Sunday, March 15, 2015

Strong Winds And Waves Batter Arctic Sea Ice

As Earth warms, the intensity of storms is rising across the globe. At least eight people died in Vanuatu, as it was hit by Cyclone Pam. "It hit Port Vila at an incredible 340 kilometres an hour", mentions a recent news report. The left part of the image below shows Cyclone Pam reaching speeds as high as 144 kilometers an hour (89.48 mph, green circle) on March 12, 2015, 1500Z, while three further cyclones feature on the Southern Hemisphere. 

At the same time, on the Northern Hemisphere, winds reached speeds as high as 101 km/h (62.76 mph, bottom green circle), 120 km/h (74.56 mph, middle green circle) and 112 km/h (69.59 mph, top green circle), as shown on the right part of above image.

The image on the right shows winds with speeds as high as 125 km/h (77.67 mph) batter the coast of Greenland on March 13, 2015 (green circle).

The image below shows strong winds moving from the North Atlantic into the Arctic Ocean on March 13, 2015. 

The video below, with forecasts for March 13 - 20, 2015, shows strong winds battering the Arctic Ocean at both the Pacific and Atlantic ends.

The combination image below shows winds around Greenland (top) and winds penetrating the Arctic Ocean (bottom).

Waves as high as 41.5 ft (12.65 m) were recorded between Svalbard and Norway on March 13, 2015 (green circle on the left part of the image below), while waves as high as 23.13 ft (7.05 m) were recorded close to the edge of the sea ice on March 15, 2015 (green circle on the right part of the image below).

The updated image below shows waves higher than 10 m (33 ft) near Svalbard close to the edge of the sea ice on March 16, 2015 (green circle).

Meanwhile, it more and more looks like the 2015 sea ice extent maximum was reached on February 25, as illustrated by the image below.

Strong winds can cause high waves that can break up the sea ice. At the same time, strong winds can speed up currents that push sea ice out of the Arctic Ocean, while bringing warmer water into the Arctic Ocean, as illustrated by the image below.

The image below shows sea surface temperatures of 20.9°C (69.62°F, green circle left) recorded off the coast of North America on March 14, 2015, an anomaly of 12.2°C (21.96°F).

The image below shows sea surface temperature anomalies in the Arctic Ocean on March 15, 2015.

The big danger is that warm water will trigger further releases of methane from the seafloor of the Arctic Ocean. Peak daily methane levels recorded in early 2015 averaged a very high 2370 parts per billion, as illustrated by the image below.

Natalia Shakhova et al. estimate the accumulated methane potential for the Eastern Siberian Arctic Shelf (ESAS, rectangle on image right) alone as follows:
- organic carbon in permafrost of about 500 Gt;
- about 1000 Gt in hydrate deposits; and
- about 700 Gt in free gas beneath the gas hydrate stability zone.

Hydrates can become destabilized by pressure changes that can be caused by earthquakes and resulting shockwaves and landslides, or that can be caused by wild temperature swings.

Hydrates can also become destabilized by a small temperature rise that can be caused by influx of warmer water from outside the Arctic Ocean or by warm surface water being mixed down by storms.

Waters in the ESAS are quite shallow, averaging less than 50 m depth over its 2x10ˆ6 km2 area, while methane hydrates in the ESAS can exist at depths as shallow as 20 m.

Where heat is able to penetrate the sediment along cracks, some hydrate destabilization can occur, which in turn can trigger larger destabilization, as methane escaping from a hydrate expands to 160 times its earlier volume; this explosive expansion can cause further destabilization of sediments containing methane in the form of hydrates and free gas.

The situation is dire and calls for comprehensive and effective action, as discussed at the Climate Plan blog.

Monday, March 9, 2015

September 2015 without Arctic Sea Ice?

The image below shows that Arctic sea ice extent, on March 8, 2015, was merely 14.263 square km.

What would happen if the Arctic sea ice kept falling to, say, under 11 million square km by end April and then followed a trajectory similar to 2012 for the next four months? As the animation below shows, such a scenario could wipe out all Arctic sea ice for more than a month from September 1st, 2015.

The following image is a contribution by Albert Kallio.

Sea ice thickness image, Naval Reserach Laboratory
Albert Kallio comments: "The latest sea ice thickness measurement (9th March 2015) for the US Navy submarines shows that the thick and rigid multiyear sea ice congestion has cleared from the Fram Strait between Greenland and the Svalbard Archipelago. That means sea ice is weak; new ice with saline residues and pack ice is made of numerous thin sea ice slabs that have been compressed to thick piles, rather than fewer thick slabs of multiyear sea ice. That means: more sea ice surface area is exposed to sea water and the heat within it. As a result, sea ice is likely melt even faster once it escapes from the Fram Strait. The wave penetration is also stronger within soft and highly fragmented seasonal ice packs. So, the sea ice is now primed for faster transport out of the Arctic Ocean."

So, what would happen if the sea ice was wiped out like that?

Sunlight that previously went into melting the sea ice, as well as sunlight that was previously reflected back into space by sea ice, would be absorbed by the Arctic Ocean instead. In other words, we can expect massive warming. In an earlier post, Prof. Peter Wadhams warned that warming due to Arctic snow and ice loss may well exceed 2 W per square m, i.e. it could more than double the net warming causing by all emissions by all people of the world.

Professor Peter Wadhams on albedo changes in the Arctic
The resulting temperature rise is likely to start wildfires all over the Northern Hemisphere, which would not only send huge amounts of greenhouse gases and soot into the air, but could also threaten entire cities and cause much of the grid to stop functioning. In 2007, a main power line burnt in Australia causing power outages for many homes and traffic lights in Melbourne. Many power plants require extensive water cooling, which can come under threat during intense heatwaves, as happened in France in 2009. Such events may be dwarfed by future heatwaves. Fuel is often transported by rail to power plants, and the railway tracks could bend during heatwaves. The health threat posed by heatwaves, wildfires and soot may result in critical employee loss at power plants.

As a result, electricity supply could stutter, and much industrial activity may stop, while there may be lots of traffic problems, etc. This is only one of the problems, though, as discussed in the 2007 post Ten Dangers of Global Warming. Food supply will come under threat due to crop loss and reduced supply of food to shops, made worse by traffic problems. As discussed back in 2011, much of the soot from firestorms in Siberia could settle on the ice in the Himalaya Tibetan plateau, melting the glaciers there and causing short-term flooding followed by rapid decrease of the flow of ten of Asia’s largest river systems that originate there, with more than a billion people’s livelihoods depending on the continued flow of this water.

Less industrial activity will not cause an immediate fall of tenmperatures, though. Instead, it would make that the aerosols that are currently sent up in the air by such activities and that are currently masking the full wrath of global warming, will fall out of the air in a matter of weeks. Until now, about half of the global temperature rise is suppressed by such aerosols. Stopping aerosols release overnight could make temperatures rise abruptly by 1.2°C (2.16°F) in a matter of weeks.

Methane eruptions from the seafloor of the Arctic Ocean typically start becoming huge around the end of October.

Conclusion from a paper presented at the 2008 EGU conference, on background
of a frame from a video interview by Nick Breeze with Natalia Shakhova.

Further warming of the Arctic Ocean could cause methane to erupt from the seafloor of the Arctic Ocean in quantities that could quickly double and tripple the amount of methane in the atmosphere.

The combined impact of such feedbacks could wipe out crops, deplete water supplies and make a huge number of species go extinct very quickly, including human beings.

In conclusion, the situation is dire and calls for comprehensive and effective action, as discussed at the Climate Plan blog.

Friday, March 6, 2015

Save the Arctic sea ice while we still can!

The Arctic Ocean is coming close to complete summer meltdown, writes John Nissen - indeed it could happen as soon as September, triggering a severe deterioration in climate across the northern hemisphere. With fast-rising temperatures predicted in the coming decade, we must act now to save the Arctic, before it's too late.

By John Nissen

John Nissen: "Nothing has been said by the
IPCC. Nothing has been said in the
mainstream media. Nothing has been said
by the scientific community at large. This
is a terrible omission. It is quite scandalous."
Fossil fuel companies, and their supporters in government, seem blissfully unaware of the dangers ahead, threatening everybody on this planet.

The sea ice is declining far more rapidly than anyone expected. It is declining towards disappearance in summer months, yet the colossal negative impact of a low albedo Arctic has hardly been discussed. This is tragic because the whole situation could have been avoided with good leadership at negligible economic cost.

And as reported this week on The Ecologist, new scientific research indicates that the apparent 'pause' in global warming has, in fact, been no such thing. Instead the surplus heat - two Hiroshima bombs-worth a second - has simply been 'buried'
deep in the Pacific Ocean.

That's because of two important climate cycles, the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation, whose operation has masked the warming. But soon they will tip the other way and the 'Big Heat' is set to begin - a five to ten year burst of rapid warming that will be most severe in the Arctic.

Commercial advantages for some ...

If you read the mainstream media, only the positive impact of a melting Arctic is mentioned: an Arctic ripe for exploitation.

Through not grasping the huge negative impact of a low albedo Arctic, the fossil fuel companies still appear entirely happy for the sea ice to disappear as quickly as possible - the sooner the better. Therefore they naturally resist any action to save the sea ice. In particular they don't want geoengineering deployed to cool the Arctic, because it might succeed in saving it!

Certain fossil fuel companies have already invested heavily in exploiting the vast store of oil and gas in the Arctic. These companies, and the governments who support them, are preparing for a bonanza when the sea ice disappears in summer: it will be so much easier and safer to extract the fossil fuel when the sea ice and freezing conditions have gone during summer months.

Furthermore, the disappearance of the sea ice will open up the Northwest Passage and the Northern Sea Route (formerly known as the Northeast Passage) to trade through summer months. So China and nations bordering the Atlantic (including the UK) are expecting to benefit enormously. Russia is investing heavily in ports and infrastructure to support the anticipated heavy traffic.

Various environment groups and the UK Environment Audit Committee have argued against drilling in the Arctic because they are concerned about oil spills and gas blow-outs which could ruin the local environment. They also seek to protect the wild life and Arctic ecosystem. But their arguing will be futile once the sea ice has gone in summer. It will be too late to protect the environment.

Environmentists have less concern about the opening up of the trade routes, because this will reduce CO2 emissions from transport of goods which at present have much longer journeys.

The Arctic bombshell is waiting to go off

While there is all this talk of exploiting the Arctic, little or nothing is said about the adverse effects of having an Arctic free of sea ice during summer months.

Nothing has been said by the IPCC. Nothing has been said in the mainstream media. Nothing has been said by the scientific community at large. This is a terrible omission. It is quite scandalous.

While most experts agree that there will come a time when the Arctic Ocean will be free of ice during summer months, there is no such agreement on the time-scale. Models suggest that it will take decades.

But observations of an exponential trend of sea ice decline suggest that this time could be within a decade. Scientific reports of especially rapid temperature rise in Alaska have also emerged. For example Barrow, Alaska, has experienced a 7°C temperature rise over 34 years, attributed to the decline in sea ice.

So what are the effects? During summer months, a vast area of reflective ice will have been replaced by open water, absorbing 90% of sunshine and warming the Arctic air above. It is clear that the Arctic will be warming much faster than at present - likely at over 2°C per decade.

As heat dissipates around the planet, there will be a huge contribution to global warming in the long term. Estimates put this at equivalent of 3.3 W/m2 (Flanner, 2011) or about twice the current warming from CO2.

But what are the immediate consequences of this super-rapid warming in the Arctic? At present we have an acceleration of three particular processes, affected by Arctic warming to date:
  • Firstly, we have a dramatic rise in Northern Hemisphere weather extremes, as the jet stream behaviour is disrupted.
  • Secondly we have an exponential increase in meltwater from the Greenland Ice Sheet, flowing through moulins on the surface of the ice into the sea and raising the sea level.
  • And thirdly we have a dramatic increase in methane emissions from the Arctic Ocean seabed.
As the temperature in the Arctic continues to increase, these processes will continue almost indefinitely. We can expect worsening Northern Hemisphere climate causing widespread crop failures; faster sea level rise causing progressive flooding of low-lying regions; and growing methane emissions leading to even more catastrophic global warming.

These are three immediate results of the switching on of heat as the Arctic Ocean enters the low sea-ice state. The combination will be devastating for all mankind - with mass starvation and mass migration liable to trigger a world war.

This is the terrifying bombshell. The bonanza will be short-lived, as the effects of a seasonally ice free Arctic Ocean begin to bite.

For a few billion dollars a year, we can save the Arctic

Something must be done to prevent the ocean entering this low-ice state. Therefore the Arctic must be cooled enough to save the sea ice.

The first moment at the end of summer that the sea ice finally disappears from the ocean is called the 'blue ocean event'. It is significant because it could mark the entry of the ocean into a permanent low-ice state for subsequent years - the point of no return. The point of no return could be a soon as next September.

By any ordinary standards, we have left it too late to cool the Arctic. But any reduction in the risk of passing the point of no return is worthwhile, when all our futures are at stake.

Fortunately researchers are increasingly confident that a stratospheric aerosol haze, produced from sulphur dioxide, SO2, could provide significant cooling of the Arctic for modest expenditure of the order of a few billion dollars per year.

This type of cooling could be replaced by cloud brightening using ultra-fine seawater droplets when the technology is ready for large-scale deployment within a year or two.

There should be no significant negative economic impact from this action, except that the resources in the Arctic become frozen assets. But they should be frozen assets in any case if global warming is to be kept below 2°C, according to a recent paper.

There should be positive political impact, because governments will be working together in a common cause to protect their own citizens and all the citizens of the world. The fossil fuel industry has to be persuaded that preserving the Arctic sea ice is essential for the future of themselves and their stakeholders.

Objections from the anti-geoengineering lobby have to be overcome, because we have no other realistic option to reduce the colossal risk of passing a point of no return this September.

John Nissen is Chair of the Arctic Methane Emergency Group
This post earlier appeared in The Ecologist

March 4, 2015 - Arctic Sea Ice Extent Hits Record Low

Sea surface temperature anomalies as high as 12°C (21.6°F) recorded off the east coast of North America have been described earlier, in he post 'Watch where the wind blows'. The Jet Stream reaching high speeds has also been described earlier, in the post 'Climate Changed'.

As feared, this is pushing warm water, water vapor and air from the North Atlantic into the Arctic Ocean. The three images below show forecasts for March 8, 2015, of - from top to bottom - the jet stream, surface winds and temperature anomalies.

Above image shows that the Arctic is forecast to reach a temperature anomaly of more than +4 degrees Celsius (more than +7 degrees Fahrenheit) on March 8, 2015, with temperature anomalies at the top end of the scale forecast for most of the Arctic Ocean.

On March 4, 2015, Arctic sea ice extent hit a record low for the time of the year, as illustrated by the image below.

As the March 5, 2015, Naval Research Laboratory image on the right illustrates, there is little scope for Arctic sea ice extent to grow over the next few weeks, since the only areas where it could possibly expand would be the Pacific and the North Atlantic, the very areas that are under pressure from ocean heat and high surface temperatures.

In other words, the situation looks set to deteriorate further.

Huge amounts of heat are still going into melting the sea ice. Furthermore, the sea ice is still able to reflect a lot of sunlight back into space. With continued demise of the snow and ice cover, more and more heat will be absorbed in the Arctic.

The big danger is that warm water will trigger further releases of methane from the seafloor of the Arctic Ocean. Peak daily methane levels recorded in early 2015 averaged a very high 2372 parts per billion, as illustrated by the image below.

Methane extent has been especially high over the Arctic Ocean. The images below are from the earlier post 'Temperature Rise'. The post added that, as the Gulf Stream keeps carrying ever warmer water into the Arctic Ocean, methane gets released in large quantities, as illustrated by the images below showing high methane levels over the East Siberian Arctic Shelf (red oval left) and over Baffin Bay (red oval right) with concentrations as high as 2619 ppb.

click on image to enlarge
The images below show methane levels on Jan 25 (top), and Jan 26, 2015 (bottom).

Meanwhile, Arctic sea ice extent as reported by reached a new record low for the time of the year with 14.358 million square km on March 4, 2015, and another record low with 14.308 million square km on March 7, 2015.

Temperature anomaly for the Arctic on March 8, 2015 (daily average) was even higher tha forecast, at +4.26 degrees Celsius, with peaks at +4.37 degrees Celsius.

High waves were registered in the North Atlantic on March 7, 2015, moving into the Arctic Ocean and causing waves more than 4 m high close to the edge of the sea ice on March 8, 2015.

The situation is dire and calls for comprehensive and effective action, as discussed at the Climate Plan blog.

Saturday, February 28, 2015

The Mechanism

What is the mechanism behind accelerated warming of the Arctic Ocean, huge abrupt methane eruptions from the seafloor of the Arctic Ocean and skyrocketing temperatures?

1. Potential for Methane Release in Arctic

Vast amounts of methane are stored in hydrates under the seafloor of the Arctic Ocean. Furthermore, vast amounts of methane in the form of free gas are contained in sediments under the seafloor of the Arctic Ocean. Thirdly, vast amounts of carbon are frozen in the permafrost and much may enter the atmosphere in the form of methane as the permafrost copntinues to melt.

Natalia Shakhova et al. in 2010 estimated the accumulated potential for the East Siberian Arctic Shelf (ESAS) region alone (image on the right) as follows:
- organic carbon in permafrost of about 500 Gt
- about 1000 Gt in hydrate deposits
- about 700 Gt in free gas beneath the gas hydrate stability zone.

In early 2014, Sam Carana estimated annual methane emissions from hydrates and permafrost at 100 Tg (i.e. 0.1 Gt). This methane will contribute to further warming of the air over the Arctic and the North Atlantic, causing further further extreme weather events, such as heatwaves and storms along the path of the Gulf Stream from the North Atlantic into the Arctic Ocean, in turn triggering further releases from hydrates at the seafloor of the Arctic Ocean and escalating into runaway global warming.

Such methane eruptions are caused by warming water of the Arctic Ocean, which in turn is due to emissions by people. Some elements of the mechanism causing methane to erupt from the seafloor are described in more detail below.

2. Ocean Heat
From: Ocean Temperature Rise continues
Above graph, based on NOAA data, shows a polyomial trendline pointing at a Northern Hemisphere sea surface temperature rise of more than 5°C (9°F) by 2050, compared to the 20th century average, from an earlier post.

Waters at greater depth are also warming rapidly, as illustrated by the image on the right, from an earlier post, showing a rise in ocean heat up to 2000 m deep that has more than doubled over the past decade. Data from 2005 through to 2014 conatain a polynomial trendline that points at a similar rise by 2017, followed by an even steeper rise.

The North Atlantic is warming rapidly, with sea surface temperature anomalies as high as a 12°C (21.6°F) recorded east of North America earlier this year, as illustrated by the image below.

A warmer North Atlantic is a major contributor to the rapidly warming waters of the Arctic Ocean, since the Gulf Stream keeps carrying warmer water into the Arctic Ocean all year long.

A further contributor is a warmer North Pacific.

Further contributions come from the combined impact of numerous feedbacks, in particular changing winds and currents, cryosphere changes and methane releases, as further described below.

From: Watch where the wind blows

3. Feedbacks: Changing Winds and Currents, Cryosphere Changes and Methane

- Changed Winds and Currents

Emissions by people are not only causing temperatures of the atmosphere and oceans to rise, they are also causing winds and ocean currents to change. Such changes can in turn result in heatwaves that are more intense and that persist for prolonged periods. Furthermore, strong northbound winds, combined with strong precipitation and waves can speed up the volume of warm water carried by Gulf Stream into the Arctic Ocean, as discussed in an earlier post

- Arctic Sea Ice

A warming atmosphere, warming oceans and decline of the Arctic snow and ice cover all go hand in hand. The IPCC concluded in AR5 that, for RCP8.5, the Arctic Ocean will likely be nearly ice-free in September before mid-century. Prof. Peter Wadhams warned, back in 2012, that the Arctic Ocean could be virtually ice-free within a few years. An exponential trendline based on sea ice volume observations shows that sea ice looks set to disappear in 2019, while disappearance in 2015 is within the margins of a 5% confidence interval, reflecting natural variability, as discussed at the FAQ page.

- Permafrost

Permafrost decline will cause Arctic temperatures to rise, due to albedo change and due to carbon that is contained in the permafrost and that can be expected to be released in the form of methane or carbon dioxide as the permafrost melts. The image below pictures permafrost decline as foreseen by the IPCC in AR5. 

Obviously, rapid decline of the sea ice will come with albedo changes that will also make the permafrost decline more strongly than the IPCC foresees, while they will also cause even more extreme weather events. One of the dangers is that huge amounts of warmer water will flow from rivers into the Arctic Ocean, as discussed below.

- Warmer Water From Rivers

More sunlights getting absorbed in the Arctic will accelerate warming of the Arctic Ocean directly, while there will also be warmer water flowing into the Arctic Ocean from rivers in Siberia and North America, fueled by stronger and longer heatwaves, storms and wildfires. 

map from:
Above map shows that a number of large rivers in Siberia end up in the Arctic Ocean. Another large river is the Mackenzie River, which ends in the Beaufort Sea, north of Alaska, where sea surface temperatures of about 20°C (68°F) were recorded in 2013, as the image below illustrates.

Another area of concern, also marked with a purple oval in the image below, is located in the north of Canada.

More extreme weather events include heat waves, storms, floods and wildfires, all of which can contribute to more rapid warming of the Arctic Ocean.

The combined effect of all the above will be that methane that is now contained in the form of free gas and hydrates in sediments under the Arctic Ocean, can be expected to be increasingly released as the Arctic Ocean warms further.

- Methane 

Of the vast amounts of methane stored in the Arctic, much of it is prone to be released with further temperature rises, as discussed in this earlier post and in this earlier post. Cracks in sediments used to be filled with ice. Warmer water is now melting the ice that used to sit in cracks. This ice has until now acted as a glue, holding the sediment together. Moreover, the ice in the cracks has until now acted as a barrier, a seal, that prevented the methane contained in those sediments from escaping. In a video interview with Nick Breeze, Natalia Shakhova mentions a sample of sediment taken from the ESAS seafloor in 2011 that turned out to be ice-free to a depth of 53 m at water temperatures varying from -0.6˚C to -1.3˚C. Back in 2008, Natalia Shakhova et al. considered release of up to 50 Gt of predicted amount of hydrate storage as highly possible for abrupt release at any time.

The image below, based on data from the IPCC and the World Metereological Organization (WMO), with an added observation from a NOAA MetOp satellite image, illustrates the recent rise of methane levels and the threat that methane levels will continue to rise rapidly.

When looked at from a longer range of years, above image fits in the black square on the image below.

The image below shows exponential rise based on data of East Siberian Arctic Shelf (ESAS) releases alone, as discussed in an earlier post.

Non-linear rise is supported by the fact that methane's lifetime increases as more methane enters the atmosphere. As the image below shows, peak methane levels have been very high recently.

All these feedbacks can interact and amplify each other in non-linear ways, resulting in rapid and intense temperature rises, as illustrated by the image below.

Diagram of Doom - for more background, see Feedbacks

4. Runaway Global Warming

The threat is that such rapid temperature rises will appear at first in hotspots over the Arctic and eventually around the globe, while also resulting in huge temperature swings that could result in depletion of supply of food and fresh water, as further illustrated by the above image, from an earlier post, and the image below, from another earlier post.

Rapidly rising temperatures will cause stronger evaporation of sea water. Since water vapor is one of the strongest greenhouse gases, this can further contribute to the non-linear temperature rises pictured above.

In conclusion, the situation is dire and calls for comprehensive and effective action, as discussed at the Climate Plan blog.

Sunday, February 22, 2015

Multiple Benefits Of Ocean Tunnels

By Sam Carana and Patrick McNulty

Comprehensive climate action will do more than just cutting emissions, it will also take further action, as pictured in the image below.

Comprehensive and effective action is discussed at the Climate Plan blog
Taking a broad perspective makes it easier for proposed projects to be assessed on their benefits in a multitude of areas.

Ocean tunnels can capture vast amounts of energy from ocean currents, such as the Gulf Stream and the Kuroshio Current. These locations are close to areas with high energy demand, such as the North American East Coast and the coast of East Asia, which can reduce the need for long distance transmission lines.

Ocean tunnels provide clean energy continuously, i.e. 24 hours a day, all year long. This makes that they can satisfy demand for electricity both at peak and off-peak usage times.

  • Their ability to supply large amounts of electricity at times of peak demand will benefit the necessary transition from polluting to clean ways of generating electricity.
  • Their ability to also supply large amounts of electricity at off-peak usage times will help to reduce the price of electricity at such times, thus opening up opportunities for a number of activities that can take place at off-peak hours and that require large amounts of energy.

    Such activities include large-scale grinding of olivine rock and transport of the resulting olivine sand, and large-scale production of hydrogen through electrolysis to power transport (box right). Electrolysis can also create oxygen-enriched water that can improve the quality of waters that are oxygen-depleted.  
Hydrogen to power Shipping

Ocean tunnels can make electricity cheap at off-peak times. This will reduce the cost of recharging batteries of electric vehicles at night.

It will also reduce the cost of producing hydrogen at off-peak hours. To power ships crossing the oceans, hydrogen looks more cost-effective, as such ships cannot return to base for a nighly battery recharge. Such ships have plenty of cargo space to carry hydrogen, even when the hydrogen is not highly compressed. Some of the world's largest ports are close to strong ocean currents.

Ocean tunnels can generate electricity in two ways, i.e. by capturing the kinetic energy contained in the flow of ocean currents, and by means of Ocean Thermal Energy Conversion (OTEC) using temperature differences between cooler deeper parts of the ocean and warmer surface waters to run a heat engine to produce energy. 

Besides generating energy, ocean tunnels can assist with further activities, which will increase the value of ocean tunnels in the fight against climate change. Such activities include the following:
  • By reaching deeper parts of the ocean, OTEC can pull up sunken nutrients and put them out at surface level to fertilize the waters there, while the colder water that is the output of OTEC will float down, taking along newly-grown plankton to the ocean depths before it can revert to CO2, as described in the earlier post Using the Oceans to Remove CO2 from the Atmosphere.
  • Ocean tunnels can be used to distribute olivine sand in the water. The force of the currents and the turbines will help the process of transforming olivine into bicarbonate. This can reduce carbon dioxide levels in the water by sequestering carbon, while also reducing ocean acidification. Olivine sand contains silicate and small amounts of iron, allowing diatoms to grow that will capture additional carbon dioxide, while also raising levels of free oxygen in the water. The latter will stimulate growth of microbes that break down methane in the water before it reaches the atmosphere. Further nutrients can be added, as also discussed in this earlier post
  • Ocean tunnels can also assist with albedo changes. Ocean tunnels can act as the infrastructure to create water microbubbles along their track. Increasing water albedo in this way can reduce solar energy absorption by as much as 100 W m − 2, potentially reducing equilibrium temperatures of standing water bodies by several Kelvins, as Russel Seitz wrote back in 2010. There may also be potential for ocean tunnels to be used to spray water vapor into the air with the aim of brightening clouds over areas where it counts most.
  • The turbines in tunnels will also reduce the flow of ocean currents somewhat, thus reducing the flow of warm water into the Arctic. Furthermore, tunnels can be shaped in ways to guide the flow of warm water away from the Arctic Ocean down a southwards course along the Canary Current along the coast of West Africa. thus diverting warm water that would otherwise end up in the Arctic Ocean. This could also reduce the chance of hurricanes hitting the east coast of North America, as Sandy did in 2012.  
The Gulf Stream, carrying warm water all the way into the Arctic Ocean