Restoring the Arctic

There are numerous environmental concerns surrounding the progression of human-derived global warming. One of the most pressing is the persistent loss of Arctic ice. Due to a vast majority of global warming related heat being absorbed by the ocean all oceanic temperatures have increased, regardless of location, with the Arctic receiving the greatest temperature increase due to its lower base temperature. This increase has been significant enough that the ice extent at the summer minimum, which consistently occurs in September, has resulted in a net loss of 11% per decade since 1979 with a loss of 1.1 meters of mean ice thickness between 1980 and 2000.1,2 This loss of thickness has produced a general shift in the ice type from older multi-year ice to new single year ice resulting in an overall replacement of about 40% of the thick and old multi-year ice with single year ice.3 Coinciding with this empirical evidence various global and regional climate models have predicted that the situation will only get worse in the future.4

The chief purpose of ice in the Arctic, from a global warming standpoint, is to increase ocean albedo due to its reflective surface versus the darker surface of the water itself. When sunlight strikes the transparent/white surface of ice a vast majority of it is reflected back into the atmosphere. When sunlight strikes the dark blue, sometimes black, surface of Arctic water a vast majority of the light and its associated heat content is absorbed by the ocean rather than reflected back into the atmosphere. On a general level this heat absorption is a positive feedback effect where the more heat absorbed the more ice melts leading to even more heat absorbed, etc. Normally the ocean and its system of currents operate as a heat sink to control surface and atmospheric temperatures; however, this new massive heat absorption reduces sink efficiency allowing more heat to remain in the atmosphere increasing the detrimental effects associated with global warming. A secondary effect is that greater amounts of ice melt will increase global sea level rise in the future placing more coastal and even slightly inland cities at risk as well as negatively affecting Arctic wildlife by eliminating “land” surfaces for hunting and habitation.

With these near-future negative environmental events born from a lack of Arctic ice one would reason that it is important to find and execute a methodology that would increase Arctic ice volume and longevity. The most obvious means of increasing Arctic ice would be to eliminate the human derived excess heat, which would restore typical Arctic ocean temperatures seen in the 50s and 60s and even further past. One means of accomplishing this goal is to simply reverse the actions that lead to the heating. While reducing global carbon emissions is an important and critical step in addressing global warming, the realistic timetable for cooling the Arctic through carbon mitigation then reliance on natural processes is still decades if not even over a century away. Based on the rate of melting a more immediate solution will be required.

Recalling the albedo-heat feedback cycle from above, one method to break that cycle would be to increase the albedo of the ocean. Not surprisingly it is nearly impossible to change the natural color of the ocean due to its size and natural mixing, thus changing ocean albedo will require human intervention to change the surface albedo of the Arctic ocean. The easiest method is to mimic nature itself and increase surface ice by enhancing ice formation. Obviously enhancing ice formation will require large amounts of water; fortunately meeting this supply requirement is not a problem for water can be taken from the ocean itself and re-deposited on existing ice.

One of the principle reasons this strategy works is that ice is a quality thermal insulator, which can increase the speed of water freezing. In addition nucleation may also play a role in this ice formation enhancement where ice-forming nucleus tend to trigger freezing of under-cooled water droplets at higher temperatures when in solid contact versus liquid immersion.5-7 While the reason for this enhancement is unknown it is suspected that there are thermodynamically favorable interactions at the air-water interface8,9 leading to contact nucleation as a manifestation of an enhanced surface nucleation rate.5 Basically the liquid environment reduces the uniformity of the air-water interface reducing the efficiency of nucleation. Another important influencing factor may be that nucleation near the surface is greater because of a greater freedom of motion, thus the kinetic rate coefficient is larger at the surface than in the bulk (regardless of that bulk being solid or liquid); this change is important because the change in activation energy between phase changes is exponential.5 Overall the important point to take home is that water sprayed on to the surface of ice has a higher probability of freezing into new ice versus that water remaining adjacent or beneath the ice (all things being equal).

However, increasing ice formation will require managing the temperature increases that have lead to the reduced ice in the first place. There are two chief methods for addressing this temperature question. The first method is to take the water from the ocean and run it through a heat exchanger to remove a sufficient amount of heat to produce an appropriate freezing probability. The chief drawbacks to this method are the energy required to operate the heat exchanger and what to do with the heat absorbed from the water. The heat exchanger needs to be operated with an energy medium that has a very small carbon footprint otherwise the negative aspect of the added CO2 to the atmosphere through this method will more than likely exceed the benefits of adding more Arctic ice. In addition the heat removed from the water must be stored properly because if it is released to the environment it will either enter the atmosphere or the ocean, either result would largely mitigate any advantage to increasing Arctic ice.

The second method involves drawing ocean water not from the surface, but from deeper water near the bottom of the thermocline where the average temperature is much lower. The weakness of the first method is the reliance on the heat exchanger and its energy demands. Unfortunately while the second method eliminates the heat exchanger it cannot eliminate the need for additional energy usage because instead of using a heat exchanger a pump is required. The unknown question is which method will require more energy. Overall unless the first method is significantly more energy efficient, the second method should be favored because there is no excess heat to manage. While the power requirements for the pump and eventual energy consumption are easy to calculate experimentation will have to be conducted to identify the appropriate pumping rate, spray volume, and spray angle.

An important secondary question is what should be done about the salt in the supply water? One possibility would involve removing the salt because salt “decreases” the freezing point of water making it more difficult to form ice and could even result in ice sheet perforation. An alternative strategy would involve retaining the salt, which would strengthen down-welling currents when the ice melts. The best means to determine the best strategy would simply be to test this ice formation methodology and closely observe how the rate of secondary ice formation changes depending on the current temperature and time of year without any salt removal. If the formation rate is not sufficient then the salt will need to be removed.

If water cannot be used due to energy requirements the other major option for creating a change in the ocean surface albedo in an environmental neutral method is cover the water surface with bubbles. One of the chief advantages of this second option is that bubbles require little energy to create, thus the operational costs for such a system are low.10,11 Bubbles increase ocean surface albedo by increasing the reflective solar flux by providing voids that backscatter light.10 In addition modeling the reflective behavior of bubbles is similar to aerosol water drops because light backscattering is cross-sectional versus being mass or volume dependent and the spherical voids in the water column have the same refractive index characteristics.10 Note that ocean surface albedo varies with angle of solar incidence. Common values are less than 0.05 at 12:00, below 0.1 at 65 degrees solar zenith angle and a maximum albedo, which range from 0.2 to 0.5, at solar zenith angle 84 degrees.12-15 Based on this comparison information the principle formula governing brightening is:

DeltaF = DeltaA * Io * So * (1-Cf) * Tu * Td

where DeltaF = change in brightening; DeltaA = change in albedo on water surface; Io = solar irradiance; So = cosine of solar zenith angle; Cf = fraction of cloud cover; Tu = upwelling transmissive; Td = down-welling transmissive;10

Experiments have already demonstrated the creation of hydrosols from the expansion of air saturated water moving through vortex nozzles, which applies the appropriate level of shearing forces creating a swirling jet of water.11 Also by using an artificial two-phase flow smaller microbubbles can be created, which can even result in interfacial films through ambient fluid pressure reduction.12 Microbubbles can possibly form these films because they typically last longer than visible whitecap bubbles, which rise and bust in seconds. Note that whitecaps are froth created from breaking waves and can increase ocean albedo up to 0.22 from the common 0.05-0.1 values.16

While whitecaps from waves and wakes do provide increased surface albedo, the effect is ephemeral. Microbubble lifespan can be influenced by local surfactant concentration and fortunately the Arctic has limited natural surfactant concentration that would influence this lifespan, thus granting more control in the process of creating those bubbles (less outside factors that could unduly influence bubble lifespan). For example, if these bubbles are created through technological means additional elements can be added to the reactant water like a silane surfactant that could add hours to the natural lifespan.17 Bubble lifespan is probably the most important characteristic for this form of ocean albedo increase both from an economic and efficiency standpoint. However, while most surfactants and other agents like glycerin are typically not environmentally detrimental, the massive amounts required for increasing bubble longevity may make its use economically and environmentally unsustainable.

Another method for creating microbubbles comes from biomedical engineering where microfluidic procedures and sonication are used to enhance surfactant monolayers to stabilize microbubble formation.18 However, there are two common concerns about this method. First, it is used primarily in a laboratory largely for diagnostic and therapeutic applications, not in the field; therefore there may be questions about transition, especially for the dramatic increase in production scale that will be required for Arctic use. Second, while sonication increases stabilizing time, it limits control of microbubble size distribution, which could limit the total reflectiveness of the bubbles.19,20

An expanded and newer laboratory technique, electrohydrodynamic atomization, generates droplets of liquids and applies coaxial microbubbling to facilitate control over microbubble size. Unfortunately one concern with this technique is that as mentioned above ideal bubble size is in microns, but this technique is currently only able to create single digit millimeter sized bubbles.18 However, the increased size may be offset by the increased stability of the bubble (less overall reflection, but longer residence time). Comparison testing will be required to make the appropriate judgment.

The final method for increasing ice formation involves devising a piece of technology that can absorb excess heat from the Arctic Ocean. At first thought such an idea seems unlikely due to the size of the Arctic Ocean and its environmental inputs. However, it may not be as far-fetched as it seems. The key to making such a strategy viable is efficiency and scale within the utilized technology.

Scale is achieved through a design that is small enough that it can be produced at reasonable cost with a reasonable level of speed. Efficiency is typically achieved through producing a device that is self-cycling and thereby producing an autonomous operation. If human involvement is required beyond “pushing the start button” then efficiency is significantly compromised. Tie that efficiency loss in a single unit and multiply it by the units required for scale and the result can be devastating in both the terms of cost and viability.

If the objective is to withdraw heat from the ocean the most important element in the device is what agent will be utilized to accomplish this task. Ironically water is one of the best insulators of heat, which is why it is used for cooling purposes in power plants, thus removing heat could prove difficult. Fortunately there is promising research that supports the idea of incorporating zeolite as the heat absorbent material. Zeolite is a mineral make up of SiO2-, various AlO2 groups and alkali-ions and is capable of absorbing gaseous molecules including water due to its crystalline structure. When zeolite absorbs a gas it retains heat due to the absorption enthalpy.21 In addition because zeolite is commonly produced synthetically for use as molecular sieves and washing detergents it is cheap (50 – 75 cents /kg) and environmentally neutral.21

A good example of how zeolite is used in heat absorption is seen through their use in absorption refrigerators. Absorption refrigerators consist of two connected but independent vessels, the evaporator and absorber. The evaporator vessel acts as a quasi-vacuum containing only the vapor pressure of a liquid, which is usually water. When the valve connecting the two vessels is opened the water vapor moves into the absorption vessel and is absorbed by the zeolite reducing the vapor pressure. The loss of pressure causes a phase change as the water become liquid. Eventually the zeolite becomes saturated ceasing the heat transfer between the zeolite and the water. In the refrigerator model at a later time the zeolite is superheated condensing the absorbed water vapor and returning it to the evaporator vessel.

However, the secondary functionality of the above refrigerator design, zeolite recovery through heating, is not applicable in an oceanic environment. The water and resultant heat must be released from the zeolite so it can be reused, but this release will produce excess heat, which is similar to the problem of using a heat exchanger in the first strategy, there is no good place on the open ocean to store the heat without avoiding environmental release. One strategy to address this issue with a small movable device is when the zeolite becomes “full” the device can return, via a small battery powered motor, to a “mother” ship of sorts where the zeolite heat release process can be conducted. After restoring the zeolite to its rest state the device can return to the Arctic to withdraw more heat. After sufficient time the “mother” ship will be “full” of heat and would return to a land base, most likely Iceland due to its geothermal reserves as an energy source and well, to properly off-load the heat stores. Granted this method will place some limits on overall efficiency due to the trips between the Arctic and heat releasing stop over points, but necessary to manage the heat problem.

In the end the positive feedback associated with the warming-albedo reduction relationship is a legitimate threat to carbon mitigation and remediation strategies as a whole. Therefore, society needs to appreciate the time discrepancies associated with restoring colder temperatures to the Arctic Ocean in effort to preserve Arctic ice, especially during the summer. A technology-based solution will be required. Three possible strategies have been presented above in general detail to attempt to break this warming-albedo reduction relationship. One of the advantages of all of these strategies is that they can be experimentally explored with little overall detriment due to their ephemeral nature. Basically if the results are not similar to what is anticipated the experiments can be stopped with little environmental or economic damage. Overall something needs to be done about increased rate of warming in the Arctic and the dramatically increased rate of ice lost if global carbon mitigation strategies are going to be fully effective at reducing the detrimental effects of global warming.

Citations –

1. Perovich, D, and Richter-Menge, A. “Loss of sea ice in the Arctic.” Annu. Rev. Mar. Sci. 2009. 1:417–441.

2. Rothrock, D, Percival, D, and Wensnahan, M. “The decline in Arctic sea-ice thickness: Separating the spatial, annual, and interannual variability in a quarter century of submarine data.” J. Geophys. Res. 2008. 113:C05003.

3. Kwok, R. “Observational assessment of Arctic Ocean sea ice motion, export, and thickness in CMIP3 climate simulations.” J. Geophys. Res. 2011. 116:C00D05.

4. Bjork, G, Stranne, C, and Borenas, K. “The sensitivity of the Arctic Ocean sea ice thickness and its dependence on the surface albedo parameterization.” Journal of Climate. 2013. 26:1355-1370.

5. Shaw, R, Durant, A, and Mi, Y. “Heterogeneous surface crystallization observed in undercooled water.” Journal of Physical Chemistry B Letters. 2005. 109:9865-9868.

6. Vali, G. In Nucleation and Atmospheric Aerosols; Kulmala, M., Wagner, P., Eds.; Pergamon: New York, 1996.

7. Pruppacher, H, and Klett, J. Microphysics of Clouds and Precipitation, 2nd ed.; Kluwer Academic Pub.: Norwell, MA, 1997. Chapters 7 and 9.

8. Djikaev, Y, et Al. “Thermodynamic conditions for the surface-stimulated crystallization of atmospheric droplets.” J. Phys. Chem. A. 2002. 106:10247. doi:10.1021/jp021044s.

9. Tabazadeh, A, Djikaev, Y, and Reiss, H. “Surface crystallization of supercooled water in clouds.” PNAS. 2002. 99(25):15873-15878.

10. Seitz, F. “On the theory of the bubble chamber.” Physics of Fluids. 1958. 1: 2-10.

11. Seitz, F. “Bright Water: hydrosols, water conservation and climate change.” 2010.

12. Evans, J.R.G, et Al. “Can oceanic foams limit global warming?” Clim. Res. 2010. 42:155-160.

13. Davies, J. “Albedo measurements over sub-arctic surfaces.” McGill Sub-Arctic Res Pap. 1962. 13:61–68.

14. Jin, Z, et Al. “A parameterization of ocean surface albedo.” Geophys Res Letters. 2004. 31:L22301.

15. Payne, R. “Albedo of the sea surface.” J Atmos Sci. 1972. 29:959–970.

16. Moore, K, Voss, K, and Gordon, H. “Spectral reflectance of whitecaps: Their contribution to water-leaving radiance.” J. Geophys. Res. 2000. 105:6493-6499

17. Johnson, B, and Cooke, R. “Generation of Stabilized Microbubbles in Seawater.” Science. 1981. 213:209-211

18. Farook, U, Stride, E, and Edirisinghe, J. “Preparation of suspensions of phospholipid-coated microbubbles by coaxial electrohydrodynamic atomization.” J.R. Soc. Interface. 2009. 6:271-277.

19. Wang, W, Moser, C, and Weatley, M. “Langmuir trough study of surfactant mixtures used in the production of a new ultrasound contrast agent consisting of stabilized microbubbles.” J. Phys. Chem. 1996. 100:13815–13821.

20. Borden, M, et Al. “Surface phase behaviour and microstructure of lipid/PEG emulsifier monolayer-coated microbubbles.” Colloids Surf. B: Biointerfaces. 2004. 35:209–223.

21. Kreussler, S, and Bolz, D. “Experiments on solar adsorption refrigeration using zeolite and water.”

Methane, Siberia and Bubbles

One of the more dynamic issues regarding the progression of global warming and its ability to induce detrimental effects on society is the role of methane trapped in permafrost on land and methane hydrates in the ocean and their release into the atmosphere as surface and ocean temperatures increase. Methane garners such attention because some are concerned that once a significant and consistent amount of methane starts to discharge from natural sources a runaway effect will begin dramatically increasing the probability of detrimental environmental damage. Unfortunately the estimates surrounding this “tipping point” vary considerably with large uncertainty because no one actually understand how the environment will respond once these methane sources start emitting methane.

While surface permafrost trapped methane is important because the ocean is absorbing most of the initial additional heat created by the combustion of fossil fuels the near-term focus should be placed there. Due to millions of years of methane accumulation1-3 and sea level change during the last glacial maximum it is known that large amounts of methane are trapped in hydrates (a form of methane in a clathrate molecule containing water ice) on or beneath the sea floor; however, the actual amounts in both quantity and stability are unknown (methane estimates range from 700 to 10,000 Pg of C).1,4-6 The stability may be unknown, but more frequent plumbs of methane release, especially around the Eastern Siberian Arctic Shelf (ESAS) have begun to worry scientists.7,8 The excessive greenhouse potential of large scale methane release should be a concern, thus it is important to determine a counter-strategy to reducing the probability that significant “tipping point” amounts of methane are released from these hydrates.

Typical hydrate formation was driven by pressure as melting temperatures for given compounds increase with pressure. Most of the hydrates that formed over time did so at large ocean depths (a few hundred meters below the sea floor) due to this melting temperature change principle.1 The ocean water column also experiences a reduction in temperature with an increase in pressure. Therefore, most methane hydrates are “protected” by a double security blanket: the higher melting point and the cooler deep ocean temperatures that are further buffered by a sediment layer. There are two types of methane hydrates deposits: stratigraphic and structural with a majority of the formations being stratigraphic, which appear to contain less methane than structural.9

The ESAS is especially important in the issue of methane release because its hydrates are located in much shallower water (45-50 meters) than most others because instead of relying on pressure to induce temperature changes for formation, the ESAS, as well as some other parts of the Arctic, simply used existing lower temperatures as a driver for hydrate formation.1,8 Unfortunately now with the Earth influenced by global warming these shallower hydrates have a much higher probability of releasing methane over their deeper counterparts. Also while some climate scientists have shown concern about the land based permafrost in Siberia, the average temperature of the ESAS bottom seawater is 12 – 17 degree C warmer than the average surface temperature over land based permafrost8,10,11 making methane release from the ocean more probable than release from the land.

Of course methane release from the hydrates is only the first step for producing additional atmospheric methane and aggravating global warming. There are additional “safeguards” even after methane bubbles have formed from the hydrates. First, the production of bubbles associated with melting attempts to destabilize the sediment column, but fortunately the depth of sediment packing prevents such a catastrophic occurrence typically limiting rate of release.12 Second, because the sediment column does not collapse it acts as a physical barrier and typically remains cold enough that the methane bubbles migrating through it results in the dispersion of the bubble.1 Third, free flowing sulfate creates a chemical barrier that can oxidize the methane.1 Fourth, methanotrophic bacteria can react with the methane converting the methane to CO2 (clearly not an ideal situation).

Not surprisingly though these “safeguard” are not able to neutralize all of the released methane. The probability of successful migration is largely dependent on bubble volume as the larger bubbles can create a larger pressure differential between both the sediment and the water versus the bubble at the top and bottom of the bubble.1,8,9 Unfortunately this critical element of bubble volume is difficult to measure or model; this is one of the elements that make it difficult to accurately portray methane release.

Despite the lack of good information pertaining to creating accurate models of methane hydrate release, there is little uncertainty that continued warming of the ocean by releasing larger concentrations of CO2 and other greenhouse gases into the atmosphere will result in large amounts of methane release from methane hydrates. One of the trickier elements for this situation is that CO2 mitigation is a long-term solution, but not a short-term solution and methane release may be an all-term problem. The reason for this concern is that while reducing CO2 emissions will eventually result in a cooling atmosphere, oceanic release of heat through convection should proceed at a much slower pace maintaining the threat of methane release for a considerable period of time after CO2 mitigation is completed. Therefore, a strategy for mitigating this release probability beyond mitigation of CO2 emissions must be developed.

CO2 emission reduction is a longer-term strategy even if it rapidly occurs because of the physics of ocean heating and cooling. The surface layer of the ocean is warmed by sunlight penetration typically increasing the ocean surface temperature beyond the above atmosphere leading to heat loss. This rate of heat transfer is determined by the temperature gradient of “cool skin layer”, a thin viscous region of the ocean (0.1 to 1 mm thickness) that is in contact with the atmosphere.13,14 Due to the heat transfer between the atmosphere and the cool skin layer water molecules are forced together in a more organized formation limiting heat transfer to conduction only. When dealing with the thermodynamics of conduction temperature gradients are critical.

Addition of excess greenhouse gases to the atmosphere trap heat and redirect random percentages of the heat back to Earth including the ocean surface. This heat only penetrates the “cool skin layer” warming the top portion of the layer changing the temperature gradient.13,14 The change decreases the gradient between the atmosphere and the top portion of the “cool skin layer” and increases the gradient between the top portion and bottom portion of the “cool skin layer”. Due to these gradient changes heat will travel between the top portion and the bottom portion of the “cool skin layer” reducing the probability that heat is expelled back into the atmosphere. Thus the greenhouse gases have to be eliminated (through technological or natural processes) after mitigation to allow the ocean-atmosphere gradient to normalize for the ocean to start expelling heat into the atmosphere on a consistent basis.

There are two general short-term strategies for reducing the probability of methane release into the atmosphere: prevent the methane hydrate from melting in the first place or prevent the methane from reaching the surface and entering the atmosphere after melting. Despite potential protests from certain parties, the execution of these strategies will entail technological techniques that can be regarded as geoengineering. Two strategies come to mind when attempting to prevent the hydrates from melting: cloud thickening and increasing ocean surface albedo. One important aspect of strategy selection is to focus on locality to limit the costs and increase efficiency of the strategy. Such a consideration handicaps the injection of sulfuric aerosols into the atmosphere to promote cooling because over a significant period of time (multiple years) it is nearly impossible to maintain localization of these aerosols due to wind currents, thus the aforementioned two options become the most attractive.

Fortunately because the late fall, winter and early spring temperatures in the ESAS provide no threat to inducing methane hydrate melting any executed strategy would only need to be administered at most five months per year (early May to early October). The chief advantages of cloud thickening is its easy execution utilizing wind-propelled ships with reactants that are not environmentally detrimental and in very limited testing seems to reduce atmospheric temperatures. The chief disadvantage of cloud thickening is that it is a catalytic agent in that it only thickens existing clouds; it cannot create clouds in clear skies. Therefore, while this catalytic element is not a significant problem when considering cloud thickening for a global solar radiation management strategy, it could be significantly detrimental in its inconsistency for a local strategy.

Increasing ocean surface albedo is a little trickier because there are two chief possibilities: increase ice coverage and increase wake formation. Increasing ice coverage is almost a non-starter because it would involve fighting against decades of additional absorbed oceanic heat that has been reducing Arctic ice coverage including in the ESAS. Therefore, the increased albedo must come from something else. One possibility is increasing wake formation. While the process of creating a wake is theoretically simple, propeller generated vortices pressurize air creating submerged bubbles that rise to the surface,15,16 its overall reliability is questionable. For example to create the necessary speed to produce wake from ships would be counterproductive due to negative elements associated with the fueling components of those ships (relying on wind would not be appropriate).

Therefore, instead of directly applying a wake, one can indirectly create a wake through the production of a surface bubble layer. Bubbles require little energy to create, thus the operational costs for such a system are low.17,18 Bubbles increase ocean surface albedo by increasing the reflective solar flux by providing voids that backscatter light.17 In addition modeling the reflective behavior of bubbles is similar to aerosol water drops because light backscattering is cross-sectional versus mass or volume dependent and the spherical voids in the water column have the same refractive index characteristics. Note that ocean surface albedo varies with angle of solar incidence. Common values are less than 0.05 at 12:00, below 0.1 at 65 degrees solar zenith angle and a maximum albedo, which range from 0.2 to 0.5, at solar zenith angle 84 degrees.19-22

Experiments have already demonstrated the creation of hydrosols from the expansion of air saturated water moving through vortex nozzles, which applies the appropriate level of shearing forces creating a swirling jet of water.18 Also by using an artificial two-phase flow smaller microbubbles can be created to the point of even creating interfacial films through ambient fluid pressure reduction.19 Microbubbles can possibly form these films because they typically last longer than visible whitecap bubbles, which rise and bust in seconds. Note that whitecaps are froth created from breaking waves and can increase ocean albedo up to 0.22 from the common 0.05-0.1 values.23

While whitecaps from waves and wakes do provide increased surface albedo, the effect is ephemeral. Microbubble lifespan can be influenced by local surfactant concentration and fortunately the ESAS has limited surfactant concentration that would influence this lifespan, thus granting more control in the process of creating those bubbles (less outside factors that could unduly influence bubble lifespan). For example, if these bubbles are created through technological means additional elements can be added to the reactant water like a silane surfactant that could add hours to the natural lifespan.24 Bubble lifespan is probably the most important characteristic for this form of ocean albedo increase.

Another method for creating microbubbles comes from biomedical engineering or biology arena where microfluidic procedures and sonication are used to enhance surfactant monolayers to stabilize microbubble formation.25 However, there are two common concerns about this method. First, it is used primarily in a laboratory largely for diagnostic and therapeutic applications, not in the field; therefore there may be questions about transition. Second, while sonication increases stabilizing time, it limits control of microbubble size distribution, which limits the total reflectiveness of the bubbles.26,27

An expanded and newer laboratory technique, electrohydrodynamic atomization, generates droplets of liquids and applies coaxial microbubbling to facilitate control over microbubble size. Unfortunately one concern with this technique is that as mentioned above ideal bubble size is in microns, this technique is currently only able to create single digit millimeter sized bubbles.25 However, the increased size may be offset by the increased stability of the bubble (less overall reflection, but longer residence times). Comparison testing will be required to make the appropriate judgment.

Initially the idea of cloud brightening was dismissed above due to its catalytic ability versus an inherent driving reactant ability, but this dismissal was based on cloud brightening as a standalone application in the ESAS. However, cloud brightening could be a useful secondary component to a microbubble system. Another point of note is that over time microbubble surface application will result in hastened cooling of the ocean, especially the surface, which should increase CO2 retention capacity. Basically increasing ocean albedo should result in a very small localized increase in CO2 absorption increasing ocean acidity.

Most of the above discussion has centered on preventing the hydrates from thawing versus preventing the released methane from reaching the atmosphere. The reason for this focus is quite obvious; preventing thawing is easier than preventing released methane from reaching the atmosphere, especially in the oceanic environment itself. There are two main methane “removal” reactions utilized by nature and neither one is appealing for eliminating ocean born methane.

The first and principle method of elimination involves the reaction of methane with a free hydroxyl radical (OH-) in the troposphere or stratosphere creating water vapor and CH3- radical. This CH3- radical usually later reacts with another hydroxyl radical to form formaldehyde. While this reaction almost exclusively occurs in the upper atmosphere transferring it to the ocean in some form will not improve upon the situation. Methane can also react with natural chlorine gas to produce chloromethane and hydrochloric acid (free radical halogenation), but this is another atmospheric reaction that probably cannot be effectively transferred to an ocean medium.

The chief ocean methane reaction involves metabolization by microorganisms known as methanotrophs (or methanophiles). There are two major types of methanotrophs (ribulose monophosphate users and serine carbon assimilators) divided into numerous additional groups, which use two principle reactions with selectivity governed by the availability of oxygen.28 Note that methanotrophs are also located in soils and landfills and aerobic/anaerobic methanotrophs are of different families.28 Both the aerobic and anaerobic basic reactions are shown below (the reactions have numerous intermediates and their efficiency is largely based on what type of monooxygenases (MMO) enzyme is utilized):28,29

CH4 + 2O2 → 2H2O + CO2 (1)

CH4 + SO4(2-) → HCO3- + HS- + H2O (2)

The aerobic reaction is the principle reaction between the two, but has two drawbacks. First, the consumption of oxygen limits its ability to scale and address large amounts of methane release from melting hydrates due to the creation of oxygen limiting factor regions (a.k.a. dead zones). However, this magnitude of this drawback is limited in the ESAS because of the limited amount of life by scale. Second, the reaction produces CO2 as a product, which may be a net detriment overall because of the lifespan of CO2 and increasing ocean acidity. Unfortunately this drawback is not as limited as the first because ocean mixing will de-localize the increase in acidity. The scaling efficiency of the anaerobic reaction is the chief problem with its use because most of the oceanic available SO4 is located near the ocean floor, which limits its usefulness once the methane release concentration begins to increase significantly. Therefore, it does not appear that either relying on existing methanotrophic or other methane-oxidizing bacteria or attempting to increase their numbers will be an effective strategy for addressing methane hydrate melting.

There is a bit of question whether or not methane in the ESAS is a genuine threat. Air sampling surveys have revealed large variability in methane concentrations versus the standard global background concentration of 1.85 ppm with average increases of 5-10%. Some have also calculated a total methane flux from the ESAS of 10.64 million tons of methane per year.30 However, modeling studies suggest that permafrost lags behind changes in surface temperature, thus current outgassing is tied to long-lasting warming initiated by permafrost submergence approximately 8000 years ago versus recent Arctic warming.31 Such a conclusion is possible, but the rationality seems far-fetched due to the magnitude of the time lag.

Overall the threat of significant methane release in the ESAS is a legitimate one, but not one that demands immediate strategy implementation. While immediate strategy implementation is not required, strategies to address this melting possibility must be studied to ensure a solid and effective plan when the time for implementation comes, which appears to be soon. Currently local production of microbubbles by some form of floating device (a buoy for example) initially appears to be the best strategy for preventing methane release, but as mentioned future study must be conducted to ensure the validity of this promise.

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Works Cited

1. Archer, D, Buffett, B, and Brovkin, V. “Ocean methane hydrates as a slow tipping point in the global carbon cycle.” PNAS. 2009. 106(49): 20596-20601.

2. Davie, M, and Buffett, B. “Anumerical model for the formation of gas hydrate below the seafloor.” J Geophys Res. 2001. 106:497–514.

3. Dickens, G. “Natural Gas Hydrates: Occurance, Distribution and Detection”
(American Geophysical Union, Washington, DC). 2001. 124: 19–38.

4. Milkov, A. “Global estimates of hydrate-bound gas in marine sediments: How much is really out there?” Earth-Sci Rev. 2004. 66:183–197.

5. Dickens, G. “The potential volume of oceanic methane hydrates with variable external conditions.” Org Geochem. 2001. 32:1179–1193.

6. Holbrook, W, et Al. “Methane hydrate and free gas on the Blake Ridge from vertical seismic profiling. 1996. Science. 273:1840–1843.

7. Archer, D (2006): Destabilization of methane hydrates: a risk analysis. A Report Prepared for the German Advisory Council on Global Change (40pp). PDF

8. Shakhova, N, et Al. “Extensive methane venting to the atmosphere from sediments of the East Siberian Arctic Shelf.” Science. 2010. 327:1246-1250.

9. Milkov, A, and Sassen, R. “Economic geology of offshore gas hydrate accumulations and provinces.” Mar Petrol Geol. 2002. 19:1–11.

10. Romanovskii, N, et Al. “Offshore permafrost and gas hydrate stability zone on the shelf of the East Siberian Seas.” GeoMarine Letters. 2005. 25:167-182.

11. Flemings, B, Liu, X, and Winters, W. “Critical pressure and multiphase flow in Blake Ridge gas hydrates.” Geology. 2003. 31:1057–1060.

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Geoengineering Reality and Debate Misconceptions

One of the most obvious realities that environmentalists continue to deny is the near inevitability that the application of at least one type of geoengineering technique will be required to mitigate the worst consequences of global warming. The rationality behind this denial appears to derive from fear that the application of geoengineering technique x will fail and increase the damage to the environment beyond what global warming will do alone. On its face this fear is understandable, but its viability demands the critical assumption that society can effectively and rapidly reduce global CO2 emissions in the very near future. With CO2 emissions increasing last year to the highest levels in human industrialized history and with almost all top tier developing economies (China, India, Brazil, Russia and Mexico) experiencing positive growth in their emissions the probability of a massive global emission reduction is extremely unlikely. Even the great global recession of 2008 to 2010 only produced a 2.6% reduction in global CO2 emissions between 2007 and 2008, but despite lingering global economic “sluggishness” global CO2 emissions have increased by approximately 10.67% from 2007 to 2011 (most reliable data) because of the above developing nations.1 The fact that in May the global concentration of CO2 exceeded 400 ppm for the first time in thousands of years should further limit optimism. The graph below demonstrate that most of the highest emitters in the developing world are going the wrong direction in absolute emissions by either increasing those emissions or not reducing them (basically remaining stable even through the recession).

Three things to note for the above graph: first, the CO2 emission data was calculated from the US Department of Energy’s Carbon Dioxide Information Analysis Center (CDIAC) through either raw data collected from country agencies by the United Nations Statistics Division or calculated from emission per capita information and global census data. Second, CDIAC data and International Energy Agency (IEA) do have some differences due to the way the CO2 emission data is collected, thus the raw data is a little different, but both trend the same way at similar magnitudes.

Also both estimate methodologies typically only focus on emissions from fossil fuels and manufacturing processes (like cement), not from land use or forestry, etc., although this information is known to some extent. In addition recall that these values are only relevant for CO2 emissions, they are not CO2 equivalency figures, which would include other greenhouse gases like methane. Three, although the numbers for Brazil are more sporadic and lower than other countries, Brazil is still incredibly important to consider because it is the third-largest emitter of total greenhouse gases globally with a vast majority of those emissions derived from agriculture and forestry activities, most notably the destruction of rain forest to expand agricultural lands.2 Unfortunately after a brief period of reduced forest destruction the last few years have seen a significant increase in deforestation in Brazil.

Unfortunately in addition to their own personal denial, despite the above trends and data, some geoengineering opponents do not argue honestly when debating the virtues and vices of possible strategies. There are three common misconceptions that are utilized by these opponents to mar candid debate. The first misconception is when discussing solar radiation management (SRM) techniques opponents commonly use language that could insinuate that the cessation of the strategy, for whatever reason, will result in a greater than expected temperature increase versus if the technique was not used in the first place. While such a message may not be the intent of opponents the use of language requires specific word choice and with their selections opponents are either being unjustifiably lazy or are genuinely attempting to sabotage the debate.

For example common word use in describing the above problem is as followed: “if the SRM system fails then the Earth will warm even faster…” The actual meaning of this statement illustrated by the graph below; note that the actual numerical values in the graph are fictional and only the general trend in surface temperature change is important.

From the example graph for the first 10 years of the SRM deployment surface temperatures increased only 0.1 degrees whereas without SRM deployment surface temperatures increased 0.7 degrees. Once SRM deployment is stopped, for whatever reason, surface temperatures increase at a faster rate versus its rate of increase without SRM at all. However, there is no significant empirical or theoretical evidence to suggest that temperatures in the SRM scenario will increase to a higher maximum point than temperatures in the non-SRM scenario. This distinction is left somewhat ambiguous in the language used by geoengineering opponents. While the accelerated warming seen in the SRM scenario can be more detrimental to the environment than the gradual warming seen in the non-SRM scenario if the maximum temperature is inherently detrimental the rate of warming over that time period (15 years in this case) is irrelevant. Basically if plant/animal x cannot survive at the maximum temperature a non-consistent rate of increase does not matter because plant/animal x is going to die anyways. Finally this scenario of course assumes that the SRM technique fails in the first place.

The second misconception involves disparaging various geoengineering techniques because no single one solves all of the environmental problems created by global warming or human pollution in general. Therefore, because no geoengineering technique solves all of these problems no technique should be utilized at all. This foolish rationality is commonly demonstrated when opponents point out that SRM techniques will not have a direct rectification effect on ocean acidification. When there are multiple problems in a given scenario it is irrational to not administer a strategy that will potentially solve some of the problems solely because that strategy will not solve all of the problems, especially because in most situations a panacea solution does not exist. Even CO2 emission reduction may not be a panacea solution because of the rate in which reductions are required versus how fast these reductions will occur in reality in relation to positive environmental feedbacks.

The third misconception used by geoengineering opponents is that emission mitigation and geoengineering are mutually contradictory to the public in a way that pursuing one eliminates the desire or need to apply the other. In the recent past Joe Romm of the blog Climateprogress has seemed to push this mindset. Rational individuals realize that geoengineering is akin to a tourniquet; it is designed to ensure that the victim does not die from blood loss or infection due to a major wound until reaching an appropriate operating theater to properly repair the wound via surgery. The tourniquet is not designed as an alternative to surgery, thus it will not replace surgery similar to how geoengineering is not designed as a replacement for reducing CO2 emissions. However, when one receives a major wound not using a tourniquet is quite risky largely relying on dumb luck and positive circumstance to avoid heavy detrimental outcomes including death. Currently the Earth has a major wound and is bleeding profusely. Based on existing global emission rates it is difficult to envision a scenario where a “tourniquet” will not be required.

Some may argue that although China’s CO2 emissions increased between 2012 and 2013 the increase was very low (relatively speaking) and their government has acknowledged the severity of the pollution and emission situation thus reductions will occur in the near future. However, there are two problems with this attitude. First, it does not appreciate the fact that in the past China has produced questionable figures regarding their national carbon emissions undercutting certain values found in more provincial areas versus urban centers.3 This discrepancy in reporting makes it more difficult to trust figures produced by China, so even if it starts reporting carbon emission reductions will those reductions be genuine and how expansive will they actually be? Second, the above attitude does not consider that the scale difficulty in emission reduction is not linear. From arbitrary point x the first 30% is the easiest, the next 35% is rather difficult and the last 35% is incredibly hard based on existing technology and economic/resource availability; this exponential difficulty curve is even sharper for emitters as large as China and to a lesser extent the United States.

The attitude of quick emission reduction also rejects the reality that close to half (estimates vary widely) of the global population is still energy impoverished and despite the best hype (and in some cases outright lies) of its supporters, solar and wind are still more expensive energy options than natural gas and coal because necessary storage mediums and rare earth cost curves, among other things, are not included in cost evaluations; thus while global energy use has approximately doubled (largely thanks to China and India) between 2000 and 2010 (most recent figures) only 14% of that increase came from renewables and a majority of that was hydroelectric not solar or wind.4 So the amount of energy consumption that renewables have to replace has actually gotten worse since 2000 not better.

Unfortunately solar and wind supporters tend to get distracted by the high % increase values forgetting that those % increases are relative and their large values are due to low absolute energy origin points. They also confuse nameplate capacity with operational capacity where operational capacity is the actual amount of energy utilized by society and are commonly 20-30% of the nameplate capacity from wind and solar energy sources. In short those who believe that all society needs to do is rapidly deploy wind and solar infrastructure to solve global warming have not performed a complete and effective analysis of the global warming problem and are operating on flawed blind faith (such a solution could possibly work, but there is no solid theoretical evidence to suggest that it is the best solution or it would work while avoid large detrimental side outcomes).

It is interesting that geoengineering opponents have an incredible level of optimism regarding the ability of the global community to rapidly reduce CO2 emissions despite contrary evidence, yet have an incredible level of pessimism regarding the success probability of any geoengineering technique despite contrary evidence from nature itself that geoengineering can work successfully. The reality of the situation is that genuine scientifically controlled short-term geoengineering studies exploring various strategies need to be designed and applied to develop a better understanding of the potential outcomes beyond simple theory. For example the United Nations could spearhead a program to deposit a constant concentration of sulfur aerosols (typically sulfur dioxide) into the atmosphere over the period of six months and analyze atmospheric and surface changes during the experiment and for at least one year after its conclusion. Obviously due to wind currents it is irrational to hope for complete isolation, but the short time frame will limit unintended consequences from drift. Overall analyzing appropriate application methodologies for various geoengineering techniques is not defeatist, irrational, unnecessary or foolish, it is reasonable, intelligent, practical and a proper action by individuals who actually care about protecting the environment for future generations.

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Citations –

1. Drawn from C. emissions data pursuant to those years;

2. International Energy Agency. “CO2 Emissions from Fuel Combustion Highlights.” 2012.

3. Guan, D, et Al. “The gigatonne gap in China’s carbon dioxide inventories.” Nature Climate Change. 2012. 2:672-675.

4. Walsh, Bryan. “Nuclear Energy is Largely Safe. But can it be Cheap?” Time Magazine. July 8, 2013. http://science.time.com/2013/07/08/nuclear-energy-is-largely-safe-but-can-it-be-cheap/#ixzz2ZblqJrSH