How does climate change affect the ocean?

A polar bear and her cub on sea ice in the Arctic north of Svalbard

(Image © Larissa Beumer / Greenpeace)

From China Dialogue by David Adam

The ocean has cushioned the blow of global heating, but at a cost to the stability of climate systems and marine life

As climate change tightens its grip, the effects are being felt across the planet.
The global ocean plays a key role and has so far soaked up most of the carbon dioxide and excess heat human activities have produced.
But it is also vulnerable.
Already some significant changes are underway, and the climate disruption to our seas looks set to worsen.

1. Rising temperatures

About 90% of the excess heat trapped by atmospheric greenhouse gases is eventually soaked up by the world’s oceans.
Because oceans are so big, the temperature change to the seawater can seem small – the sea surface layer has warmed by just over 0.5C in the last century.
That’s still enough to cause significant disruption, and the warming is accelerating.

Things expand as they warm, becoming less dense and taking up more space.
The oceans are no different.

Indeed, between 1993-2010, thermal expansion is thought to have raised sea levels by an average of 1.1 millimetres a year, accounting for much of the overall rise we have seen.

The total observed rise in sea level for the 1993-2010 period was an average of 3.2mm every year, with contributions from various other sources, including water stored on land, in forms such as snow.

(Graphic: Manuel Bortoletti / China Dialogue Ocean)

Warmer water also influences the atmosphere above it.
Increased sea surface temperatures are associated with making hurricanes and tropical cyclones more powerful, potentially increasing the number of the most severe category 4 or 5 storms that strike islands and coastal areas.
Warmer water can also dissolve less carbon dioxide, which means more will stay in the atmosphere to accelerate global warming.

Just like on land, rising temperatures in the oceans generate damaging heatwaves.
They occur when unusual weather conditions or water currents cause above-average water temperatures for at least five consecutive days.
But they can last for months or even years.
A marine heatwave called “The Blob” hung around the northern Pacific from 2013-2015 and killed a million seabirds on the west coast of the United States.

2. Acidification

As carbon dioxide dissolves in seawater, it reacts to form carbonic acid: a fairly weak acid, but enough to alter the pH of seawater, which is naturally alkaline.
Since the industrial revolution, dissolved carbon dioxide is estimated to have lowered the average pH of the top layer of the oceans by 0.1 pH units, from about 8.2 to 8.1 (7 is neutral).

That change doesn’t sound much, but because pH is measured on a logarithmic scale, it actually represents a nearly 30% increase in acidity.
This has some significant knock-on effects for seawater chemistry and the ecosystems that rely on it.

 

(Graphic: Manuel Bortoletti / China Dialogue Ocean)

The increase in acidity is particularly bad news for shellfish and other forms of sea life that use the mineral calcium carbonate to form their shells and exoskeletons.
More acidic water can hold less of this mineral, so there’s less available for so-called calcifying organisms such as oysters, clams, sea urchins, shallow water corals, deep sea corals and calcareous plankton.
Worse, the change in chemistry encourages existing carbonate structures to dissolve.

Coral is particularly vulnerable.
Experiments on a small patch of Australia’s Great Barrier Reef show that artificially reducing the seawater carbon dioxide level, so restoring pH to pre-industrial levels, boosted coral calcification by 7%.
Then, when the scientists raised the amount of carbon dioxide and so decreased ocean pH to the level expected by the end of this century, calcification dropped by a third.

3. Melting ice

As climate change continues, many scientists believe it is inevitable that massive ice sheets in Greenland and Antarctica will collapse and melt entirely, eventually pouring enough water into the oceans to raise global sea levels by several metres.
It will take time – hundreds, perhaps thousands of years – but the melting is accelerating.
The UN’s climate body now projects that, under a low-emissions scenario, average sea level will rise between 61cm and 1.1m by the end of the century.

By 2050, rising seas could push peak high tides above land currently home to at least 300 million people, mostly in Asia.

 

Villagers in the Sundarbans work to repair a damaged dike after seawater flooded an adjacent paddy field.
This low-lying delta region straddles the India-Bangladesh border.
Home to an estimated 4.5 million people, it is particularly vulnerable to rising sea levels.
(Image © Peter Caton / Greenpeace)

Coastal ecosystems will be affected too.
Beach and dune environments face more severe and frequent flooding and erosion, while sensitive freshwater habitats including mudflats and marshes – needed for bird species to breed – will be swamped with seawater.

Sea ice, which forms when seawater freezes each polar winter, is also melting and thinning more and more each summer.
Melting of this ice doesn’t significantly contribute to sea levels, but it does pose big problems for creatures that rely on it for their habitat.
Most notably, polar bears need sea ice to hunt seals, and studies show many of the 25,000 bears estimated to remain in the Arctic are struggling.
One colony of animals around the Southern Beaufort Sea, in northeastern Alaska and Canada, was found to have declined by 40% between 2001 and 2010.

4. Changes in ocean currents

Ocean currents are vulnerable to the effects of climate change.
At present, those currents act as massive global conveyor belts: as winds push through the atmosphere from the warm equator to the colder poles, they drag surface water with them.
Cooled by the chilly polar air, this water becomes denser, and so sinks to the deep ocean, where it is pushed back towards the equator (becoming warmer, less dense and rising as it goes) by the next batch of denser water coming from above.
Round and round the cycles go, transporting and mixing nutrients as they swirl along.

 

(Graphic: Manuel Bortoletti / China Dialogue Ocean)

Melting ice interferes with this system.
Huge amounts of fresh water pouring in at the poles lowers the density of the seawater, making it slower to sink.
Without the same driving downward force, the whole global cycle can weaken.
In 2018, scientists suggested that the major current in the Atlantic Ocean had slowed by about 15%.
And some studies predict that could worsen to more than 30% by 2100.

Based on what has happened in the past, scientists say slower ocean currents can bring significant changes in the Earth’s atmosphere, and so to the weather.
Winters in Europe could be much colder (an idea taken to extremes in the film The Day After Tomorrow).
Meanwhile, the waters of the South Atlantic could become warmer, and because sea surface temperature influences wind and rainfall, this could disrupt monsoon cycles that are vital for crops across Asia and South America.

5. Deoxygenation

Ocean creatures rely on oxygen dissolved in seawater, just as we breathe it from the atmosphere.
But climate change is gradually draining oxygen from the seas: about 1-2% is thought to have been lost from 1960 to 2010, and that could rise to 4% by 2100.

There are several reasons.
Warmer water can hold less of the gas, while disruption to ocean currents limits the amount of oxygen transported from the surface to the depths.

A growing problem occurs when the fertiliser and other nutrients added to agricultural soils drain into rivers and eventually get dumped into coastal waters.
Boosted by the unexpected supply of food, algae can grow and proliferate rapidly to form massive floating blooms – sometimes called green (or red) tides.
These can be problematic, for example by releasing chemicals toxic to fish.
And when the algae die and sink, the microbes that work to decompose the blooms in the depths soak up oxygen from the surrounding water.

Gdansk beach in northern Poland was closed to tourists due to a toxic algal bloom in the summer of 2018 (Image: Wojciech Strozyk / Alamy)

In severe cases, dissolved oxygen levels can fall so low that parts of the deep ocean become barren.
A 2008 global survey found at least 405 of these dead zones, up from 49 in the 1960s.
Perhaps most affected is the Baltic Sea.
Despite efforts to limit agricultural run-off from surrounding countries, the Baltic still has a massive dead zone of about 70,000 square kilometres – about the size of Ireland.

6. Marine food chain collapse

Already under pressure from overfishing and pollution, marine life – from large fish down to cyanobacteria – is also affected by climate change.
As seas warm and currents shift, some sea life can simply move, for example towards the cooler water of the poles.
These shifts in distribution have knock-on effects for species that feed on them: from people trying to catch tuna, to fish looking for zooplankton.
Under stress from shifting resources, species are especially vulnerable if they are already weakened by acidification and oxygen depletion.

Changes to interconnected and complex systems of food webs are hard to predict.
Fisheries in some areas might actually get a boost as valuable new species are driven into their nets.
But, overall, the impact is likely to be bad.
A study last year suggested that warmer waters had reduced the total amount of fish that can be caught in a sustainable way by 4% since the 1930s.
The worst-affected sea was the Sea of Japan, with a 35% reduction in fishery size due to warming.
The East China Sea saw a drop of 8%.

 

(Graphic: Manuel Bortoletti / China Dialogue Ocean)

Future drops in fish catches would threaten the food security of a large fraction of the world’s growing population.
According to the UN, fish provide more than 3.1 billion people with at least 20% of their animal protein.
It’s an important source of fatty acids and micronutrients too.
Fish currently supply 17% of all the protein consumed in the world, and demand is expected to continue to increase as incomes rise in the developing world.

Links :

• NYTimes : Ocean Heat Waves Are Directly Linked to Climate Change
• World Economic Forum : Oceans have been warming at almost half the rate of land ...
• Sustainability Times : Climate change will make areas of the oceans 'uninhabitable'  
• AP : Leaders to UN: If virus doesn't kill us, climate change will
• Science Alert : The Massive 'Blob' Anomaly Has Our Fingerprints All Over It, Study Finds
• The Guardian : How our warmer oceans are contributing to climate breakdown
• Common Dreams : 'Very Bad News': Scientists Behind New Study Warn Warming Oceans 'Contributing to Climate Breakdown' 

Seaweed: The food and fuel of the future?

The cold water around the Faroe Islands is good for seaweed cultivation

From BBC by Adrienne Murray

Sunshine has given way to wind and rain, as the motorboat chugs through a fjord in the Faroe Islands.

"Its a bit windy here," says Olavur Gregarsen.
"We'll see how far we can get to the harvesting boat."

We soon reach a sheltered spot where steep mountains are looking down on hundreds of buoys bobbing in the sea.

"They are holding up a horizontal line," explains Mr Gregarsen, the managing director of Ocean Rainforest, a seaweed producer.
"At every metre another line hangs down, and that's where the seaweed grows."

Breaking waves

Anchored to the sea floor, the cultivation rig consists of 50,000m (164,000ft) of underwater lattice-like ropes, designed to withstand rough sea conditions.

"The main structure is 10m down.
That way we avoid the largest breaking waves," he says.

Despite the Danish territory's remote North Atlantic location, Mr Gregarsen says the deep, nutrient-rich, waters are well suited for growing seaweed, with a stable temperature of between 6C and 11C.

Ocean Rainforest plans to double production

Image Adrienne Murray

His firm is among a wave of seaweed farms that have sprung up in Europe and North America, spurred by a growing demand from the food industry and others.

"You have a biomass that can be used for food and feed, and replacing fossil-based products like packaging material from plastic," he says.

Mechanisation

Seaweeds are fast-growing algae.
They utilise energy from sunlight, and take up nutrients and carbon dioxide from the seawater.
Scientists suggest seaweed could help fight climate change and offset carbon emissions.

Ocean Rainforest recently won funding from the US Department of Energy to build a similar system in California, where there's interest in developing industrialised seaweed production for future biofuels.

Aboard the harvesting boat the skipper controls a mechanical arm that lifts lines from the water.
The seaweed is chopped free, filling up containers.
It's quick but messy work.
The lines are then left to regrow.
This year around 200 tonnes will be harvested.

Ocean Rainforest recently won funding from the US Department of Energy

Image Adrienne Murray

But the company is scaling up, and plans to double its capacity this year.
It isn't making money just yet, but expects to soon, Mr Gregarsen tells me.
"We can see how we can mechanise this, how we can make this a really large-scale efficient activity," he says.
"There are not many companies that do this as a profitable business, if any."

Cosmetics and medicines

Seaweed needs to be processed quickly.
At a small plant in the Faroese village of Kaldbak, machines clean the harvest.
Some is dried and supplied to food manufacturers.
The rest is fermented and shipped to animal feed producers.

Seaweed is used to make food additives, textiles and fuel

Image Adrienne Murray

Most farmed seaweed is consumed in food, but extracts are used in a wide variety of products.
Whether it is toothpaste, cosmetics, medicines or pet food, these often contain hydrocolloids derived from seaweed, which have gelling or thickening properties.

And more products are coming, with other firms working on textiles and plastic alternatives, including biodegradable packaging, water capsules, and drinking straws.

Seaweed production has boomed.
Between 2005 and 2015 volumes doubled, surpassing 30 million tonnes annually, reports the UN's Food and Agriculture Organization.
It is a business worth more than $6bn (£5bn) worldwide.

Yet only a fraction of cultivation happens outside Asia, where farming is a long-established, but mostly labour-intensive activity.

'A lot of effort'

"The labour cost is really high in Europe, so that's one major part of it," explains Annette Bruhn, who is a senior scientist at Aarhus University in Denmark.
"A lot of effort needs to be put into mechanisation and upscaling."

To make farming economical, she says "the yield needs to go up and the cost needs to go down".

But farming systems aren't easily replicated.
"Different areas in different waters, all require modifications.
There's not one solution that can be expected to fit all," says Ms Bruhn.

Seaweed uses carbon dioxide from the sea

Image Harald Bjorgvin

However, she is hopeful, and says there are "many areas where you can have breakthroughs".

That is what innovators like Sintef are trying to do.
The Norwegian scientific research group is working on new technologies to streamline farming.
"Now most of the seaweed is used for food, but in the future we want to use it for fish feed, fertilisers, biogas.
We need large volumes and we need to produce much faster," says research scientist Silje Forbord.

Dry lab

Prototype machines such as the "seaweed spinner" automatically wrap spools of seedling-carrying threads onto lines, ready for deployment at sea.

Another concept, SPoke (Standardized Production of Kelp), consists of circular farm modules where seaweed grows from lines radiating outwards.
It is designed so a robot can move along the wheel-like spokes - either attaching threads carrying juvenile seaweed or harvesting it.

"We've built one arm with a robot going back and forth.
That has been tested in a dry lab," explains Ms Forbord, but more investment will be needed.

 Land-based seaweed cultivation

No additives or fertilisers are used

Image Algaplus

In a series of ponds and tanks in northern Portugal, AlgaPlus is cultivating seaweed inland.

"It's a much more controlled environment," says managing director Helena Abreu, who thinks there are more advantages compared to farming offshore.
"We maintain the temperature and everything inside the tanks," she says.
"You have year-round production."

Ms Abreu co-founded the firm after spending five years as a marine biologist in the Azores.
Small, high-value seaweeds are produced for food companies, cosmetics makers and high-end restaurants.

Innovation

Seawater from a coastal lagoon flows into fish ponds.
It is then pumped through a filtration system into tanks growing seaweed.
There's also a hatchery breeding the seedlings.

"We had to innovate from scratch," she says.
These waters are rich in nitrogen, which the algae take up, mimicking nature.
"We don't need to use any additives, no fertiliser.
We use water from the fish to grow our seaweed," she says.

AlgaPlus produces small, high-value seaweeds

Image Algaplus 

Ms Abreu doesn't think availability of land is a limiting factor.
Former salt works and fish farms could be repurposed, she says, pointing out there are hectares of availability in Portugal, France, Italy, Greece and Turkey.

Onshore seaweed farming takes place in Canada and South Africa too.
Micro-algae are also grown in tank systems.

But there are other challenges.
"The main bottleneck is energy cost. Working with tanks you need the pumping and the aeration to keep the water moving," says Ms Abreu.

The firm can't survive on sales alone just yet.
But Ms Abreu is convinced that the seaweed market will continue to grow.
"It's a huge trend," she says.
"Every year there's more and more companies. There are newcomers in all steps of the value chain."

Links :

• CNBC : Food, fertilizer, fuel: Why the worldwide demand for seaweed ...
• Time : The Ocean Farmers Trying to Save the World With Seaweed
• The Australian Dairyfarmer : Seaweed feed, fert and eco opportunities to float new $1.5b ...

A year along the geostationary orbit

A year through the distant eyes of meteorological satellite Himawari-8 – a hypnotic stream of Earth's beauty, fragility and disasters.
Animation of satellite irradiation scan measurements, scientific data by meteorological satellite Himawari-8 courtesy of JMA/BoM/NCI.
Timecodes for meteorological/astronomical events (approximate, list to be completed):
March 9th 2016 Total Solar Eclipse: 4:44
June 2016 Kamchatka Wildfires: 7:26-8:02 (visible as large amounts of smoke emitted from a point in western Kamchatka, eventually filling a large ocean area) - also: June solstice/polar day north pole
July 2016 Super Typhoon Nepartak: 8:37-8:49
Aug 2016 Typhoon Lionrock: 10:43-11:09
Sep 2016 Super Typhoon Meranti: 11:14-11:24
Dec 2016 December solstice/polar day south pole: from 13:25
Attribution note on the data, which the images in this film are based on:
Satellite observations were originally processed by the Bureau of Meteorology from the geostationary meteorological satellite Himawari-8 operated by the Japan Meteorological Agency. Access to this dataset was provided by the National Computational Infrastructure (NCI), which is supported by the Australian Government.

Submarine sound quizz

Hold your breath, listen and guess who is making those sounds recorded on board submarines!
With the contribution of the French Navy's Acoustic Interpretation and Reconnaissance Centre.

 Whales / Shrimps / Tonerre / Oil tanker / Sperm whale / Offshore platform / Trawl / Dolphins/ Iceberg

To explore the underwater world, you have to use sound because water is practically opaque to light. The propagation and reflection of sound allows the creation of "acoustic images" and the description of the underwater world.

To do this, sounders or sonars are used.

Applications of underwater acoustics:

• Mapping the seabed and identifying its nature;
• Underwater detection (military applications: detection and classification of submarines, mines and surface ships, port surveillance);
• Monitoring and study of the impact of human noise on biodiversity;
• Surveillance of structures (renewable marine energies, port infrastructures);
• The study of water mass movements (oceanography)

Scientists baffled by orcas ramming sailing boats near Spain and Portugal

An orca feeding near a Moroccan fishing boat in the Strait of Gibraltar.

Photograph: Patty Tse/Alamy

From The Guardian by Susan Smillie

From the Strait of Gibraltar to Galicia, orcas have been harassing yachts, damaging vessels and injuring crew

Scientists have been left baffled by incidents of orcas ramming sailing boats along the Spanish and Portuguese coasts.

In the deep: a pod of highly intelligent killer whales, or orcas.

Constant harassment by boats affects their ability to hunt, and has a negative impact on their behaviour.

Photograph: Rand McMeins/Getty Images

In the last two months, from southern to northern Spain, sailors have sent distress calls after worrying encounters.
Two boats lost part of their rudders, at least one crew member suffered bruising from the impact of the ramming, and several boats sustained serious damage.

'I've never seen or heard of attacks': scientists baffled by orcas harassing boats

The latest incident occurred on Friday afternoon just off A Coruña, on the northern coast of Spain.
Halcyon Yachts was taking a 36ft boat to the UK when an orca rammed its stern at least 15 times, according to Pete Green, the company’s managing director.
The boat lost steering and was towed into port to assess damage.

Around the same time there were radio warnings of orca sightings 70 miles south, at Vigo, near the site of at least two recent collisions.
On 30 August, a French-flagged vessel radioed the coastguard to say it was “under attack” from killer whales.
Later that day, a Spanish naval yacht, Mirfak, lost part of its rudder after an encounter with orcas under the stern.

1:15 'It broke the rudder!': orcas damage Spanish naval yacht – video

other video

Highly intelligent social mammals, orcas are the largest of the dolphin family.
Researchers who study a small population in the Strait of Gibraltar say they are curious and it is normal for them to follow a boat closely, even to interact with the rudder, but never with the force suggested here.

The Spanish maritime authorities warned vessels to “keep a distance”.
But reports from sailors around the strait throughout July and August suggest this may be difficult – at least one pod appears to be pursuing boats in behaviour that scientists agree is “highly unusual” and “concerning”.
It is too early to understand what is going on, but it might indicate stress in a population that is endangered.

On 29 July, off Cape Trafalgar, Victoria Morris was crewing a 46ft delivery boat that was surrounded by nine orcas.
The cetaceans rammed the hull for over an hour, spinning the boat 180 degrees, disabling the engine and breaking the rudder, as they communicated with loud whistling.

It felt, she said, “totally orchestrated”.
Earlier that week, another boat in the area reported a 50-minute encounter; the skipper said the force of the ramming “nearly dislocated the helmsman’s shoulder”.

‘The noise was really scary. They were ramming the keel, there was this horrible echo, I thought they could capsize the boat.’

Illustration: Andrea Ucini

Boats off Spain damaged in orca encounters

At 11.30 the previous night, British couple Beverly Harris and Kevin Large’s 40ft yacht was brought to a sudden halt, then spun several times; Harris felt the boat “raise a little”.

Earlier that evening, Nick Giles was motorsailing alone when he heard a horrific bang “like a sledgehammer”, saw his wheel “turning with incredible force”, disabling the steering as his 34ft Moody yacht spun 180 degrees.
He felt the boat lift and said he was pushed around without steering for 15 minutes.

It is not known if all the encounters involve the same pod but it is probable.
Dr Ruth Esteban, who has studied the Gibraltar orcas extensively, thinks it unlikely two groups would display such unusual behaviour.

Alfredo López, a biologist from the Coordinator for the Study of Marine Mammals in Galicia, said orcas made their way up the coast each September from the Gulf of Cadiz to chase tuna into the Bay of Biscay.

Morris’s sailing job was abandoned after the boat was lifted for repair, and she was diverted to another delivery.
She is currently sailing down the Spanish coast and in the early hours of Friday a VHF radio warning came in.
“All ships, all ships,” it began.
“Orca just north of Vigo” – five miles from her location.

After her last experience, Morris is a little jumpy, but, as a science graduate with plans to study marine biology, she is concerned for this vulnerable population of orcas and interested to learn more.
She’d just prefer not to get too close a view next time.

Links :

• The Guardian : Full story: ‘I’ve never seen or heard of attacks’ – scientists baffled by orcas harassing boats / Spain bans yachts from stretch of sea after orcas damage boats / 'They were having a real go': man tells of orca encounter off Spain
• Insider : A pod of killer whales is accused of 'orchestrated' attacks on boats, terrifying the sailors and baffling scientists 
• NYTimes : Rough Play or Bad Intentions? Orca Encounters Off Iberia Baffle Experts