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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.

sidd

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.

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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
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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

Quote
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

Quote
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 »

gerontocrat

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Re: Carbon Cycle
« Reply #472 on: March 15, 2018, 12:41:37 PM »
CO2, ph in the ocean and coral reefs.

http://www.bbc.co.uk/news/science-environment-43391388

Rising carbon dioxide levels impair coral growth
By Mary Halton
Science reporter, BBC News
Quote

Coral reefs are under threat if atmospheric carbon dioxide levels continue to rise, new research has shown. When CO2 dissolves in the ocean, it raises the water's acidity level. This prevents a build up of calcium carbonate, which corals draw from seawater to build their skeleton.

The study, published today in Nature, was conducted on the Great Barrier Reef in Australia.

Coral neighbourhoods
Previous lab-based studies have focused on how particular organisms are impacted by ocean acidification.

"But when we try to scale that to understanding how individual ecosystems respond, it would be comparable to looking at a single tree and saying that's how a rainforest would respond," said Dr Rebecca Albright from the California Academy of Sciences, lead author on the study.

Dr Albright and her team worked on One Tree Island, off the coast of Queensland. The system of lagoons on the site have a very particular structure, which means that water flows in one direction across the reef flat for 60 minutes just after low tide each day. This allowed the scientists to introduce CO2-saturated water to the lagoon and observe its impact.

The study was conducted across 30 days in 2016 and showed drop of about a third in calcification - the amount of calcium carbonate sucked out of the water by coral.

This reduction doesn't lead directly to coral death in the way that bleaching does, explained Dr Albright. But it does impair the coral's growth, and ability to repair and reproduce. In the wake of bleaching events, which are caused by increased temperatures, corals will be less able to recover if the ocean's pH continues to drop. The team replicated the ocean acidity levels that are likely to be present by the middle of this century.

Pre-industrial-era oceans had a pH of 8.2. Current measurements at the site are 8.1, and the acidified water introduced for the study had a value of approximately 8.0, marking a significant impact on the ecosystem from a relatively minor change.



https://www.nature.com/articles/nature25968.epdf?referrer_access_token=RC1nRBHSjKaPC9FCqV1NntRgN0jAjWel9jnR3ZoTv0O4KHHBNa_fHAekziAr_qaA8pCZ-QBK2cMad1beRwSoIEik0A7DWv9aNFqD3VwxX9y7AD5SI_GgTwMwHTBjtYbhcNrd9g3uOx0mdgY1rpJOZmbtGL80S9OD7WzlqWcwsMqm3XQP_EUo-S8bw_fF9-kTG4FKBG8ll4Zfy8B0bgjFSq2d3Ubyn4gh0bW7haBvdh0%3D&tracking_referrer=www.bbc.co.uk
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Bruce Steele

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Re: Carbon Cycle
« Reply #473 on: April 04, 2018, 06:50:21 PM »
We can add diatoms to the list of phytoplankton that are negatively affected by ocean acidification. Although they build their shell with silica they need carbonates in seawater to utililize iron . Low levels of  Iron in seawater can restrict bio productivity . With available carbonates to drop 50% by 2100
Coccolithophores, foraminifera, pteropods  AND diatoms will all be negatively affected. What ever hit to the ocean carbon sink resulting will last ~ 100,000 years. That's the part that troubles me most. Ocean acidification caused by a three century energy spree by humans will have repercussions for all life for 
A very long time.

  https://www.newark.rutgers.edu/news/health-crucial-plants-base-marine-food-chains-disrupted-ocean-acidification

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Re: Carbon Cycle
« Reply #474 on: April 14, 2018, 02:27:55 AM »
Here is a nice overview of how phytoplankton are expected to react to warming and acidification. This review anticipates diatoms to be benifited by future conditions but the paper I linked up thread questions how diatoms will fare. Because there are both species that benefit or are negatively affected
making projections about the health of the future ocean carbon sinks isn't attempted.

http://www.mdpi.com/2071-1050/10/3/869/htm

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Re: Carbon Cycle
« Reply #475 on: May 30, 2018, 04:31:36 AM »
Well, here's yet another carbon feedback that I didn't know about and never would have imagined...I wonder how many more of these there are in the 'wings'?

Some thing new in the ocean uptake of co2 and as with a lot of research these days (it seems) it’s not good.
Invisible scum on sea cuts CO2 exchange with air ‘by up to 50%. from the Guardian

https://www.theguardian.com/environment/2018/may/28/invisible-scum-on-sea-cuts-co2-exchange-with-air-by-up-to-50

“The world’s oceans absorb around a quarter of all man-made carbon dioxide emissions, making them the largest long-term sink of carbon on Earth.

Greater sea turbulence increases gas exchange between the atmosphere and oceans and until now it was difficult to calculate the effect of “biological surfactants”.

Teams from the Natural Environment Research Council, the Leverhulme Trust and the European Space Agency developed a system that compares “the surfactant effect” between different seawaters in real time.

They found surfactants can reduce carbon dioxide exchange by up to 50%.

Dr Ryan Pereira, a Lyell research fellow at Heriot-Watt University in Edinburgh, said: “As surface temperatures rise, so too do surfactants, which is why this is such a critical finding.

“The warmer the ocean surface gets, the more surfactants we can expect, and an even greater reduction in gas exchange”

the paper from Nature can be found here
https://www.nature.com/articles/s41561-018-0136-2
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Re: Carbon Cycle
« Reply #476 on: May 30, 2018, 06:41:45 AM »
Heat slows down the forward reaction from CO2 (gas) <-> CO2 (aqueous), and it sounds like these surfactants add another layer of buffering. So while it would keep more CO2 in the atmosphere it would slow down the rate of ocean acidification. Win some, lose some.

I was also under the impression that a significant slowdown of the thermohaline circulation would result in less deepwater upwelling which would dampen this effect, but the authors indicate that this effect should increase as warming increases. Looks like paywalled and I don't see the paper on scihub yet so not sure how they came to this conclusion.
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Re: Carbon Cycle
« Reply #477 on: June 19, 2018, 10:34:52 PM »
Apparently carbon uptake by land an ocean has been significantly misunderstood: Resplandy et al. find a coupling between heat and carbon transport and use the relation to show that

"This heat-based constraint requires a 20–100% stronger ocean and river carbon transport from the Northern Hemisphere to the Southern Hemisphere than existing estimates, and supports an upward revision of the global riverine carbon flux from 0.45 to 0.78 PgC/yr . These systematic biases in existing ocean/river carbon fluxes redistribute up to 40% of the carbon sink between northern, tropical and southern land ecosystems. As a consequence, the magnitude of both the southern land source and the northern land sink may have to be substantially reduced."


doi: 10.1038/s41561-018-0151-3

https://phys.org/news/2018-06-ocean-atmospheric-carbon.html

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Re: Carbon Cycle
« Reply #478 on: June 25, 2018, 02:33:47 PM »
I'm trying to find out the extra heating that comes adding an extra tonne of CO2 (& CH4) to the atmosphere. 

I think I'd like the answer in joules/sec, with perhaps the immediate change and some sense of the decay function. (CO2 - not much decay? CH4 - almost disappearing after a decade or so?)

Anyone know of an easily accessible source?

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Re: Carbon Cycle
« Reply #479 on: June 27, 2018, 01:20:35 PM »
Not sure where to post this, but this surely has an impact on the global carbon cycle:

http://www.wri.org/blog/2018/06/2017-was-second-worst-year-record-tropical-tree-cover-loss

2017 Was the Second-Worst Year on Record for Tropical Tree Cover Loss
         
Last year was the second-worst on record for tropical tree cover loss, according to new data from the University of Maryland, released today on Global Forest Watch. In total, the tropics experienced 15.8 million hectares (39.0 million acres) of tree cover loss in 2017, an area the size of Bangladesh. That’s the equivalent of losing 40 football fields of trees every minute for an entire year.

Despite concerted efforts to reduce tropical deforestation, tree cover loss has been rising steadily in the tropics over the past 17 years. Natural disasters like fires and tropical storms are playing an increasing role, especially as climate change makes them more frequent and severe.  But clearing of forests for agriculture and other uses continues to drive large-scale deforestation.

gerontocrat

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Re: Carbon Cycle
« Reply #480 on: June 27, 2018, 10:18:04 PM »
Not sure where to post this, but this surely has an impact on the global carbon cycle:

http://www.wri.org/blog/2018/06/2017-was-second-worst-year-record-tropical-tree-cover-loss

2017 Was the Second-Worst Year on Record for Tropical Tree Cover Loss
         
Last year was the second-worst on record for tropical tree cover loss, according to new data from the University of Maryland, released today on Global Forest Watch. In total, the tropics experienced 15.8 million hectares (39.0 million acres) of tree cover loss in 2017, an area the size of Bangladesh. That’s the equivalent of losing 40 football fields of trees every minute for an entire year.

Despite concerted efforts to reduce tropical deforestation, tree cover loss has been rising steadily in the tropics over the past 17 years. Natural disasters like fires and tropical storms are playing an increasing role, especially as climate change makes them more frequent and severe.  But clearing of forests for agriculture and other uses continues to drive large-scale deforestation.

I posted it on the Global Forest Watch thread.

The effect on the carbon cycle is both immediate and long-term.

Much of the cleared forest is simply burnt as part of land clearance for agriculture (annual crops, grazing, and plantations). Immediate CO2 emissions.

The crops, grazing and plantations are a feeble shadow of the carbon sink of the wild forest they replace. I wonder how many gigawatts of new renewable energy installations simply mitigate the loss to the Forest CO2 sink.
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Re: Carbon Cycle
« Reply #481 on: June 28, 2018, 08:03:14 AM »
Let's hope those flying environmentalist globetrotters out there will compensate by planting even more trees.

Joking aside, planting trees to compensate for flying is delusional.
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Re: Carbon Cycle
« Reply #482 on: June 28, 2018, 12:41:12 PM »
Let's hope those flying environmentalist globetrotters out there will compensate by planting even more trees.

Joking aside, planting trees to compensate for flying is delusional.

YES, that's what i think each time they gather in masses in nice sunny places while tech allows for solutions with a much smaller footprint

jai mitchell

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Re: Carbon Cycle
« Reply #483 on: June 30, 2018, 04:22:59 PM »
I'm trying to find out the extra heating that comes adding an extra tonne of CO2 (& CH4) to the atmosphere. 

I think I'd like the answer in joules/sec, with perhaps the immediate change and some sense of the decay function. (CO2 - not much decay? CH4 - almost disappearing after a decade or so?)

Anyone know of an easily accessible source?

I have seen a quote by Dr. Ken Caldiera that said the amount of heat applied to the earth from a single CO2 molecule was 10,000 times the heat energy that was released producing the molecule by combustion.  This was measured over a time period of thousands of years (I think)
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Re: Carbon Cycle
« Reply #484 on: June 30, 2018, 05:58:25 PM »
Interesting question & a good memory (i think i would drop the last 0 over time too because 10k is already so bad).

They found that the carbon dioxide-caused warming exceeds the amount of heat released by a lump of coal in just 34 days. The same phenomenon is observed in 45 days for an isolated incident of oil combustion, and in 59 days for a single instance of burning natural gas.

“Ultimately, the warming induced by carbon dioxide over the many thousands of years it remains in the atmosphere would exceed the warming from combustion by a factor of 100,000 or more,” Caldeira said.

and more on:
https://carnegiescience.edu/news/greenhouse-gas-caused-warming-felt-just-months

http://iopscience.iop.org/article/10.1088/1748-9326/9/12/124002

also see:
http://4hiroshimas.com/#Science

Several Skeptical Science contributors worked together to publish a scientific paper1 which combined the land, air, ice, and ocean warming data. It found that for recent decades the earth has been heating at a rate of 250 trillion Joules per second.
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Re: Carbon Cycle
« Reply #485 on: August 16, 2018, 09:32:42 PM »
https://phys.org/news/2018-08-abrupt-permafrost-beneath-lakes-significantly.html

'Abrupt thaw' of permafrost beneath lakes could significantly affect climate change models
August 16, 2018 by Jeff Richardson, University of Alaska Fairbanks

Quote
they determined the "abrupt thaw" beneath such lakes is likely to release large amounts of permafrost carbon into the atmosphere this century. The lake activity could potentially double the release from terrestrial landscapes by the 2050s.
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Re: Carbon Cycle
« Reply #486 on: August 26, 2018, 09:13:04 PM »
Subtropical forests with older trees and higher number of tree species seem to accelerate the carbone cycle and store significantly more carbon according to a new long term research in several forest compartiments in China:

"Tree specie richness increases ecosystem carbon storage in subtropical forests"
Xiaojuan Liu et al, August 22, 2018, Proceedings of the Royal Society B

http://rspb.royalsocietypublishing.org/content/285/1885/20181240

"Abstract
Forest ecosystems are an integral component of the global carbon cycle as they take up and release large amounts of C over short time periods (C flux) or accumulate it over longer time periods (C stock). However, there remains uncertainty about whether and in which direction C fluxes and in particular C stocks may differ between forests of high versus low species richness. Based on a comprehensive dataset derived from field-based measurements, we tested the effect of species richness (3–20 tree species) and stand age (22–116 years) on six compartments of above- and below-ground C stocks and four components of C fluxes in subtropical forests in southeast China. Across forest stands, total C stock was 149 ± 12 Mg ha−1 with richness explaining 28.5% and age explaining 29.4% of variation in this measure. Species-rich stands had higher C stocks and fluxes than stands with low richness; and, in addition, old stands had higher C stocks than young ones. Overall, for each additional tree species, the total C stock increased by 6.4%. Our results provide comprehensive evidence for diversity-mediated above- and below-ground C sequestration in species-rich subtropical forests in southeast China. Therefore, afforestation policies in this region and elsewhere should consider a change from the current focus on monocultures to multi-species plantations to increase C fixation and thus slow increasing atmospheric CO2 concentrations and global warming."

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Re: Carbon Cycle
« Reply #487 on: September 10, 2018, 06:34:22 PM »
Royal Society.  Open access
 Title.   Placing our current" hyperthermal " in the context of rapid climate change in our geological past
 Foster, Hull, Lunt, & Zachos
 Sept 2018

http://rsta.royalsocietypublishing.org/content/376/2130/20170086

Putting our hyperthermal in context of past events. A warning in the final sentences that biological impacts may exceed  any caused by climate change over the last 56 million years. But that assumes we continue our emissions to consume most fossil fuel reserves.

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Re: Carbon Cycle
« Reply #488 on: November 09, 2018, 08:49:10 PM »
Biogeosciences open access 
https://www.biogeosciences.net/15/6649/2018/

A mesocosm study that shows DMS reductions of 28% at atmospheric CO2 1000ppm compared to
400ppm .

"Over a period of 5 weeks, P. tricornuntum outcompeted T. weissflogii and E. huxleyi, comprising more than 99% of the final biomass. During the logarithmic growth phase (phase I), mean DMS concentration in high pCO2 mesocosms (1000µatm) was 28% lower than that in low pCO2 mesocosms (400µatm)"

Sleepy

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Re: Carbon Cycle
« Reply #489 on: November 11, 2018, 07:01:49 AM »
Drivers of future seasonal cycle changes in oceanic pCO2
https://www.biogeosciences.net/15/5315/2018/

4 Conclusions
Quote
In this study, we used output from seven CMIP5 global models, subjected to the RCP8.5 radiative forcing scenarios, to provide a comprehensive analysis of the characteristics and drivers of the intensification of the seasonal cycle of pCO 2 between present (2006–2026) and future (2080–2100) conditions. By 2080–2100 the δpCO 2 will be 1.5–3 times larger compared to 2006–2026. The projected amplification by the Earth system models and the possible causes of it are consistent with observation-based amplification for the period from 1982 to 2015 (Landschützer et al., 2018). However, the models slightly overestimate the present-day amplification, probably due to the larger pCO 2 trends in models than observations (Tjiputra et al., 2014).
The models confirm the well-established mechanisms controlling present-day δpCO 2 (Takahashi et al., 2002; Sarmiento and Gruber, 2006; Fay and McKinley, 2017). DIC s and T contributions are the main counteracting terms dominating the seasonal evolution of δpCO 2 . Furthermore, the models show that under future conditions the controlling mechanisms remain unchanged. This result confirms the findings of Landschützer et al. (2018) that identified the same regional controlling mechanism for the past 30 years. The relative role of the DIC and T terms is regionally dependent. High latitudes and upwelling regions, such as the California current system and the coast of Chile, are dominated by DIC s and the temperate low latitudes are driven by T. Only in the North Atlantic and northwestern Pacific do the models show a dominance of thermal effects over nonthermal effects, which is in disagreement with observations. This further illustrates the urgent need for models to accurately represent regional oceanographic features to accurately reproduce the δpCO2 characteristics.
In agreement with Landschützer et al. (2018), the model projections towards the end of this century also demonstrate that the global amplification of δpCO2 is due to the overall
long-term increase in anthropogenic CO2. A higher oceanic background CO2 concentration enhances the effect of T-driven solubility changes on δpCO2 and alters the seawater carbonate chemistry, also enhancing the DIC seasonality effect. The spatial differences of δpCO 2 amplification, however, are determined by the regional sensitivities and seasonality of pCO2 drivers.For example, polar regions show larger sensitivity to DIC and T and larger seasonal cycles of DIC and T. Therefore, these areas present a strong enhancement of δpCO2 in spite of smaller changes in mean pCO2.
Moreover, the pCO 2 seasonal cycle amplitude depends on the relative magnitude and phase of the contributions. The models ensemble mean reproduces the highly effective compensation of DIC s and T contributions when they are 6 months out of phase, confirming previous studies (Takahashi et al., 2002; Landschützer et al., 2018). The compensation of DIC and T prevents a larger amplification of δpCO2, even when both contributions are largely amplified.
The amplification of the TA and S contributions has a small impact on δpCO2 in most regions, except in the high latitudes at which the TA contribution complements the DIC one, enhancing the nonthermal effect in this region.
The use of Earth system models allowed us to state the importance of including future changes in driver seasonalities for future δpCO2 projections. The T seasonality is projected to increase in most of the ocean basins, thereby reinforcing the δpCO2 amplification. The δT increase is consistent with an increase in stratification that will confine the seasonal changes in net heat fluxes to a shallower mixed layer (Alexander et al., 2018). The DIC s seasonality decreases in some cold areas and its reduction prevents a larger amplification. For the sensitivities, while γ DIC increases, γ T decreases.
The latter phenomenon needs further study.
The increasing amplitude of δpCO 2 might have implications for the net air–sea flux of CO2, in particular in regions where there is an imbalance between winter and summer values (Gorgues et al., 2010). Examples of such behavior can be found in the Southern Ocean (between 50 and 60 ◦ S) (Takahashi et al., 2014a) and in the latitude band from 2–40 ◦ in both hemispheres (Landschützer et al., 2014). Moreover, seasonal events of high pCO 2 could have an impact on acidification, aragonite undersaturation events (Sasse et al., 2015), and hypercapnia conditions (McNeil and Sasse, 2016). Therefore, understanding the drivers of future δpCO2 may help to better assess the response of marine ecosystems to future changes in carbonate chemistry. Finally, our complete analytical expansion of δpCO2 in terms of its four variables provides a practical tool to accurately and quickly diagnose temperature and salinity sensitivities from observational or modeling data sets.
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Re: Carbon Cycle
« Reply #490 on: June 13, 2019, 05:59:00 PM »
Solving the Mystery of Why Atmospheric Carbon Dioxide was Lower During Ice Ages
https://phys.org/news/2019-06-mystery-atmospheric-carbon-dioxide-ice.html

Since scientists first determined that atmospheric carbon dioxide (CO2) was significantly lower during ice age periods than warm phases, they have sought to discover why, theorizing that it may be a function of ocean circulation, sea ice, iron-laden dust or temperature.

A new study published this week in Science Advances provides compelling evidence for a solution—the combination of sea water temperature variation and iron from dust off Southern Hemisphere continents.

"Many of the past studies that analyzed ocean temperatures made the assumption that ocean temperatures cooled at the same rate over the entire globe—about 2.5 degrees (Celsius)," said Andreas Schmittner, a climate scientist at Oregon State University and co-author on the study. "When they ran their models, temperature thus accounted for only a small amount of atmospheric CO2 decrease.

"We now know that the oceans cooled much more in some regions, as much as five degrees (C) in the mid-latitudes. Since cold water has a higher degree of CO2 solubility, it had the potential to soak up a lot more carbon from the atmosphere than past studies accounted for—and it realized more of that potential.

Schmittner and his colleagues estimate that colder ocean temperatures would account for about half of the decrease in CO2 during the last glacial maximum—or height of the last ice age. Another third or so, they say, was likely caused by an increase in iron-laden dust coming off the continents and "fertilizing" the surface of the Southern Ocean. An increase in iron would boost phytoplankton production, absorbing more carbon and depositing it deep in the ocean.

Schmittner said the remaining amount of reduced carbon may be attributable to variations in nutrient availability and/or ocean alkalinity.

"The increase in iron likely resulted from ice scouring the landscape in Patagonia, Australia and New Zealand, pulling iron out of the rocks and soil," Schmittner said. "Since it was very cold and dry, the iron would have been picked up by the wind and deposited in the ocean.

"Our three-dimensional model of the global ocean agrees well with observations from ocean sediments from the last glacial maximum, giving us a high degree of confidence in the results."


Fig. 1 Schematic of ocean carbon decomposition.: (A) The concentration of dissolved inorganic carbon (DIC) in the ocean interior is determined by surface (“preformed”) carbon (Cpref) transported passively by ocean circulation and regenerated carbon (Creg = Csoft + Ccaco3) that has accumulated in a water parcel since it was last at the surface. Typically, the efficiency of the biological pump is measured as the total amount of Creg in the ocean, which is dominated by Csoft. (B) However, biology (shown in green) also affects surface DIC by limited outgassing of upwelling regenerated carbon at high latitudes, which increases Cpref over its equilibrium value (Csat) to create a positive disequilibrium (Cdis,bio). Likewise, carbon removal from the surface through photosynthesis and slow ingassing creates a negative Cdis,bio in low-latitude oligotrophic regions of the ocean. Physical processes (black) such as surface heat fluxes (red) similarly lead to disequilibrium (Cdis,phy). North Atlantic Deep Water (NADW) is relatively well equilibrated with the atmosphere because of its long surface exposure before sinking, whereas Antarctic Bottom Water (AABW) and Antarctic Intermediate Water (AAIW) exhibit larger disequilibria due to short surface exposure before sinking.

Open Access: S. Khatiwala et al. Air-sea disequilibrium enhances ocean carbon storage during glacial periods, Science Advances (2019).

----------------------

Related Subject @ https://forum.arctic-sea-ice.net/index.php/topic,888.msg29131.html#msg29131
h/t AbruptSLR
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Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

Tom_Mazanec

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Re: Carbon Cycle
« Reply #491 on: June 15, 2019, 07:52:28 PM »

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Re: Carbon Cycle
« Reply #492 on: June 21, 2019, 05:24:03 AM »
METHANE BUBBLE ESCAPE FROM GAS HORIZON IN MUDDY AQUATIC SEDIMENT UNDER PERIODIC WAVE LOADING

First published: 14 June 2019 https://doi.org/10.1029/2019GL083100

Abstract
Ebullition of greenhouse methane (CH4) from the aquatic sediments is often observed at various hydrostatic pressure drops: at low tides, waves, and even at atmospheric pressure drops. It is especially pronounced at the different vent structures, e.g., pockmarks, mud volcanoes, and cold seeps. The modelling conducted in the current study suggests that long timescale (glacial to centennial frequency) sea level drops may induce “stable” bubble ascent and control the position of the gas horizon in muddy aquatic sediment. Bubbles escape in the “dynamic” regime from the shallow gas horizon and subsequently to the water column is more feasible under shorter‐period waves of higher amplitude travelling in shallow water. Otherwise, they will ascend in the “stable” regime remaining close to the gas horizon. These findings are illustrated by examples of various vent structures (e.g., pockmarks), pronounced in shallow straits and bays, described in the literature.

Plain Language Summary
 
Release of greenhouse methane bubbles is often observed at various hydrostatic pressure drops: at low tides, waves, and even at atmospheric pressure drops in marine and lacustrine settings. It is pronounced at the different vent structures, e.g., pockmarks, mud volcanoes, and cold seeps. It has been shown that long timescale (glacial to centennial frequency) sea level drops induce a stable bubble ascent and control a position of the gas horizon in muddy aquatic sediment. Bubble escape from the gas horizon is more feasible under shorter‐period (internal and surface) waves of higher amplitude travelling in shallow water. In this case the bubble starts a rapid unrestricted ascent and will ultimately be released into the water column. Otherwise, the bubble will migrate in the stable regime remaining close to the gas horizon. These findings are illustrated by examples of various vent structures (e.g., pockmarks), especially emphasized in shallow straits and bays, described in the literature. These important insights improve our understanding of the global carbon cycle in general, and of bubble ascent from the gas horizon in aquatic sediment, in particular.

2bad this is not open access....Id post it over on the forum
Wait.. what?  Oh, I already did   

bligh

vox_mundi

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Re: Carbon Cycle
« Reply #493 on: July 09, 2019, 01:31:35 AM »
Breaching a 'Carbon Threshold' May Lead to Mass Extinction
http://news.mit.edu/2019/carbon-threshold-mass-extinction-0708

Daniel Rothman, professor of geophysics and co-director of the Lorenz Center in MIT's Department of Earth, Atmospheric and Planetary Sciences, has found that when the rate at which carbon dioxide enters the oceans pushes past a certain threshold—whether as the result of a sudden burst or a slow, steady influx—the Earth may respond with a runaway cascade of chemical feedbacks, leading to extreme ocean acidification that dramatically amplifies the effects of the original trigger.

This global reflex causes huge changes in the amount of carbon contained in the Earth's oceans, and geologists can see evidence of these changes in layers of sediments preserved over hundreds of millions of years.

Rothman looked through these geologic records and observed that over the last 540 million years, the ocean's store of carbon changed abruptly, then recovered, dozens of times in a fashion similar to the abrupt nature of a neuron spike. This "excitation" of the carbon cycle occurred most dramatically near the time of four of the five great mass extinctions in Earth's history.

It didn't matter what initially caused the events; for roughly half the disruptions in his database, once they were set in motion, the rate at which carbon increased was essentially the same. Their characteristic rate is likely a property of the carbon cycle itself—not the triggers, because different triggers would operate at different rates.

According to Rothman, today we are "at the precipice of excitation," and if it occurs, the resulting spike—as evidenced through ocean acidification, species die-offs, and more—is likely to be similar to past global catastrophes.

"Once we're over the threshold, how we got there may not matter," says Rothman, who is publishing his results this week in the Proceedings of the National Academy of Sciences. "Once you get over it, you're dealing with how the Earth works, and it goes on its own ride."
« Last Edit: July 09, 2019, 06:23:25 AM by vox_mundi »
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Apocalypse4Real

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Re: Carbon Cycle
« Reply #494 on: July 09, 2019, 05:17:54 AM »
Thanks Vox, sobering piece. Now to find the article.

vox_mundi

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Re: Carbon Cycle
« Reply #495 on: July 09, 2019, 06:18:20 AM »
Characteristic disruptions of an excitable carbon cycle, Proceedings of the National Academy of Sciences (2019).
https://www.pnas.org/content/early/2019/07/02/1905164116
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longwalks1

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Re: Carbon Cycle
« Reply #496 on: July 11, 2019, 06:39:34 AM »
In Re 493 Breaching CO2

Breaching a 'Carbon Threshold' May Lead to Mass Extinction.    MIT  and NASA funded research with no link to the most recent of Rothmans works.  Sigh.   

Rothmans publications are at http://rothmangroup.mit.edu/publications

On his home page Subsection Kinetic complexity of the carbon cycle (where there is no mention of the DOI, just volume and pages)  Find the DOI Go to the hub (Oh Nature, can't you give away a mere "letter" - not an article) via       DOI https://doi.org/10.1038/s41586-019-1280-6   yields a 4 page letter with references.

 
Quote
This result requires increasing bond-strength
diversity, consistent with the formation of organo-mineral bonds
but inconsistent with selective preservation. Radiocarbon ages
further reveal that high-energy, mineral-bound organic carbon
persists for millennia relative to low-energy, unbound organic
carbon. Our results provide globally coherent evidence for the
proposed  importance of mineral protection in promoting organic
carbon preservation. We suggest that similar studies of bond-
strength diversity in ancient sediments may reveal how and why
organic carbon preservation—and thus atmospheric composition
and climate—has varied over geological time.

Clearly a good paper, but not the one looked for. 

Under the Subsection   Co-evolution of life and the environment
DH Rothman, Characteristic disruptions of an excitable carbon cycle, Proceedings of the National Academy of Sciences (2019). PDF available upon request.  https://www.pnas.org/content/early/2019/07/02/1905164116

This would appear to be the pertinent paper.  Via "The hub"

Quote
Significance
The  great  environmental  disruptions  of  the  geologic  past
remain  enigmatic.  Each  one  results  in  a  temporary  change
in  the  oceans’  store  of  carbon.  Although  the  causes  remain
controversial,  these  changes  are  typically  interpreted  as  a
proportionate response to an external input of carbon. This
paper suggests instead that the magnitude of many disrup-
tions is determined not by the strength of external stressors
but  rather  by  the  carbon  cycle’s  intrinsic  dynamics.  Theory
and  observations  indicate  that  characteristic  disruptions  are
excited by carbon fluxes into the oceans that exceed a thresh-
old. Similar excitations follow influxes that are either intense
and brief or weak and long-lived, as long as they exceed the
threshold. Mass extinction events are associated with influxes
well above the threshold.

I have not gone through it yet. 

The referenced paper of his from 2017 Mit web page the dire prediction -- Mathematics predicts a sixth mass extinction By 2100,
https://news.mit.edu/2017/mathematics-predicts-sixth-mass-extinction-0920   appears to be based on

Thresholds of catastrophe in the Earth system
https://advances.sciencemag.org/content/3/9/e1700906

Quote
The history of the Earth system is a story of change. Some changes are gradual and benign, but others, especially those associated with catastrophic mass extinction, are relatively abrupt and destructive. What sets one group apart from the other? Here, I hypothesize that perturbations of Earth’s carbon cycle lead to mass extinction if they exceed either a critical rate at long time scales or a critical size at short time scales. By analyzing 31 carbon isotopic events during the past 542 million years, I identify the critical rate with a limit imposed by mass conservation. Identification of the crossover time scale separating fast from slow events then yields the critical size. The modern critical size for the marine carbon cycle is roughly similar to the mass of carbon that human activities will likely have added to the oceans by the year 2100.

edit  seems I duplicated the PNAS, you posted the link to the primary source as I was slogging through.  Thanks for putting in the primary source. 
« Last Edit: July 12, 2019, 03:34:32 AM by longwalks1 »

Bruce Steele

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Re: Carbon Cycle
« Reply #497 on: July 11, 2019, 05:44:18 PM »
"The modern critical size for the marine carbon cycle is roughly similar to the mass of carbon that human activities will likely have added to the oceans by the year 2100."
 We have emitted about 633 GT carbon to date and BAU takes us to something like 5000 GT by 2100.
Most of the worlds surface oceans will be undersaturated by 2100 and the carbonate sink will be less effective. The area of sea floor that calcium carbonate can accumulate will also shrink so the area of sea floor that supports the ocean sedimentation sink will be much reduced.
 Some areas of the worlds oceans are already experiencing surface undersaturation so in the next few decades we will get a better idea about what percent of the carbonate sink will fail with surface undersaturation. We are having ecological problems in those areas of the Calif. Current that are experiencing summer periods of surface ocean undersaturation but it is very difficult to assign cause and effect to biological systems with multiple concurrent stressors. We will get better at assigning risk but the ocean will remain mysterious and we will never understand the true ramifications for acidification on ocean biology because eighty years isn't enough time to study the thousands of species affected.
 IMO , if we screw this up humans will go extinct right along with tens of thousands of other species.

vox_mundi

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Re: Carbon Cycle
« Reply #498 on: July 25, 2019, 09:42:44 AM »
Clues On How Soils May Respond to Climate Change Found
https://phys.org/news/2019-07-clues-soils-climate.html

Rock core samples from a period of warming millions of years ago indicate soils contributed to a rapid rise in atmospheric greenhouse gas and suggest modern climate models may overestimate Earth's ability to mitigate future warming, according to an international team of scientists.

Researchers discovered a drastic drop in organic material preserved in sections of core samples from the Paleocene-Eocene Thermal Maximum (PETM), a global warming event 55.5 million years ago that's considered the best analogue for modern climate change.

Quote
... "We see the amount of carbon drops drastically, by orders of magnitude, during this PETM event," ... So at least in Wyoming, my data suggests soils acted as a source, not a sink, for carbon dioxide

The findings, according to the researchers, suggest ancient soils from a site in modern day Wyoming acted as a source of atmospheric carbon dioxide, emitting the greenhouse gas into the atmosphere, and not a sink, trapping and storing carbon underground.

The researchers said this could mean global climate models, which expect soils to be a sink, may overstate the ability of terrestrial ecosystems to lessen the impacts of climate change.

The researchers found the 130-foot section they believe to represent the PETM had the lowest weight of total carbon and biomarkers of any part of the core.

"At least in the Bighorn Basin, it appears that high PETM temperature, seasonally intense precipitation, or a combination, accelerated organic matter decay rates such that they outpaced plant productivity and ultimately resulted in reduced soil organic carbon during the PETM," Baczynski said.

The PETM is marked by global rise in temperatures, from about 9 to 15 degrees Fahrenheit, and a rapid increase in atmospheric carbon dioxide. The carbon dioxide from this time has a unique isotopic signature, and scientists can identify it in tree and plant fossils that absorbed the carbon.

Allison A. Baczynski et al, Carbon Isotope Record of Trace n ‐alkanes in a Continental PETM Section Recovered by the Bighorn Basin Coring Project (BBCP), Paleoceanography and Paleoclimatology (2019)
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kassy

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Re: Carbon Cycle
« Reply #499 on: July 25, 2019, 10:44:05 AM »
Thanks Vox!

This looks like another chunk out of the budget?

And this makes me wonder about how climate models actually interact with soils...
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