We already know how best to capture atmospheric carbon.
The ocean, all 65M km^2 of it, is already capturing atmospheric carbon. This would be good, except that it is also making the top layer of the ocean acidic, which threatens to kill the whole damn ocean ecosystem; and the top layer is getting saturated, so not capturing as much.
So, the solution is to pump surface water down deep, where there is more capacity and where it can do less harm. Maybe pump deep water to the surface, too, so that water not already saturated with carbon can better absorb it; and maybe deliver that to reefs, which need it. You can float wind turbines on buoys in deep water, and pay for them with carbon credits.
Of course this does no good at all unless you also stop piling more carbon into the atmosphere. But you can start doing it before that, and then get increasing benefit after.
When CO2 dissolves in the ocean, some of it will eventually end up as methane ice in ocean mud [0]. Methane ice releases its methane when warmed slightly. More methane ice means higher chances of runaway global warming.
Hint: CO2 does not turn into methane. Methane clathrates on the sea bottom got there by seeping out from bottom mud, and froze there. Sometimes the methane was excreted by microbes in sea-bottom mud; other times it comes from the rocks. Often, methane and other seeped hydrocarbons are oxidized to CO2 by microbes.
Yes, and it's saturating the top levels of the ocean. GP suggested mixing the ocean to saturate more of it.
> CO2 does not turn into methane.
CO2 gets turned into many things, as part of the ocean carbon cycle [0]. Algae near the surface absorb CO2, incorporating it into their cells. Algae is the bottom of the ocean food chain. Increasing the algae increases the overall amount of life in the ocean, increasing the rate of organic detritus accumulating on the ocean floor [1], forming more mud. Bacteria in the mud consume the organic detritus and emit methane [2].
Methane ice is one of the few ways that carbon can exit the cycle. Therefore increasing the volume of carbon in the cycle will make methane ice accumulate faster. Over centuries, the world's CO2 pollution could get converted into methane ice on continental shelves. Then a minor warming event could trigger the release of all that carbon. But the carbon is methane now, which is 70x more warming than CO2. The warming effect could be catastrophic for our ecosystem. I think this is a risk of utilizing the ocean as a CO2 sink. People in the year 4,000 may curse us for our carbon pollution and the resources they must spend to clean it up and convert methane ice into something more stable.
Hint: Methane clathrates on the deep sea floor will not be releasing their methane. That is possible only where temperature is changing and pressure is low, neither of which will happen without surface changes catastrophic enough to make methane irrelevent. In any case, accumulation happens over eons. There is exactly zero risk of carbon stirred into the deep ocean becoming methane released into the atmosphere in this eon.
Carbon in surface water can be metabolized, and may then be released as methane. Carbon moved to deep water is removed from that process.
> Methane clathrates on the deep sea floor will not be releasing their methane. That is possible only where temperature is changing and pressure is low, neither of which will happen without surface changes catastrophic enough to make methane irrelevent.
Methane ice forms under certain temperature and pressure. See the phase diagram at [1]. When methane ice forms on a sloping ocean floor, there is a boundary where the methane ice formation stops. The boundary depends on the temperature and pressure (depth). When water warms, this boundary moves deeper and all methane ice above it will convert to gas and eventually leave the ocean.
How much deeper does the boundary move per 1C of temperature rise? I examined the phase diagram in Figure 6 of [1]. I found two points: (20 MPa, 275 K) and (40 MPa, 278 K). A change of 10.06 m increases pressure by 1 atm [2] or 101325 Pa [3], about 10 kPa per m or 1 MPa per 100m. So a 3 K increase in temperature results in the boundary pressure increasing 20 MPa or 2 km of ocean depth, a 1.5 K increase moves the boundary down 1000 m.
The world's CO2 pollution is expected to raise surface temps by 1.5K. Given that methane is 70x more warming than CO2, if we were to convert most of the world's CO2 to methane and then release 1/70 or 1.4% of it, we would have the same amount of warming and could expect a similar 1.5 K temp rise.
What percentage of methane ice will form near the boundary? To answer that, we would need to analyze ocean floor topography. I searched for a chart of depth to area and found none.
Do you think the top-most 1km of methane ice forming areas would hold 1.4% of the ocean's recently-formed methane ice? The deepest part of the ocean is 10km deep. If the top-most 1km holds much more than 1.4% then there is the risk of runaway warming.
Another risk is a change in ocean currents. Currents keep large areas of the ocean floor cold. If a current is disrupted, even for a short time, the clathrates in that region could release their methane, triggering runaway warming.
> You are reaching. It is not a good look.
Personal insults are boring and against the site guidelines [4]. Please don't write them any more on this site.
Air temperature rising 1.5 degrees does not mean a corresponding increase in temperature at depth -- or anything close to it, and that not for centuries. Meanwhile, sea level rises as glaciers melt, so pressure increases. The line will move up, not down.
The only substantial changes in temperature at depth would be effects of changes in current, e.g. a warm current diverted to where clathrates have accumulated over eons. These are local, affecting only isolated deposits. Methane escaping dissolves in water until it saturates, and is made available to microbes to metabolize. Methane only saturates, bubbling out, when melting is fast enough. The deeper it is, the more opportunity it has to dissolve before it gets to the surface. Only methane breaching the surface contributes to warming.
And, CO2 inserted at middling depth still needs eons for some trace of it to be incorporated into methane clathrates. It takes a lot of energy to get oxygen unstuck from carbon, and most life would rather stick some back on than let the carbon float off as methane.
We can presume that humans will stop making new CO2 pollution in the next 100 years. It will take hundreds or thousands of years for the CO2 to convert to methane clathrates. I worry about creating a problem for people far in the future. It's like setting a climate bomb with a timer of 2,000 years.
> Methane escaping dissolves in water
This is a good point. Let's see if the ocean can hold enough methane. Methane dissolves 0.04g/l in pure water at 0C ant 1atm [0]. Seawater has about 35g salt per L [1], or about 3.5% NaCl by weight. Methane has slightly lower solubility in salt water than in pure water (see tables starting on page 11 of [2]). Ocean pressure increases 10 kPa per m, or 1.45 psi per m [3]. At 25C, increasing pressure from 1,000 psi (700m depth) to 2,500 psi (1700m depth) increases the solubility of methane in salt water by 2x, and 5x at 15,000 psi (10km depth). I couldn't find data for lower temperatures.
Methane ice forms in mud starting at 300m depth [4]. Humans have burned fossil fuels and released about 380 GtC [5]. Converting this carbon into methane yields about 500 Gt methane. Let's assume that the ocean slopes linearly down to 10,000m depth. Then the ocean floor from 300m-1300m is 10% of the ocean floor and contains approximately 10% of the methane ice, about 50 Gt of methane. The volume of water above it is (300m + 0.5 x 1000m) x 0.10 x 361,900,000 km-km (the area of the ocean [6]), about 29,000,000 km-km-km or 2.9x10^22 l. About 1.160x10^21 g or 1,600,000 Gt methane can dissolve in this water.
Let's assume that the average solubility in the ocean is 2x the solubility at the surface, or 0.08g/l of methane in sea water. Then the entire 1.335x10^9 km-km-km ocean could dissolve about 1.068x10^23 g or 100,000,000 Gt methane. You are right. The ocean could dissolve all of man's fossil fuel CO2 pollution as methane.
Since the methane would probably not bubble up, the rate of methane escaping into the air would be very low. I think it would be slow enough that the methane would stay in the ocean's carbon cycle and not escape fast enough to trigger runaway warming.
I feel relieved.
> So, you are still reaching. Why?
Describing my analysis as "reaching" is incorrect. I think you mean it as a personal attack, which breaks the site's guidelines [7]. Removing the insult yields "Why do you care about this issue?" The reason is that I think it is interesting and important.
By "reaching", I mean inventing and posting technical objections you have not thought through, and that distract from what is important.
I commend you for following through, in the end.
The imminent maritime disaster we face arises from carbonic acid saturation at the surface by direct diffusion from the atmosphere, which is ongoing as I write this. To mitigate disaster we must focus on that phenomenon.
I encourage you to get some bubble solution and just stop to admire bubbles for a little bit... even if you understand the physics of the whole thing, they feel a little like magic. Watch how the air flows in the room, blow some on a warm day and see how far the breeze takes them.
I also find that if you put the solution in your hands, at the right concentration, and then form an oval with your thumbs and forefingers, you can blow very large bubbles.
You have to start slowly, until a large curve forms, then expand the bubble until it can bud off as complete. Also it can help with a small amount of spit! :)
the linked 'gas marble' article is good too, in particular the construction method for the marbles
> Timounay found that if the frame was wide enough and the microspheres were at least several hundred micrometers in diameter, then lifting the frame generated a gas marble. During lifting, the film on the frame would spontaneously fold in on itself and detach to form a gas marble that would drop to the liquid surface below. “The full mechanism of gas-marble creation is not fully understood for the moment, but their creation is reproducible,”
28 comments
[ 3.2 ms ] story [ 77.9 ms ] threadBut pleasantly surprised and happier that it's something interesting!
The ocean, all 65M km^2 of it, is already capturing atmospheric carbon. This would be good, except that it is also making the top layer of the ocean acidic, which threatens to kill the whole damn ocean ecosystem; and the top layer is getting saturated, so not capturing as much.
So, the solution is to pump surface water down deep, where there is more capacity and where it can do less harm. Maybe pump deep water to the surface, too, so that water not already saturated with carbon can better absorb it; and maybe deliver that to reefs, which need it. You can float wind turbines on buoys in deep water, and pay for them with carbon credits.
Of course this does no good at all unless you also stop piling more carbon into the atmosphere. But you can start doing it before that, and then get increasing benefit after.
There is way more "bottom" than most people can conceive of.
[0] https://en.wikipedia.org/wiki/Methane_clathrate
Hint: CO2 does not turn into methane. Methane clathrates on the sea bottom got there by seeping out from bottom mud, and froze there. Sometimes the methane was excreted by microbes in sea-bottom mud; other times it comes from the rocks. Often, methane and other seeped hydrocarbons are oxidized to CO2 by microbes.
Yes, and it's saturating the top levels of the ocean. GP suggested mixing the ocean to saturate more of it.
> CO2 does not turn into methane.
CO2 gets turned into many things, as part of the ocean carbon cycle [0]. Algae near the surface absorb CO2, incorporating it into their cells. Algae is the bottom of the ocean food chain. Increasing the algae increases the overall amount of life in the ocean, increasing the rate of organic detritus accumulating on the ocean floor [1], forming more mud. Bacteria in the mud consume the organic detritus and emit methane [2].
Methane ice is one of the few ways that carbon can exit the cycle. Therefore increasing the volume of carbon in the cycle will make methane ice accumulate faster. Over centuries, the world's CO2 pollution could get converted into methane ice on continental shelves. Then a minor warming event could trigger the release of all that carbon. But the carbon is methane now, which is 70x more warming than CO2. The warming effect could be catastrophic for our ecosystem. I think this is a risk of utilizing the ocean as a CO2 sink. People in the year 4,000 may curse us for our carbon pollution and the resources they must spend to clean it up and convert methane ice into something more stable.
[0] https://en.wikipedia.org/wiki/Carbon_cycle
[1] https://en.wikipedia.org/wiki/Plankton#Carbon_cycle
[2] https://en.wikipedia.org/wiki/Methane#Seafloor_sediments
Carbon in surface water can be metabolized, and may then be released as methane. Carbon moved to deep water is removed from that process.
You are reaching. It is not a good look.
Methane ice forms under certain temperature and pressure. See the phase diagram at [1]. When methane ice forms on a sloping ocean floor, there is a boundary where the methane ice formation stops. The boundary depends on the temperature and pressure (depth). When water warms, this boundary moves deeper and all methane ice above it will convert to gas and eventually leave the ocean.
How much deeper does the boundary move per 1C of temperature rise? I examined the phase diagram in Figure 6 of [1]. I found two points: (20 MPa, 275 K) and (40 MPa, 278 K). A change of 10.06 m increases pressure by 1 atm [2] or 101325 Pa [3], about 10 kPa per m or 1 MPa per 100m. So a 3 K increase in temperature results in the boundary pressure increasing 20 MPa or 2 km of ocean depth, a 1.5 K increase moves the boundary down 1000 m.
The world's CO2 pollution is expected to raise surface temps by 1.5K. Given that methane is 70x more warming than CO2, if we were to convert most of the world's CO2 to methane and then release 1/70 or 1.4% of it, we would have the same amount of warming and could expect a similar 1.5 K temp rise.
What percentage of methane ice will form near the boundary? To answer that, we would need to analyze ocean floor topography. I searched for a chart of depth to area and found none.
Do you think the top-most 1km of methane ice forming areas would hold 1.4% of the ocean's recently-formed methane ice? The deepest part of the ocean is 10km deep. If the top-most 1km holds much more than 1.4% then there is the risk of runaway warming.
Another risk is a change in ocean currents. Currents keep large areas of the ocean floor cold. If a current is disrupted, even for a short time, the clathrates in that region could release their methane, triggering runaway warming.
> You are reaching. It is not a good look.
Personal insults are boring and against the site guidelines [4]. Please don't write them any more on this site.
[0] https://en.wikipedia.org/wiki/Methane_clathrate#Natural_depo...
[1] https://doi.org/10.1021/acs.jpcb.7b10581
[2] https://oceanservice.noaa.gov/facts/pressure.html
[3] https://en.wikipedia.org/wiki/Pascal_(unit)
[4] https://news.ycombinator.com/newsguidelines.html
The only substantial changes in temperature at depth would be effects of changes in current, e.g. a warm current diverted to where clathrates have accumulated over eons. These are local, affecting only isolated deposits. Methane escaping dissolves in water until it saturates, and is made available to microbes to metabolize. Methane only saturates, bubbling out, when melting is fast enough. The deeper it is, the more opportunity it has to dissolve before it gets to the surface. Only methane breaching the surface contributes to warming.
And, CO2 inserted at middling depth still needs eons for some trace of it to be incorporated into methane clathrates. It takes a lot of energy to get oxygen unstuck from carbon, and most life would rather stick some back on than let the carbon float off as methane.
So, you are still reaching. Why?
> Methane escaping dissolves in water
This is a good point. Let's see if the ocean can hold enough methane. Methane dissolves 0.04g/l in pure water at 0C ant 1atm [0]. Seawater has about 35g salt per L [1], or about 3.5% NaCl by weight. Methane has slightly lower solubility in salt water than in pure water (see tables starting on page 11 of [2]). Ocean pressure increases 10 kPa per m, or 1.45 psi per m [3]. At 25C, increasing pressure from 1,000 psi (700m depth) to 2,500 psi (1700m depth) increases the solubility of methane in salt water by 2x, and 5x at 15,000 psi (10km depth). I couldn't find data for lower temperatures.
Methane ice forms in mud starting at 300m depth [4]. Humans have burned fossil fuels and released about 380 GtC [5]. Converting this carbon into methane yields about 500 Gt methane. Let's assume that the ocean slopes linearly down to 10,000m depth. Then the ocean floor from 300m-1300m is 10% of the ocean floor and contains approximately 10% of the methane ice, about 50 Gt of methane. The volume of water above it is (300m + 0.5 x 1000m) x 0.10 x 361,900,000 km-km (the area of the ocean [6]), about 29,000,000 km-km-km or 2.9x10^22 l. About 1.160x10^21 g or 1,600,000 Gt methane can dissolve in this water.
Let's assume that the average solubility in the ocean is 2x the solubility at the surface, or 0.08g/l of methane in sea water. Then the entire 1.335x10^9 km-km-km ocean could dissolve about 1.068x10^23 g or 100,000,000 Gt methane. You are right. The ocean could dissolve all of man's fossil fuel CO2 pollution as methane.
Since the methane would probably not bubble up, the rate of methane escaping into the air would be very low. I think it would be slow enough that the methane would stay in the ocean's carbon cycle and not escape fast enough to trigger runaway warming.
I feel relieved.
> So, you are still reaching. Why?
Describing my analysis as "reaching" is incorrect. I think you mean it as a personal attack, which breaks the site's guidelines [7]. Removing the insult yields "Why do you care about this issue?" The reason is that I think it is interesting and important.
[0] https://www.engineeringtoolbox.com/gases-solubility-water-d_...
[1] https://en.wikipedia.org/wiki/Seawater
[2] https://doi.org/10.3133/ofr80371
[3] https://en.wikipedia.org/wiki/Pound_per_square_inch
[4] https://en.wikipedia.org/wiki/Methane_clathrate
[5] https://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_at...
[6] https://en.wikipedia.org/wiki/Ocean#Geography
[7] https://news.ycombinator.com/newsguidelines.html
I commend you for following through, in the end.
The imminent maritime disaster we face arises from carbonic acid saturation at the surface by direct diffusion from the atmosphere, which is ongoing as I write this. To mitigate disaster we must focus on that phenomenon.
You have to start slowly, until a large curve forms, then expand the bubble until it can bud off as complete. Also it can help with a small amount of spit! :)
> Timounay found that if the frame was wide enough and the microspheres were at least several hundred micrometers in diameter, then lifting the frame generated a gas marble. During lifting, the film on the frame would spontaneously fold in on itself and detach to form a gas marble that would drop to the liquid surface below. “The full mechanism of gas-marble creation is not fully understood for the moment, but their creation is reproducible,”