Saturday, July 8, 2017

Silent Killers: The power of photography to change the oceans

What if I told you that a single abandoned fishing net could last for up to 400 years in the ocean... killing and tangling marine life, and coral reefs?
They call them ghost nets, but I call them... silent killers.
For this series, I’m asking you to commit to a 30 day challenge to use hashtag #SilentKillers, and spread the word through social media about businesses and initiatives that are helping to turn reclaimed ghost nets into sustainable products.
Because together, we can champion ocean heroes. And become them ourselves.

From Fstoppers by Jennifer Tallerico
Photography is one of the most powerful tools used in influencing and changing perspectives.
All across social media are images that move the emotion range from tugging at heartstrings to enraging the senses.
So when one photographer needed to convey the message of the threats to ocean life she turned to photography.

A few months ago in a post titled Jelly Fish Soup, artist Christine Ren worked with a team to create image specific to bring awareness of overfishing.
Ren is back at it with a powerful message about discarded fishing nets and the threats they carry.

In the video Ren states, "that a single abandoned fishing net can last for up to 400 years in the ocean - tangling and killing marine life and coral reefs."
They are called ghost nets however Ren refers to them as silent killers.
When fishing vessels abandon or lose their nets or other gear it will cause a major impact for the marine life and ocean ecosystems.



With the widespread access to multi social medias, it is not uncommon for images to be seen of ocean life struggling in these ghost nets such as manta rays, sharks, and sea turtles.
Ren's work is to help generate awareness of not just what has been done, but rather how people can help stop it and recover what already has taken place.
She feels this is not just an ocean issue but a human issue as well.

As such, the idea of this shoot was to use people to highlight the struggle, pain, and resignation that these nets cause in the ocean - whether tangling life or being ingested.
To create emotionally-evocative, eerie yet awe-inspiring, underwater photos to bring mass attention to this issue, and its solutions.

Partnering with photographer Jose Cano, Ren created this series in his underwater studio in Nelson New Zealand.
The pair met during a Kickstarter campaign Ren was running for the series which did not get fully funded.
With little hope that the series would be obtainable, Cano flew Ren out to his studio for a few shooting opportunities.


The safety issues on this particular project were most anticipated and unsettling with the concept of being tied and tangled in the netting.
The team created safety precautions as well as Ren stating, "you just have to push yourself past our fears sometimes to make things that matter to you happen."
Between the makeup artists, costume design, and multiple models on set, the image of Ren dream was coming to life.

Ren continues to pursue ways to bring conservation and awareness to mainstream.
She has a second series launching end of July, titled the 11th Hour about raising awareness on climate change.

To stop derelict gear being left in the first place, requires international policy change and regulations and monitoring of the fishing industry - which I tentatively have a media colleague on board to create a tangential coverage piece on that side of the ghost fishing solutions.

Ren has asked readers to a 30 day challenge to spread the word about business that are turning reclaimed ghost nets into sustainable products.
These companies are working to train fisherman to reclaim lost gear and then regenerating nylon waste into new material products.
These products range from skateboards to swimwear.


Friday, July 7, 2017

The Dutch have solutions to rising seas. The world is watching.

The Erasmus bridge runs over the River Maas in Rotterdam.
For the Dutch, living below sea level is not all about a bunch of dykes and dams, but a way of life
AFP/Getty

From The Independant by Michael Kimmelman

In the waterlogged Netherlands, climate change is considered neither a hypothetical nor a drag on the economy.
Instead, it’s viewed as an opportunity.


The wind over the canal stirred up whitecaps and rattled cafe umbrellas.
Rowers strained toward a finish line and spectators hugged the shore.
Henk Ovink, hawkish, wiry, head shaved, watched from a VIP deck, one eye on the boats, the other, as usual, on his phone.

 Breezanddijk with the GeoGarage platform

Ovink is the country’s globetrotting salesman-in-chief for Dutch expertise on rising water and climate change.
Like cheese in France or cars in Germany, climate change is a business in the Netherlands.
Month in, month out, delegations from as far away as Jakarta, Ho Chi Minh City, New York and New Orleans make the rounds in the port city of Rotterdam.
They often end up hiring Dutch firms, which dominate the global market in high-tech engineering and water management.

That’s because from the first moment settlers in this small nation started pumping water to clear land for farms and houses, water has been the central, existential fact of life in the Netherlands, a daily matter of survival and national identity.
No place in Europe is under greater threat than this waterlogged country on the edge of the Continent.
Much of the nation sits below sea level and is gradually sinking.
Now climate change brings the prospect of rising tides and fiercer storms.

From a Dutch mindset, climate change is not a hypothetical or a drag on the economy, but an opportunity.
While the Trump administration withdraws from the Paris accord, the Dutch are pioneering a singular way forward.

It is, in essence, to let water in, where possible, not hope to subdue Mother Nature: to live with the water, rather than struggle to defeat it.
The Dutch devise lakes, garages, parks and plazas that are a boon to daily life but also double as enormous reservoirs for when the seas and rivers spill over.
You may wish to pretend that rising seas are a hoax perpetrated by scientists and a gullible news media.
Or you can build barriers galore.
But in the end, neither will provide adequate defence, the Dutch say.

 Ninety per cent of the city of Rotterdam lies below sea level, with the northern districts most at risk from a rising ocean (red shaded areas are 5 metres below sea level)

And what holds true for managing climate change applies to the social fabric, too.
Environmental and social resilience should go hand in hand, officials here believe, improving neighbourhoods, spreading equity and taming water during catastrophes.
Climate adaptation, if addressed head-on and properly, ought to yield a stronger, richer state.

This is the message the Dutch have been taking out into the world.
Dutch consultants advising the Bangladeshi authorities about emergency shelters and evacuation routes recently helped reduce the numbers of deaths suffered in recent floods to “hundreds instead of thousands,” according to Ovink.
“That’s what we’re trying to do,” he said.
“You can say we are marketing our expertise, but thousands of people die every year because of rising water, and the world is failing collectively to deal with the crisis, losing money and lives.”
He ticks off the latest findings: 2016 was the warmest year on record; global sea levels rose to new highs.
He proudly shows off the new rowing course just outside Rotterdam, where the World Rowing Championships were staged last summer.
The course forms part of an area called the Eendragtspolder, a 22-acre patchwork of reclaimed fields and canals – a prime example of a site built as a public amenity that collects floodwater in emergencies.
It is near the lowest point in the Netherlands, about 20 feet below sea level.
With its bike paths and water sports, the Eendragtspolder has become a popular retreat.
Now it also serves as a reservoir for the Rotte River Basin when the nearby Rhine overflows, which, because of climate change, it’s expected to do every decade.

 Rowing teams practice at the Eendragtspolder, a site intended to be both a public amenity and a reservoir for floodwater (Flickr)

The project is among dozens in a nationwide program, years in the making, called Room for the River, which overturned centuries-old strategies of seizing territory from rivers and canals to build dams and dikes.
The Netherlands effectively occupies the gutter of Europe, a lowlands bounded on one end by the North Sea, into which immense rivers like the Rhine and the Meuse flow from Germany, Belgium and France.
Dutch thinking changed after floods forced hundreds of thousands to evacuate during the 1990s.
The floods “were a wake-up call to give back to the rivers some of the room we had taken”, as Harold van Waveren, a senior government adviser, recently explained.
“We can’t just keep building higher levees, because we will end up living behind 10-metre walls,” he said.
“We need to give the rivers more places to flow.
Protection against climate change is only as strong as the weakest link in the chain, and the chain in our case includes not just the big gates and dams at the sea but a whole philosophy of spatial planning, crisis management, children’s education, online apps and public spaces.”

Van Waveren was talking about a national GPS-guided app created so that residents always know exactly how far below sea level they are.
To use public pools unrestricted, Dutch children must first earn diplomas that require swimming in their clothes and shoes.
“It’s a basic part of our culture, like riding a bike,” Rem Koolhaas, the Dutch architect, told me.

 Deltapark Neeltje Jans tells the story of the famous Delta Works
GeoGarage Netherlands NLHO layer

In the Netherlands, scholarly articles about changes to the Arctic ice cap make front-page headlines.
Long before climate change deniers began to campaign against science in the United States, Dutch engineers were preparing for apocalyptic, once-every-10,000-years storms.
“For us, climate change is beyond ideology,” said Rotterdam’s mayor, Ahmed Aboutaleb.
He took me one morning around new waterfront development in a formerly poor, industrial neighbourhood, to show how urban renewal dovetails with strategies to mitigate the effects of climate change.
“If there is a shooting in a bar, I am asked a million questions,” Aboutaleb said of his city.
“But if I say everyone should own a boat because we predict a tremendous increase in the intensity of rain, nobody questions the politics. Rotterdam lies in the most vulnerable part of the Netherlands, both economically and geographically. If the water comes in, from the rivers or the sea, we can evacuate maybe 15 out of 100 people. So evacuation isn’t an option. We can escape only into high buildings. We have no choice. We must learn to live with water.”

 At the artificial island Neeltje-Jans, at one end of the barrier,
a plaque is installed with the words "Hier gaan over het tij, de wind, de maan en wij"
which translates to "Here the tide is ruled by the wind, the moon and we (the Dutch)"

A Moroccan-born Muslim and a rising star in the Dutch political world who denounces religious radicals and reactionary nationalists alike, the mayor runs a traditionally tough, working-class city.
Rotterdam today is anything but a paradise.
It is riven by social fissures and discord over immigration.
But it has begun to improve in recent years as it has become greener and more diverse.
When asked about climate threats, the mayor talks about creating a less divided, more attractive, healthier city – more capable of facing the stresses climate change imposes on society.

“That’s just common sense,” Aboutaleb said.
The Eendragtspolder is one example, he pointed out, repaying Rotterdam’s investment with green spaces and the rowing course, which has the added perk of aiding a prospective Dutch bid for the 2028 Olympics.

 A storm surge in 1953 flooded the Dutch coastline, killing more than 1,800 people (AFP/Getty)

Levelled by bombs during the Second World War, Rotterdam is not quaint and touristic like Amsterdam but industrial, down to earth, a surprisingly stylish sleeper among Europe’s cultural hubs, with a legacy of radical architecture, attracting young designers and entrepreneurs.
Its tradition of openness has made it a magnet for outsiders and helped it recover from years of hardship, when, during the Seventies, Eighties and Nineties, it became notoriously crime-ridden and filthy, a place wealthy people fled.

Lately the city, accustomed to starting over, has reinvented itself as a capital of enterprise and environmental ingenuity.
It has pioneered the construction of facilities like those parking garages that become emergency reservoirs, ensuring that the city can prevent sewage overflow from storms now predicted to happen every five or 10 years.
It has installed plazas with fountains, gardens and basketball courts in under-served neighbourhoods that can act as retention ponds.
It has reimagined its harbours and stretches of its formerly industrial waterfront as incubators for new businesses, schools, housing and parks.

These are all stops on the standard tour for visiting foreign delegations: proof-of-concept urban interventions, if not actually all-encompassing solutions, that address climate threats in ways that incrementally serve the economy and social needs.

“A smart city has to have a comprehensive, holistic vision beyond levees and gates,” as Arnoud Molenaar, the city’s climate chief, put it.
“The challenge of climate adaptation is to include safety, sewers, housing, roads, emergency services.
You need public awareness.
You also need cyber-resilience, because the next challenge in climate safety is cybersafety.
You can’t have vulnerable systems that control your sea gates and bridges and sewers.
And you need good policies, big and small.

“This starts with little things, like getting people to remove the concrete pavement from their gardens so the soil underneath absorbs rainwater,” Molenaar said.
“It ends with the giant storm surge barrier at the North Sea.”

A Vast Floodgate

That would be the Maeslantkering, built near the mouth of the sea, about a half-hour drive west from downtown Rotterdam – the city’s first line of defence.
It is the size of two tubular Eiffel Towers, toppled over.

 The Maeslantkering, an immense sea gate conceived decades ago to protect the port of Rotterdam

In the 20 years since it opened, the Maeslantkering hasn’t actually been needed to prevent a flood, but it is tested regularly just in case.
Picnickers line the shore to watch.
The trial closings are a little like the Dutch version of the Macy’s Thanksgiving Day Parade.

I drove with van Waveren to see it one day.
It is not uncommon here to witness the astonishing sight of ships cruising by overhead.
This happens in a country where the highways are frequently below sea level.

Maeslantkering with the GeoGarage platform

The Maeslantkering is a consequence of repeated historic calamities.
In 1916, the North Sea overwhelmed the Dutch coastline, inaugurating a spate of protective construction that failed to hold back the water in 1953 when an overnight storm killed more than 1,800 people.
The Dutch still call it the Disaster.

 Construction Of Dam In Delta Works Project (1966)

They redoubled national efforts, inaugurating the Delta Works project that dammed two major waterways and produced the Maeslantkering – the giant sea gate, completed in 1997, keeping open the immense waterway that services the entire port of Rotterdam.

Protecting the port is paramount.
Once the world’s busiest, Rotterdam’s port remains the most important in Europe, each year serving tens of thousands of ships from around the world, supplying steel to Germany, petrochemicals to South America and pretty much everything else to everywhere.
The port is still the bedrock industry in this city of more than 600,000, according to port officials, accounting for 90,000 jobs, not to mention another 90,000 workers whose businesses depend on the port, too.

The port supports five oil refineries, whose owners include Shell and the Koch brothers, along with a massive coal-fire power plant.
Officials say the port accounts for 17 per cent of the entire nation’s carbon footprint.
A central paradox – and to sceptics, the ultimate hypocrisy – of this city’s environmental self-branding is that, at heart, Rotterdam’s economy continues to rely on the fossil fuel industry.

How the port eventually transitions to a greener economy, authorities concede, is the greatest challenge they face, along with climate change.
They describe plans for immense wind farms in the North Sea and strategies to capture heat from fuel-burning factories to warm the greenhouses that supply the country’s agricultural yield.
The Netherlands exports nearly $100bn (£786bn) a year in agricultural products, second only to the United States.

In any case, the safe transport of all those raw materials, not to mention the responsibility of keeping the feet of people in the city dry, now and in the future, depends on the Maeslantkering.

The idea behind it, first discussed decades ago, was unprecedented – a monumental gate with two arms, resting on either side of the canal, each arm as tall and twice as heavy as the Eiffel Tower.
It was a staggering work of engineering.
Wim Quist, the architect, devised an object of surpassing beauty, one of modern Europe’s lesser-known marvels.

Van Waveren described how it works.
When the gate is closed, the arms float out onto the canal, meet and lock, the tubes filling with water and sinking onto a concrete bed, making an impenetrable steel wall against the North Sea.
The process takes two and a half hours.
Pressure from the sea is then transferred from the wall to the largest ball joints in the world, embedded in the banks on either side of the river.

Computers, using a closed electronic system to avoid cyberattack, monitor sea levels hourly and can shut the gate automatically – or open it.
This is critical: 30 pumps inside the gate are linked to one of the country’s power grids.
They extract water from the tubes when it is time for the Maeslantkering to be reopened.

If the grid fails, there is a backup grid and, as a last resort, a generator, because even more dangerous than the gate’s not closing is the gate’s not reopening.
In that case, water pouring down from the Rhine and Meuse rivers could not flow into the sea and would overwhelm Rotterdam even more swiftly than the North Sea could.
As Aboutaleb noted, escape would be impossible.

Ovink said only half-jokingly, “the last resort would be to blow it up”.
The Maeslantkering was clearly built with Hollywood disaster-movie scenarios in mind: there are redundancies to redundancies, and the barrier is prepared for the most extreme climate change models, with sea levels rising beyond current forecasts.

Even so, Rotterdam port officials have plans underway to add another two feet to the height of the gate.

The Delta Works in the Netherlands (Holland) is the largest flood protection project in the world.
This project consists of a number of surge barriers, for examples:
1- The Oosterscheldekering is the largest of the 13 ambitious Delta Works series of dams and storm surge barriers and it is the largest surge barrier in the world, 9 kilometres (5.6 mi) long. The dam is based on 65 concrete pillars with 62 steel doors, each 42 metres wide. It is designed to protect the Netherlands from flooding from the North Sea.
2- The Maeslantkering is a storm barrier with two movable arms; when the arms are open the waterway remains an important shipping route however when the arms close a protective storm barrier is formed for the city of Rotterdam. Closing the arms of the barrier is a completely automated process done without human intervention.

Reshaping Neighbourhoods

Beyond the Maeslantkering, back in town, there are countless fortifications, big and small, knitted into streets and squares.
One sunny afternoon, I met Wynand Dassen, manager of Rotterdam’s resilience team, and Paul van Roosmalen, who oversees rooftop development for the city, at the Dakpark, a dyke in a poor, largely immigrant neighbourhood bordering industrial waterfront.
The site of the Dakpark used to be a railway switching station, a grim nowhere place abutting a cluster of social housing blocks.
This was a red-light district, notorious for drug dealers and crime.

The dyke does a lot more than just hold back water.
It has a shopping centre, which the neighbourhood needed, and a park on the roof.
Shops face the waterfront and help pay to keep up the park.
The park slopes from the roof down to streets and housing blocks, creating a grassy hill that links park and neighbourhood.

When the weather is good, sunbathers sprawl on the grassy roof and toss Frisbees.
Formal gardens open onto acres of well-kept lawns.
The park is a kilometre long.
And wonderful.
Its success – not only as a barrier but also as a boon to business and the area – has persuaded officials to consult neighbourhoods and set aside money for community-initiated projects.
“We became invested in getting more people involved in all kinds of civic issues,” Dassen told me, “and water inevitably becomes an integral part of this process.
We believe you get the smartest solutions when communities are engaged and help make the links between water and neighbourhood development.”


 A water plaza in the Spangen neighbourhood of Rotterdam was created to capture floodwater 

Van Roosmalen agreed.
“It’s an example of what you can do if you connect storm-water management with social welfare and neighbourhood improvements,” he said.
“It’s what we mean here in Rotterdam by ‘resilience planning’.”

In a neighbourhood nearby, where drug addicts used to trek all the way from France to buy cheap heroin, I came across Marleen ten Vergert, a single parent supporting a young daughter on a civil servant’s modest salary.
Women in hijabs lugged groceries, old men lounged on park benches and children rode skateboards over broken concrete paths, past aged housing blocks.
One block of houses surrounded a water plaza created to capture floodwater.
Young families were enticed by prices of a single euro to buy abandoned houses around it.
Many families came and went.
The water park was vandalised.
But, slowly, little by little, it has come to be embraced by the neighbourhood.
“Now, for the most part, it works,” Vergert told me.
“People want the water square, so they take better care of it.
There’s a greenhouse nearby run by a Turkish community.
The value of houses in the neighbourhood has gone up.”

A few blocks away, a startup in a converted industrial waterfront building is developing solar-powered sailing drones for collecting plastic trash from the sea, and, back in the middle of the city, a warehouse with a Brooklynesque mix of artisanal food stalls, a circus academy and a pinball museum has rejuvenated a formerly dingy pier.
Where the old Hotel New York, a century-old landmark, used to be the tallest building along a stretch of waterfront, skyscrapers have sprung up, producing a whole new business district in Rotterdam, with a photography museum across the street from the city’s signature office tower, De Rotterdam, by Koolhaas, and Ben van Berkel’s harp-like Erasmus Bridge.

Rotterdam is clearly trying to cast itself as a model of inventive urbanism.
A local businessman, Peter van Wingerden, envisions floating dairy farms along the waterfront.
One in every three trucks coming into the city carries food, he said.
Floating farms would reduce truck traffic and carbon emissions, supplying the city with its own milk.
With the city’s encouragement, he is constructing a $2.2m prototype, for 40 cows, producing a half-million litres (about 130,000 gallons) of milk a year.
“The river is no longer just for industry,” he told me.
“We need to find new uses, which keep us safe from climate change, and help the city grow and prosper.”

That’s the city’s mantra.
When I asked van Wingerden if it was unsettling to live in a waterfront city mostly below sea level, he said: “It seems to us less dangerous than living on the San Andreas Fault.
At least when we flood, we’ll have some warning before our feet get wet.”

To the Dutch, what’s truly incomprehensible, he added, is New York after Hurricane Sandy, where too little has been done to prepare for the next disaster.
People in the Netherlands believe that the places with the most people and the most to lose economically should get the most protection.

The idea that a global economic hub like Lower Manhattan flooded during Hurricane Sandy, costing the public billions of dollars, yet still has so few protections, leaves climate experts here dumbfounded.

Molenaar, Rotterdam’s climate chief, summed up the Dutch view: “We have been able to put climate change adaptation high on the public agenda without suffering a disaster in many years because we have shown the benefits of improving public space – the added economic value of investing in resilience.
“It’s in our genes,” he said.
“Water managers were the first rulers of the land. Designing the city to deal with water was the first task of survival here and it remains our defining job. It’s a process, a movement.
“It is not just a bunch of dykes and dams, but a way of life.”

Links :

Thursday, July 6, 2017

The giant undersea rivers we know very little about


From BBC by Richard Gray

Far below the surface of the sea, the seabed is being scoured by rivers of sediment that can flow thousands of miles from land.

The river cascades through steep-sided gorges and churns around isolated towers of rock, before winding across a vast plain beyond.
It is a torrent to rival the mighty Colorado River that carved out the Grand Canyon.

Yet this dramatic natural wonder has never appeared in any tourist photographs, nor does it feature on any maps.
The reason?
It lies two miles (3.2km) beneath the surface of the Pacific Ocean.

Stretching away from the coast of California, the Monterey Canyon has been shaped over millions of years by this bizarre “undersea river”.
Beyond the mouth of the canyon, the flow has cut a valley into the sea floor that extends for nearly 200 miles before spilling onto the abyssal plain of the deep ocean.

Similar channels can be found etched into seabeds all over the world.
They have been found off the coasts of Greenland, the Amazon, the Congo and Bengal, to name a few.
The largest are several miles wide and run for thousands of miles out into the ocean depths, where they provide vital sustenance to the creatures living there.
But these undersea rivers are among the least understood phenomena on our planet.


The canyons can flow far out to sea (Credit: David Fierstein/MBARI)

In many ways, undersea rivers are similar to the rivers we see on land.
They have banks on either side. Smaller rivers called “tributaries” feed into larger ones.
The rivers carve valleys into the sea floor.
They follow meandering paths and can even change course, resulting in abandoned sections similar to oxbow lakes.
Ultimately, they spill out onto the abyssal plain in the ocean depths in similar ways to a river estuary.

“If you drained all the water away, it would look exactly like a river system with bends and meanders, except there are no trees along the banks,” says Dan Parsons, a sedimentologist at the University of Hull, UK, who travels the world to study undersea rivers .

These submarine channels were almost completely unknown until the 1980s, when sonar mapping of the seafloor began to reveal them.
Many extend out into the ocean from the mouths of major rivers like the Amazon and the Congo, following tortuous routes across the thick sediment on the seafloor.
At the time, scientists compared them to mature river systems on land, such as the lower reaches of the Mississippi River.

The underwater canyons cut into the continental shelf can be compared to the headwaters of a river system. From there, a river will spill into large meandering channels that extend out on the floor of the continental slope and the continental rise.

There, the channels tend to be bounded by huge levees that have built up over time.
Some of these levees stand hundreds of feet above the sea floor.
“These submarine channel systems are some of the biggest in the Solar System,” says Parsons.

However, it was only in the late 1990s that it became clear how these channels were created.

Scientists drilled into the sediments in the channels, and the sediment cores indicated they had formed through repeated deposits of sediment that appeared to spill down the channels.

Rather than flows of fresh (or at least salty) water, undersea rivers are slurries of silt and sand that cascade along channels on the seabed.
Each particle tumbles through the water under its own weight.
A new river starts on the continental shelf like an avalanche in the mountains, picking up speed and momentum as it moves until it flows like a liquid.
Once started, an undersea river can flow for weeks and even months at a time, moving the same amount of sediment in one go that all the world’s land-based rivers transport in an entire year.
“The flows that come down them are more like snow avalanches or volcanic pyroclastic flows,” says Parsons.
However, studying these processes in the deep sea has proven difficult.
“When you compare them to what we know about rivers on land, we have practically no measurements of these flows under the sea,” says Parsons.


Despite the intense cold and pressure, life seems to thrive near the flows (Credit: MBARI)

Part of the reason for this is the difficulty in studying an environment at that depth. Many of the channels are found more than a mile (2km) down and can flow to depths of 2.5 miles (4km).
To reach these inky depths requires specialised remote controlled deep-sea submarines.

Worse, the rivers only flow some of the time.
After a flow has passed, the channel may be inactive for weeks, months or even years.
It can cost over £25,000 a day to use a research vessel that can launch remotely operated vehicles (ROVs) to explore the deep ocean, so it is hardly surprising few scientists have been able to study these undersea flows.

“People have just not had the capacity to go and look before,” says Jeff Peakall, a sedimentologist at the University of Leeds, UK.
“In fact, we have better resolution of the far side of the Moon than we do under our oceans. We know remarkably little about these underwater rivers.”

Instead, for many years researchers had to rely on laboratory simulations, mixing seawater with building plaster or mud in large tanks to create turbidity currents.
Footage of these experiments reveals that the currents are similar to avalanches or pyroclastic flows, as the sediment billows and surges along the bottom of the tanks.

Now a small band of intrepid researchers are beginning to explore these deep-sea channels and learn more about how they work and what lives around them.
“We are now at the stage where the technology is letting us measure the flows in the real world at full scale,” says Parsons.
“That has not been possible until relatively recently.”
“In Monterey, we are repeatedly mapping the canyon to see how it changes over time,” says Parsons. His team is using autonomous underwater vehicles to show how the flows are changing the seafloor.
Parsons is also conducting similar research off the coast of British Columbia.
There, meltwater from glaciers and snow in the mountains delivers sand and mud to a delta at the top of a fjord known as Bute Inlet, which will then collapse and flow down the submarine channel in a powerful “turbidity current” – the name given to these cascades of sediment laden water.

In a study published in 2010, Peakall and Parsons sent a robotic submarine down to a deep undersea channel that runs across the bottom of the Black Sea.
Here, they found another type of current is carving the river channel, this time a flow of salty water, which originally comes from the Mediterranean, spills into the Black Sea through the narrow Bosphorus strait and then into the channel.


The benthic event detectors (or Beds) are placed on the seabed, and measure the activity around them (Credit: MBARI)

Since the Mediterranean water is saltier, and so denser, than the Black Sea, it remains separate, flowing at a speed of around 4mph (6.4km/h).
Every second, around 22,000 cubic metres of water passes through the channel.

“We were trying to map the water coming out of the Bosphorus strait, to understand how flows move through undersea rivers,” says Parsons.
“It was a warm-up for looking at the really big systems driven by mud and sand in the offshore submarine channels.”

Only in the last few years have researchers witnessed an undersea mud river in the real world. In 2013, Charlie Paull of the Monterey Bay Aquarium Research Institute and his colleagues were using an ROV to explore a relatively small underwater canyon, just a few miles from the Californian coast. The ROV was tethered to a ship on the surface, around 1,500ft (400m) above.

Without warning, a turbidity current came roaring down the canyon and the ROV was caught in it. One of the ROV pilots described the experience as being like “flying an ROV in a tornado”.
The five-ton ROV was lifted off the seafloor and pushed sideways.

It beamed back video, which revealed a dense layer of muddy water surging and billowing across the canyon valley.
Clumps of kelp, torn from the seabed further upstream, could be seen rushing past. But before they could learn more, the team had to pull the ROV out of the flow, for fear it would be torn free of its tether.

A 2014 analysis by Esther Sumner of the University of Southampton showed that the sediment flow, which was 295ft (90m) thick from top to bottom, had travelled down the canyon at around 3.8mph (6.1km/h).

 The violence of the events and deep depths makes it impossible for humans to observe firsthand (Credit: MBARI)

Yet this was a relatively small flow.
Oceanographers at the Monterey Bay Aquarium Research Institute are now leading the development of new technologies to study bigger rivers.
They have developed acoustic “speed cameras”, which can measure the speed of the flows tumbling down the Monterey Canyon and into the valley beyond.

They have made “smart boulders”: beach-ball-sized instrument arrays, also known as benthic event detectors or Beds.
These can sit on the floor of the channel.
When a sediment river cascades down, they are picked up and carried along.
They send back information about how they roll, glide and lift from the sea floor.

Yet the sheer power of these enormous flows of sediment can make studying them a challenge.
In January 2016, Paull and his team lost a fixed monitoring device, along with the one-tonne tripod it was mounted on, when a powerful sediment flow swept down the Monterey Canyon at 12mph (19.3km/h).
They eventually found it, after following the pings from its beacon - three miles from its original position, almost completely buried in mud.
When they managed to pull it out, they found steel plates on the frame had been bent out of shape and ground down to a knife-edge.
A float on top of the tripod, made of carbon fibre and titanium, had also been badly eroded.
Ten months later, they lost a second tripod in a similar manner, while another event saw an entire mooring dragged four miles (7.1km) out of position.

“It is sobering to think those sort of events are going on under the seabed,” says Paull.
“When I look out of my window at the ocean, there is no sign of these powerful events taking place, but on the sea floor they are powerful enough to drag entire boulders with them.”

Faced with this kind of destructive force, it is hard to imagine much life surviving along the length of these undersea channels.
Yet some species, at least, seem to thrive.

“These sediment flows have a major impact on canyon biodiversity,” says Craig McClain of the Louisiana University Marine Consortium, who has been working with the team at Monterey Canyon. “For some types of species, this disturbance causes a boom allowing their numbers to grow quickly, while for others their numbers plummet. It depends on whether a species is a ‘weedy’ species with fast growth and reproduction or not.”

With Jim Barry at the Monterey Bay Aquarium Research Institute, McClain has shown that the channel beds teem with snails, clams, crustaceans, urchins, sea cucumbers and worms.

What’s more, beyond the safety of the canyon, the nutrients and oxygen carried by the flows seems to help life survive on the comparative desert of the ocean’s abyssal plain.
To find out what is going on, scientists have looked at sandstone that was formed from sediment flows under prehistoric oceans.
Telltale holes in the rocks suggest small worms once burrowed through the sediment.


Due to the force of the flows, the recording instruments need to be tough (Credit: Roberto Gwiazda/MBARI)

“What appears to happen is the flows not only bring oxygen and nutrients down to the deep ocean, but they also carry life with them too,” says Peakall.
“These worms are swept down from shallower depths and live in the sediment when it settles, until they run out of oxygen.”

A 2016 experiment by Sumner suggests that polychaete worms – brightly-coloured marine creatures, covered in bristles like a pipe cleaner – may be able to survive such a journey intact.

The organisms living in the sediment may also play an important role in the way these undersea rivers flow in the first place.

A 2015 study by Jaco Baas of the University of Bangor, UK, and his colleagues showed that microorganisms living in the mud help to bind it together, allowing sediment to pile up – until it fails catastrophically.
This helps explain why undersea rivers only flow periodically.

“The biggest flows are probably triggered by a failure in the sediment building up on the continental shelf,” says Peter Talling, a geologist at the University of Durham, UK. “Flooding or waves during storms can cause an underwater avalanche. Fresh water from rivers filled with sediment can also be denser than sea water, and so plunge to the bottom of the ocean.”

It now seems that something strange happens to the flows as they go downstream.
Studies of undersea rivers off the coast of the Congo show that they stretch as they go downstream.
This means an event that lasts an hour at the top can go on for days or weeks at the bottom of the channel.

One of the most active undersea sediment rivers can be found in the Nazaré Canyon off the coast of Portugal.
The river runs down a narrow channel inside the five-mile-wide (8km) canyon, before flowing across the abyssal plain nearly 2.5 miles (4km) beneath the surface, where it is contained with large levees.
Around four times a year, small flows spill down the Nazaré Canyon for a few kilometres at a time before running out of steam.
But the canyon is sometimes hit by more violent events.

“At the extreme end are what we call ‘canyon flushing’ turbidity currents,” says Josh Allin of Southampton University in the UK, who has been studying the Nazaré canyon. “These are much more violent and are capable of eroding very large volumes of sediment – tens of cubic kilometres – from the canyon and transporting it out onto the deep ocean floor. They appear to occur on hundred- to thousand-year timescales, but they have never been directly observed and we know very little about their characteristics.”


The organisms carried in the sediment may help feed other animals that flourish nearby (Credit: MBARI)

While canyon flushing turbidity currents are rare, it could still be important to understand them.
For starters, they help to lock away huge volumes of carbon in the sediment at the bottom of the ocean, slightly slowing the rise in greenhouse gases that is causing climate change.
But they can also have more immediate effects on our lives.

In 1929, 23 underwater telegraph cables were cut close to Newfoundland.
It was suggested later that an offshore earthquake had struck the nearby Grand Banks, dislodging a bank of sediment, which then roared down a channel in the continental shelf and out onto the abyssal plain.

Today, nearly all of the world’s internet and banking transactions are conducted over underwater cables, so if a lot of these cables were cut it would cause major problems.
Many of the cables connecting the US to Europe cross the path of this same underwater river channel that runs south from Newfoundland.
Scientists estimate the flow that came down that channel in 1929 reached speeds of 57mph (93km/h) and carried debris more than 683 miles (1,100km) across the sea floor.

“If we saw a repeat of that now, it could be disastrous,” says Talling.
His research is partly funded by the International Cable Protection Committee, which looks after underwater infrastructure.
“These are incredibly powerful and destructive flows,” says Parsons. “It is important we understand how they work.”

Wednesday, July 5, 2017

What happens to island nations that are lost to rising sea levels?


 published by World Economic Forum

From Inverse by Jacqueline Ronson

Earth’s political boundaries will always shift as conflict rises and regimes fall.
We are used to this sort of change and the out-of-date maps it produces.
But nothing in the history of human diplomacy has prepared us for what’s coming next — countries that physically cease to exist as the land they are made of is swallowed up by rising seas.

The Maldives is made up of 1,192 small coral islands with an average elevation of three feet.
Photos via NASA / Wikimedia


For low-lying nation states like the Maldives, Tuvalu, the Marshall Islands, and Kiribati, it’s not a question of if, but when.
Keeping the world to two degrees Celsius of warming, the stated goal of the Paris Agreement on climate change, would still result in 15 feet of future sea level rise, according to analysis by Climate Central.
At 16 feet, the Maldives and Tuvalu would be completely submerged.
The Marshall Islands would be 99 percent underwater, and Kiribati 97 percent.
Even a few feet of sea level rise — within the realm of possibility for this century — would devastate these countries and permanently change their landscapes.

“Life is difficult enough on these small islands, surrounded by the vastness of the ocean, without adding the challenges of sea level rise, more dangerous extreme weather, and the loss of food and fresh water resources,” write Andrew Holland and Esther Babson of the American Security Project in a recent report for the Center for Climate and Security.
The islands have made up for their small populations and poor resources by forming alliances with each other, and yet a humanitarian crisis is almost guaranteed.

Kiribati has made some effort to plan for the future, by purchasing land in Fiji that currently grows food for the people of Kiribati and may one day house them as well.
But it’s most likely that the exoduses will happen in sudden moments of crisis, when storm surges flood whole islands and poison freshwater resources.
“What we should expect is more uncontrolled migration from island to island, to cities and developed countries,” write Holland and Babson.




The island of Funafuti is one of nine that make up Tuvalu, and is home to about 6,000 people. 

Where will climate change refugees go when their homes are destroyed, and will they be welcomed when they arrive?
Will the magnitude of the crisis prompt nationalist, reactionary policies that see borders shut down and xenophobia climb?
You might say that’s already happening today, with refugees from Syria’s brutal war, set off in part by climate change, being portrayed as potential threats in the mainstream discourse of the United States, Europe, and elsewhere.

And what happens to the political entity of a nation state when its physical land is abandoned?
What rights do former inhabitants still claim to that region and the economic resources it may still hold?
Currently the island nations lay claim to an exclusive economic zone that extends 200 miles in all directions.
Who will own the rights to fish when the land is all but gone?
The international community has yet to grapple with these questions, and there will be no easy answers.


The Kwajalein Atoll is one of 29 that make up the Republic of Marshall Islands.

China has shown an increasing interest in the region, and has upped climate change aid to these countries dramatically.
One motivation could be a desire to ultimately have more say in who gets to control these island resources when the people move away.

A power struggle between countries vying for influence is possible, and preventing it will depend on a great deal of international cooperation in a forum where the ground rules have yet to be invented.


Kiritimati is the largest atoll in the Republic of Kiribati.

The recent promise of United States President Donald Trump to withdraw from the Paris Agreement ups chances that nations will look to their own interests before helping their neighbors.
The U.S., after all, is the richest country in the world and the one that has contributed the most to climate change.
If it will shirk responsibility for the damage it has wrought, why would another step up?

And the rest of the world will certainly have its own troubles.
“These problems are not unique to small, poor island nations,” write Holland and Babson.
“It is only that they will be forced to deal with them first.”


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Tuesday, July 4, 2017

Plastic pollution in the world's oceans: Interactive map reveals where 5.25 trillon pieces of waste end up



This interactive map shows how much plastic is found in the world's oceans.
Most of the plastic comes from rubbish dumped into rivers, which is then carried into the sea
(Credit: Dumpark)

From DailyMail by Harry Pettit

  • Map visualises the estimated concentration of floating plastic waste in the world's oceans
  • Densities of plastic are shown as white dots around the map, each of which represents 20 kilograms (44lbs)
  • Eight million tonnes of plastic is dumped into our oceans every year, endangering marine and human life
  • The map was created to underline the issue of plastic pollution and encourage people to take action

As much as 8 million tonnes of plastic is dumped into our oceans every year, endangering marine life and, if it enters the food chain, endangering humans too.
Now, an interactive map has revealed where the 5.25 trillion pieces of plastic adrift in our oceans end up.
Densities of plastic are shown as white dots around the map, each of which represents 20 kilograms (44 lbs) of damaging ocean waste.

In the Sailing Seas of Plastic map, graphic designers at New Zealand-based data firm Dumpark visualised the estimated concentration of floating plastic debris in the world's oceans.
When zoomed out, the map seems to show that plastics in the ocean are large floating landfills, 'but as you zoom in you realise the complexity of the issue: The ocean is quite a vast surface, and similar to a starry night, there are a lot of little bright dots,' said map researcher Mr Laurent Lebreton.

The graphic reveals that the North Pacific Ocean suffers the most from plastic pollution, with an estimated 2 trillion individual pieces adrift in its waters.
This works out at around 87 million kilograms (193 million lbs) of waste in total, nearly one third of plastic pollution in all oceans.
Much of this waste is focused around China and Japan, tracing the North Pacific gyre, one of Earth's five major gyres, which are powerful circular ocean current systems caused by wind patterns and the rotation of the Earth.
The map shows that the Indian Ocean is a hot spot for global plastic pollution, with 1.3 trillion pieces of floating plastic.
Previous research has shown that as much as 60 per cent of the world's plastic waste comes from just five countries: China, Indonesia, Philippines, Vietnam, and Thailand.
This is likely the reason the North Pacific and Indian Oceans are so heavily polluted, as gyres carry waste outwards from the coasts of these nations.

The map is based on a study titled 'Plastic Pollution in the World's Oceans' from oceanographer Dr Marcus Eriksen.
According to the study, there are 5.25 trillion pieces of plastic in our oceans, enough to circulate our equator 425 times.
Dr Eriksen and his team went on 24 nautical expeditions between 2007 and 2013 across all five of the Earth's major gyres.

 Densities of plastic are shown as white dots around the graphic, each of which represents 20 kilograms (44 lbs) of damaging ocean waste

When zoomed out, the map seems to show that plastics in the ocean are large floating landfills, 'but as you zoom in you realise the complexity of the issue.
The ocean is quite a vast surface, and similar to a starry night, there are a lot of little bright dots,' said map researcher Mr Laurent Lebreton.
Pictured is the amount of plastic waste found in the Atlantic Ocean

The researchers took in 680 loads of plastic on their trip and noted down 891 visual assessments of floating waste, then crafted a statistical model to work out how plastic is spread around the world's oceans.
They found that, when added up, all of the ocean's plastics weigh more than 38,000 African elephants.
'The plastic industry suggests the only solution is through our own efforts — recycling, incineration, responsible personal waste management,' Dr Eriksen told Vox.

 The graphic reveals that the North Pacific Ocean (pictured) suffers the most from plastic pollution, with an estimated 2 trillion individual pieces of plastic adrift in its waters

The map shows that the Indian Ocean is a hot spot for global plastic pollution, with 1.3 trillion pieces of floating plastic.
Previous research has shown that as much as 60 per cent of the world's plastic waste comes from just five countries: China, Indonesia, Philippines, Vietnam, and Thailand (pictured)

'But the reality is that the industry itself needs a design overhaul - they should strive to recover 100 per cent of their products, or make them 100 per cent environmentally harmless.'
Dr Eriksen and his team also investigated what types of plastic were polluting the oceans most.
'We found an astounding number of those little balls in deodorant roll-ons,' he said.
'The bigger items tend to be solid plastic: Toothbrushes, army men, bouncy balls, milk jugs, buckets...'

The map is based on a 2014 study in which a team of oceanographers went on 24 nautical expeditions between 2007 and 2013 across all five of the Earth's major gyres.
Pictured is the field locations where count density (right) was measured for different sizes of plastic fragments (bottom left of each grid)

This image shows the numbers (right) of different sizes of plastic fragments (bottom left of each grid) that the team found.
Red indicates a high density while green shows a low density.
The team took in 680 loads of plastic on their trip and noted down 891 visual assessments of floating waste, then crafted a statistical model to work out how plastic waste is spread

But the researchers said that most of the pieces of plastic they found was in confetti-sized shreds.
Of the 5.25 trillion particles Dr Eriksen's team calculated, 92 per cent are microplastics, either broken-up bits of larger plastic items, or small pieces like facial scrub microbeads.
'Most of these microplastics are so small you can't really tell what they are,' Dr Eriksen said.
'You drag a net through the ocean and come up with a handful of plastic confetti - particles the size of fish food.'

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Monday, July 3, 2017

New volcanic island unveils explosive past

A newly formed volcanic cone between the Tonga islands of Hunga Tonga and Hunga Ha‘apai erupts on 15 January 2015, releasing dense, particle-rich jets from the upper regions and surges of water-rich material around the base.
The monthlong Hunga eruption created a new island that is now the subject of study and promises to reveal new aspects of the region’s explosive volcanic past.
Credit: New Zealand High Commission, Nuku’alofa, Tonga

From EOS

A recent volcanic eruption near Tonga in the southwest Pacific created a new island, giving scientists a rare opportunity to explore the volcanic record of this remote region.

In late December 2014, an undersea volcano erupted between two small islands in the Tonga volcanic arc northeast of New Zealand, sending steam and dense ash plumes high into the air.
By the time the eruption ended about 5 weeks later, a new island had formed, eventually bridging the gap between the original islands.
Winds and ocean waves then began rapidly reshaping the newly emerged volcanic cone.

Ten months after the eruption, we visited the new island, which we unofficially nicknamed Hunga Island.
There, we attempted to characterize the volcanology of the eruption, begin tracking the rate of erosion on the new island, and assemble a history of volcanism in this region of the southwest Pacific.
Our findings reveal a shallow submarine volcanic caldera adjacent to the new volcanic island, and they highlight how incomplete the volcanic record can be at remote oceanic volcanoes.

Hunga Tonga and Hunga Ha‘apai with the GeoGarage platform
(Linz nautical chart & CNES imagery 2017)

Signs of Eruption

The uninhabited islands of Hunga Tonga and Hunga Ha‘apai lie 65 kilometers north of Nuku‘alofa, the capital city of the Kingdom of Tonga. Between 19 December 2014 and 28 January 2015, residents of Nuku‘alofa witnessed several large volcanic plumes rising from an eruption in the direction of the two islands [Global Volcanism Program, 2015], as seen in the news video below.

Newly awakened Hunga Ha'apai volcano creates large new Tongan island.
(see ABC news

The plumes were the result of an explosive interaction between seawater and magma rising from a plateau about 150 meters below the ocean surface.
The plateau is part of Hunga, a massive, submerged volcanic edifice that rises more than 2000 meters from the surrounding seafloor and the site of volcanic activity as recently as 1988 and 2009 [Global Volcanism Program, 2009].

The 2014–2015 Hunga eruption deposited material between the islands of Hunga Tonga and Hunga Ha‘apai, initially creating an isolated third island before connecting with Hunga Ha‘apai.
In less than 3 weeks, the eruption built up a circular area of land with a diameter of about 2 kilometers and a height of 120 meters.

 This oblique aerial view shows the new Hunga cone and crater on 6 November 2015, stretching between the islands of Hunga Ha‘apai and Hunga Tonga (top).
The crater rim is about 550 meters in diameter.
Credit: Brendan Hall

A Violent Volcano Under the Sea

Hunga Ha‘apai, Hunga Tonga, and a reef to their south sit on the rim of a submarine caldera known as Hunga Tonga–Hunga Ha‘apai.
The islands and reef are the only surface features betraying the presence of the largely submerged Hunga volcano (Figure 1).


Fig. 1. Water depth measurements show the Hunga edifice on which the islands of Hunga Tonga and Hunga Ha‘apai lie. Neighboring volcanoes include the active Metis Shoal.
The inset shows the Tonga archipelago’s location within the Kermadec-Tonga volcanic arc at the boundary between the Pacific Plate and the Indo-Australian Plate.
Credit: Shane Cronin

Hunga volcano is one of many volcanoes in the Tonga-Kermadec volcanic arc that formed in response to subduction of the Pacific Plate beneath the Indo-Australian Plate.

Many highly explosive eruptions along this chain have had significant regional consequences [see, e.g., Caulfield et al., 2011].
These occurrences suggest that Hunga volcano may itself have had a similarly violent past.

Past research indicates that radiating, outward dipping lava flows and pyroclastic deposits on the two older Hunga islands represent small remnants of the rim of a very large volcano surrounding a caldera structure [Bryan et al., 1972].
This volcano may have suffered catastrophic collapse or prolonged erosion, obscuring it from view.


A nautical chart recently created for Nishinoshima island has fallen behind the growth of the real island.
The red curves on the center left of the island, apart from contour lines, indicate the locations of pre-eruption coastlines.
(Provided by the Japan Coast Guard via The Asahi Shimbun)

Field Observations

In November 2015, we conducted a land and ocean survey of Hunga Tonga–Hunga Ha‘apai and the new island.
Our goals were to characterize the recent eruption and collect baseline quantitative topographic data for tracking erosion rates.
We also wanted to assemble a longer history of the area’s volcanic and tsunami activity by surveying the older Hunga islands and surrounding shallow waters.

On the new island, we discovered that coarse deposits from falling water-rich jets of pyroclastic rock fragments form the lower beds of the cone, consistent with videos and photos of the eruption in progress.
Where waves have cut into the shoreline, the pyroclastic deposits appear poorly consolidated and poorly sorted.

The upper part of the cone is steeper and reflects a gradual “drying” (decrease in water interaction with magma) of the eruption as it proceeded.
This upper region is made up of thin, fine-grained beds of ash deposits, interspersed with ash-dominated sediments typical of lateral currents of particles, air, and steam.

The cone reached its maximum diameter by 7 January 2015 but continued to increase in height over the next 2 weeks.
Once the vent was completely surrounded by pyroclastic deposits, much higher eruption columns began.
Such Surtseyan eruptions—from a shallow sea or lake water—have only rarely been witnessed since the phenomenon was first seen during the formation of Surtsey, Iceland, in 1963 [Kokelaar, 1983].

A new crater lake sits atop the Hunga cone, created in the recent eruption between the islands of Hunga Ha‘apai and Hunga Tonga in the Tonga volcanic arc.
Credit: Marco Brenna 

Rilling of the island’s surface—forming dendritic erosion patterns—started during the cone growth, but it accelerated with rainfall once the eruption ceased. In addition, wave erosion began to rapidly attack the base of the island.
Wave erosion was strongest on the southern side of the cone, exposed to the southeast trade winds and associated ocean swells.
There, the island has shrunk by more than 500 meters from its initial posteruption shore, leaving 40-meter-high collapsing cliffs.


Strong rilling and gullying of the fresh volcanic material making up the new island that abuts Hunga Ha‘apai underscore the rapid rate of erosion in the area.
Coastal erosion has cut into the initial posteruption shore by more than 500 meters, leaving 40-meter-high collapsing cliffs on the island’s south side.
Author Shane Cronin stands near a large gully.
Credit: Marco Brenna

In the 2.5 years since its formation, the primary volcanic cone lost about 40% of its original footprint, which spanned roughly 8 square kilometers.
However, the island has remained roughly the same in overall area because erosion has been matched by long-coast redisposition of the volcanic material in beach bars, altering the island’s shape.
Taking Samples

Shortly after the eruption, we carried out a photogrammetric survey using a drone and real-time kinematic GPS control points to provide a baseline for future monitoring.

We collected samples to chemically characterize the new volcanic material and compare it with deposits of the broader volcano.
On the older Hunga Ha‘apai islands, we found welded pumice-rich ignimbrite units and nonwelded pyroclastic flow deposits, laid down by superheated flows of gas and particles.
Such deposits attest to past huge explosive eruptions from this long-lived volcano.

One pyroclastic flow deposit contained charcoal, which we dated to the period 1040–1180 CE.
This deposit correlates closely in age and chemistry to ashfall deposits found on Tongatapu Island, 65 kilometers to the southwest [Cronin, 2015].
It also corresponds, within uncertainty bounds, to an unknown tropical eruption in 1108 CE that produced more than 1°C of global cooling [Sigl et al., 2015].

Seafloor Mapping
We also mapped the seafloor surrounding the new island at a resolution of about 1 meter using a WASSP® multibeam sounder.


Fig. 2. A bathymetric sonar survey of the seafloor near the islands of Hunga Tonga and Hunga Ha‘apai, conducted in November 2015, shows the summit platform of the submerged Hunga volcanic edifice.
The dashed black line outlines a previously undocumented caldera, which lies 150 to 180 meters below the surface.
Traces of past eruptions along the caldera rim are clearly visible; the inset gives the locations of the 1988 eruptions in greater detail.
Areas colored white represent depths greater than 200 meters, beyond the range of the sonar system.
Credit: Simon Barker

The seafloor survey revealed a large closed depression to the south (Figure 2), consistent with the caldera postulated by Bryan et al. [1972].
The depression is approximately 150 meters deep and measures about 4 × 2 kilometers, with its northern and southern portions filled by younger volcanic deposits.

A broad, shallow area is associated with the 2009 eruptions south of the island formed in 2015 and a chain of cones formed in 1988 to the southeast.
Numerous other cones surround the rim of the caldera.

The caldera likely formed when an older Hunga edifice collapsed violently into the sea.
This collapse may be the source of the unknown South Pacific eruption about 1000 years ago.

Next Steps

Our first observations highlight how rapidly new volcanic forms are eroded in this area and imply that the volcanic record in the Tonga region is extremely fragmentary.
In future visits, we will continue investigating past eruptions while extending submarine surveys and sampling around the new island to monitor the ongoing changes in response to storms and other events.

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