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Daniel B.

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Re: Carbon Cycle
« Reply #450 on: October 26, 2017, 12:42:12 AM »
For example, I am very concerned about ocean acidification impacting phytoplankton in the oceans and the long term impact on organic carbon deposition and the resultant levels of atmospheric CO2 and oxygen.

https://pubs.geoscienceworld.org/geology/article-abstract/24/10/867/206380/carbon-isotopes-and-the-rise-of-atmospheric-oxygen?redirectedFrom=fulltext

We know, for example, that seasonal variations in northern hemisphere terrestrial plant activity and the resultant carbon uptake causes the seasonal variation in atmospheric CO2.

http://onlinelibrary.wiley.com/doi/10.1029/JD090iD06p10529/full

Doesn't this suggest that any negative impacts on plant activity caused by increasing CO2 levels (ocean acidification) can impact O2 levels as well? More simply, reduced carbon uptake necessarily means reduced oxygen production and atmospheric oxygen levels, doesn't it?

Since I am not a scientist, I do not know if my fear is warranted.

(Would love to have my concerns set aside by contributions here from people better informed than me.)

Oxygen levels would be a concern, if the atmospheric levels were on the same order as carbon dioxide, as one molecule of oxygen is consumed for every molecule of carbon dioxide generated.  However, the atmosphere consists of 21% oxygen, but only 0.04% carbon dioxide.  Recent, the carbon dioxide levels increased ~0.01%, which would mean a resulting drop of oxygen by a comparable amount.  This is a 35% increase for carbon dioxide, but a  0.5% drop in atmospheric oxygen - not a notable difference.  The increased plant growth that would occur under such a scenario would have a negligible impact on animal growth.

AbruptSLR

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Re: Carbon Cycle
« Reply #451 on: November 05, 2017, 10:23:45 AM »
Understanding the impacts of recent biotic disturbances on US forest carbon cycling is critical for developing a better understanding of how these biotic disturbances will intensify under continued global warming, and the linked reference provides this legwork:

M. Kautz, P. Anthoni, A. J. H. Meddens, T. A. M. Pugh & A. Arneth (3 November 2017), "Simulating the recent impacts of multiple biotic disturbances on forest carbon cycling across the United States", Global Change Biology, DOI: 10.1111/gcb.13974 

http://onlinelibrary.wiley.com/doi/10.1111/gcb.13974/abstract?utm_content=buffer0b718&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Abstract: "Biotic disturbances (BDs, e.g., insects, pathogens and wildlife herbivory) substantially affect boreal and temperate forest ecosystems globally. However, accurate impact assessments comprising larger spatial scales are lacking to date, although these are critically needed given the expected disturbance intensification under a warming climate. Hence, our quantitative knowledge on current and future BD impacts, e.g., on forest carbon (C) cycling, is strongly limited. We extended a Dynamic Global Vegetation Model to simulate ecosystem response to prescribed tree mortality and defoliation due to multiple biotic agents across United States forests during the period 1997-2015, and quantified the BD-induced vegetation C loss, i.e., C fluxes from live vegetation to dead organic matter pools. Annual disturbance fractions separated by BD type (tree mortality and defoliation) and agent (bark beetles, defoliator insects, other insects, pathogens, and other biotic agents) were calculated at 0.5° resolution from aerial-surveyed data and applied within the model. Simulated BD-induced C fluxes totaled 251.6 Mt C (annual mean: 13.2 Mt C yr−1, SD ±7.3 Mt C yr−1 between years) across the study domain, to which tree mortality contributed 95% and defoliation 5%. Among BD agents, bark beetles caused most C fluxes (61%), and total insect-induced C fluxes were about five times larger compared to non-insect agents, e.g., pathogens and wildlife. Our findings further demonstrate that BD-induced C cycle impacts (i) displayed high spatio-temporal variability, (ii) were dominated by different agents across BD types and regions, and (iii) were comparable in magnitude to fire-induced impacts. This study provides the first ecosystem model-based assessment of BD-induced impacts on forest C cycling at the continental scale and going beyond single agent-host systems, thus allowing for comparisons across regions, BD types and agents. Ultimately, a perspective on the potential and limitations of a more process-based incorporation of multiple BDs in ecosystem models is offered."
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jai mitchell

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Re: Carbon Cycle
« Reply #452 on: November 05, 2017, 06:44:15 PM »
This study appears to be limited to the United States.  Since the majority of the worlds forests are located in Canada and Siberia I wonder what the projection of total global forest impacts would be.
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sidd

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Re: Carbon Cycle
« Reply #453 on: November 07, 2017, 07:35:32 PM »
Comprehensive review of soil carbon stocks, taking into bedrock horizons, mineralization and food webs.

"The global SOC stock in the upper 2 m of soil is 2,273 Pg C, with the boreal forest biome containing 623 Pg, or 27% of the global total (Table 2). Peatlands contain 543 Pg SOC, most of it in boreal, temperate broadleaf and tropical, moist broadleaf forest biomes; permafrost regions contain 582 Pg SOC, or 26% of the global total (Table 2)."

They have limited data on the 2-3m carbon stock, but they attempt it:

"Thus, the global total soil carbon pool to a depth of 3 m is estimated as 2,800 Pg C. Deeper (>3 m) deposits include an additional ~300–500 Pg OC in the permafrost region (Schuur et al. 2015), ~30–50 Pg C in tropical peatlands, and an unknown quantity of OC in other environments with deep sediments such as deltas, floodplains, and loess deposits."

doi:10.1146/annurev-ecolsys-112414-054234

open access. Read all about it. I attach table 2.

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sidd

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Re: Carbon Cycle
« Reply #454 on: November 28, 2017, 10:15:06 PM »
I wasn't sure where to put this article reference, but it has relevance to the carbon cycle. Chalk et al. have a paper out arguing that the reason for the transition from 40Kyr to 100Kyr cycle was due to changing dust fertilization of southern oceans, and  find an increase in temperature sensitivity to CO2 across the transition.

"We argue that neither ice sheet dynamics nor CO 2 change in isolation can explain the MPT. Instead, we infer that the MPT was initiated by a change in ice sheet dynamics and that longer and deeper post-MPT ice ages were sustained by carbon cycle feedbacks related to dust fertilization of the Southern Ocean as a consequence of larger ice sheets. "

"The observed changes in the SL to ΔR CO2 relationships contain elements of both end member scenarios shown in Fig. 2 A and B, in which a greater slope is possibly related to changes internal to the ice sheets (scenario 1) and amplified glacial to interglacial CO 2 climate forcing is linked (this study) to increased glacial dustiness that causes enhanced Southern Ocean iron fertilization (scenario 2). Therefore, we propose a hybrid scenario (Fig. 2C) that incorporates both heightened ice sheet sensitivity to CO 2 forcing and dust-driven ocean sequestration of CO 2 to represent the observed climate system change across the MPT."

doi:10.1073/pnas.1702143114

open access, read all about it.

I attach fig 3.

sidd

AbruptSLR

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Re: Carbon Cycle
« Reply #455 on: December 01, 2017, 05:43:12 PM »
The linked reference indicates that current models of methane emissions from peatlands need to be improved to account for hotspots in the peat/soil with varying conditions (including varying ground water elevation):

Yang et al. (2017), "Evaluating the Classical Versus an Emerging Conceptual Model of Peatland Methane Dynamics", Global Biogeochemical Cycles, doi: 10.1002/2017GB005622

http://onlinelibrary.wiley.com/doi/10.1002/2017GB005622/abstract;jsessionid=120CA9C25B38DF660F8C127A470C3997.f02t01?systemMessage=Wiley+Online+Library+will+be+unavailable+on+2nd+Dec+2017+starting+from+0800+EST+%2F+1300+GMT+%2F+21.00+SGT+for+2.5+hours+due+to+urgent+server+maintenance.+Apologies+for+the+inconvenience.

See also:

Thompson, E. (2017), A new model yields a better picture of methane fluxes, Eos, 98, https://doi.org/10.1029/2017EO086831

https://eos.org/research-spotlights/a-new-model-yields-a-better-picture-of-methane-fluxes?utm_source=eos&utm_medium=email&utm_campaign=EosBuzz120117

Extract: "… generally speaking, methane is produced below the water table, where there is little to no oxygen, and it is destroyed above the water table, especially right at the boundary, where the most methane accumulates. When the water table is high, a greater proportion of the soil falls into methane-producing conditions. Likewise, when the water table drops, more soil is exposed to oxygen and thereby able to destroy methane. Current models commonly use this relationship to predict net methane production essentially on the basis of water table height.

Now Yang et al. suggest updating this classical conceptual model to include new information on methane dynamics gleaned from recent studies: For example, oxygen-poor pockets within the soil produce methane even above the water table, and methane can be destroyed below the water table in the absence of oxygen, depending on the presence of specific microbes and molecules in the soil that can play the role of oxygen to gain the electrons lost by methane."
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AbruptSLR

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Re: Carbon Cycle
« Reply #456 on: December 04, 2017, 08:47:24 PM »
The linked article documents how trees are the dominant source of methane emissions in the Amazon wetlands:

Title : "Trees are the dominant source of methane emissions in Amazon wetlands"

https://www.carbonbrief.org/guest-post-trees-are-the-dominant-source-of-methane-emissions-in-amazon-wetlands

Extract: " … trees needing to get oxygen down to their roots to keep them alive in an otherwise anaerobic soil. The methane produced in the soil is emitted in the opposite direction, out of the stems and into the atmosphere.

Scaling up our findings using maps of known floodplain extent, we estimate that wetland trees emit between 14m and 25m tonnes of methane each year.

This is similar in size to emissions from Arctic tundra, all the oceans combined or the total emission from wild animals and termites across the world combined.

Remarkably, we found that tree stems contributed around half of all methane emissions from the Amazon, which – when added to the emissions from other pathways – gave very close agreement with the top-down aircraft based emissions estimates."

See also:

Pangala, S. R. et al. (2017) Large emissions from floodplain trees close the Amazon methane budget, Nature, doi:10.1038/nature24639

http://www.nature.com/articles/nature24639
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TerryM

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Re: Carbon Cycle
« Reply #457 on: December 04, 2017, 09:21:58 PM »
Ouch!
I thought the Amazon was a carbon sink.
Terry

AbruptSLR

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Re: Carbon Cycle
« Reply #458 on: December 04, 2017, 10:20:00 PM »
Ouch!
I thought the Amazon was a carbon sink.
Terry

On the bright side, the methane emissions from these wetland tropical trees have been relatively constant for millennia, and who knows where deforestation (thus reducing the number of trees as methane sources) vs potential increased methane from more decaying submerged deadwood (due to deforestation), will result in an increase trend, or a decreasing trend, in methane emissions from the Amazon wetland trees (which currently do absorb a lot of CO2).
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Daniel B.

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Re: Carbon Cycle
« Reply #459 on: December 05, 2017, 03:48:49 AM »
Ouch!
I thought the Amazon was a carbon sink.
Terry

Fear not.  It still is.  "For the nations of the Amazon basin as a whole this means that since 1980 the carbon uptake has matched the entire combined emissions from deforestation and fossil fuels."

https://phys.org/news/2017-02-carbon-uptake-amazon-forests-region.html

gerontocrat

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Re: Carbon Cycle
« Reply #460 on: December 07, 2017, 04:25:21 PM »
Off topic but perhaps worth pointing out that atmospheric CO2 concentrations continue to rise at an unabated rate.
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AbruptSLR

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Re: Carbon Cycle
« Reply #461 on: January 24, 2018, 04:45:06 PM »
It looks like future methane emissions from shallow lakes in agricultural areas have likely been underestimated due to the synergy between nutrients (from the agriculture) and future warming:

Title: "Combined nutrients and warming massively increase methane emissions from lakes"

https://phys.org/news/2018-01-combined-nutrients-massively-methane-emissions.html

Extract: "Shallow lakes in agricultural landscapes will emit significantly greater amounts of methane, mostly in the form of bubbles (ebullition) in a warmer world, which is a potential positive feedback mechanism to climate warming.

The present study used the longest-running freshwater mesocosm climate change experiment in the world to investigate how warming and eutrophication might interact to change methane ebullition in the future.
The results here were striking as they showed that the combination of increased nutrient loading and warming had a synergistic effect on the ebullition of methane. In the absence of nutrient enrichment, warming alone increased annual methane ebullition by around 50 percent and its relative contribution to total methane emission rose from about 50 percent to 75 percent.
In stark contrast, when nutrient levels were high, warming increased total methane emission by at least six-fold, and in some cases, 17-fold, and the proportion of ebullition increased to 95 percent of total annual methane flux."

See also:

Thomas A. Davidson et al, Synergy between nutrients and warming enhances methane ebullition from experimental lakes, Nature Climate Change (2018). DOI: 10.1038/s41558-017-0063-z
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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wolfpack513

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Re: Carbon Cycle
« Reply #462 on: February 03, 2018, 11:23:48 PM »
Correcting for ENSO and natural variability, CO2 concentration is still accelerating.  2017’s growth was lower than 2016 and 2015 but that was clearly Niño related.  Just like 1999 wasn’t the beginning of deacceleration after the 1997-1998 super Niño. 


Thomas Barlow

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Re: Carbon Cycle
« Reply #463 on: February 09, 2018, 01:02:16 AM »
Don't know where to post this, but how much CO2 did Elon Musk put into the atmosphere yesterday?
Edited - May have got my maths wrong.
This person in the link below says it is more than an average diesel car would produce driving one million miles.
330,000kg of CO2 in 2.5 minutes. Still staggering to me. And the Falcon Heavy that just went up is much bigger than the SpaceX rocket used for the calculations this post below, so I'm going to say more like 500 metric tonnes for this newest rocket.

Does this sound right?
https://www.quora.com/What-is-the-carbon-footprint-of-a-SpaceX-rocket
« Last Edit: February 10, 2018, 12:30:56 AM by Thomas Barlow »

SteveMDFP

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Re: Carbon Cycle
« Reply #464 on: February 09, 2018, 04:33:12 PM »
Don't know where to post this, but how much CO2 did Elon Musk put into the atmosphere yesterday?
This person in the link below says it is more than an average diesel car would produce driving one million miles. (330,000kg)
Considering the annual global human emissions are about 36 billion metric tonnes, that would be about 200 metric tonnes per 5 minutes. In 5 minutes, Elon Musk put about 400 metric tonnes into the atmosphere (and his rocket that was supposed to land ... crashed into the ocean at 300mph. Twice the GLOBAL emissions for a 5 minute timeframe. Staggering to me.

Does this sound right?
https://www.quora.com/What-is-the-carbon-footprint-of-a-SpaceX-rocket

This is where I think Musk's vision of establishing humanity as a multi-planet species might be counterproductive.
Until off-world colonies become fully self-sufficient, the carbon footprint of a single human being living off-world will be ENORMOUS.  Food, water, medical care, manufactured goods, electronics, shelter.  Almost all of this will need to be shipped from earth's surface for a long time.

I can imagine a way that the endeavor might be done in a way that won't devastate Earth, but it will take a lot more time.  What I think is needed is to send a number of AI-controlled autonomous robots.  They need to do mining and manufacturing to build more of themselves.  Building electronic chip factories off-world will ultimately be needed.  They'll need to build the habitat and start farming some foodstuffs. 

When development reaches the point where humans merely need to be delivered to a home-like (mostly subterranean) environment, then we could maybe tolerate the ecologic footprint to start sending some humans.  Decades, for sure.  Maybe a century or two.

But regardless of how well and efficiently that might be accomplished, I'd think establishing a secure, sustainable habitat on earth would *always* be far less expensive.  Even one built to withstand nuclear fallout, high CO2 levels, hydrogen sulfide in the atmosphere, zero land or sea agriculture, whatever--would be far cheaper.  An inhospitable Earth environment is always going to be more amenable to human engineering than the Moon or Mars.

TerryM

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Re: Carbon Cycle
« Reply #465 on: February 09, 2018, 08:18:43 PM »
Don't know where to post this, but how much CO2 did Elon Musk put into the atmosphere yesterday?
This person in the link below says it is more than an average diesel car would produce driving one million miles. (330,000kg)
Considering the annual global human emissions are about 36 billion metric tonnes, that would be about 200 metric tonnes per 5 minutes. In 5 minutes, Elon Musk put about 400 metric tonnes into the atmosphere (and his rocket that was supposed to land ... crashed into the ocean at 300mph. Twice the GLOBAL emissions for a 5 minute timeframe. Staggering to me.

Does this sound right?
https://www.quora.com/What-is-the-carbon-footprint-of-a-SpaceX-rocket

This is where I think Musk's vision of establishing humanity as a multi-planet species might be counterproductive.
Until off-world colonies become fully self-sufficient, the carbon footprint of a single human being living off-world will be ENORMOUS.  Food, water, medical care, manufactured goods, electronics, shelter.  Almost all of this will need to be shipped from earth's surface for a long time.

I can imagine a way that the endeavor might be done in a way that won't devastate Earth, but it will take a lot more time.  What I think is needed is to send a number of AI-controlled autonomous robots.  They need to do mining and manufacturing to build more of themselves.  Building electronic chip factories off-world will ultimately be needed.  They'll need to build the habitat and start farming some foodstuffs. 

When development reaches the point where humans merely need to be delivered to a home-like (mostly subterranean) environment, then we could maybe tolerate the ecologic footprint to start sending some humans.  Decades, for sure.  Maybe a century or two.

But regardless of how well and efficiently that might be accomplished, I'd think establishing a secure, sustainable habitat on earth would *always* be far less expensive.  Even one built to withstand nuclear fallout, high CO2 levels, hydrogen sulfide in the atmosphere, zero land or sea agriculture, whatever--would be far cheaper.  An inhospitable Earth environment is always going to be more amenable to human engineering than the Moon or Mars.


I'm not sure that we have "a lot more time."


Anything that distracts us from finding peaceful solutions to our political spats, solutions to the pollution of land, water and the air we breathe, the political will to close down everything that spews GHGs into our atmosphere, and a way to feed the additional billions that we're breeding is not something that should be celebrated.


I don't think our culture survives, but I hope that I'm wrong.
Terry

Thomas Barlow

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Re: Carbon Cycle
« Reply #466 on: February 10, 2018, 12:20:59 AM »
I think I got my maths wrong, so it's not as drastic as I thought (but it is close to 500 metric tonnes in 2.5 minutes), but Elon Musk wants to go to Mars and create a space colony of a million people there, as a sort-of 'back-up' for the human race, like backing up computer files. Not a bad idea.
But how many of those rockets will it take to put a million people up there in time?
I guess we are up against impossible odds in all directions with this current political intransigence worldwide.
« Last Edit: February 10, 2018, 12:31:56 AM by Thomas Barlow »

Shared Humanity

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Re: Carbon Cycle
« Reply #467 on: February 10, 2018, 06:26:00 PM »
Humanity's fate is inextricably linked to the fate of this planet. Musk and his ilk are a distraction from the task at hand.

gerontocrat

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Re: Carbon Cycle
« Reply #468 on: February 10, 2018, 07:52:37 PM »
Forget Musk, we are talking small beer about Falcon Heavy compared with :-

https://www.bloomberg.com/news/articles/2018-02-09/co2-emissions-seen-on-the-rise-this-year

A strong economy and low gasoline prices can be a bad combination for planet Earth. U.S. carbon-dioxide emissions from power plants, vehicles and other sources are forecast to rise for the first time this year since 2014, according to the U.S. Energy Information Administration. The 1.8 percent uptick comes even as cleaner-burning natural gas and renewable energy replaces coal-fired power plants. “When the economy is doing well, energy demand is doing well,” Rhodium Group director John Larsen said in an interview Friday.

This is after:

https://www.carbonbrief.org/analysis-global-co2-emissions-set-to-rise-2-percent-in-2017-following-three-year-plateau

Over the past three years, global CO2 emissions from fossil fuels have remained relatively flat. However, early estimates from the Global Carbon Project (GCP) using preliminary data suggest that this is likely to change in 2017 with global emissions set to grow by around 2%, albeit with some uncertainties.

Renewables and less coal haven't started to reduce emissions yet (plus expected world economic growth in 2018 at 3.9%)
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Bruce Steele

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Re: Carbon Cycle
« Reply #469 on: February 13, 2018, 08:28:43 PM »
Meridional overturning circulation conveys fast acidification to the deep Atlantic Ocean
Published 13 February 2018   
Since the Industrial Revolution, the North Atlantic Ocean has been accumulating anthropogenic carbon dioxide (CO2) and experiencing ocean acidification1, that is, an increase in the concentration of hydrogen ions (a reduction in pH) and a reduction in the concentration of carbonate ions. The latter causes the ‘aragonite saturation horizon’—below which waters are undersaturated with respect to a particular calcium carbonate, aragonite—to move to shallower depths (to shoal), exposing corals to corrosive waters2,3. Here we use a database analysis to show that the present rate of supply of acidified waters to the deep Atlantic could cause the aragonite saturation horizon to shoal by 1,000–1,700 metres in the subpolar North Atlantic within the next three decades. We find that, during 1991–2016, a decrease in the concentration of carbonate ions in the Irminger Sea caused the aragonite saturation horizon to shoal by about 10–15 metres per year, and the volume of aragonite-saturated waters to reduce concomitantly. Our determination of the transport of the excess of carbonate over aragonite saturation (xc[CO32−])—an indicator of the availability of aragonite to organisms—by the Atlantic meridional overturning circulation shows that the present-day transport of carbonate ions towards the deep ocean is about 44 per cent lower than it was in preindustrial times. We infer that a doubling of atmospheric anthropogenic CO2 levels—which could occur within three decades according to a ‘business-as-usual scenario’ for climate change4—could reduce the transport of xc[CO32−] by 64–79 per cent of that in preindustrial times, which could severely endanger cold-water coral habitats. The Atlantic meridional overturning circulation would also export this acidified deep water southwards, spreading corrosive waters to the world ocean.

 


Perez F. F., Fontela M., García-Ibáñez M. I., Mercier H., Velo A., Lherminier P., Zunino P., de la Paz M., Alonso-Pérez F., Guallart E. F. & Padin X. A., in press. Meridional overturning circulation conveys fast acidification to the deep Atlantic Ocean. Nature.

As the saturation horizon rises so too the long term sink for carbonates is reduced in size. For the short time spans we humans tend to worry about this may not seem catastrophic but it is a a problem that earth will have to deal with for ~ 100,000 years after we finally quit emitting CO2.  The calcium carbonate that would otherwise settle onto the shelves will instead desolve and reenter the oceans as DIC . The DIC will circulate and eventually upwell where it can again enter the atmospheric carbon pool. Our legacy is a very long term truncation of the ability of the oceans to sink carbon. Sad that, a legacy of death.
Bruce
« Last Edit: February 13, 2018, 08:34:46 PM by Bruce Steele »

TerryM

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Re: Carbon Cycle
« Reply #470 on: February 13, 2018, 09:04:50 PM »
DIC=Dissolved Inorganic Carbon


Is this shoaling simply a case of the deeper regions becoming saturated and filling up? or is there some other mechanism at work here?
Terry

Bruce Steele

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Re: Carbon Cycle
« Reply #471 on: February 13, 2018, 10:00:11 PM »
Terry, The shallow oceans are saturated and the deep oceans are undersaturated. As the ocean up takes CO2 it is transformed into carbonic acid. Carbonic acid then combines with seawater to form carbonate,  bi-carbonate and a hydrogen ion. The hydrogen ions that are released are measured as a decrease in pH. Downwelling takes this low pH water to depth along with organic matter and calcium carbonate from phytoplankton . The organic matter is bacterially reduced and releases bound CO2 where it meets the saturation horizon because it doesn't sink after the calcium carbonate dissolves .
 In short the surface supplied CO2 and organic matter is carried to depth where it increases hydrogen ions and reduces pH . This it somewhat complicated because as the calcium carbonate dissolves it reabsorbs some of the hydrogen ions.  There is however a net increase in deep ocean pooled hydrogen ions . As this proceeds the saturation horizon gets closer to the surface.
 In the area of the ocean above the saturation calcium carbonate builds up on the sea floor. This pool of carbon is very long lived and eventually is moved tectonically onto the continents as limestone , or other mineral forms. Thus the oceans are responsible for carbon sinks that can hold carbon for millions of years. As the saturation horizon moves closer to the surface there is less and less ocean bottom where calcium carbonate can build up.
 
« Last Edit: February 13, 2018, 11:09:54 PM by Bruce Steele »