome engineering at Amity University) compared their genomes to those of their echinoderm counterparts.
Specifically, the researchers were interested in studying lanosterol synthase, a highly evolutionarily conserved enzyme that is critical for sterol and saponin biosynthesis.
It folds their precursor molecules into intricate origami-like shapes.
The team discovered that sea cucumbers just don’t have it.
Instead, they have two enzymes that are from the same family but are drastically different in biological function: One gives rise to the saponins found in juvenile sea cucumbers, the other creates their cholesterol alternative and also generates saponins found in their outer walls.
One change from the traditional lanosterol synthase sequence in the amino acid chain was all it took to create these two sea cucumber-specific enzymes with completely different functions—an evolutionary adaptation that was “simple, but very elegant,” says Thimmappa.
This work of characterizing and determining the functions of single chemical compounds in sea cucumbers is “super cool,” says Leah Dann, a PhD student at the University of Queensland who studies island conservation and was unaffiliated with the study.
For sea cucumbers, which don’t have adaptive immunity (the ability to generate antibodies that can prevent future diseases), these saponins might help protect against harmful microbes or fungi.
And, since they don’t have a spiny outer shell, these chemical defenses may explain why many organisms leave them alone.
“They look so yummy,” Dann says.
“But most fish will not touch them.”
“They explained why sea cucumbers have triterpenoid saponins,” says Lina Sun, a professor at the Institute of Oceanology at the Chinese Academy of Sciences.
(Sun is unaffiliated with the study, and her comments have been translated from Chinese.) Discovering and characterizing the two synthase pathways that generate these saponins and special sterols is “very important,” she adds.
From this work, Sun is interested to see how, in other echinoderm species, the genes associated with saponin biosynthesis might differ from those in sea cucumbers.
A compound that attacks cholesterol has some intriguing implications for human health care.
“Sea cucumbers are highly valued both for food and for health,” Osbourn says.
“Sea cucumber extracts, which are rich in saponins, are very valuable.”
They have long been harvested as a culinary delicacy—and revered for their antioxidant and anti-inflammatory health benefits.
(The saponin dosage in certain sea cucumbers, while sometimes lethal for fish and other small critters, can be edible and even beneficial for humans.)
(The saponin dosage in certain sea cucumbers, while sometimes lethal for fish and other small critters, can be edible and even beneficial for humans.)
Studies have previously found that sea cucumber saponins can reduce cholesterol and inhibit inflammation to alleviate atherosclerotic plaques in mice, and have been connected with anti-tumor activity against cancer.
Saponins also have other uses for home and personal care, like for making soap.
Originally named after their presence in the roots of the soapwort plant (Saponaria), saponins can dissolve in water to create a frothy broth.
“Nature is so good at making chemicals,” Osbourn says admiringly.
In the future, she and her team are interested in learning how to synthesize more of these naturally derived compounds—to recreate them on a larger scale without having to harm any sea cucumbers, and to “harness all of the triterpene diversity that’s out there in nature.”
Saponins also have other uses for home and personal care, like for making soap.
Originally named after their presence in the roots of the soapwort plant (Saponaria), saponins can dissolve in water to create a frothy broth.
“Nature is so good at making chemicals,” Osbourn says admiringly.
In the future, she and her team are interested in learning how to synthesize more of these naturally derived compounds—to recreate them on a larger scale without having to harm any sea cucumbers, and to “harness all of the triterpene diversity that’s out there in nature.”
Ultimately, she thinks, such molecules could be designed and made on demand, to be used as medicines, or commercialized as foaming agents or emulsifiers.
In the meantime, though, one of the most likely places you’ll find sea cucumbers and their compounds is in soup—something Osbourn was once served for lunch when attending a conference in China.
“It was quite chewy,” she says.
“I’m sure it was good for me.”
In the meantime, though, one of the most likely places you’ll find sea cucumbers and their compounds is in soup—something Osbourn was once served for lunch when attending a conference in China.
“It was quite chewy,” she says.
“I’m sure it was good for me.”
Links :
Wednesday, July 20, 2022
How vulnerable Is the Mediterranean to tsunami risks?
Credit: Beverly Goodman-Tchernov
From Haaretz by Ruth Schuster
Over 2,500 years ago a Greek general identified the link between quakes and tsunamis, but how often have tsunamis plagued the Mediterranean?
An
expert tells us how to identify mega-waves of the distant past – and the
future risks
On Saturday evening, an underwater volcano in the South Pacific erupted.
As steam, volcanic ash and debris shot 20 kilometers (12 miles) into the air, the shock waves sent tsunamis spreading in all directions, first hitting the adjacent island nation of Tonga and later Hawaii, California, New Zealand and Japan.
The waves making landfall weren’t huge, but damage did ensue.
As of this writing, three possible casualties in Tonga had been reported, though not confirmed.
But actually any undersea eruption of noticeable magnitude is bound to unleash tsunami waves, says Prof. Beverly Goodman-Tchernov, head of the University of Haifa’s Marine Geosciences Department at the Charney School of Marine Sciences.
The question is what sort of tsunami waves.
Experts refer to two categories of sources: “near-field,” a nearby source such as a landslide, which tends to have a more localized effect, and “far-field” large events that occur offshore, which can affect a greater range of coastlines.
The Hunga-Tonga-Hunga-Ha’apai volcano was a far-field type.
We who live on the balmy Mediterranean Sea may feel we’re safe from the mega-quakes and tsunamis that have wreaked devastation in the Pacific, and more rarely in the Atlantic.
We are not.
The Mediterranean region is seismically frisky, boasts a few impressive volcanoes (even a super-volcano, Campi Flegrei) and has a history of tsunami action, not that there are clear records of the anomalous waves.
The fact is, most people in a position to closely observe a paleo-tsunami probably drowned, and the survivors wouldn’t necessarily have understood the context.
So what applies worldwide applies to the Mediterranean as well.
Undersea volcanism is only one of many potential causes of tsunamis, which are usually not a single event but a series of waves – in the ocean, a sea, even lakes.
And most dangerously for the likes of Tel Aviv, they spread inland via river valleys.
The most common cause that people have heard of is an underwater earthquake.
When a portion of seabed rises or falls in a quake, so does the water column above it.
The displaced water “wants” to spread.
As the waves advance from deep to shallower water and approach the shore, their volume and energy is preserved, thus they erode the seafloor, their speed slows and their height grows.
A tsunami mere centimeters high in the open ocean may be meters high when it hits the shore.
The highest tsunami in recorded history reached 524 meters (1,720 feet), dousing the Lituya Fjord in Alaska in 1958 after a quake.
That quake didn’t directly cause the tsunami at Lituya Bay.
What did was the ensuing landslide into the sea.
That calamity originated on land, but underwater landslides are a thing too and a key cause of tsunamis on the Israeli coast.
“The reality is that anything that causes significant-enough water displacement can result in a tsunami,” Goodman-Tchernov says.
“If sediment on a submerged slope builds up to a point that it fails, as that material moves, it pushes the water and displaces it – that can create quite large tsunamis.”
How large? Potentially enormous; a collapse along the Norwegian continental shelf 8,000 years ago is believed to have triggered a series of mega-tsunamis that washed over the Doggerland land bridge and rolled high onto the Paleolithic British coast.
Another potential cause is meteorite impact.
The asteroid that killed almost all the dinosaurs slammed into the Gulf of Mexico, setting off world-spanning mega-tsunamis as much as a mile high, scientists estimate.
The wave could have been higher if the meteorite had hit deep ocean rather than shallow sea.
One last cause is we.
“There have been man-made tsunamis – minor, but still – from testing bombs,” Goodman-Tchernov says.
At least we’ve never created one that’s been terribly damaging, she adds.
Well, the day is young.
Shaky in the Mediterranean ‘ocean’
Though it hasn’t suffered a mega-tsunami like those seen in the Indian Ocean or Japan in recent history, the Mediterranean has had, and will have, its share of these waves, including – it seems – one monster that’s believed to have hit Dor on the Israeli coast about 4,500 years ago.
“The Mediterranean has all of the hazards. People think of it as a quiet vacation destination, but the reality is, it has all the features of the large ocean, including the tectonic activity and deep basins.
It has the bathymetry [underwater topography] that includes the potential for landslides, and it even has a few volcanoes,” Goodman-Tchernov says, referring chiefly to Italy’s Etna and Thera on Santorini island in the Aegean.
“Meteorite impacts are, of course, equal opportunity worldwide, including the Mediterranean.”
Historical records of tsunamis are rare and oblique, but what else could the Athenian general and historian Thucydides have been talking about in his “History of the Peleponnesian War” written 2,500 years ago?
On Saturday evening, an underwater volcano in the South Pacific erupted.
As steam, volcanic ash and debris shot 20 kilometers (12 miles) into the air, the shock waves sent tsunamis spreading in all directions, first hitting the adjacent island nation of Tonga and later Hawaii, California, New Zealand and Japan.
The waves making landfall weren’t huge, but damage did ensue.
As of this writing, three possible casualties in Tonga had been reported, though not confirmed.
But actually any undersea eruption of noticeable magnitude is bound to unleash tsunami waves, says Prof. Beverly Goodman-Tchernov, head of the University of Haifa’s Marine Geosciences Department at the Charney School of Marine Sciences.
The question is what sort of tsunami waves.
Experts refer to two categories of sources: “near-field,” a nearby source such as a landslide, which tends to have a more localized effect, and “far-field” large events that occur offshore, which can affect a greater range of coastlines.
The Hunga-Tonga-Hunga-Ha’apai volcano was a far-field type.
We who live on the balmy Mediterranean Sea may feel we’re safe from the mega-quakes and tsunamis that have wreaked devastation in the Pacific, and more rarely in the Atlantic.
We are not.
The Mediterranean region is seismically frisky, boasts a few impressive volcanoes (even a super-volcano, Campi Flegrei) and has a history of tsunami action, not that there are clear records of the anomalous waves.
The fact is, most people in a position to closely observe a paleo-tsunami probably drowned, and the survivors wouldn’t necessarily have understood the context.
So what applies worldwide applies to the Mediterranean as well.
Undersea volcanism is only one of many potential causes of tsunamis, which are usually not a single event but a series of waves – in the ocean, a sea, even lakes.
And most dangerously for the likes of Tel Aviv, they spread inland via river valleys.
The most common cause that people have heard of is an underwater earthquake.
When a portion of seabed rises or falls in a quake, so does the water column above it.
The displaced water “wants” to spread.
As the waves advance from deep to shallower water and approach the shore, their volume and energy is preserved, thus they erode the seafloor, their speed slows and their height grows.
A tsunami mere centimeters high in the open ocean may be meters high when it hits the shore.
The highest tsunami in recorded history reached 524 meters (1,720 feet), dousing the Lituya Fjord in Alaska in 1958 after a quake.
That quake didn’t directly cause the tsunami at Lituya Bay.
What did was the ensuing landslide into the sea.
That calamity originated on land, but underwater landslides are a thing too and a key cause of tsunamis on the Israeli coast.
“The reality is that anything that causes significant-enough water displacement can result in a tsunami,” Goodman-Tchernov says.
“If sediment on a submerged slope builds up to a point that it fails, as that material moves, it pushes the water and displaces it – that can create quite large tsunamis.”
How large? Potentially enormous; a collapse along the Norwegian continental shelf 8,000 years ago is believed to have triggered a series of mega-tsunamis that washed over the Doggerland land bridge and rolled high onto the Paleolithic British coast.
The coast at the Israeli city of Caesarea, which "has been a tsunami magnet."
Credit: Beverly Goodman-Tchernov
Another potential cause is meteorite impact.
The asteroid that killed almost all the dinosaurs slammed into the Gulf of Mexico, setting off world-spanning mega-tsunamis as much as a mile high, scientists estimate.
The wave could have been higher if the meteorite had hit deep ocean rather than shallow sea.
One last cause is we.
“There have been man-made tsunamis – minor, but still – from testing bombs,” Goodman-Tchernov says.
At least we’ve never created one that’s been terribly damaging, she adds.
Well, the day is young.
Shaky in the Mediterranean ‘ocean’
Though it hasn’t suffered a mega-tsunami like those seen in the Indian Ocean or Japan in recent history, the Mediterranean has had, and will have, its share of these waves, including – it seems – one monster that’s believed to have hit Dor on the Israeli coast about 4,500 years ago.
“The Mediterranean has all of the hazards. People think of it as a quiet vacation destination, but the reality is, it has all the features of the large ocean, including the tectonic activity and deep basins.
It has the bathymetry [underwater topography] that includes the potential for landslides, and it even has a few volcanoes,” Goodman-Tchernov says, referring chiefly to Italy’s Etna and Thera on Santorini island in the Aegean.
“Meteorite impacts are, of course, equal opportunity worldwide, including the Mediterranean.”
Historical records of tsunamis are rare and oblique, but what else could the Athenian general and historian Thucydides have been talking about in his “History of the Peleponnesian War” written 2,500 years ago?
The Peloponnesians and their allies invaded but were deterred by earthquakes, he wrote.
As Thucydides put it, “About the same time (Euboea being then troubled with earthquakes), the sea came in at Orobiae on the part which then was land and, being impetuous withal, overflowed most part of the city, whereof part it covered and part it washed down and made lower in the return so that it is now sea which before was land.
And the people, as many as could not prevent it by running up into the higher ground, perished.” (Translated by Thomas Hobbes in 1843.)
Thucydides then described similar events in Atalanta and Peparethus.
The historian may have been among the first to deduce the underlying trigger: “And it seemeth unto me that without an earthquake such an accident could never happen”
Goodman-Tchernov notes that a terrestrial quake may trigger not only landslides on land and at sea, but also a sequence of quakes along the same system.
Caesarea, tsunami magnet
An expert on identifying paleo-tsunamis, Goodman-Tchernov has done a great deal of work in Caesarea, a port city on the Mediterranean that goes back more than two thousand years and flourished in the Roman, Islamic and Crusader periods.
There she has spent over 20 years recording and analyzing deposits both on land and in the sea with the Israel Antiquities Authority and other partners, identifying both historically noted tsunamis as well as ones without any known written record.
Absent historical records either because there were no witnesses or because the observers died, fled or were illiterate, records did not survive, or the witnesses couldn’t write in the first place.
Thus the discovery of physical remains is the only recourse.
Students doing tsunami research in the lab.
Credit: Beverly Goodman-Tchernov
As Thucydides put it, “About the same time (Euboea being then troubled with earthquakes), the sea came in at Orobiae on the part which then was land and, being impetuous withal, overflowed most part of the city, whereof part it covered and part it washed down and made lower in the return so that it is now sea which before was land.
And the people, as many as could not prevent it by running up into the higher ground, perished.” (Translated by Thomas Hobbes in 1843.)
Thucydides then described similar events in Atalanta and Peparethus.
The historian may have been among the first to deduce the underlying trigger: “And it seemeth unto me that without an earthquake such an accident could never happen”
Goodman-Tchernov notes that a terrestrial quake may trigger not only landslides on land and at sea, but also a sequence of quakes along the same system.
Caesarea, tsunami magnet
An expert on identifying paleo-tsunamis, Goodman-Tchernov has done a great deal of work in Caesarea, a port city on the Mediterranean that goes back more than two thousand years and flourished in the Roman, Islamic and Crusader periods.
There she has spent over 20 years recording and analyzing deposits both on land and in the sea with the Israel Antiquities Authority and other partners, identifying both historically noted tsunamis as well as ones without any known written record.
Absent historical records either because there were no witnesses or because the observers died, fled or were illiterate, records did not survive, or the witnesses couldn’t write in the first place.
Thus the discovery of physical remains is the only recourse.
Students doing tsunami research in the lab.
Credit: Beverly Goodman-Tchernov
Identifying such prehistoric or later unrecorded tsunamis relies on identifying anomalous sediment layers, debris and destruction with the hallmarks of tsunami inundation; for example, seashells a couple of kilometers inland.
Identifying paleo-tsunamis relies on basic sedimentology.
“We look at what is deposited on the landscape and try to reconstruct what its source was,” Goodman-Tchernov explains.
Researchers compare with bona fide tsunami deposits, going through an exhaustive elimination process regarding what could have caused anomalous deposits; for instance, agglomerations that seem to have elements of land, sea, river, garbage and debris.
“We’re not proving anything; we’re disproving every other possibility.”
Her work has led her to the observation that near-field tsunamis can have quite localized impacts; you might find evidence of an ancient inundation along the shore in one place but not in nearby sites.
“Caesarea has been a tsunami magnet.
It’s unusual,” she says, though immediately qualifies for the benefit of the city’s residents that this could be due to sampling bias; that is, that’s where the researchers have been looking.
Or it could be that Caesarea really is in the sweet spot for more than one of the offshore slumps along the coast.
Why might the impact of a landside-triggered tsunami be lesser than, say, the Tongo volcano blowing underwater?
The models suggest that a slump pushes water away from it outward; the least-impacted places seem to be immediately in front of where the slide happened, Goodman-Tchernov notes.
When you have an undersea earthquake or eruption, the shock spreads as concentric circles from a single point.
So there are slumps off Israel’s coast – at Palmahim, the Dor disturbance – offshore mapping shows where there have been past sediment failures.
And it’s possible that these cause the tsunamis at Caesarea.
When you have an undersea earthquake or eruption, the shock spreads as concentric circles from a single point.
So there are slumps off Israel’s coast – at Palmahim, the Dor disturbance – offshore mapping shows where there have been past sediment failures.
And it’s possible that these cause the tsunamis at Caesarea.
“The bottom line is that there are different sources. Some will affect a larger part of the Mediterranean – which doesn’t mean the waves are bigger, necessarily. They may be bigger in the distribution of the effect but not necessarily in terms of the impact on each coastline,” she says.
“Take the far-field 1956 quake along the Hellenic arc near Crete that caused very large tsunamis nearby.
Crete was hit by waves some 10 meters high or more. The waves reached the Israeli coast too but had petered out; the only evidence for it was a perturbance recorded on tidal gauges. The normal pattern changed. But it didn’t cause any local damage that we know of.”
Tsunami-tinted glasses
Whether a tsunami roaring toward Israel was caused by earthquakes near Greece or Turkey, or an offshore slump near Caesarea, what matters to us is how much warning time we have.
Can they be predicted? Nope, not until a triggering event has occurred.
Not that there is such thing as estimating how frequent tsunamis can be anywhere.
“When talking about frequency in the Mediterranean, we hear a lot of people throwing out a value of a significant tsunami around every 600 years. This number is a little bit misleading,” Goodman-Tchernov puts it courteously, then proceeds to rubbish the theory.
“It presumes that, one, we know about all the tsunamis, and, two, it gives us the false impression that these things occur in some kind of consistent pattern, which is absolutely untrue. An average of 600 years means nothing. In fact, what I’m seeing through my research is that the variation in the gaps between events are extreme.”
Goodman-Tchernov at work on the coast.
Credit: Evi Nominkou
Credit: Evi Nominkou
In some cases, she sees evidence for tsunamis so close in time that they may actually have been from the same triggering event, or within a year of each other.
Or nothing for a thousand years.
Caesarea, for example, seems to have had quiet for 1,600 years; there is no evidence of a tsunami in that time.
So does that mean one is overdue? Again: No.
Could be.
We don’t know, and Tel Avivians, snigger not.
We’re at special risk because if and when, displaced seawater could come roaring up the Yarkon River where it feeds into the sea.
So averages and suchlike don’t help us whatsoever.
“As people we love to have averages, but it’s really artificial. We do it all the time, talking of 50-year storms, but these numbers are relevant mainly to insurance companies, not the natural world,” Goodman-Tchernov says.
Indeed, in this era of climate change, such figures are rendered more irrelevant than ever before.
Could global warming and ocean warming affect the tsunami risk? Apparently not; finally something isn’t a function of climate change.
But doesn’t it seem, just as our planet is warming, that tsunamis are on the rise?
They are not – not necessarily – the professor reassures us.
It’s just that after the horrendous Indonesian tsunamis of 2004, more attention – including by the Israeli government – is being paid to the phenomenon.
People are wearing tsunami-tinted glasses, Goodman-Tchernov laughs.
But as sea levels rise, and they are, more and more communities are at risk with the commensurate potential for property damage and loss of life.
And if you’re in Tel Aviv, don’t snort at the “tsunami evacuation route” signs.
You may think you’re running madly for higher ground, but actually you’ll be racing full speed toward the Yarkon River Valley.
It’s just that after the horrendous Indonesian tsunamis of 2004, more attention – including by the Israeli government – is being paid to the phenomenon.
People are wearing tsunami-tinted glasses, Goodman-Tchernov laughs.
But as sea levels rise, and they are, more and more communities are at risk with the commensurate potential for property damage and loss of life.
And if you’re in Tel Aviv, don’t snort at the “tsunami evacuation route” signs.
You may think you’re running madly for higher ground, but actually you’ll be racing full speed toward the Yarkon River Valley.
Links :
- The Guardian : Marseille, Alexandria and Istanbul prepare for Mediterranean tsunami
- Nature : The enigmatic 1693 AD tsunami in the eastern Mediterranean Sea: new insights on the triggering mechanisms and propagation dynamics
- Victims of Thera Eruption 3,600 Years Ago Finally Found, in Turkey
Prehistoric Mega-tsunamis Split Britain From Europe Long Before Brexit
Doggerland Wasn’t Destroyed by Tsunami but by Climate Change, New Study Suggests
Tuesday, July 19, 2022
Rising seas are the next crisis for the world’s ports
The port of Los Angeles and Long Beach, October 2021.
Photographer: PATRICK T. FALLON/AFP
From Bloomberg by Francis Wilkinson
The delicate choreography of ships, trains and trucks at the world’s ports has been badly disrupted by the pandemic, and the turmoil is not likely to end soon.
If a virus can have such an adverse impact on the journey of a plastic toy or automobile from Point A to Point B, consider the potential impact of something even more pervasive and powerful: water.
In the years ahead, sea level rise, more intense storm surge and jacked-up tropical storms will be visiting many of the world’s roughly 3,800 ports.
Most of those ports are coastal; roughly a third are located in a tropical band vulnerable to the most powerful effects of climate change.
“If sea levels rise and storms become stronger as expected in the future due to climate change, the magnitude and costs of these disruptions are expected to grow,” states a report from the Environmental Defense Fund.
Ports cannot easily escape the influence of water.
When extreme rains led to flooding in Itajai, Brazil, in 2017, the floodwaters produced currents strong enough to prevent ships from berthing.
The port was closed for three weeks.
Just as too much water poses a threat, so too does not enough.
Extended drought along Germany’s River Rhine in 2018 lowered the water table and made it impossible for some ships to pass.
“Ports, working waterfronts and coastal infrastructure more generally have a lot of pressures on them from a number of sides,” said Austin Becker, chair of the department of marine affairs at the University of Rhode Island.
“They’re located in highly sensitive environments that are often in estuaries where riverine systems meet the ocean. They’re there because that was a nice way to get cargo from one country to another, and then get it inland through a riverine system.”
Because ports were early tenants of waterfront cities, there is no place to which they can easily retreat from rising seas.
As Becker told me, cities grew up around the ports.
And then the cities pushed the ports further toward the sea.
As cities have enveloped ports, so have the transportation networks that enable goods to travel from the sea inland.
“They need all these other infrastructure connections that have grown around them over the years — rail systems and highway systems and pipelines and that kind of thing,” Becker said.
In most prosperous, or even middling, cities, the land necessary for such systems is long spoken for.
As a result, most train tracks, roadways, warehouses and other infrastructure adjacent to ports will not be moved to higher ground away from the water; they will have to be adapted to manage the rising threat.
Port infrastructure is constantly evolving, noted Philip Orton, a professor of ocean engineering at Stevens Institute of Technology.
Ports are accustomed to incorporating new technologies — and the biggest ports, which have had to evolve to handle the needs of enormous, 1,300-foot-long container ships, tend to be the most flexible.
But the loading and transit areas behind ports are generally less innovative and less resilient.
When storm surge from Hurricane Marie hit Southern California in August 2014, damage to the Port of Long Beach caused shipping operations to halt for several days.
But as a subsequent report noted, it was months before the surrounding roads and facilities were back to normal.
The seas have been rising incrementally for centuries, but the projected rise in this century is markedly different, as are the consequences.
The basic formula is this: Greenhouse gas emissions produce higher temperatures.
Those higher temperatures warm the water, expanding the volume of the seas.
As temperatures rise, ice stored at the poles and elsewhere — including mountain glaciers — melts, further increasing water volume.
It is a powerful feedback loop that will cause the rate of sea rise to increase dramatically as the 21st century progresses.
More than 200 feet of potential global sea rise is currently stored in ice.
According to the United Nations Conference on Trade and Development, the world’s glaciers will lose between 18% and 36% of their ice mass this century.
Meanwhile, the Greenland and Antarctic ice sheets are melting at a faster pace than previously expected.
Millions of years ago, before those ice sheets materialized, water covered far more of the earth than it does now.
The northern rim of the Gulf of Mexico, for example, was not along the beaches of what we now call Alabama and Mississippi.
It was in present-day Illinois.
The Gulf will not be flooding Chicago anytime soon.
But at sea level, one foot of vertical rise can produce about 100 feet of horizontal spread.
In many low places, that translates to a lot of flooding.
Sea level rise will not be consistent across the globe.
But according to US government projections, if the world significantly reduces greenhouse gas emissions, there may be about two feet of rise by 2100.
If it doesn’t, the National Oceanic and Atmospheric Administration notes, average sea level rise for the contiguous US could be more than seven feet.
Ports, like other coastal real estate and infrastructure, are very much in the flood zone.
A paper by a team of researchers at Princeton and Rutgers points to a “preparedness dilemma” in the US.
“While the federal government seeks to protect citizens from natural disasters, it has limited control over efforts to do so,” the researchers write.
“Both the exposure and vulnerability to a coastal hazard are largely shaped by state and local land use and building codes.”
One thing that helps to galvanize political and financial support for resilience upgrades, they say, is a whopping storm:
In one model of the policy process, floods, hurricanes, and other extreme weather events have been viewed as “focusing events,” whereby they refocus the attention of elected officials and publics on an existing problem.
During a focusing event, a “policy window” of opportunity opens for a short period, and advocates emerge, racing to push their preferred solutions through before the window closes.
For the Port Authority of New York and New Jersey, Hurricane Sandy in 2012 was a focusing event.
Sandy shut down most of the port for a week, which resulted in 25,000 shipping containers being diverted to other ports.
Waterways had to be surveyed and cleared.
Some cargo terminals and maritime support facilities were out of commission longer, due to power failures and damaged equipment.
Oil terminals, for example, couldn’t offload product from tankers because they lacked power.
Damages to port authority operations, which include commuter rail, reached an astonishing $2.2 billion.
The Port Authority’s resilience and sustainability efforts after the storm included complex analysis of the port’s future but also some very basic problem solving.
For example, engineers realized that motors for container cranes can be raised higher off the ground to avoid being inundated.
For the most part, cranes, like electrical substations and other vital infrastructure, are not owned by the Port Authority.
So upgrading — which often means elevating — requires coordinated action with various private partners.
Mitigation efforts at U.S. ports, said Austin Becker, will require disparate interests coming together.
Given the central role that ports play in global commerce, however, those interests include more than those of shipping companies and others directly engaged in port activities.
All kinds of businesses and consumers, including the most landlocked, depend on ports.
Yet not all of those ports will prove dependable in the face of the 21st century’s rising waters.
“Thousands of small and medium ports that provide these really essential services to their local economies and local regions don’t have the resources they need and are already working with outdated infrastructure,” Becker said.
Giants such as Long Beach and the Port of New York and New Jersey have the financial power and expertise to ride out the rising seas.
As the water rises, however, hundreds of smaller ports are left hoping their luck doesn’t collide with the next waterborne “focusing event.”
Links :
- CNN : A drop in the ocean
- Mongabay : Amid rising pressure, Indonesia’s sea-based communities adapt to change
- The Guardian : The seas are rising on Pacific islands nations – but so is their powerful resistance
- Forbes : New Study Suggests Sea Levels Could Rise More Than Scientists Previously Thought
- Popular Science : What a century of rising seas can tell us about the next 30 years
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