Arctic Sea Ice : Forum

AGW in general => Science => Topic started by: AbruptSLR on June 05, 2014, 03:16:06 PM

Title: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 05, 2014, 03:16:06 PM
As I think that the CO2 concentration over Antarctica that A4R identified in the Mauna Loa CO2 thread, deserves its own thread, I am opening this topic on Southern Ocean Venting of CO2, by showing the two attached images from the MetOp-1 satellite for June 4 2014 at 892mb (near the ocean surface) that indicates to me that the sea ice extent is beginning to influence the amount of CO2, as more CO2 is shown near the Amundsen Sea Embayment where the sea ice extent is relatively low; and 506mb indicating that at this elevation much of the CO2 has moved away from the coastline and has moved more over the middle of Antarctica.  I will slowly add more to this thread, when I have time, but for the moment this phenomena appears to me to be a legitimate positive feedback mechanism that with cause polar amplification in Antarctica due to GHG concentration with the geopotential height well over Antarctica (which will cause the circumpolar winds to blow harder that will cause more venting)
Title: Re: Southern Ocean Venting of CO2
Post by: TerryM on June 05, 2014, 08:07:48 PM
When did this high concentration first show up in the Antarctic?
Is this seasonal or a year round feature?

I thought that I recalled low readings throughout the SH in the past so this has been a slap in the face.

Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 05, 2014, 11:14:27 PM

I couldn't agree more that significant CO2 venting from the Southern Ocean seems like a slap in the face, as I was not expecting this to happen now.  From the information at A4R's website: (

it appears that venting of this magnitude (+410ppm) only began this austral Fall (boreal Spring).  However, I suspect that some lower level of venting has been occurring for some years now as the westerly winds over the Southern Ocean have been anomalously high for many years due to ozone hole, and I believe that the amount of venting occurring is a function of many different factors in the Southern Ocean including: eddies, storms, GHG concentrations, sea ice cover, SAM, PDO, AMO, IPO, and natural variability.  In any event the posts in the "Mauna Loa CO2" thread from Reply #240 to #259, make it clear that this phenomenon has been occurring in a seesaw fashion for millions of years.  But the slap in the face part is that this venting appears to be happening now on top of all the anthropogenic GHG emissions, BC, and all the other positive feedback factors (eg Arctic albedo drop, permafrost degradation, tropical forest degradation, etc) that are ramping up concurrently.  I will post later some of my thoughts about the possible implications of this venting if it continues to trend upward.

Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 06, 2014, 01:05:23 AM
The linked reference (with a free pdf), indicates that heat input directly into the high latitudes, is about three times more effective at promoting mean global temperature rise, than an equal heat input into the tropics (also see the attached image).  This polar amplification emphasizes the importance of the Southern Ocean venting CO₂ directly into the high latitude Southern Atmosphere, as well as the reduce OHU in the Southern Ocean due to the slow-down in the AABW production rate:

Rose, B. E. J., K. C. Armour, D. S., Battisti, N. Feldl, and D. D. B. Koll, (2014)," The dependence of transient climate sensitivity and radiative feedbacks on the spatial pattern of ocean heat uptake", Geophys. Res. Lett., 41, doi:10.1002/2013GL058955. (

Abstract: "The effect of ocean heat uptake (OHU) on transient global warming is studied in a multimodel framework. Simple heat sinks are prescribed in shallow aquaplanet ocean mixed layers underlying atmospheric general circulation models independently and combined with CO2 forcing. Sinks are localized to either tropical or high latitudes, representing distinct modes of OHU found in coupled simulations. Tropical OHU produces modest cooling at all latitudes, offsetting only a fraction of CO2 warming. High latitude OHU produces three times more global mean cooling in a strongly polar-amplified pattern. Global sensitivities in each scenario are set primarily by large differences in local shortwave cloud feedbacks, robust across models. Differences in atmospheric energy transport set the pattern of temperature change.  Results imply that global and regional warming rates depend sensitively on regional ocean processes setting the OHU pattern, and that equilibrium climate sensitivity cannot be reliably estimated from transient observations."
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 06, 2014, 01:22:09 AM
Getting back to Terry's question, the following linked reference indicates that at least through 2009, the Southern Ocean has been absorbing CO2.

Sea–air CO2 fluxes in the Southern Ocean for the period 1990–2009
by: A. Lenton et al, 2013;
Biogeosciences, 10, 4037–4054, 2013; (;) doi:10.5194/bg-10-4037-2013 (
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 06, 2014, 05:30:38 AM
Corinne Le Quere et al (2007), see the linked references below, showed that the increase in the westerly wind velocities in the Antarctic (largely due to the ozone hole) was reducing the sequestration of CO₂ in the Southern Ocean as the increase wind increase upwelling that increased venting of CO₂.  The first attached image by Le Quere shows her original field data compared to the previously expected CO₂ absorption projections for the Southern Ocean (see the caption below).  The second image shows the increase in the wind velocities, primary due to the ozone hole.  The third image shows Le Quere et al's model projections for CO₂ absorption without wind and the CO₂ venting with the increased wind velocities.

Unfortunately, many other scientists disputed Le Quere et al's results for several years, but it is now generally accepted as correct, and Le Quere is one of the lead authors for AR5:

Corinne Le Quéré, Christian Rödenbeck, Erik T. Buitenhuis, Thomas J. Conway, Ray Langenfelds, Antony Gomez, Casper Labuschagne, Michel Ramonet, Takakiyo Nakazawa, Nicolas Metzl, Nathan Gillett, Martin Heimann, (2007),"Saturation of the Southern Ocean CO₂ Sink Due to Recent Climate Change", Science, Vol. 316, no. 5832  pp. 1735-1738, DOI: 10.1126/science.1136188 ( (

Abstract: "Based on observed atmospheric carbon dioxide (CO2) concentration and an inverse method, we estimate that the Southern Ocean sink of CO2 has weakened between 1981 and 2004 by 0.08 petagrams of carbon per year per decade relative to the trend expected from the large increase in atmospheric CO2. We attribute this weakening to the observed increase in Southern Ocean winds resulting from human activities, which is projected to continue in the future. Consequences include a reduction of the efficiency of the Southern Ocean sink of CO2 in the short term (about 25 years) and possibly a higher level of stabilization of atmospheric CO2 on a multicentury time scale."

Caption for the first image: " Le Quéré expected to see a steady increase in the amount of carbon dioxide absorbed by the Southern Ocean between 1981 and 2004 (blue line). Instead, weather station measurements (red line) suggested year-to-year variability, but no long-term increase over time. (Graph by Corrine Le Quéré, University of East Anglia.)"

See also: ( (
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 06, 2014, 04:15:09 PM
The following DIMES (Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean, see the first attached image for the project location) link, briefly discusses the portion of the Southern Ocean where it interfaces with the Atlantic Ocean and the Meridional Overturning Circulation (MOC).  The following extracted discussion, and the second attached image of the stratification of the Southern Ocean where the MOC contributes to upwelling in this area, indicates how complex both the upwelling and associated CO₂ ventilation is (e.g.: the influence of the rough bathymetry), and illustrates why current RCMs have had difficulty projecting the correct levels of CO₂ venting, and thus justifying the need for the extensive DIMES program in order to better calibrate the RCMs: (

Extract: "The Meridional Overturning Circulation (MOC) of the ocean is a critical regulator of the Earth's climate processes. Climate models are highly sensitive to the representation of mixing processes in the southern limb of the MOC, within the Southern Ocean, although the lack of extensive in situ observations of Southern Ocean mixing processes has made evaluation of mixing somewhat difficult. Theories and models of the Southern Ocean circulation have been built on the premise of adiabatic flow in the ocean interior, with diabatic processes confined to the upper-ocean mixed layer. Interior diapycnal mixing has often been assumed to be small, but a few recent studies have suggested that diapycnal mixing might be large in some locations, particularly over rough bathymetry. Depending on its extent, this interior diapycnal mixing could significantly affect the overall energetics and property balances for the Southern Ocean and in turn for the global ocean. The goals of DIMES are to obtain measurements that will help us quantify both along-isopycnal eddy-driven mixing and cross-isopycnal interior mixing."

Caption for the second attached image: "Schematic representation of Southern Ocean meridional overturning circulation. The isopycnal upwelling of Upper and Lower Circumpolar Deep Water (UCDW and LCDW, with sources in the North Atlantic) is supported by mean geostrophic mass fluxes below the level of topographic obstacles to the ACC and by mesoscale eddy-driven mass fluxes at mid-depth. The upwelled water changes density through air-sea-ice interaction. It then returns northward in the wind-driven Ekman layer to form Antarctic Intermediate Water (AAIW), and as Antarctic Bottom Water (AABW) in mean geostrophic flows. The magnitude of interior diapycnal mixing and the rate of along-isopycnal mixing are open for investigation and are the DIMES objectives."
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 06, 2014, 04:31:51 PM
As Bruce Steele indicated in his Reply #254 of the "Mauna Loa CO2" thread, that the mode water circulation (note that mode water is the water influenced by the winds, and thus are likely to be venting CO2 in the Southern Ocean) is more active than the Antarctic Bottom Water, AABW, current (which is sequestering CO2 but which has been slowing down for the past three decades, and see the second figure in my immediate past post), the net balance of CO2 flux results in greater emission of CO2 into the atmosphere (in the areas of upwelling in the Southern Ocean).

However, the portion of the MOC (see my last immediate post) is not the only area of the Southern Ocean where the increased Westerly wind velocities have increased upwelling, as the Amundsen Bay Embayment is famous for the influence of the upwelled Circumpolar Deep Water, CDW, on the basal melting of marine glaciers in this area (and this upwelled CDW probably is also venting CO2).  Furthermore, the Humboldt Current is another famous example of the venting of CO2 due to the upwelling of deeper intermediate mode water as explained by Bruce Steele in the following two extracts:

From Bruce Steele's Reply#107 of the "2014 El Nino?" thread:

Most of the pmel.NOAA  TAO buoys are currently not sending info but two of them at 110W and 155W still are working. The cold pool in the equatorial eastern pacific is ventilating Co2 with ~ 700 ppm surface water pCO2.
at the 110 W buoy. The last month has had Co2 levels that are the highest in the recording history of that buoy. If 110 W keeps working those high Co2 levels should drop as warm water suppresses the cold upwelled water should the El Nino develop over the next several months.
 Will the Mauna Loa Co2 records deviate from trend due to this change in ocean ventilation or does the anthropogenic signal totally dominate ?  Hope 110W holds in there for the next few months. ( (

From Bruce Steele's Reply #128 of the "2014 El Nino?" thread:

The different Co2 content of the upwelled or downwelled water is due to it's different sources. The intermediate water upwelled under normal conditions in the eastern equatorial pacific is older water that has accumulated Co2 due to bacterial decomposition of organic matter. Organic matter is ballasted by calcium carbonate and sinks till it hits the saturation horizon which is at intermediate depths in the pacific. Once the calcium carbonate dissolves the organic surface supplied material is remineralized by bacteria.  The warm water in the graphs above are downwelled in the western pacific. These waters are much younger and haven't spent much time at depth so they don't have the high Co2 content.
Under normal conditions the eastern equatorial pacific contributes about 72% of all oceanic Co2 ventilation. When the warm western supplied water is pushed to the surface by the Kelvin wave is suppresses the cold high Co2 water and because the cold water no longer has surface contact with the atmosphere it stops ventilating. So the immediate effects of an El Nino are a reduction in natural supplies of oceanic derived Co2 but later as drought and terrestrial conditions increase the terrestrial supplies of Co2 dominate. (

Bruce's posts make it clear that the intermediate mode water contains a lot of CO2 due to the plankton shells (that are plentiful in the Southern Ocean).
Title: Re: Southern Ocean Venting of CO2
Post by: crandles on June 06, 2014, 04:51:23 PM
From the information at A4R's website: (

it appears that venting of this magnitude (+410ppm) only began this austral Fall (boreal Spring).  However, I suspect that some lower level of venting has been occurring for some years now as the westerly winds over the Southern Ocean have been anomalously high for many years due to ozone hole, and I believe that the amount of venting occurring is a function of many different factors in the Southern Ocean including: eddies, storms, GHG concentrations, sea ice cover, SAM, PDO, AMO, IPO, and natural variability.

from that site the oldest map I could find was 26 th Feb 2012


While there doesn't seem much yellow there, note that it is much clearer in some levels than the average for the whole column:



for the whole column there doesn't seem much less on 26th Feb 14 than on 3 March 14 and hence there still may be quite a lot there on 26 Feb 14 at the right level. Perhaps nearly as much as shown for level 95 on 3 March.

So it goes back to Feb 14 and possibly further but I haven't found any older pics.

I can't rule out 410ppm having occurred there before Feb 14.

Even if not 410 last year, might it have been ~408ppm last year such that it isn't particularly odd just more noticeable due to colour change?
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 06, 2014, 04:53:05 PM
Per Wikipedia:

"The Antarctic oscillation (AAO, to distinguish it from the Arctic oscillation or AO) is a low-frequency mode of atmospheric variability of the southern hemisphere. It is also known as the Southern Annular Mode (SAM) or Southern Hemisphere Annular Mode (SHAM). It is defined as a belt of westerly winds or low pressure surrounding Antarctica which moves north or south as its mode of variability. In its positive phase, the westerly wind belt contracts towards Antarctica, while its negative phase involves this belt moving towards the Equator."

Therefore, one would expect more CO2 venting during periods of positive AAO/SAM/SHAM as the westerly winds accelerate then.  Also, one would expect more CO2 venting in the austral Fall when the cyclones count is high and the Antarctic sea ice extent is not at its maximum.
Title: Re: Southern Ocean Venting of CO2
Post by: crandles on June 06, 2014, 05:08:22 PM
Most recent station data in the area I can find is from drake passage: (

2013 Feb to April data shows rise from 391.1 to 391.9.

2014 Feb to April data shows rise from 393.2 to 393.8.

That seems remarkably normal though possibly too far away to have noticed by April 2014?

South Pole and Palmer station only have measurements to Jan 2014, and other stations don't have anything more current.
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 06, 2014, 06:49:12 PM

I agree that the amount of CO2 venting from the Southern Ocean is no more than what is occurring in the Northern Hemisphere as the near surface MetOp satellite images show and as can be seen when comparing the Mauna Loa CO2 trend line from 1975-2014 (see the first attached image) with the South Pole CO2 trend line from 1975-2014 (see the second attached image), which are roughly comparable.  What is actually unusual is that before 2007 most researchers assumed that the Southern Ocean would act as a relatively strong CO2 sink so that under the old assumption the South Pole CO2 readings should be lower than they are (and should not be roughly tracking Mauna Loa).

That said, I am concerned that the geopotential height well over Antarctica may be allowing local higher level readings of CO2 say at 500mb +/- 250mb, which could be maintaining (or deepening) the geopotential height well even as the ozone hole slowly repairs itself; which would either maintain the current high westerly wind velocities, or possibly increase them in the future.  Thus the Southern Hemisphere situation is different than the Northern Hemisphere, in that these high westerly winds not only promote more CO2 venting, but also ice mass loss from marine glaciers.

Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 06, 2014, 07:20:33 PM
In regards to my concluding comment in my that post, that the increased westerly wind velocities not only promote CO2 venting from the Southern Ocean but also marine glacier ice mass loss from the WAIS, I note that in the following linked extract about the Lake Elgygtgyn paleo-findings, historically the WAIS has collapsed repeatedly and each time that it did the Arctic warmed shortly later.  So if the WASI collapses this century, it will deepen the water depth in the Bering Strait, which will direct more warm Pacific water into the Arctic for yet another round of positive feedback for global warming: (

Extract: "Antarctica and the Arctic
Climate at the North and South pole are connected. Sediment records from Antarctica show that the West Antarctic ice sheet melted at various times in history. Following many of those events, the Arctic warmed. These recurring intervals of paired warming show that climate in the two hemispheres is linked – it’s called inter-hemispheric climate coupling.
“When the West Antarctic ice sheet pulls back we see a corresponding warmth in the high lattitudes again, probably affecting the size of the Greenland ice sheet with major implications for changes in sea level,” says Julie Brigham-Grette. “Our results mesh with what glaciologists are seeing today. Seven of the 12 major ice shelves around the Antarctic are melting or are gone. We suspect the tipping point for the gradual de-glaciation of Greenland and the Arctic may be lower than glaciologists once thought.”
Complex systems
Earth is a complicated place. We can’t explain past warming using only orbital dynamics or levels of Carbon Dioxide. Scientists affiliated with the project outlined some past events that might explain the rapid warming the sediment records show occurred in both Antarctica and the Arctic around similar times.
When you imagine Antarctica, the picture includes large ice shelves that hang off the rocky edge of the ice-covered continent. Normally that ice keeps nearby ocean water very cold. The cold water travels along currents toward the north Pacific where it wells up to the surface. Ocean circulation can be affected, though. If Antarctic ice sheets disintegrate or melt away, they no longer enforce cold water currents that journey to the Arctic. Instead, surface ocean waters in the Arctic become warmer.
When Antarctica’s ice sheets disintegrate the ocean gains more water and sea levels rise globally. The Bering Strait usually restricts how much warm surface water approaches the Arctic from the south, but higher sea levels would mean warm surface water didn’t have to squeeze through such a narrow space, letting more warm water past the Bering Strait into the Arctic Ocean.
Either way, a warmer ocean means higher temperatures and more rainfall for the Arctic, which impacts paleoclimatology and sea ice history. Grasping the climate connections between the hemispheres gives us insight into our near future."
Title: Re: Southern Ocean Venting of CO2
Post by: Bruce Steele on June 06, 2014, 07:23:30 PM
ASLR, in post #128 I should have said that over 80% of DOM ( dissolved organic matter ) in North Pacific Intermidiate Waters are supplied in formation processes with ballasting of surface supplied matter adding to DOM and extra DIC due to bacterial remineralization as the water travels and ages. (

I haven't seen work on the origins of DOM in Antarctic Intermidiate Waters but from what I have read the age of AAIW when it reaches the equator is similar to North Pacific Intermidiate Waters when they are upwelled along the coast of North America at about thirty-five years. So any intensification of antarctic intermidiate water formation processes will deliver their Co2 load fairly quickly.
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 06, 2014, 08:10:00 PM

Thanks for the clarification, which made me think of the following reference that shows that that earlier in the Holocene polar shifting of the Antarctic westerly winds triggered CO2 venting in the Northwest Pacific.  The linked reference (with a free access paper) represents a challenge of both Global and Regional Circulation Models related to the influence of the Southern Ocean during the Holocene (8,000 yrs age the mean global temperatures were a bit higher than now so calibrating the GCMs, & RCMs, to match the observed Holocene record should improve the model projections as to what we can expect in a few years time).  Thus the strengthening of the Antarctic westerly winds poses a risk of not only CO2 venting in the Southern Ocean, but also of ventilation of the Northwest Pacific Ocean, as indicated by the title, abstract and attached image:

S. F. Rella    & M. Uchida, (2014),"A Southern Ocean trigger for Northwest Pacific ventilation during the Holocene?", Scientific Reports 4, Article number: 4046 doi:10.1038/srep0404 (

Abstract: "Holocene ocean circulation is poorly understood due to sparsity of dateable marine archives with submillennial-scale resolution. Here we present a record of mid-depth water radiocarbon contents in the Northwest (NW) Pacific Ocean over the last 12.000 years, which shows remarkable millennial-scale variations relative to changes in atmospheric radiocarbon inventory. Apparent decoupling of these variations from regional ventilation and mixing processes leads us to the suggestion that the mid-depth NW Pacific may have responded to changes in Southern Ocean overturning forced by latitudinal displacements of the southern westerly winds. By inference, a tendency of in-phase related North Atlantic and Southern Ocean overturning would argue against the development of a steady bipolar seesaw regime during the Holocene."
Title: Re: Southern Ocean Venting of CO2
Post by: jai mitchell on June 06, 2014, 08:13:00 PM
I cannot conceive of a source for CO2 venting in the southern oceans.  We know that the general surface temp anomaly has been colder, so any surface transport water experience a higher solubility of CO2.  Any major upwelling would bring water with lower CO2 concentrations. 

If regional water was warming in the Austral spring then that would cause a release, as the northern hemisphere also causes a release in the fall due to aerobic decomposition.

Therefore, any "venting" of co2 in the southern hemisphere would be a normal part of the global CO2 cycle and part of the annual fluctuations recognized in the Keeling curve.  In this case, it simply exacerbates the emissions produced in the boreal fall/winter.

this is not a "source" of CO2, nor is it a result of decreased carbon sink capacity (not on an annual basis)
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 06, 2014, 08:38:53 PM

Your logic is not dissimilar to that cited by Zickfeld et al 2008 in their critique of Le Quere et al (2007); so while it is understandable that this is a contentious topic (note that Le Quere generally won this debate and is a lead author for AR5), it is clear that the DOM (dissolved organic matter) can concentrate CO2 in deeper mode water that will vent CO2 when they upwell to the surface; however, many/most GCM's/RCM's do not include this behavior, so we are likely in for some faster warming rates than our current models project:

Kirsten Zickfeld, John C. Fyfe, Michael Eby, Andrew J. Weaver, (2008), "Comment on "Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change"" (

Comment: "We disagree with the conclusion of Le Quéré et al. (Reports, 22 June 2007, p. 1735) that poleward intensifying winds could continue to weaken the Southern Ocean sink in the future. We argue that altered winds, along with rising atmospheric carbon dioxide, will likely increase the efficiency of this sink in the 21st century."

Again, this is a confusing topic but the paleo-evidence that I posted in the Mauna Loa CO2 thread confirms that CO2 venting from mode water has been driving global warming for millions of years.

Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 06, 2014, 10:24:25 PM
While I do not want to make too big of a deal of the fact that the Southern Ocean is periodically venting CO2 (depending mostly on wind and sea ice extent conditions), in excess of what the AABW is sequestering, and certainly the periodic venting events are no bigger than comparable CO2 emissions (say from permafrost degradation) than in the Northern Hemisphere.

However, neither do I want to downplay the role that this positive feedback factor (triggered by the ozone hole since at least the 1980's), can play when we are now starting to exceed mean global temperatures last seen in the Holocene Maximum and are headed towards conditions experienced in the Eemian maximum (MIS 5e).  The possible acceleration of the collapse of the WAIS (driven by CDW upwelled by the high velocity westerlies) raising water depth in the Bering Strait & driving warm Pacific water into the Arctic Ocean, that I previously cited, is only one example of the consequence of this CO2 venting, other examples include:
(a) Earlier than forecast retreat of the Antarctic sea ice extent (which has been projected to be associated with the early collapse of the Filichner-Ronne Ice Shelf); which would both accelerate more CO2 venting, would decrease local albedo, and should decrease AABW production.
(b) Earlier acidification of the Southern Ocean surface waters, which could reduce CO2 absorption by plankton (note that the wind driving mode water can be super saturated with CO2 and is thus acidic to the shells of many plankton species).
(c) Increased storm activity in the Southern Ocean, and increased Antarctic Atmospheric humidity (with possible seasonal rainfall, and surface ice melting, in the future).
(d) Accelerated ice mass loss from the coastal marine glaciers and ice shelves in Eastern Antarctica.
(e) The poleward movement of the westerly winds should expand the Southern Hadley cell; which should contribute to more droughts in South Africa and Australia.

Obviously, there are other positive feedback mechanisms associated with Southern Ocean venting of CO2; however, as the current GCMs/RCMs cannot yet correctly capture the response of even these feedbacks; we all may find-out first hand in a few more years what the consequences are, even before the models are updated to provide more accurate projections.

Title: Re: Southern Ocean Venting of CO2
Post by: Bruce Steele on June 06, 2014, 11:13:51 PM
ASLR, In post #4 you linked a "Biogeoscience" article that on p.4039 states " In the Ausral winter, the net uptake of Co2 in the PFZ (polar frontal zone ) and SAZ( subantarctic zone ) is reduced relative to summer, and in some areas a net outgassing occurs as a result of deep winter mixing entraining carbon rich waters from the ocean interior into the surface mixed layer." Metzl et al 1999"
"McNeil et al 2007" (

The current high Co2 levels may not be unique, but part of an annual cycle. Maybe 410 ppm will be followed in a few years with higher Austral winter ventilation numbers due to enhanced upwelling and increased winds ?  But maybe all the carbon we have been dumping into the oceans will find a way to come back and visit us in ways we never suspected? 

Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 06, 2014, 11:34:33 PM

Thanks for the insightful comment.  While no one has a crystal ball to read the future (including me); the  following linked reference provides both paleo, and model, - evidence that as GHG concentrations increase over Antarctica (including CO₂ vented from the Southern Ocean) that the SAM will trend towards more positive values, and the westerly winds will continue to contract polewards, and New Zealand, Australia and South Africa, will experience more droughts (see attached image):

Nerilie J. Abram,  Robert Mulvaney,  Françoise Vimeux,  Steven J. Phipps,  John Turner  & Matthew H. England, (2014), "Evolution of the Southern Annular Mode during the past millennium", Nature Climate Change, doi:10.1038/nclimate2235 (

Abstract: "The Southern Annular Mode (SAM) is the primary pattern of climate variability in the Southern Hemisphere, influencing latitudinal rainfall distribution and temperatures from the subtropics to Antarctica. The positive summer trend in the SAM over recent decades is widely attributed to stratospheric ozone depletion; however, the brevity of observational records from Antarctica—one of the core zones that defines SAM variability—limits our understanding of long-term SAM behaviour. Here we reconstruct annual mean changes in the SAM since AD 1000 using, for the first time, proxy records that encompass the full mid-latitude to polar domain across the Drake Passage sector. We find that the SAM has undergone a progressive shift towards its positive phase since the fifteenth century, causing cooling of the main Antarctic continent at the same time that the Antarctic Peninsula has warmed. The positive trend in the SAM since ~AD 1940 is reproduced by multimodel climate simulations forced with rising greenhouse gas levels and later ozone depletion, and the long-term average SAM index is now at its highest level for at least the past 1,000 years. Reconstructed SAM trends before the twentieth century are more prominent than those in radiative-forcing climate experiments and may be associated with a teleconnected response to tropical Pacific climate. Our findings imply that predictions of further greenhouse-driven increases in the SAM over the coming century also need to account for the possibility of opposing effects from tropical Pacific climate changes."

Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 07, 2014, 05:47:53 AM
Hopefully, the two attached figures will help to illustrate two of the points that I am trying to make. 

The first figure shows the Earth's atmospheric circulation cells, and shows that there is a geopotential height well over Antarctica where CO2 vented from the Southern Ocean can tend to concentrate (within limits).

The second figure shows the principal water circulation system in the Southern Ocean, and illustrates how wind driven upwelling can vent CO2 from the mode water.
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 09, 2014, 04:49:02 PM
The following linked research indicates that global warming can reduce CO₂ uptake in the oceans, particularly in areas with high upwelling (see attached image and following caption), such as the Southern Ocean:

L. E. Pichevin, R. S. Ganeshram, W. Geibert, R. Thunell & R. Hinton, (2014), "Silica burial enhanced by iron limitation in oceanic upwelling margins", Nature Geoscience doi:10.1038/ngeo2181 (

Abstract: "In large swaths of the ocean, primary production by diatoms may be limited by the availability of silica, which in turn limits the biological uptake of carbon dioxide. The burial of biogenic silica in the form of opal is the main sink of marine silicon. Opal burial occurs in equal parts in iron-limited open-ocean provinces and upwelling margins, especially the eastern Pacific upwelling zone. However, it is unclear why opal burial is so efficient in this margin. Here we measure fluxes of biogenic material, concentrations of diatom-bound iron and silicon isotope ratios using sediment traps and a sediment core from the Gulf of California upwelling margin. In the sediment trap material, we find that periods of intense upwelling are associated with transient iron limitation that results in a high export of silica relative to organic carbon. A similar correlation between enhanced silica burial and iron limitation is evident in the sediment core, which spans the past 26,000 years. A global compilation also indicates that hotspots of silicon burial in the ocean are all characterized by high silica to organic carbon export ratios, a diagnostic trait for diatoms growing under iron stress. We therefore propose that prevailing conditions of silica limitation in the ocean are largely caused by iron deficiency imposing an indirect constraint on oceanic carbon uptake. "

Image Caption: "The distribution of biogenic silica fluxes and molar biogenic silica (Si) to organic carbon (Si/Corg) ratios shows the variability in Si/Corg ratio among a wide range of oceanic provinces. Ocean Data View map and shading are derived from the US Joint Global Ocean Flux study. HNLC regions (dotted white ellipses) and the North East Pacific margin exhibit higher Si/Corg export ratio than the surrounding open ocean. Courtesy: authors and Nature Geoscience"

The following extract comes from the following linked University of Edinburgh news release:

Extract: "Researchers found that those periods when silicon was least abundant in ocean waters corresponded with relatively warm climates, low levels of atmospheric iron, and reduced CO2 uptake by the oceans’ plankton.
Scientists had suspected that iron might have a role in enabling plankton to absorb CO2. However, this latest study shows that a lack of iron at the ocean surface can limit the effect of other key elements in helping plankton take up carbon.
This effect is magnified in the southern ocean and equatorial Pacific and coastal areas." (

See also: (

Title: Re: Southern Ocean Venting of CO2
Post by: jai mitchell on June 11, 2014, 01:48:41 AM
You do realize the MOC implications from your SST anomaly graphic above. . . right?

The slow down of MOC is actually a much larger factor in reducing the Ocean's CO2 uptake (reduced upwelling = more surface water at current saturation levels.)

also: (

Fish are great at fighting climate change. Too bad we’re eating them all.
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 11, 2014, 02:53:23 AM

If we are looking at the same figure, its caption is: "The distribution of biogenic silica fluxes and molar biogenic silica (Si) to organic carbon (Si/Corg) ratios shows the variability in Si/Corg ratio among a wide range of oceanic provinces. Ocean Data View map and shading are derived from the US Joint Global Ocean Flux study. HNLC regions (dotted white ellipses) and the North East Pacific margin exhibit higher Si/Corg export ratio than the surrounding open ocean. Courtesy: authors and Nature Geoscience."

The image does not show SSTA, only that the (Si/Corg) ratios change with increasing AGW.

Also, I note that almost all GCMs include the influence of fish swimming, otherwise they would have too much error to be acceptable.

Title: Re: Southern Ocean Venting of CO2
Post by: jai mitchell on June 11, 2014, 07:48:15 AM
fish swimming and butterflies flapping.  .  .  8)

well, I am surprised I did not read the caption correctly on your graphic.  I have been looking at pacific (north and south) SST anomalies.

hmm is there a correlation of high SST anomaly to high (Si/Corg)?

I will have to review.  these two metrics are very light on my reading list, I know that high organic carbon is a runoff factor.  I imagine that high silica is a function of desert aerosols, i.e. sahara dust.  It seems to me that these concentrations are so low that the ratios in the open ocean could mean just about anything.

isn't there a better metric for determining regional Catm sequestration?  say, dissolved carbonium concentrations. . .
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 11, 2014, 04:56:24 PM

The link that I provided contains the following extract:

"Fresh insight into how the oceans can affect CO2 levels in the atmosphere shows that rising temperatures can indirectly increase the amount of the greenhouse gas emitted by the oceans.

Scientists studied a 26,000-year-old sediment core taken from the Gulf of California to find out how the ocean’s ability to take up atmospheric CO2 has changed over time.

They tracked the abundance of the key elements silicon and iron in the fossils of tiny marine organisms, known as plankton, in the sediment core.

Plankton absorb CO2 from the atmosphere at the ocean surface, and can lock away vast quantities of carbon.

Ocean chemistry

Researchers found that those periods when silicon was least abundant in ocean waters corresponded with relatively warm climates, low levels of atmospheric iron, and reduced CO2 uptake by the oceans’ plankton.

Scientists had suspected that iron might have a role in enabling plankton to absorb CO2. However, this latest study shows that a lack of iron at the ocean surface can limit the effect of other key elements in helping plankton take up carbon.

This effect is magnified in the southern ocean and equatorial Pacific and coastal areas.

These are known to play a crucial role in influencing levels of CO2 in the global atmosphere.

Complex relationship

Researchers from the University of Edinburgh say their findings are the first to pinpoint the complex link between iron and other key marine elements involved in regulating atmospheric CO2 by the oceans.

Their findings were verified with a global calculation for all oceans.

The study, published in Nature Geoscience, was supported by Scottish Alliance for Geoscience Environment Society and the Natural Environment Research Council.

Iron is known to be a key nutrient for plankton, but we were surprised by the many ways in which iron affects the CO2 given off by the oceans."

This indicates that the Si is tightly correlated to the iron, both of which would come from dust.  As the topic of this thread is the Southern Ocean, this dust would come from primarily from South Africa and Australia, and during warm periods the circumpolar westerly winds migrate southward (due to the geopotential height well associated with both the ozone hole and GHGs); which take this winds away from South Africa and Australia so there is less dust entering the Southern Ocean.  The Corg in the Southern Ocean is primarily related to plankton (not runoff factor), and the loss of the dust would normally reduce plankton absorption of CO2; however, I should note that if the Antarctic marine glaciers degrade fast enough then for that period of time, they can also contribute iron into the Southern Ocean, which for a few decades time many replace the atmospheric iron deduced due to the reduced dust.

Good luck with your reading on SSTA and Si/Corg.
Title: Re: Southern Ocean Venting of CO2
Post by: jai mitchell on June 11, 2014, 05:57:00 PM
Wow, that is some very esoteric stuff.  Yes I remember reading over it but have been skimming more lately.  . .  The interesting thing I have always wondered about the obvious correlation to today's environments was to consider the vast ecological impacts that human activities have had on these mechanisms.

i.e. old growth boreal forests vs. what we have today and the hundreds of millions of tons of more bony fish than we have today.  The earth looked so very differently during the Eemian than it does today.  All other things being equal (and they are not) would show that the Earth's response mechanism has been severely compromised.

What gives me pause then is the fact that the paleo analysis of climate sensitivity is the source of the fat tail of the potential (up to 6 degrees C for a doubling of carbon)  It actually is even higher than that but the authors cut off the most extreme values.

so, from my obviously low level of understanding of this topic you posit, I must ask you, can you qualify the amounts of CO2 sequestration differential that the high/low indirect capture of CO2 rates would yield?
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 11, 2014, 06:35:26 PM

The question of bounding the likely high/low CO2 sequestering potential of the Southern Ocean, this century, is too complex for me to handle (perhaps Bruce Steele can add some insight).  Not only is there the AABW production slow-down, and the increase in mode water venting (due to increased westerly winds and increased cyclone activity), but as I mentioned in the current reduction in dust can locally be supplemented by iron from ice sheet melting as is currently the case in the Amundsen Sea as cited in the following abstract from the 2013 WAIS workshop; which can resulting phytoplankton blooms that can temporarily sequester CO2:

Melting west Antarctic Ice sheets fuels high biological productivity in the coastal ocean
Kevin Arrigo, Anne-Carlijn Alderkamp, Loes J. A. Gerringa, Matthew M. Mills, Charles-Edouard Thuróczy, and Gert L. van Dijken
Stanford University, Stanford, CA

Abstract: "Polynyas of the Amundsen Sea in West Antarctica harbor the highest concentrations of phytoplankton anywhere in the Southern Ocean. At the southern end of Pine Island Bay, circumpolar deep water upwells under the Pine Island Glacier, bringing nutrients (including iron) to the surface and melting the base of the glacier. Concentrations of dissolved iron (DFe) in waters near the Pine Island Glacier and the more westward lying Crosson, Dotson, and Getz Ice Shelves varied between 0.40 and 1.31 nM, depending on the relative magnitude of upwelling, turbulent mixing, and glacial melting. These values represent maximum concentrations since associated ligands (which increase the solubility of Fe in seawater) were saturated with Fe. DFe concentrations were very high compared to what previously has been measured in the Southern Ocean. In the Pine Island Polynya, macronutrients and DFe were consumed by the phytoplankton bloom and concentrations were very low. Atmospheric dust contributed <1% of the Fe necessary to sustain the phytoplankton bloom, while vertical turbulent eddy diffusion from the sediment, sea ice melt, and upwelling contributed 1.0-3.8%, 0.7-2.9%, and 0.4-1.7%, respectively. The largest source was Fe input from the Pine Island Glacier, which satisfied the total Fe demand by the phytoplankton bloom by lateral advection of Fe over a range of 150 km from the glacier. The role of TDFe as a phytoplankton nutrient remains unclear, perhaps representing an important indirect Fe source via dissolution and complexation by dissolved organic ligands."

Regarding your search for information about paleo-evidence of higher climate sensitivities (say over 6 degrees C for a doubling of CO2); you might want to review the "Forcing" thread in the Antarctic folder (see the link below), and while all the posts there are valuable, Reply #188 cites evidence of " ...Earth Systems Sensitivity, ESS, was about 9.6 +/- 1.4 degrees C" in the early Pliocene (over 4 million years ago). (
Title: Re: Southern Ocean Venting of CO2
Post by: Bruce Steele on June 11, 2014, 07:37:10 PM
 Jai, In general 50% of Co2 emissions go into the atmosphere , 25% into the oceans, and 25% into the terrestrial sinks( forests, peat, soils ). As the atmospheric levels have risen from ~ 280 ppm too
~400 ppm those 50%25%25% numbers have stayed the same. Over time as trees die and their organic carbon is remineralized the resultant Co2 goes back into the atmosphere where the oceans then can take it up. This result is the oceans absorb the vast majority of anthropogenic Co2 over time( 100s to thousands of years) The processes that take the dissolved surface water Co2 and take it to depth are largely biological. Diatoms, silica shelled phytoplankton take their organic carbon load to the bottom when they die an sink. Coccoliths and forams do the same but because their shells are calcium carbonate
they carry a larger carbon load to the depths. As they sink past the carbonate saturation depth their shells begin to dissolve and bacteria begin to remineralize the organic carbon in their bodies. This releases very large volumes of Co2 into the deep oceans ~ 37,000 gt C.    A much smaller percentage of carbon is deposited in the very long term sink as calcium carbonate in it's mineral form on the ocean floor.
 In the L.E. Pichevan et al paper the Si/C org percentage stays the same at the surface and when captured in sediment traps placed at depth so for diatoms much of the bacterial remineralization of Organic carbon must happen within the bottom sediments.
 The physical processes that move surface water to depth with downwelling where convergent currents meet or upwelling where divergent currents meet and along continental margins are the engines that drive this system but biological processes are responsible for converting Co2 into it's long lived mineral forms and the large deep ocean carbon sinks. So far the sinks have been able to keep up with the  large carbon additions we have been providing but how well the phytoplankton perform and whether diatoms gain a larger advantage over calcarious phytoplankton , thereby compromising the efficiency
of the ocean carbon sink is but one large question among many.  Stratification of the water column ,heating, and a slowdown in the physical mixing of water masses can also play a large roll. Intensification of physical processes also can play a role as is currently happening in Antarctic Waters.
 In that this is a Carbon emissions rate that exceeds any precedent we are performing a grand experiment with unknown and unknowable outcomes. I think we can currently quantify the various carbon sinks with reasonable accuracy but venturing a guess on what would happen should there be a large shift in the component phytoplankton assemblages?  Not good. 
 The article     
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 11, 2014, 08:40:35 PM
Great post Bruce!

Thanks for filling in again on one of my many areas of ignorance.

Title: Re: Southern Ocean Venting of CO2
Post by: Laurent on June 11, 2014, 08:54:09 PM
Do we have global estimates of the futur release of CO2 via the acidification, I am thinking CACO3 should be eaten by the acids and release some CO2...?
Title: Re: Southern Ocean Venting of CO2
Post by: jai mitchell on June 11, 2014, 09:50:34 PM

I have it under good authority that 3-5% of the entire biosequestered atmospheric CO2 inventory is removed annually via downwelling in the north sea.

Thank you for your post, it is clear that we are still figuring out where the CO2 is going but our understanding of what will happen vs. what may happen (constrained by our limited understanding of the magnitude of change and feedbacks associated with that variance) is completely disassociated.

I see a large amount of "magical thinking" from the scientific community on this.  It basically looks like this:

1.  We know that these feedbacks (i.e. permafrost melting, arctic ice loss, land-carbon cycle) are potentially STRONGLY positive and that the likely response to warming of the oceans is a reduced sequestration capacity leading to a significant increase in annual Atmospheric Fraction values)


2.  The extent of these responses are dependent on warming rates and response mechanisms that are subject to high uncertainty.   


3.  If we put them in and it gets picked up by the press and we are wrong we will look like the chicken littles of the day and detract from the real dangers of climate change, plus our careers will be severely impacted and we really can't defend them because of the uncertainties in #2 above.


4.  lets just add an ambiguous fat tail at the high end of the uncertainty, say there are significant potentials for higher atmospheric and sensitivity responses, and play it safe (for our careers)


5.  there just *MIGHT* be an unknown "savior mechanism" that we do not know of yet that exists and will take the likely (though unknown extent) positive feedbacks out of the picture before complete catastrophic devastation is wrought upon all of life on planet Earth.

Title: Re: Southern Ocean Venting of CO2
Post by: Bruce Steele on June 11, 2014, 10:35:45 PM
Laurent, You are correct about calcium carbonate dissolving and releasing it's Co2 but this largely happens at depth.Bacterial decomposition of organic matter adds extra Co2 into this process. This results is increased DIC ( dissolved inorganic carbon )and decreased pH at depth  but this dissolved Co2 can be released back into the atmosphere when deep water upwells back into surface waters. There are two water masses that are deep enough for this organic to inorganic transition to take place, intermediate waters with a formation to ventilation time of about 35 years in both Antarctic and North Pacific processes, and deep water processes and the movement of MOC waters. These deep and bottom water processes are much slower with a formation to ventilation time of about up to a  thousand years. So the increased Co2 we put out 35+ years ago is already resurfacing with Intermediate Waters and this is a big part of why the oysters are having a hard time in the Pacific Northwest. A large portion of the Co2 we are sinking into the oceans will not show up again for 100-1000 years. There is also a portion of our Anthropogenic Carbon that is put away into bottom sediments and can be held in geologic processes for extremely long periods.
 So the impacts from remineralization of organic matter and dissolution of carbonate shells will be concentrated in those places where intermediate water processes upwell saturated waters  back into surface waters. This acidification of surface waters and potential atmospheric ventilation will have a more immediate effect on sea life     
than terrestrial life in the 10-100 time frame. IMO
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 11, 2014, 10:55:31 PM

While Bruce knows much more about the topic of ocean acidification than I do, I can refer you to Reply #68 of the "Trends of the Southern Ocean" thread in the Antarctic folder, which includes the two attached images, indicating that if we stay on the RCP 8.5 pathway to 2100 then about 60% of the Southern Ocean surface waters (on an annual average basis) will be corrosive to the aragonite-shelled organisms (eg pteropods, which are a major part of the marine food chain in the Southern Ocean).

Another bad trend that Bruce pointed out to me is that particularly in the Arctic Ocean (and maybe soon in the Southern Ocean) nano-plankton are out-competing the regular plankton as the sea ice retreats, and the nano-plankton does not sink and sequester CO2 like the regular plankton does.  This is a complex and dynamic situation.

Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 11, 2014, 11:00:48 PM
I note that in the "Trends of the Southern Ocean" thread in the Antarctic folder (see link below), that the original post & the following Replies deal with CO2 absorption/venting in the Southern Ocean: #1, 3, 9, 10, 11, 13, 19, 26, 27, 51 and 69.,406.50.html (,406.50.html)
Title: Re: Southern Ocean Venting of CO2
Post by: Bruce Steele on June 11, 2014, 11:18:19 PM
Jai, I think what we know about this subject is rapidly evolving and I have seen papers that lay out very disturbing outcomes. Many .  Although the carbon cycle is fairly complicated it is the process that makes life on this planet livable. 
 The North Atlantic deep water formation you refer to plays a major role in carbon sequestration processes on a global scale. Much of what we know about heat transfer in the upper 2000 feet of ocean has been collected with Argo floats that haven't been able to go deeper than 2000 feet but there is now a deep water Argo that can retrieve  data from deep waters with patchy monitoring and sampling to date. Technology is at once enabling our understanding and securing our fate.
 ASLR, thanks for the quantified reply. I usually need to plan my links before I post so sorry if I haven't provided better links to peer reviewed sources. Sometimes I have to think two or three days after you put up links to articles before I venture a response . Thanks for all the great links and the Si/C org paper had me thinking long and hard. Iron, nutrient competition, and changes in physical forcing. The paper doesn't much describe how calcium carbonate shelled phytoplankton compete with diatoms in Fe constrained conditions. Not well apparently .     
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 12, 2014, 01:20:03 AM

The use of a Big Data approach to is the only answer that I can think of for getting scientists (or even better decision makers) to make more comprehensive/meaningful forecasts about the implications of climate change, and according to the linked article the UN agrees with me, so they are sponsoring a Big Data Climate Change Challenge competition: (

I know that Eric Rignot has a Big Data project in order to better assess the risk of the WAIS collapsing this century; but I am sure that this approach could be used on any aspect of climate change, including CO2 absorption/venting from the ocean.

Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 12, 2014, 03:30:42 AM
Talking about esoteric butterfly effects, it occurs to me that there is potentially a significant difference between the type of CO₂ absorbed in the Southern Ocean say by the AABW or plankton, versus the CO₂ vented by Southern Ocean mode water, in that the venting probably occurs episodically in relatively high concentrations (say between 400 to 700ppm), with the episodes associated with large eddies/vortices and local upwelling events. Such episodic CO₂ emissions, coupled with the geopotential height well over Antarctica, allows for a positive feedback mechanism where the temporarily concentrated CO₂ over Antarctica strengthens the geopotential height well, which in-turn strengthens the westerly winds, which causes more episodic CO₂ emissions (which is concentrated due to the decomposition of organic material in the mode water).  I image that if this positive feedback mechanism is correct then it would be difficult to detect the CO₂ concentration over the Antarctic from flask samples taken at the South Pole station, and would be even harder to identify in RCMs.

If the vented CO₂ from the mode water were not concentrated, of if the ozone hole had not formed the geopotential height well over Antarctica, then this potential positive feedback mechanism might not exist; and if this positive feedback mechanism did not exist, it is possible that when the ozone hole heals itself the geopotential height well might disappear for a hundred years, or more, while the GHG slowly built-up.  Thus our current situation may drive climate change faster than paleo-evidence would suggest; which would imply that Earth System Sensitivity, ESS, values well above 4.5 degrees C may be probable this century [not to mention my current concern that bark beetles (and associated forest fires due to all the dead trees) will quickly destroy the boreal forests this century, which would also invalidate paleo- ESS values as boreal forests not only absorb CO₂, the also emit aerosols that promote cloud formation, which historically would have prevented mean global temperature increases, that may happen this century due to the possible rapid degradation of the boreal forests over the next few decades].
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 12, 2014, 11:51:34 AM
I note that even though the Antarctic Sea Ice Extent is well above average for this time of year  and should be blocking CO2 venting (see the first image for June 9 2014); that the average atmospheric CO2 concentration over large parts of Antarctica are still above 410ppm (see the second attached image for June 10 2014), due to the high winds and storminess over the Southern Ocean at this time of year.
Title: Re: Southern Ocean Venting of CO2
Post by: Bruce Steele on June 15, 2014, 07:18:26 AM
Here is an old (2004) abstract that ties increased Antarctic intermediate water ventilation + changes in deep water ventilation in a Carbon 13 excursion in the fossil record. Said same current increases in ventilation might also be reflected in carbon 12/carbon 13 ratios? That would be something to ponder. 
"We suggest that variations in the dominance and direction of AAIW circulation in the Tasman Sea, and increased oceanic ventilation, can account for the rapid change in the water column δ13Cplanktonic-benthic offset during the glacial-interglacial transition. Our results support the hypothesis that intermediate water plays an important role in propagating climatic changes from the polar regions to the tropics. In this case, climatic variations in the Southern Hemisphere may have led to the rapid ventilation of deep water and AAIW during Termination 1, which contributed to the postglacial rise in atmospheric CO2." (
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 15, 2014, 07:30:15 PM
Hopefully data from NASA's Orbiting Carbon Observatory-2 satellite (OCO-2), to be launched on July 1 from Vandenberg Air Force Base in California, will provide more precise atmospheric CO₂ concentration measurements, that will help clarify CO₂ venting from the ocean.  See the following NASA link and reference with a free access pdf: (

Christian Frankenberg, Chris O'Dell, Joseph Berry, Luis Guanter, Joanna Joiner, Philipp Köhler, Randy Pollock, Thomas E. Taylor (2014) Prospects for chlorophyll fluorescence remote sensing from the Orbiting Carbon Observatory-2, Remote Sensing of Environment, Vol 147, 5 May. 2014, Pgs 1-12, ( (

Abstract: "The Orbiting Carbon Observatory-2 (OCO-2), scheduled to launch in July 2014, is a NASA mission designed to measure atmospheric CO2. Its main purpose is to allow inversions of net flux estimates of CO2 on regional to continental scales using the total column CO2 retrieved using high-resolution spectra in the 0.76, 1.6, and 2.0 μm ranges. Recently, it was shown that solar-induced chlorophyll fluorescence (SIF), a proxy for gross primary production (GPP, carbon uptake through photosynthesis), can be accurately retrieved from space using high spectral resolution radiances in the 750 nm range from the Japanese GOSAT and European GOME-2 instruments. Here, we use real OCO-2 thermal vacuum test data as well as a full repeat cycle (16 days) of simulated OCO-2 spectra under realistic conditions to evaluate the potential of OCO-2 for retrievals of chlorophyll fluorescence and also its dependence on clouds and aerosols.   We find that the single-measurement precision is 0.3–0.5Wm−2sr−1 μm−1 (15–25% of typical peak values), better than current measurements from space but still difficult to interpret on a single-sounding basis. The most significant advancement will come from smaller ground-pixel sizes and increased measurement frequency, with a 100-fold increase compared to GOSAT (and about 8 times higher than GOME-2). This will largely decrease the need for coarse spatial and temporal averaging in data analysis and pave the way to accurate local studies.  We also find that the lack of full global mapping from the OCO-2 only incurs small representativeness errors on regional averages.  Eventually, the combination of net ecosystem exchange (NEE) derived from CO2 source/sink inversions and SIF as proxy for GPP from the same satellite will provide a more process-based understanding of the global carbon cycle."
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 16, 2014, 03:08:57 AM
The following linked research indicates how important the blocking of the venting of CO₂ from the Southern Ocean by expanded sea ice extent was in contributing to the development of the Last Glacial Maximum, LGM.  By extension this research supports the concept that if the Southern Ocean vents more CO₂ into the atmosphere (due to increase wind velocity and storminess), this will contribute to global warming:

Raffaele Ferrari, Malte F. Jansen, Jess F. Adkins, Andrea Burke, Andrew L. Stewart, and Andrew F. Thompson, (2014), "Antarctic sea ice control on ocean circulation in present and glacial climates", PNAS, doi: 10.1073/pnas.1323922111 ( (

Significance: "The ocean’s role in regulating atmospheric carbon dioxide on glacial–interglacial timescales remains an unresolved issue in paleoclimatology. Many apparently independent changes in ocean physics, chemistry, and biology need to be invoked to explain the full signal. Recent understanding of the deep ocean circulation and stratification is used to demonstrate that the major changes invoked in ocean physics are dynamically linked. In particular, the expansion of permanent sea ice in the Southern Hemisphere results in a volume increase of Antarctic-origin abyssal waters and a reduction in mixing between abyssal waters of Arctic and Antarctic origin."

Abstract: "In the modern climate, the ocean below 2 km is mainly filled by waters sinking into the abyss around Antarctica and in the North Atlantic. Paleoproxies indicate that waters of North Atlantic origin were instead absent below 2 km at the Last Glacial Maximum, resulting in an expansion of the volume occupied by Antarctic origin waters. In this study we show that this rearrangement of deep water masses is dynamically linked to the expansion of summer sea ice around Antarctica. A simple theory further suggests that these deep waters only came to the surface under sea ice, which insulated them from atmospheric forcing, and were weakly mixed with overlying waters, thus being able to store carbon for long times. This unappreciated link between the expansion of sea ice and the appearance of a voluminous and insulated water mass may help quantify the ocean’s role in regulating atmospheric carbon dioxide on glacial–interglacial timescales. Previous studies pointed to many independent changes in ocean physics to account for the observed swings in atmospheric carbon dioxide. Here it is shown that many of these changes are dynamically linked and therefore must co-occur."

Also see the extracts from the following link: (

Extracts: "They discovered that the massive amount of ice covered the only region where the deep ocean was able to breathe, preventing the Southern Ocean’s CO2 from being exhaled into the atmosphere. Furthermore, the study authors found a link between sea ice change and a large-scale ocean water rearrangement contained in the LGM’s paleoclimate record.
“Under the expanded sea ice, a greater amount of upwelled deep water sank back downward. Southern Ocean abyssal water eventually filled a greater volume of the entire midlevel and lower ocean – lifting the interface between upper and lower waters to a shallower depth, such that the deep, carbon-rich waters lost contact with the upper ocean,” the Institute said. “Breathing less, the ocean could store a lot more carbon.”
The fact that the Southern Ocean was covered with ice, unable to release its carbon dioxide, helps explain the sizable drop in atmospheric CO2 during the LGM, they noted. The National Science Foundation-funded study also demonstrates a possible dynamic link between sea-ice expansion and the increase in ocean water insulated from the atmosphere – two events that scientists had long viewed as separate and distinct phenomena.
“This insight takes on extra relevance in light of the fact that paleoclimatologists need to explain not just the very low levels of atmospheric CO2 during the last ice age, but also the fact that this happened during each of the last four glacial periods, as the paleoclimate record reveals,” the Institute explained.
In contrast to the previous belief that independent changes caused CO2 levels to be reduced by the same amount in every ice age, Ferrari explained that the new study indicates “that all the events that co-occurred must be incredibly tightly linked, without much freedom to drift beyond a narrow margin. If there is a causality effect among the events at the start of an ice age, then they could happen in the same ratio.”"
Title: Re: Southern Ocean Venting of CO2
Post by: LRC1962 on June 16, 2014, 05:07:44 AM
The following linked research indicates that global warming can reduce CO₂ uptake in the oceans, particularly in areas with high upwelling (see attached image and following caption), such as the Southern Ocean:

L. E. Pichevin, R. S. Ganeshram, W. Geibert, R. Thunell & R. Hinton, (2014), "Silica burial enhanced by iron limitation in oceanic upwelling margins", Nature Geoscience doi:10.1038/ngeo2181 (
Now if I am following their argument correctly is that heat +CO2 > lack of iron > few diatoms.
So I did some digging as I have no chemistry background, and I came up with this reasoning based on these 2 articles. ( and (
The reasoning goes this way. The highly acidic nature of the oceans, because of too much CO2 means acidic ocean which allows greater creation of hexaaquairon(III) which then reacts to the water which then produces more CO2 and Fe(H2O)3(OH)3(s) which is not normally soluble in water and therefore probably not in a form that is usable by diatoms. Ergo less iron more CO2 fewer diatoms which means less CO2 consumption. Unlike "sceptics" who say more CO2 more plants. If my logic is faulty please forgive me as I was trying to think of a way to get ride of iron from the food chain in the ocean.
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 16, 2014, 12:30:32 PM

I primarily know about the case in the Southern Ocean, as I believe that the sources of iron and silica in the ocean varies depending on location.  In the Southern Ocean when the world is cold (as in during glacial periods like the last ice age) the track of the circumpolar Antarctic westerly winds expands north to as to extend over both Australia and Southern Africa, which allows these winds to pick-up dust (which contains both iron and silica) and deposits the dust into the Southern Ocean; which then promotes plankton growth, which absorbs more CO2, thus acting promoting more cooling.  However, during periods of global warming the westerly winds migrate southward, away from Australia and Southern Africa; resulting in less dust deposited in the Southern Ocean, thus reducing plankton growth, resulting in less CO2 absorption, thus acting as a positive feedback for more global warming.

It is likely that ocean chemistry plays a part in this process; however, I am not familiar with that part of the story.

Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 17, 2014, 08:01:25 PM
The average atmospheric CO2 concentration over large parts of Antarctica are still above 410ppm (see the attached image for June 16 2014):
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 18, 2014, 12:36:37 AM
The linked reference (with a free access pdf) discusses the different roles of the Southern Ocean and the North Atlantic in changes of atmospheric radiocarbon.  This paper discusses some of the mechanisms that influence the venting of CO₂ from the Southern Ocean:

Hain, M.P., Sigman, D.M., and Haug, G.H., (2014), "Distinct roles of the Southern Ocean and North Atlantic in the deglacial atmospheric radiocarbon decline", Earth and Planetary Science Letters, 394, 198-208, doi: 10.1016/j.epsl.2014.03.020. (

"Abstract: In the context of the atmospheric CO2 14C/C (Δ14Catm) changes since the last ice age, two episodes of sharp Δ14Catm decline have been related to either the venting of deeply sequestered low-14C CO2 through the Southern Ocean surface or the abrupt onset of North Atlantic Deep Water (NADW) formation. In model simulations using an improved reconstruction of 14C production, Atlantic circulation change and Southern Ocean CO2 release both contribute to the overall deglacial Δ14Catm decline, but only the onset of NADW can reproduce the sharp Δ14Catm declines. To fully simulate Δ14Catm data requires an additional process that immediately precedes the onsets of NADW. We hypothesize that these “early” Δ14Catm declines record the thickening of the ocean’s thermocline in response to reconstructed transient shutdown of NADW and/or changes in the southern hemisphere westerly winds. Such thermocline thickening may have played a role in triggering the NADW onsets."

Also see: (

Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 18, 2014, 12:54:27 AM
For those interested in studying the various mechanisms (including chemical and biological) influencing the absorption and/or venting of CO2 into/from the ocean, I can recommend the following linked reference (with a free access pdf):

MP Hain, DM Sigman, and GH Haug, (2014), The Biological Pump in the Past, Elsevier Ltd. All rights reserved. (
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 19, 2014, 10:04:58 PM
The following linked reference indicates that oceanic CO₂ content for "… the high-latitude Southern Ocean and eastern equatorial Pacific have the weakest growth rates, remaining below the atmospheric pCO2 growth rate." 

Thus the CO₂ content of the Southern Ocean will exceed that indicated by the attached image from Tjiputra et al 2014 illustrating the average ocean situation:

Tjiputra, J. F., Olsen, A., Bopp, L., Lenton, A., Pfeil, B., Roy, T., Segschneider, J., Totterdell, I., and Heinze, C., "Long-term surface pCO2 trends from observations and models," Tellus B, 66, 23083,2014. (

Abstract: "We estimate regional long-term surface ocean pCO2 growth rates using all available underway and bottled biogeochemistry data collected over the past four decades. These observed regional trends are compared with those simulated by five state-of-the-art Earth system models over the historical period. Oceanic pCO2 growth rates faster than the atmospheric growth rates indicate decreasing atmospheric CO2 uptake, while ocean pCO2 growth rates slower than the atmospheric growth rates indicate increasing atmospheric CO2 uptake. Aside from the western subpolar North Pacific and the subtropical North Atlantic, our analysis indicates that the current observation-based basin-scale trends may be underestimated, indicating that more observations are needed to determine the trends in these regions. Encouragingly, good agreement between the simulated and observed pCO2 trends is found when the simulated fields are subsampled with the observational coverage. In agreement with observations, we see that the simulated pCO2 trends are primarily associated with the increase in surface dissolved inorganic carbon (DIC) associated with atmospheric carbon uptake, and in part by warming of the sea surface. Under the RCP8.5 future scenario, DIC continues to be the dominant driver of pCO2 trends, with little change in the relative contribution of SST. However, the changes in the hydrological cycle play an increasingly important role. For the contemporary (1970–2011) period, the simulated regional pCO2 trends are lower than the atmospheric growth rate over 90% of the ocean. However, by year 2100 more than 40% of the surface ocean area has a higher oceanic pCO2 trend than the atmosphere, implying a reduction in the atmospheric CO2 uptake rate. The fastest pCO2 growth rates are projected for the subpolar North Atlantic, while the high-latitude Southern Ocean and eastern equatorial Pacific have the weakest growth rates, remaining below the atmospheric pCO2 growth rate. Our work also highlights the importance and need for a sustained long-term observing strategy to continue monitoring the change in the ocean anthropogenic CO2 sink and to better understand the potential carbon cycle feedbacks to climate that could arise from it."
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 21, 2014, 08:52:37 PM
The following extracts from the linked Princeton article, indicates: (a) that the Southern Ocean has been critical in recent years for both absorbing much of the anthropogenic CO₂ and for absorbing heat from the atmosphere and sequestering in the deep ocean; and (b) that as global warming increases the Southern Ocean will absorb less CO₂ both due to increased vertical mixing resulting in more CO₂ venting, and less atmospheric iron (ie less dust) reducing CO₂ absorption and sequestering by plankton (see the attached image from the article illustrating the complex balance between CO₂ absorption and venting in the Southern Ocean); and also less heat absorption due to the reduction of the rate of AABW production:

Key extracts:" Though it makes up less than a third of the world’s ocean coverage, the Southern Ocean surrounding Antarctica soaks up about half of the man-made carbon dioxide absorbed by the world’s oceans from the atmosphere each year.
This frigid water also absorbs heat: the Southern Ocean has helped prevent the planet from warming up as much as it might have by now from human activity, according to Jorge Sarmiento, the George J. Magee Professor of Geoscience and Geological Engineering. Because its waters are so cold, the Southern Ocean absorbs about 60 percent of the excess heat that moves annually from the atmosphere into the ocean.

“It’s old, it’s cold and it’s rich,” said Sarmiento. These traits, he explained, enable the Southern Ocean to have the influence that it does over global climate and nutrient regulation — and challenges scientists to find out how this massive storage vessel for carbon, nutrients and heat might react to rising carbon emissions and climate change.
A key question is whether rising carbon emissions will boost or hamper the Southern Ocean’s ability to sponge up carbon dioxide. Changing wind and rainfall patterns due to a warming Earth could shift how much carbon and heat the Southern Ocean can store in either direction, according to Daniel Sigman, the Dusenbury Professor of Geological and Geophysical Sciences. If winds pick up, for example, then mixing between the Southern Ocean’s deep and shallow waters may pick up as well. If high-latitude rainfall increases, more freshwater on the polar ocean’s surface may mean a higher density difference between the surface and deep waters, leading to less mixing. Depending on the response of ocean biology to this range of possible changes in ocean circulation, the rate of carbon uptake may either rise or fall.

The Southern Ocean actually releases some carbon dioxide into the atmosphere because phytoplankton, which consume carbon dioxide as they grow, cannot keep up with the rapid supply of nutrients and carbon from the underlying deep ocean and leave much of it unused.
Sarmiento has continued to investigate the ocean’s role in global climate over the three decades since, with a particular focus on the Southern Ocean. In 1996, he constructed a model that predicted how future global warming would affect the ocean’s ability to absorb carbon dioxide: he suggested that warming would weaken the ocean’s circulation, which would in turn compromise the movement of carbon dioxide to deep waters.

An essential nutrient for phytoplankton, iron is relatively scarce in the Southern Ocean. The lack of iron prevents phytoplankton populations from growing to numbers large enough for them to fully consume the ocean’s nutrients, including carbon dioxide. This means that a lot of carbon dioxide can leak right back into the atmosphere.
These two factors — more dust-borne iron and more mixing of waters — could have allowed the Southern Ocean to absorb more carbon dioxide in the past. These findings may hint at how the Southern Ocean will change as the Earth warms in the next few years, Sigman said, with the possibility of more mixing and less iron input."
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on June 30, 2014, 02:57:22 AM
As we have left the austral Fall and have entered the austral Winter, the attached NOAA plot (issued on June 29 2014) shows that the atmospheric CO2 concentration over Antarctica is remaining anomalously high:
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on July 08, 2014, 03:23:33 AM
While the linked article is about increased venting of CO2 from ocean areas other than the Southern Ocean; nevertheless, the article does say that the venting increases with increasing latitude, and all CO2 venting from the ocean contributes to global warming:

W. J. Sydeman, M. García-Reyes, D. S. Schoeman, R. R. Rykaczewski, S. A. Thompson, B. A. Black, S. J. Bograd, (2014), "Climate change and wind intensification in coastal upwelling ecosystems", Science, Vol. 345 no. 6192 pp. 77-80, DOI: 10.1126/science.1251635 (

Abstract: "In 1990, Andrew Bakun proposed that increasing greenhouse gas concentrations would force intensification of upwelling-favorable winds in eastern boundary current systems that contribute substantial services to society. Because there is considerable disagreement about whether contemporary wind trends support Bakun’s hypothesis, we performed a meta-analysis of the literature on upwelling-favorable wind intensification. The preponderance of published analyses suggests that winds have intensified in the California, Benguela, and Humboldt upwelling systems and weakened in the Iberian system over time scales ranging up to 60 years; wind change is equivocal in the Canary system. Stronger intensification signals are observed at higher latitudes, consistent with the warming pattern associated with climate change. Overall, reported changes in coastal winds, although subtle and spatially variable, support Bakun’s hypothesis of upwelling intensification in eastern boundary current systems."
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on July 11, 2014, 12:48:53 AM
The linked reference (with a free access pdf) provides additional information on CO2 absorption and venting from the ocean in general:

Long Cao et al 2014, "Sensitivity of ocean acidification and oxygen to the uncertainty in climate change", Environ. Res. Lett. 9 064005, doi:10.1088/1748-9326/9/6/064005 (

Abstract: "Due to increasing atmospheric CO2 concentrations and associated climate change, the global ocean is undergoing substantial physical and biogeochemical changes. Among these, changes in ocean oxygen and carbonate chemistry have great implication for marine biota. There is considerable uncertainty in the projections of future climate change, and it is unclear how the uncertainty in climate change would also affect the projection of oxygen and carbonate chemistry. To investigate this issue, we use an Earth system model of intermediate complexity to perform a set of simulations, including that which involves no radiative effect of atmospheric CO2 and those which involve CO2-induced climate change with climate sensitivity varying from 0.5 °C to 4.5 °C. Atmospheric CO2 concentration is prescribed to follow RCP 8.5 pathway and its extensions. Climate change affects carbonate chemistry and oxygen mainly through its impact on ocean temperature, ocean ventilation, and concentration of dissolved inorganic carbon and alkalinity. It is found that climate change mitigates the decrease of carbonate ions at the ocean surface but has negligible effect on surface ocean pH. Averaged over the whole ocean, climate change acts to decrease oxygen concentration but mitigates the CO2-induced reduction of carbonate ion and pH. In our simulations, by year 2500, every degree increase of climate sensitivity warms the ocean by 0.8 °C and reduces ocean-mean dissolved oxygen concentration by 5.0%. Meanwhile, every degree increase of climate sensitivity buffers CO2-induced reduction in ocean-mean carbonate ion concentration and pH by 3.4% and 0.02 units, respectively. Our study demonstrates different sensitivities of ocean temperature, carbonate chemistry, and oxygen, in terms of both the sign and magnitude to the amount of climate change, which have great implications for understanding the response of ocean biota to climate change."
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on July 11, 2014, 01:01:49 AM
The linked reference (with free pdf, images and supplemental data) provides paleo-evidence that CO2 ventilation from the Southern Ocean can contribute significantly to global warming:

Skinner, Luke C. and Waelbroeck, Claire and Scrivner, Adam E. and Fallon, Stewart J. (2014) "Radiocarbon evidence for alternating northern and southern sources of ventilation of the deep Atlantic carbon pool during the last deglaciation," Proceedings of the National Academy of Sciences, 111 (15). pp. 5480-5484. ISSN 0027-8424, 1091-6490, doi: 10.1073/pnas.1400668111 (

Abstract: "Recent theories for glacial–interglacial climate transitions call on millennial climate perturbations that purged the deep sea of sequestered carbon dioxide via a “bipolar ventilation seesaw.” However, the viability of this hypothesis has been contested, and robust evidence in its support is lacking. Here we present a record of North Atlantic deep-water radiocarbon ventilation, which we compare with similar data from the Southern Ocean. A striking coherence in ventilation changes is found, with extremely high ventilation ages prevailing across the deep Atlantic during the last glacial period. The data also reveal two reversals in the ventilation gradient between the deep North Atlantic and Southern Ocean during Heinrich Stadial 1 and the Younger Dryas. These coincided with periods of sustained atmospheric CO2 rise and appear to have been driven by enhanced ocean–atmosphere exchange, primarily in the Southern Ocean. These results confirm the operation of a bipolar ventilation seesaw during deglaciation and underline the contribution of abrupt regional climate anomalies to longer-term global climate transitions."
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on July 11, 2014, 01:45:52 AM
For more serious investigators, the following link leads to a reference on how to estimate ventilation from the ocean using overturning stream functions:

Thompson, B., Nycander, J., Nilsson, J., Jakobsson, M., and Döös, K., (2014), "Estimating ventilation time scales using overturning stream functions", Ocean Dynamics, Vol 64, Issue 6, Doi: 10.1007/s10236-014-0726-5 (

Abstract: "A simple method for estimating ventilation time scales from overturning stream functions is proposed. The stream function may be computed using either geometric coordinates or a generalized vertical coordinate, such as potential density (salinity in our study). The method is tested with a three-dimensional circulation model describing an idealized semi-enclosed ocean basin ventilated through a narrow strait over a sill, and the result is compared to age estimates obtained from a passive numerical age tracer. The best result is obtained when using the stream function in salinity coordinates. In this case, the reservoir-averaged advection time obtained from the overturning stream function in salinity coordinates agrees rather well with the mean age of the age tracer, and the corresponding maximum ages agree very well."
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on July 21, 2014, 04:04:04 PM
morganism in the "Trends for the Southern Ocean" thread in the "Antarctic" folder provided the following links to references about the DIMES program that provides physically measured parameters supporting the position that increases in the wind velocities of the Southern Hemisphere Westerlies, will result in increased venting of CO₂ from the Southern Ocean:

K. L. Sheen, A. C. Naveira Garabato, J. A. Brearley, M. P. Meredith, K. L. Polzin, D. A. Smeed, A. Forryan, B. A. King, J-B. Sallée, L. St. Laurent, A. M. Thurnherr, J. M. Toole, S. N. Waterman & A. J. Watson, (2014), "Eddy-induced variability in Southern Ocean abyssal mixing on climatic timescales", Nature Geoscience, doi:10.1038/ngeo2200 (

Abstract: "The Southern Ocean plays a pivotal role in the global ocean circulation and climate. There, the deep water masses of the world ocean upwell to the surface and subsequently sink to intermediate and abyssal depths, forming two overturning cells that exchange substantial quantities of heat and carbon with the atmosphere. The sensitivity of the upper cell to climatic changes in forcing is relatively well established. However, little is known about how the lower cell responds, and in particular whether small-scale mixing in the abyssal Southern Ocean, an important controlling process of the lower cell, is influenced by atmospheric forcing. Here, we present observational evidence that relates changes in abyssal mixing to oceanic eddy variability on timescales of months to decades. Observational estimates of mixing rates, obtained along a repeat hydrographic transect across Drake Passage, are shown to be dependent on local oceanic eddy energy, derived from moored current meter and altimetric measurements. As the intensity of the regional eddy field is regulated by the Southern Hemisphere westerly winds, our findings suggest that Southern Ocean abyssal mixing and overturning are sensitive to climatic perturbations in wind forcing."

See also: (
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on September 13, 2014, 01:21:51 AM
The linked reference provides insight about the influence of sea ice in the Southern Ocean on CO₂ absorption and release:

Bruno Delille, Martin Vancoppenolle, Nicolas-Xavier Geilfus, Bronte Tilbrook, Delphine Lannuzel, Véronique Schoemann, Sylvie Becquevort, Gauthier Carnat, Daniel Delille, Christiane Lancelot, Lei Chou, Gerhard S. Dieckmann and Jean-Louis Tison, (2014), "Southern Ocean CO2 sink: The contribution of the sea ice", Journal of Geophysical Research: Oceans, DOI: 10.1002/2014JC009941 (

Abstract: "We report first direct measurements of the partial pressure of CO2 (pCO2) within Antarctic pack sea ice brines and related CO2 fluxes across the air-ice interface. From late winter to summer, brines encased in the ice change from a CO2 large over-saturation, relative to the atmosphere, to a marked under-saturation while the underlying oceanic waters remains slightly oversaturated. The decrease from winter to summer of pCO2 in the brines is driven by dilution with melting ice, dissolution of carbonate crystals and net primary production. As the ice warms, its permeability increases, allowing CO2 transfer at the air-sea ice interface. The sea ice changes from a transient source to a sink for atmospheric CO2. We upscale these observations to the whole Antarctic sea ice cover using the NEMO-LIM3 large-scale sea ice-ocean, and provide first estimates of spring and summer CO2 uptake from the atmosphere by Antarctic sea ice. Over the spring-summer period, the Antarctic sea ice cover is a net sink of atmospheric CO2 of 0.029 PgC, about 58% of the estimated annual uptake from the Southern Ocean. Sea ice then contributes significantly to the sink of CO2 of the Southern Ocean."
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on August 26, 2015, 01:11:32 AM
The linked reference provides observational findings that the Subantarctic Zone (SAZ) is important when assess the propensity for the Southern Ocean to vent CO₂:

E. H. Shadwick, T. W. Trull, B. Tilbrook, A. J. Sutton, E. Schulz & C. L. Sabine (2015), "Seasonality of biological and physical controls on surface ocean CO2 from hourly observations at the Southern Ocean Time Series site south of Australia", Global Biochemical Cycles, Volume 29, Issue 2, Pages 223–238, DOI: 10.1002/2014GB004906 (

Abstract: "The Subantarctic Zone (SAZ), which covers the northern half of the Southern Ocean between the Subtropical and Subantarctic Fronts, is important for air-sea CO2 exchange, ventilation of the lower thermocline, and nutrient supply for global ocean productivity. Here we present the first high-resolution autonomous observations of mixed layer CO2 partial pressure (pCO2) and hydrographic properties covering a full annual cycle in the SAZ. The amplitude of the seasonal cycle in pCO2 (∼60 μatm), from near-atmospheric equilibrium in late winter to ∼330 μatm in midsummer, results from opposing physical and biological drivers. Decomposing these contributions demonstrates that the biological control on pCO2 (up to 100 μatm), is 4 times larger than the thermal component and driven by annual net community production of 2.45 ± 1.47 mol C m−2 yr−1. After the summer biological pCO2 depletion, the return to near-atmospheric equilibrium proceeds slowly, driven in part by autumn entrainment into a deepening mixed layer and achieving full equilibration in late winter and early spring as respiration and advection complete the annual cycle. The shutdown of winter convection and associated mixed layer shoaling proceeds intermittently, appearing to frustrate the initiation of production. Horizontal processes, identified from salinity anomalies, are associated with biological pCO2 signatures but with differing impacts in winter (when they reflect far-field variations in dissolved inorganic carbon and/or biomass) and summer (when they suggest promotion of local production by the relief of silicic acid or iron limitation). These results provide clarity on SAZ seasonal carbon cycling and demonstrate that the magnitude of the seasonal pCO2 cycle is twice as large as that in the subarctic high-nutrient, low-chlorophyll waters, which can inform the selection of optimal global models in this region."
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on November 17, 2016, 06:58:26 PM
The linked article discusses both the reality and consequences of the changing nature of CO₂ absorption/release and heat uptake by the Southern Ocean.  The extracts below only focus on the risks that the Southern Ocean may soon start venting more CO₂ than it is absorbing.

Jeff Tollefson (17 November 2016), "How much longer can Antarctica’s hostile ocean delay global warming?", Nature, Volume: 539, Pages: 346–348, doi:10.1038/539346a (

The waters of the Southern Ocean have absorbed much of the excess heat and carbon generated by humanity.

Although controversial when she encountered it back in 1994, this powerful upwelling is now recognized as a hallmark of the Southern Ocean, a mysterious beast that swirls around Antarctica, driven by the world’s strongest sustained winds. The Southern Ocean absorbs copious amounts of carbon dioxide and heat from the atmosphere, which has slowed the rate of global warming. And its powerful currents drive much of the global ocean circulation.

Already, initial data from an array of ocean floats suggest that upwelling waters could be limiting how much CO2 the Southern Ocean absorbs each year. This raises new questions about how effective these waters will be as a brake on global warming in decades to come.

“The Southern Ocean is doing us a big climate favour at the moment, but it’s not necessarily the case that it will continue doing so in the future,” says Michael Meredith …

Indirect evidence suggests that the Southern Ocean is a net carbon sink and has absorbed as much as 15% of the carbon emissions emitted by humanity since the industrial revolution. But at some times of year and in specific places in this region, carbon-rich surface waters release CO2 into the atmosphere.

Now, researchers are getting some of their first glimpses in near-real time of what happens in the Southern Ocean, particularly in winter. “Right off the bat, we are seeing CO2 fluxes into the atmosphere that are much greater than we had estimated before,” Sarmiento says. “It’s just revolutionary.”

The unpublished analysis is based on just 13 floats that have been in the water for at least a year, so the question now is whether the higher CO2 emissions during winter represent larger trends across the entire Southern Ocean.

“It’s pretty tantalizing,” says Alison Gray, a postdoctoral researcher at Princeton who is leading the study. “It would imply that potentially there is a much weaker carbon sink in the Southern Ocean than has been estimated.”

Hints of something similar have been seen before. In 2007, a team led by Corinne Le Quéré, now director of the Tyndall Centre for Climate Change Research in Norwich, UK, published a study in Science indicating that the rate of carbon uptake by the Southern Ocean decreased between 1981 and 2004. The authors blamed the changes on the winds that encircle the Antarctic continent. The speed of those winds had increased during that time, probably as a result of the hole in the stratospheric ozone layer over Antarctica and possibly because of global warming. Stronger winds are better able to pull up deep, ancient water, which releases CO2 when it reaches the surface. That would have caused a net weakening of the carbon sink.

If that trend were to continue, atmospheric CO2 levels would rise even faster in the future. However, a study in Science last year found that the carbon sink started to strengthen in the early 2000s (see ‘The unreliable sink’).

Le Quéré says it’s unclear whether that rise in CO2 absorption is a return to normal or a deviation from the long-term weakening of the sink. Regardless, she says, it’s now clear that the Southern Ocean might be much more fickle than scientists thought."
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on January 23, 2017, 07:20:48 PM
The linked reference indicate that current models likely do not accurately represent CO₂ ventilation from the equatorial Pacific (& Atlantic) Ocean(s) during periods of deglaciation.  The reference states: "In addition, both gradual and rapid deglacial radiocarbon changes in these Pacific records are coeval with changes in the Atlantic records.  This in-phase behavior suggest that the Southern Ocean overturning was the dominant driver of changes in the Atlantic and Pacific ventilation during deglacitions."  This does not bode well for our future.

Natalie E. Umling & Robert C. Thunell (2017), "Synchronous deglacial thermocline and deep-water ventilation in the eastern equatorial Pacific", Nature Communications, doi:10.1038/ncomms14203 (
Title: Re: Southern Ocean Venting of CO2
Post by: jai mitchell on January 23, 2017, 09:21:13 PM
the paleoclimate analog is not accurate for the current system.  They are looking at warming and venting from the ocean that is at saturation with the current atmosphere.  These deeper ocean currents are much undersaturated as we continue to (rapidly) increase our atmospheric CO2 abundance.  So they won't vent according to the paleoclimate history, at least not the deeper, older currents that are not in contact with the atmosphere.
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on January 24, 2017, 12:38:11 AM
the paleoclimate analog is not accurate for the current system.  They are looking at warming and venting from the ocean that is at saturation with the current atmosphere.  These deeper ocean currents are much undersaturated as we continue to (rapidly) increase our atmospheric CO2 abundance.  So they won't vent according to the paleoclimate history, at least not the deeper, older currents that are not in contact with the atmosphere.

See Replies #1615 & 1616 in the Conservative Scientists ... thread.,1053.msg100292.html#msg100292 (,1053.msg100292.html#msg100292)
Title: Re: Southern Ocean Venting of CO2
Post by: jai mitchell on February 09, 2017, 04:29:38 AM
New study models increased CO2 venting from overturning circulation in the southern oceans, with the last paragraph I was thinking of posting this on 'conservative scientists' (

DeVries, T. et al. (2017) Recent increase in oceanic carbon uptake driven by weaker upper-ocean overturning, Nature, doi:10.1038/nature21068 Mikaloff-Fletcher, S.E. (2017) Ocean circulation drove increase in CO2 uptake, Nature (

“My working hypothesis is that it is natural variability, but only time will tell. I say this because model simulations suggest that the point where the human-caused impact on the ocean carbon sink is clearly separable from natural variability is rather distant in the future.”
Title: Re: Southern Ocean Venting of CO2
Post by: Bruce Steele on February 09, 2017, 06:25:51 AM
Jai, I didn't see a retraction of your
These deeper ocean currents are much undersaturated as we continue to (rapidly) increase our atmospheric CO2 abundance. 

You again make some claim that there is an increase in venting when the article you site says
" stronger ocean overturning,as seen in the 1990s, brings more carbon -rich water up from the deeper ocean "
The graphic in the article shows a 3 gigatonne decrease in venting to the atmosphere relative to the 1990s not an increase in venting.

Maybe I am confused with your choice of terms but to me ocean venting implies an ocean to atmosphere CO2 transfer whereas ocean ventilation is a transfer of CO2 from the atmosphere to the ocean. If you might spell out which transfer you intend it might help me to better understand your meaning. At any rate the deep ocean is not undersaturated relative to current atmospheric levels and that is why there was a larger ocean to atmosphere CO2 transfer in the 1990s when upwelling was bringing more deep water to the surface. Again you might better explain your choice of the word undersaturated because it is used as a definition for the solubility of aragonite. I think you mean there is less CO2 at depth but that is incorrect.
I also think you should respect Grubers contention that we don't know whether the more recent conditions represent a longer term trend. I would much consider Gruber an expert and accept his opinion that variability is responsible . He is a top notch biogeochemist . Not a field easily mastered .
I have read his predictions for U.S. West Coast surface water undersaturation and they are Not conservative . Undersaturation is the point that aragonite dissolves and Gruber has predicted months long periods of undersaturation by 2035. I will tract down numbers when I get a chance.

Title: Re: Southern Ocean Venting of CO2
Post by: jai mitchell on February 10, 2017, 08:25:48 PM
from the article

If the weak circulation patterns continue, this “may help to enhance the oceanic CO2 sink for some time”, the paper says. But there is also the distinct possibility that the changes we are seeing now are temporary, says DeVries:

“The overturning circulation [could] switch back to a more vigorous state in the next decade. In this case, the changes would be reversed, and we would go back to a weaker ocean CO2 sink (like in the 1990s).”

and yes, I felt that ASLRs response to my statement was more than adequate.  I was incorrect in asserting that deep ocean currents were undersaturated since I was thinking of the atmospheric exchange function only, not the larger chemical processes involved with deep ocean currents. 
Title: Re: Southern Ocean Venting of CO2
Post by: Bruce Steele on February 11, 2017, 05:24:15 AM
Jai, yes well it is kinda difficult disagreeing without coming off like a dick. Didn't intend to be rude.
More importantly I too worry that a switch back to the earlier conditions of the 1990s would result in an extra 3GT additional  CO2 moving from the ocean carbon sink back into the atmosphere annually . It is also unnerving that even though the Southern Oceans are currently functioning as a weak sink Mauna Loa is accelerating. If the southern Oceans hadn't become a more effective sink the atmospheric CO2 levels would have grown even faster. 
Title: Re: Southern Ocean Venting of CO2
Post by: AbruptSLR on December 05, 2017, 07:57:00 PM
I suspect that the bipolar seesaw has something to do with observed trends of the Southern Ocean carbon sink; but who knows what the future holds for this issue.

R. Ritter et al. (4 December 2017), "Observation-based Trends of the Southern Ocean Carbon Sink", Geophysical Research Letters, DOI: 10.1002/2017GL074837

Abstract: "The Southern Ocean (SO) carbon sink has strengthened substantially since the year 2000, following a decade of a weakening trend. However, the surface ocean pCO2 data underlying this trend reversal are sparse, requiring a substantial amount of extrapolation to map the data. Here, we use 9 different pCO2 mapping products to investigate the SO trends and their sensitivity to the mapping procedure. We find a robust temporal coherence for the entire SO, with 8 of the 9 products agreeing on the sign of the decadal trends, i.e., a weakening CO2 sink trend in the in the 1990s (on average 0.22±0.24 Pg C yr−1 decade−1), and a strengthening sink trend during the 2000s (-0.35±0.23 Pg C yr−1 decade−1). Spatially, the multi-product mean reveals rather uniform trends, but the confidence is limited, given the small number of statistically significant trends from the individual products, particularly during the data sparse 1990-1999 period."