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Those categories, the Saffir–Simpson hurricane scale, were introduced by the National Hurricane Center in the 1970s. Originally the scale was meant to convey both wind and water destruction but was simplified in 2010 to focus solely on wind hazards, while storm surge and precipitation risks are now communicated separately.

The scale is open-ended with Category 5 storms being the top with sustained winds greater than 157 miles per hour (70 m/s).  This open-endedness originated from the belief that the cumulative impact of wind, surge, and rainfall in a Category 5 event could utterly destroy any structure. But Category 5 may no longer be enough.

A new study suggest that we need a Category 6 that categorizes storms greater than 192 miles per hour (86 m/s).  Numerous storms have already reached wind speeds comparable to those in in the Category 6 range. In the past nine years, five storms have surpassed the hypothetical Category 6 threshold. Notably, the most intense of these, Hurricane Patricia, struck Jalisco, Mexico while the others occurred in the Western Pacific, including Haiyan and Goni which hit heavily populated areas of the Philippines. Haiyan, considered by some as deserving of a Category 6 designation, caused extensive damage and casualties in the Philippines. Another storm, Meranti, caused damage in the Philippines and Taiwan before making landfall in eastern China, resulting in severe flooding.

In addition, increases in Emanuel’s Potential Intensity (PI) index indicate that human influence on the climate system has elevated the risk of such storms reaching Category 6 levels. You can think of hurricane as engine that transport that energy, i.e. heat, from the ocean surface to an outflow at the boundary between the troposphere from the stratosphere.  The PI measures the strength of this hurricane engine. Looking at data from 1979 to 2018, the authors found that the likelihood of storms reaching Category 6 strength has increased significantly due to global warming. Comparing the periods from 1999 to 2018 and 1979 to 1998, almost three times more instances of storms exceeding the Category 6 threshold occurred. The authors note, “Overall, the chances of PI exceeding the category 6 threshold have more than doubled since 1979.”

Additionally, climate model simulations conducted by the authors predict further increases of these Category 6 hurricanes. The authors demonstrate that when they run long-term simulations using three advanced global climate models, they all predict the greater occurrence of Category 6 storms in conditions hotter than what we have today. Even if we manage to meet the relatively modest global warming goals outlined in the Paris Agreement, these simulations still show a significant rise in the likelihood of Category 6 storms happening.

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However, in the deep Gulf of Mexico the  devastation was hidden 2 kilometers below in the dark depths of the ocean .  

Investigations of the site began just months after the oil spill using a remote operated vehicle. Dramatic losses of deep-sea biodiversity in the immediate aftermath of the spill were documented by Louisiana State University researchers.  Additional surveys continued for one year until the summer of 2011. Meanwhile, ship-board collection of sesdiments monitored the slow recovery of life, noting a 40-90% reduction in diversity, on the deep-sea floor until 2014

…after which monitoring stopped. 

In 2017, Clifton Nunnally and I with a team of scientists revisited the DWH wreckage and Macondo wellhead site for the first time since monitoring ceased in 2011.  Video captured a deep sea unrecovered after 7 years.  Showing a seafloor, marred by wreckage, physical upheaval and sediments covered in black, oily marine snow unrecognizable from the healthy habitats in the deep Gulf of Mexico.

Near the wreckage and wellhead, many of the animal characteristic of other areas of the deep Gulf of Mexico, including sea cucumbers, Giant Isopods, glass sponges, and whip corals, were absent.  What remained was a homogenous wasteland in contrast to the rich heterogeneity of life seen in healthy deep sea.  

Conspicuously absent were the sessile animals that typically cling to any type of hard structure in an otherwise soft, muddy habitat.  Hard substrate in the deep sea is a valuable commodity but at the Deepwater Horizon site metal and other hard substrates were devoid of typical deep-sea colonizers.

Sea floor communities at the impact site were also characterized by high densities of decapod shrimp and crabs.  Crabs showed clearly visible physical defects and sluggish behavior compared to the healthy crabs outside of the impacted zone of the Deepwater Horizon wellhead.  

We hypothesize these crustaceans are drawn to the site because degrading hydrocarbons may serve as luring sexual hormone mimics. Once these crustaceans reach the site they may become too unhealthy to leave in a La Brea Tarpit scenario.

The scope of impacts may extend beyond the impacted sites with the potential for impacts to pelagic food webs and commercially important species.

Our Recommendations:

1. Longer funding cycles are needed to assess the recovery of deep-sea ecosystems.
2. Increased commitment to fund pre-impact baseline surveys.
3. Stronger, more explicit policy to support future monitoring efforts.

Overall, deep-sea ecosystem health, 7 years post spill, is recovering slowly and lingering effects may be extreme. 

In an ecosystem that measures longevity in centuries and millennia the impact of 4 million barrels of oil constitutes a crisis of epic proportions. 

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From the darkness emerges a boot. An old leather, steel-toed, work boot. It shouldn’t be there resting on the seafloor nearly two kilometers deep. I’m speachless. Even knowin this was going to be one of the toughest dives of my career, I’m still not prepared.

Seven years prior in 2010, Marla Valentine and Mark Benfield were the first scientist to visit the deep-sea floor after the Deepwater Horizon accident. On 20 April 2010, and continuing for 87 days, approximately 4 million barrels spilled from the Macondo Wellhead making it the largest accidental marine oil spill in history. Just months after the oil spill, Valentine and Benfield conducted video observations with a remotely operated vehicle (ROV) of the deep-sea impact. Overall, they found a deep-sea floor ravaged by the spill. Much of the diversity was lost and the seafloor littered with the carcasses of pyrosomes, salps, sea cucumbers, sea pens, and glass sponges.

Researchers continued to find severe impacts on deep-sea life. The numerical declines were staggering within the first few months; forams (↓80–93%), copepods (↓64%), meiofauna (↓38%), macrofauna (↓54%) and megafauna (↓40%). One year later, the impacts on diversity were still evident and correlated with increases in total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAH), and barium in deep-sea sediments. In 2014, PAH was still 15.5 and TPH 11.4 times higher in the impact zone versus the non-impact zone, and the impact zones still exhibited depressed diversity. Continued research on corals found the majority of colonies still had not recovered by 2017. However, studies examining the impacts of the DWH oil spill on most deep-sea life ended in 2014.

This gap in knowledge on the lingering impacts of one of the largest oil spills of all time is why I sit here in this cold, dark, ROV control room staring at a work boot in the abyss. A year prior, I had reached out to Mark Benfield about replicating his ROV methods and locations. I am here seven years after his study beginning to replicate his first video transect.

Within minutes of reaching the seafloor with the ROV, every scientist on the vessel staring at monitors showing live video from remote seafloor knew something was wrong. As Mark Benfield, Clif Nunnally, and I report in a new open-access article, the deep sea was not recovering at the impact site.  The seafloor was unrecognizable from the healthy habitats in the deep Gulf of Mexico, marred by wreckage, physical upheaval and sediments covered in black, oily marine snow.

Near the wreckage and wellhead, many of the animals characteristic of other areas of the deep Gulf of Mexico, including sea cucumbers, Giant Isopods, glass sponges, and whip corals, were absent.  What we observed was a homogenous wasteland, in great contrast to the rich heterogeneity of life seen in a healthy deep sea.

Conspicuously absent were the sessile animals that typically cling to any type of hard structure in an otherwise soft, muddy habitat.  Hard substrate in the deep sea is a valuable commodity but at the Deepwater Horizon site metal and other hard substrates were devoid of typically deep-sea colonizers.

The seafloor at impact site was characterized by high numbers of shrimps and crabs.  Crabs showed clearly visible physical abnormalities and sluggish behavior compared to the healthy crabs we had observed elsewhere.  We believe these crustaceans are drawn to the site because degrading hydrocarbons serve as luring sexual hormone mimics. Once these crustaceans reach the site they may become too unhealthy to leave much like those prehistoric mammals and the Le Brea tarpits.

The ROV dive began with a boot belonging to one of the workers on the Deepwater Horizon rig. The dive ended at the wellhead, now capped with a memorial to those workers who lost their lives. A dive bookended with reminders of the human tragedy of the oil spill. The narrative that unfolded between these was an environmental catastrophe. In an ecosystem that measures longevity in centuries and millennia the impact of 4 million barrels of oil continues to constitutes a crisis of epic proportions.

Valentine, Marla M., and Mark C. Benfield. “Characterization of epibenthic and demersal megafauna at Mississippi Canyon 252 shortly after the Deepwater Horizon Oil Spill.” Marine Pollution Bulletin 77.1-2 (2013): 196-209.

McClain, Craig R., Clifton Nunnally, and Mark C. Benfield. “Persistent and substantial impacts of the Deepwater Horizon oil spill on deep-sea megafauna.” Royal Society Open Science 6.8 (2019): 191164.

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A four-leaf clover represents just one kind of rareness. One might find a 4-leaf clover just about anywhere. Four-leaf clovers are not just restricted to Ireland. Four-leaf clovers are rare because at any given locality they occur in very minuscule numbers.

The idea of whether rareness imparts values has tormented philosophers, including Nietzsche. “Whatever can be common always has little value. In the end it must be as it is and always has been: great things remain for the great, abysses for the profound, nuances and shudders for the refined, and, in brief, all that is rare for the rare.” But of course, Nietzsche does not define rare. What does “all that is rare for the rare even mean?” Freakin’ Nietzsche.

We all feel we know what rare means. But contrast the case of four-leaf clovers with platinum. Platinum is special for me. For my 10th wedding anniversary, I had a custom wedding ring made of platinum for my wife. This platinum band was to replace one from our youth when I had more limited income and could afford a metal less “precious” and less “rare.” Yet, platinum represents another kind rarity, occurring in great abundance but only at a few locations. Locally abundant but geographically restricted.

In a classic 1981 paper, Dr. Deborah Rabinowitz, a professor at the University of Michigan, laid out the seven forms of rarity. What makes something rare depends on three characteristics; geographic range, habitat specificity, and local population size. First, is a species found globally or only at a single location? Two, is species seen at any given site in low numbers? Third, is the species only found in a specific type of habitat?

As Rabinowitz notes in elegant writing., “If each of these attributes is dichotomized, a 2 x 2 x 2 or eight-celled block emerges. Although creating the hazard of false reification – that is, converting an idea into an object – such a simple scheme can aid in focusing our thoughts, and this is my intention. The patina – a gloss or incrustation conferred by age – of monolithic rarity may have hindered our understanding of an exceedingly heterogeneous assemblage of organisms. Since the products of rarity are diverse, the causes of rarity and the genetic and population consequences of rarity are undoubtedly equally multiple.”

But obviously, 2x2x2 does not equal 7. One state is lost, a species found everywhere, in high numbers, and several different kinds of habitats. This species isn’t rare at all! You can think of the seven forms of rarity as three singe type cases (geographically limited/small numbers/habitat specialist), the three double type cases (geographically limited and small numbers/geographically limited and habitat specialist/small numbers and habitat specialist), and the last triple case (geographically limited and small numbers and habitat specialist).

The most uncommon form of rarity is a species found all over but in limited numbers at a single location. One such species is the exceptionally beautiful deep-sea snail Oocorys sulcata found in the eastern and western corridors fo the Atlantic and reaching will into the Indian Ocean and the western Pacific. Oocorys sulcata also show incredible depth tolerance found all the way from the shelf at 150 meters down to the deepest abyss over 5000 meters. Yet, despite this fantastic distribution, it is rarely found. A famous sampling effort off of New England did not capture a single individual in 41 samples. Another 24 samples later as part of later effort only yielded a single specimen. Indeed, based on some very rough calculations, you would probably only find about 15 every square kilometer or roughly 45 Manhattan city blocks.

Hydrothermal vents possess mollusks that are both unique and fascinating. A snail first described in 2003, the unusual snail Chrysomallon squamiferum, maybe the most exciting find thus far at a hydrothermal vent. I admit my bias here, as most of my interest lies with studying deep-sea snails. Nonetheless, the discovery of “gold-footed” snails a the Kairei vent field in the Indian Ocean is fascinating.

At this point, I should state that the foot of the snail is mineralized with pyrite and greigite. Many of you might note the misnomer here, as pyrite is only ‘Fool’s Gold,’ but in deciding on a temporary ordinary name Fool’s Gold-Footed Snail seemed a bit lengthy. I hope all will forgive the intentional misnomer for the sake of creative writing. Although other names due include the big-hearted iron snail (it also possesses an abnormally large heart for its size). And of course the scaly foot snail. So maybe the big-hearted, iron gold, scaly foot snail.

The scales, or sclerites, that cover the entire length of the snail’s foot can be up to 8mm long. The presence of mineralized scales is remarkable in itself, but the existence of iron sulfide as skeletal material is unknown from any other animal. The purity of sulfides, among other lines of evidence, suggest that the building of the scales is controlled by the gastropod itself. The sclerites are thought to have evolved recently and homologous to the operculum. It is believed they may serve as a defense against cone shells also occurring at the vent.

Chrysomallon squamiferum is rare, not only for the oddity of its features amongst the animal kingdom but because the snail is known from only three hydrothermal vents in the Indian Ocean. While abundant at any of these vents it is geographically restricted, like platinum. The scaly foot is actually a “double rare” case both geographically restricted and a habitat specialist. Given this potential habitat of only a few square meters, some of which endangered by deep mining interests, led a new paper by Dr. Sigwart and colleagues establishing Chrysomallon squamiferum as endangered on the IUCN RedList. This listing places the big-hearted, iron gold, scaly foot snail with 25 species all either bony fish, cartilaginous fish, or cephalopods all assessed to be either endangered or critically endangered.

Helen Macdonald writes in H is for Hawk “The rarer they get, the fewer meanings animals can have. Eventually rarity is all they are made of. The condor is an icon of extinction. There’s little else to it now but being the last of its kind. And in this lies the diminution of the world. How can you love something, how can you fight to protect it, if all it means is loss?”

I am hoping for future where Chrysomallon squamiferum I remember this elegant mollusk for the rarity of beauty, adaptation, and morphological marvel not the rarity of its existence.

Sigwart, J. D., Chen, C., Thomas, E. A., Allcock, A. L., Böhm, M., & Seddon, M. (2019). Red Listing can protect deep-sea biodiversity. Nature Ecology & Evolution, 1.

Rex, M.A., Stuart, C.T., Etter, R.J., & McClain, C.R. (2010). Biogeography of the deep-sea gastropod Oocorys sulcata Fischer 1884. Journal of Conchology, 40, 287.

Rabinowitz, Deborah. (1986). Seven forms of rarity and their frequency in the flora of the British Isles. Conservation Biology: The Science of Scarcity and Diversity 

Rabinowitz, Deborah. (1981) Seven forms of rarity. Biological Aspects of Rare Plant Conservation

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On Thursday, The Ocean Cleanup published a blog post in reply to my concerns. I was incredibly hopeful up until this point that they would listen. After all, my efforts to raise awareness have been met with tremendous support from fellow scientists and the general public.

I’m not going to lie, the frustration I felt when reading their response was real and heavy. I love this ecosystem, I wouldn’t be putting myself out there if I didn’t. But their response felt profoundly dismissive, not only of me, but of the scientific evidence. So this is my second attempt at explaining to The Ocean Cleanup, and to its funders, why it’s logic is flawed, and why it is putting entire species and whole ecosystems at risk as a result.

1) Boyan Slat and The Ocean Cleanup claim floating animals are ubiquitous.

Here are the exact words of their blog post reply, with the exact studies they reference, and what those exact studies actually say.

The studies they reference almost immediately prove them wrong. The third sentence of the first study says, “Analyses of neustonic concentration and population structure showed regional and temporal differences in the fauna.” And the second study states: “The present study represents an original insight into the structure of the neuston community in the Mediterranean Sea, providing strong evidence of the spatial variability of its diversity patterns.”

Perhaps The Ocean Cleanup and Boyan Slat meant to point out that some species are mentioned in both papers. But species identification for poorly-known invertebrates is notoriously difficult. Often biologists will unknowingly use the same species name for many similar species. Only when we study them more do we realize our oversight. In fact, two newly discovered blue sea dragons were only described in 2014, before this time they were all called by one name. Even worse, these two species are only found in the North Pacific Subtropical Gyre, exactly where The Ocean Cleanup plans to launch their massive fleet.

To sum it all up? No matter how you look at it, neuston are not ubiquitous.

Now, let’s go a step further.

Why has The Ocean Cleanup been so obsessed with documenting the distribution of plastics in the ocean? Because they know floating objects are not ubiquitous. Why they understand this fact for plastic, yet fail to grasp it for floating animals, is beyond me.

2) Boyan Slat and The Ocean Cleanup claim they will be in only one small spot in the ocean, so they will not have a big impact on floating animals.

But wait, are they admitting they will only clean this small spot of the ocean? No. They are not.

They’re not just working in a small spot of the ocean. They’re working in very special small spots. These spots in the ocean are akin to giant whirlpools, called gyres. Just like the whirlpool in your kitchen sink, gyres spin on a massive scale, concentrating objects at the surface, just like soap bubbles going down the drain. The Ocean Cleanup is focusing on these gyres because floating objects collect in them.

So let’s look at their logic again: The Ocean Cleanup is intentionally working where floating objects are most concentrated. They claim they that they will remove 90% of ocean plastic by 2040, even while working in these tiny spots, because much of the ocean’s surface plastics are funneled into these regions at some point.

If you are collecting plastic that is continually entering the ocean by using these spots, you will also be collecting neuston even if they are continuously reproducing.

Some animals, like the two new species of blue sea dragon, have only been found in the gyres. Harvest plastic from one gyre, potentially harvest two newly discovered species.

3) Boyan Slat and The Ocean Cleanup claim that floating life likely multiplies quickly, so it’ll be ok.

They justify this by talking about bacteria. It’s true: Some floating bacteria do reproduce quickly. Animals are not bacteria. We do not know how long it takes floating animals to reproduce. But let’s say they do reproduce quickly. Does that mean there is no problem? No.

Quick reproduction may help floating animals overcome destructive storms, which can kill floating life. But storms pass. The Ocean Cleanup’s proposed fleet of 60 systems in the open ocean are not storms. They are intended to be at sea for years. They will not pass.

4) Boyan Slat and The Ocean Cleanup claim they are collecting lots of data on these issues.

But who are the biologists performing this work? I offered to speak with biologists at The Ocean Cleanup nearly a month ago, and was placed in touch with the person who conducted the Environmental Impact Assessment. We had a thoughtful exchange, but he informed me that he’s not part of the actual Ocean Cleanup team, and doesn’t work for them. If The Ocean Cleanup is so open to feedback, why aren’t they actually talking to people with the greatest concerns for the ecosystem?

5) Boyan Slat and The Ocean Cleanup claims also reveal something else:

They knew about floating animals, and they know we need more data, yet they still argue that there is no scientific basis for environmental concern. In his blog post Boyan Slat defends his Environmental Impact Assessment by saying “all species that have previously been observed near the deployment site of our cleanup system are referenced [in a table of the Environmental Impact Assessment].” Of course, this is not true: nowhere in his EIA or in his post does he mention the two species of blue sea dragon found only in his deployment area. Further, the fact that some floating animals were in a table only proves that they have known about the issue of floating surface life for some time.

He also attempts to brush aside some of the best information we have: a massive ocean survey of floating animals conducted by USSR scientist Savilov, which shows 7 distinct floating ecosystems, including one unique ecosystem found right where The Ocean Cleanup intends to work. Yet Boyan Slat says that “the validity of using a single, 51-year-old source could be questioned,” before going on to justify why it’s not worth worrying about anyway (because neuston are “ubiquitous”). But this is exactly my point: we don’t have good modern data. Why does The Ocean Cleanup brush off the data we do have?

In summary: The Ocean Cleanup’s claims only reiterate what we already know: neuston are not ubiquitous. Neuston may be concentrated where The Ocean Cleanup wants to work, due to the same physical forces that concentrate plastic. The life cycles of floating animals are poorly understood and The Ocean Cleanup may have major negative consequences on this ecosystem.

Far from alleviating my concerns, Boyan Slat’s reply to my article only increases my alarm. The Ocean Cleanup underestimates the negative impacts they will have and are not looking at the scientific evidence to the contrary.

The concerns of myself and others are very well-founded, Mr. Slat. You may be putting whole ecosystems at risk, and threatening species that were only recently discovered. Any attempt to suggest a “lack of scientific basis” for our claims only serves to prove what we’re already suggesting: that you’re not listening to scientists, and that you may be endangering an entire ecosystem as a result.

The post The Ocean Cleanup struggles to prove it will not harm sea life first appeared on Deep Sea News.

Introduction

The Ocean Cleanup, brainchild of Dutch inventor Boyan Slat, was in the news again this past week after announcing that in addition to the fact that their system is unable to collect plastic as intended, it suffered a mechanical failure. “Wilson” is currently being towed to Hawaii, where it will undergo repairs and upgrades, presumably to be towed back out to the garbage patch for a second trial.

I am not a mechanical engineer, so I don’t intend to comment on the details of their mechanical failure. I am, however, a sea-going oceanographer. Which means that I am used to the sorts of situations with scientific research equipment that was so succinctly paraphrased by Dr. Miriam Goldstein:

Designing for physics

But beyond the engineering, there are the questions of what the *physics* are that TOC are relying on for their system to be successful. Some of you may recall that the original design was to moor (i.e. *anchor*) their device in 6000m (20000 feet) of water, and let existing ocean currents sweep garbage into the U-shaped structure. Thankfully, they realized the challenges associated with deep-ocean moorings, and abandoned that idea.

The latest design iteration (misleadingly called “System 001”, as though they haven’t built and tested any other previous to it), is to have a freely-drifting system, avoiding the use of anchors. TOC claim that under the influence of current, wind, and waves, their design will drift *faster* than the plastic — causing it to accumulate in the U, making for easy pickup. They summarize the concept with a little explainer video on their website, with a representative screen shot below:

Based on a quick Twitter rant that I had after thinking about all this for a few minutes (see here), I wanted to explain out the various points that have either a) been missed by TOC design team, or b) deliberately excluded from their rosy assessment of how they expect their system to actually collect garbage. What follows is a “first stab” at a physical oceanographic assessment of the basic idea behind “System001”, and what TOC would need to address to convince the community (i.e. scientists, conservationists, etc) that their system is actually worth the millions of dollars going into development and testing.

The premise

As outlined in the video, the premise of System001 as a garbage collection system is that through the combined action of wind, waves, and currents, the U-shaped boom will travel faster through the water than the floating plastic, thereby collecting and concentrating it for eventual removal. This appears to be based on the idea that while both the boom and the plastic will drift with the current, because the boom protrudes from the water (like a sail), it will actually move faster than the surface water by catching wind.

There are some issues with this premise. Or, at least, there are some real aspects of oceanography that have either been ignored or missed in thinking that such a system will behave in the predictable way described by TOC. I’ll try and outline them here.

Stokes drift

Any of you who may have had an introduction to ocean waves may have heard that during the passage of a wave, the water particles move in little circles (often called wave orbital motion). While not a bad “first-order” description, it turns out that for real ocean waves there is also some drift in the direction of wave propagation. This drift is named after Gabriel Stokes, who first described it mathematically in 1847 (see wikipedia article here).

The amount of drift depends nonlinearly on both the amplitude and the wavelength of the wave. For example, for a 0.5m amplitude wave with a wavelength of 10m and period of 10s (something like typical ocean swell), the drift velocity is about 10 cm/s right at the surface.

Of course, the Stokes’ solution describes the motion of the water parcels being moved by the wave. For those water parcels to then have an effect on anything in the water, one would need to consider the various components of force/impulse/momentum (i.e. our buddy Sir Isaac Newton). Needless to say, it seems obvious that a smallish piece of neutrally buoyant plastic will respond to the Stokes drift much more readily than a 600m long floating cylinder with a large mass (and therefore large inertia).

This alone could be enough to quash the idea of a passive propagating collection system. Mr Slat?

Ekman currents

While we’re talking about long-dead European fluid mechanics pioneers, any study of the effect of winds and currents wouldn’t be complete without a foray into the theories proposed by Swedish oceanographer Vagn Walfrid Ekman in 1905. What Ekman found was that when the wind blew over the surface of the ocean, the resulting current (forced by friction between the air and the water) didn’t actually move in the same direction as the wind. The reason for this is because of the so-called “Coriolis effect”, whereby objects moving on the surface of the Earth experience an “acceleration” orthogonal to their direction of motion that appears to make them follow a curved path (for those who want to go down the rabbit hole, the Coriolis acceleration is essentially a “fix” for the fact that the surface of the Earth is non-inertial reference frame, and therefore doesn’t satisfy the conditions for Newton’s laws to apply without modification).

Anyway — the consequence is that in an ideal ocean, with a steady wind blowing over the surface, the surface currents actually move at an angle of 45 degrees to the wind direction! Whether it’s to the left or right of the wind depends on which hemisphere you are in — I’ll leave it as an exercise to determine which is which. And what’s cooler, is that the surface current then acts like a frictional layer to the water just below it, causing it to move at an angle, and so on, with the effect being that the wind-forced flow actually makes a SPIRAL that gets smaller with depth. This is known as the Ekman spiral.

The actual depth that the spiral penetrates to depends on a mysterious ocean parameter called Az, which describes the vertical mixing of momentum between the layers — kind of like the friction between them. What is clear though, is that a small particle of plastic floating close to the surface and a 3m deep floating structure will likely not experience the same wind-forced current, and therefore won’t move in the same direction. Hmmm … that’s going to make it hard to pick up pieces of plastic.

What is a “Gyre” anyway?

The final point I wanted to make in this article (I have more, which I’ll summarize at the end for a possible future article), is to try and give a sense of what currents in the ocean (including in the “gyre” or in the region often referred to as the “Great Pacific Garbage Patch”) actually look like. The conception that there is a great swirling current 1000’s of km across is true only when the currents are averaged for a very long time. At any given instant, however, the ocean current field is a mess of flows at various space and time scales. An appropriate term for describing typical ocean flow fields is “turbulent”, as in an oft-viewed video made by NASA from satellite ocean current data.

To illustrate this, I took some screenshots of current conditions from the wonderful atmosphere/ocean visualization tool at earth.nullschool.net showing: ocean currents, surface waves, and wind.

These images illustrate the potential problem with TOC idea, by highlighting the fact that the wind, wave, and current fields of the ocean (including even in the “quiet” garbage patch) are highly variable spatially and temporally, and are almost never aligned at the same period in time. What’s more, is that the currents and waves at a given time and location are not always a result of the wind at that location. Eddies in the ocean are generated through all kinds of different processes, and can propagate across ocean basins before finally dissipating.

Similarly, surface waves have been measured to cross oceans (i.e. the famous “Waves across the Pacific” study pioneered by the transformative oceanographer Walter Munk).

Other issues

Following the “rule of three”, I tried to hit what I consider to be the biggest concerns with TOC system design and principle, from my perspective as a physical oceanographer. However, there are other issues that should be addressed, if the system as designed is really believed by the TOC team to be capable of doing what they say. And really, it seems like a crazy waste of time on behalf of everyone involved to have spent this much time on something if they aren’t sure it will even work theoretically … not to mention the money spent thus far. So, part of me *has* to believe that all the dozens of people involved care deeply about making something that might actually work, and they have studied and considered all the effects and potential issues I (and others) have raised.

Anyway, the other issues are:

• What is the actual response of the system to a rapid change in wind/wave direction? Wind can change direction pretty quickly, especially compared to ocean currents. What’s to prevent a bunch of accumulated plastic getting blown out the open end of the U after a 180 degree shift in wind but before the system can re-orient?
• What about wave reflection from the boom structure itself? It is a well-known fact that objects (even floating ones) can reflect and “scatter” waves (scattering is when the reflected waves have a shorter wavelength than the original ones), and it seems like this could create a wave field in the U that might actually causes drift *out* of the system.
• The idea that all wildlife can just “swim under” the skirt (because it’s impermeable) is not supported by anything that I consider to be rigorous fluid mechanics, aside from the fact that much of what actually lives in the open ocean are non-motile or “planktonic” species. There are a lot of communities in the open ocean that float and drift at the surface, and I see no way that if the System collects floating plastic as it is designed that it won’t just sweep up all those species too. The latest EIA brushed off the effect of the System on planktonic organisms by stating that they “are ubiquitous in the world’s oceans and any deaths that occur as a result of the plastic extraction process will not have any population level effects”. But that doesn’t take into account that the stated mission is to deploy 60 such systems, which are estimated to clean the garbage patch of surface material at a rate of 50% reduction every 5 years. It stands to reason that they would also clean the Pacific of its planktonic communities by the same amount.

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