Hydrogen Sulfide Producing Bacteria in the Ocean

[AbruptSLR]

Robert Scribbler posts a disturbing article that hydrogen sulfide producing bacteria are starting to show-up on the US West Coast:

http://robertscribbler.com/

Extract: "Are we already starting to awaken some of the horrors of the ancient hothouse ocean? Are dangerous, sea and land life killing, strains of primordial hydrogen sulfide producing bacteria starting to show up in the increasingly warm and oxygen-starved waters of the US West Coast? This week’s disturbing new reports of odd-smelling, purple-colored waves appearing along the Oregon coastline are a sign that it may be starting to happen.

…

The purple sulfur reducing bacteria, though not dangerous themselves, live in a kind of conjoined relationship with the much more deadly hydrogen sulfide producing bacteria. The purple, is therefore, a tell-tale of the more deadly bacteria’s presence. And hydrogen sulfide producing bacteria may well be the most dangerous organism ever to have existed on the planet — largely responsible for almost all the great extinction events in Earth’s deep history. For hydrogen sulfide itself is directly toxic to both land and ocean-based life. Its deadly effects are increased at higher temperatures. And not only is it directly toxic in both water and air, if it enters the upper atmosphere it also destroys the ozone layer."

[Bruce Steele]

ASLR, I posted a response to Theta on this RScribbler piece yesterday.

Theta, I think Robert may be jumping the gun a bit here. A Canfield ocean will be accompanied by mass fish kills , huge drops in oxygen content, and very low pH. Although the Oregon coast may be one of the first places on earth to experience these somewhat end times conditions the purple waves are not in this case not a sign we have arrived. A large bloom of salps ( a jellyfish type animal ) is apparently the cause.
 Oregon has experienced fish kills and hypoxic conditions but I do not believe those conditions currently exist. The switch to a warm water PDO phase will likely push the intermediate waters deeper and lessen the chances of upwelling those waters and repeating the hypoxic conditions that resulted in those fish kills earlier this decade so we , and the fish, may get a break for awhile.We have buoys with pH meters in place that can be monitored real time and some very good scientists monitoring condition on the Oregon Coast. Canfield is IMO + 2000-3000 Gt carbon away and several centuries into the future ... So we have lots to worry about first.

http://www.beachconnection.net/news/salppurp082815_725.php

For some current buoy data here is a buoy of Washington state showing very healthy water condition.High pH relative to atmosphere illustrating the ocean as a carbon sink.

http://www.pmel.noaa.gov/co2/story/Cape+Elizabeth

And if you would like to look through other locations with real time pH go here

http://c-can.msi.ucsb.edu/resources/links-to-california-current-environmental-data/buoy-data

So someone might of smelled sulfur but it isn't from any progression towards a Canfield ocean ,it is more likely bacterial reduction of dead salps.

[AbruptSLR]

Bruce,

Thanks for providing such valuable & relevant context, and in particular for showing that the presence of hydrogen sulfide consuming bacteria does not mean that hydrogen sulfide producing bacteria are present (as the salps provide a food source & there apparently is sufficient oxygen in to ocean water to inhibit hydrogen sulfide producing bacteria).  And perhaps I should have made it clearer that Robert Scribbler was more pointing to the degrading conditions of the ocean rather than to an imminent return to a Canfield Ocean condition.

That said, I cannot help but to wonder whether the current pace of ocean degradation may accelerate the production of hydrogen sulfide producing bacteria sooner than the 2000-3000 Gt atmospheric carbon conditions that you cite.  Perhaps my biggest concern is that Hansen et al. (2015) may be correct that abrupt ice sheet mass loss into the oceans in the coming decades could effectively double the current planetary energy imbalance by slowing ocean circulation and driving large amounts of heat content into the oceans this century (assuming a 10-year doubling time for ice sheet contributions to SLR).  Other concerns that I have include that the current positive PDO/IPO phase is synchronized with a negative AMO phase that maybe stabilizing the ridiculously resilient ridge, and which together with increasing frequency of strong El Nino events could accelerate Artic Amplification.

Therefore, while I concur that there is no value in getting overly excited about purple surf zone water off the Oregon coast; I do think that the Earth Systems are much more sensitive to high rates of anthropogenic forcing than the scientific mainstream is willing to acknowledge, and thus I wonder whether hydrogen sulfide producing bacteria could be a legitimate concern as early as 2100.

Best,
ASLR

[AbruptSLR]

For those not familiar with the Canfield Ocean model I provide the following Wikipedia link and extract:

https://en.wikipedia.org/wiki/Canfield_ocean

Extract: "The Canfield Ocean model refers to the Ocean composition theorized by geologist Donald Canfield. In a seminal paper in Nature in 1998, Canfield argued that the Ocean had become partially anoxic and sulfidic during Proterozoic.

Peter Ward studies the effects of ocean hypoxia (anoxic) and sulfidic oceans and climate change. He found warming of the ocean caused by a rise of carbon dioxide levels to about 1000 parts per million as a trigger for mass extinction."

While CO₂ ppm and CO₂ equivalent are different things; nevertheless, I point-out that currently our CO₂ equivalent value exceeds 485ppm while following RCP 8.5 to 2100 results in a CO₂ equivalent value of 1250 ppm.

[Bruce Steele]

ASLR, I have great respect for RobertScribblers efforts and I wish I had half the knowledge about earth system processes that you each posting demonstrate. I have done my homework on but one fairly focused field of ocean acidification but it leads quite quickly into hypoxia/anoxia , physical oceanography and the processes of the carbon cycle that regulate not only ocean but terrestrial life systems. Everything is connected and so acidification problems for shellfish has lead me far afield and.what happens to Antarctic and Arctic meteorology and ice melt will influence stratification and ventilation of the deep ocean. We have talked about the changes occurring in bottom water formation and MOC changes that ultimately lead to hypoxic/anoxic conditions in the deep ocean. The paleo record of deep time allow some view into that world . I still think we are talking centuries to thousand year timescales before the oxygen already present in the deep oceans gives way to Canfield conditions but once the great polar icesheets melt that progression will be unstoppable . The oceans will become a huge anoxic carbon sink and those regions of earth that upwell that water will be the first to experience those sulfur reducing bacteria and witness the terrestrial ramifications.
 Some of the first work I studied was by Andy Knoll and his work on the great dying. He has worked on the end Cambrian paleorecord. He talked about trigger and kill mechanisms. I have said before we are messing with the trigger and once you pull it the time till it's inevitable result occurs is irrelevant. 

[AbruptSLR]

Bruce,

Thinking of how large the oceans are, it is somewhat reassuring to read your words of insight, as I am a civil engineer and not an oceanographer.  Nevertheless, the paleo-examples that you point to do not include any anthropogenic forcing, which to my mind does not only include GHG emissions at rates over 6-times faster than the Earth has ever experienced but also: pollution, over-fishing, de-forestation, and extensive erosion.  Per the following extract & the first image from Robert Scribbler's article from June 4 2015, nutrient driven dead zones are expanding along the various coastlines of the world.

Extract: "The world ocean is now a region of expanding oxygen-deprived dead zones.
It’s an upshot of a human-warmed ocean system filled with high nutrient run-off from mass, industrialized farming, rising atmospheric nitrogen levels, and increasing dust from wildfires, dust storms, and industrial aerosol emissions. Warming seas hold less oxygen in solution. And the nutrient seeding feeds giant algae blooms that, when they die and decompose, further rob ocean waters of oxygen. Combined, the two are an extreme hazard to ocean health  …"

Also per the following EGU & Biogeoscience links such dead zones are now moving from the coastlines into eddies in the middle of the ocean:

http://www.egu.eu/news/165/dead-zones-found-in-atlantic-open-waters/

Extract: "A team of German and Canadian researchers have discovered areas with extremely low levels of oxygen in the tropical North Atlantic, several hundred kilometres off the coast of West Africa. The levels measured in these ‘dead zones’, inhabitable for most marine animals, are the lowest ever recorded in Atlantic open waters. The dead zones are created in eddies, large swirling masses of water that slowly move westward. Encountering an island, they could potentially lead to mass fish kills. The research is published today in Biogeosciences, an open access journal of the European Geosciences Union (EGU)."

J. Karstensen, B. Fiedler, F. Schütte, P. Brandt, A. Körtzinger, G. Fischer, R. Zantopp, J. Hahn, M. Visbeck and D. Wallace (2015), "Open ocean dead zones in the tropical North Atlantic Ocean", Biogeosciences, 12, 2597-2605, doi:10.5194/bg-12-2597-2015

http://www.biogeosciences.net/12/2597/2015/bg-12-2597-2015.html

Abstract: "Here we present first observations, from instrumentation installed on moorings and a float, of unexpectedly low (<2 μmol kg−1) oxygen environments in the open waters of the tropical North Atlantic, a region where oxygen concentration does normally not fall much below 40 μmol kg−1. The low-oxygen zones are created at shallow depth, just below the mixed layer, in the euphotic zone of cyclonic eddies and anticyclonic-modewater eddies. Both types of eddies are prone to high surface productivity. Net respiration rates for the eddies are found to be 3 to 5 times higher when compared with surrounding waters. Oxygen is lowest in the centre of the eddies, in a depth range where the swirl velocity, defining the transition between eddy and surroundings, has its maximum. It is assumed that the strong velocity at the outer rim of the eddies hampers the transport of properties across the eddies boundary and as such isolates their cores. This is supported by a remarkably stable hydrographic structure of the eddies core over periods of several months. The eddies propagate westward, at about 4 to 5 km day−1, from their generation region off the West African coast into the open ocean. High productivity and accompanying respiration, paired with sluggish exchange across the eddy boundary, create the "dead zone" inside the eddies, so far only reported for coastal areas or lakes. We observe a direct impact of the open ocean dead zones on the marine ecosystem as such that the diurnal vertical migration of zooplankton is suppressed inside the eddies."


Furthermore, the following extract and second image from Robert Scribbler December 3 2013; indicates that nitrogen fixation in the ocean is happening multiple times faster now than the past.


Extract regarding Owen Sherwood et al 2014: "The study analyzed the sediment composition of coral growth layers to determine changes in ocean states since the 1850s. As the corals sucked up the dead bodies of micro-organisms over the past 1,000 years, the researchers were able to analyze what was happening to the cyanobacteria at the base of the food web.
What they found was that the bacteria increased their rate of nitrogen fixation by about 17 to 27 percent over the past 150 year period. And that this pace of change was ten times more rapid than that observed at the end of the Pliestocene and beginning of the Holocene 12,000 years ago.
…

Increasing nitrogen fixation is an indicator of ocean stratification because cyanobacteria species under stress evolve to fix higher amounts of nitrogen from the surface transfer boundary with the air if particulate nitrogen levels in their environment drop. In a healthy, mixed ocean environment, nitrogen from various sources (terrestrial, run-off, etc), is readily traded between ocean layers due to the mixing action of ocean currents. In cooler oceans, more nitrogen is also held in suspension. But as oceans become warmer and more stratified, a loss of mixing and solubility results in lower nitrogen levels.
The researchers believe that this increase in nitrogen fixation is a clear indication that the region of the Pacific they observed is rapidly becoming more stratified and that this rate of increase is probably an order of magnitude faster than what occurred during the last major transition at the end of the last ice age.
“In comparison to other transitions in the paleoceanographic record, it’s gigantic,” Lead author Sherwood noted. “It’s comparable to the change observed at the transition between the Pleistocene and Holocene Epochs, except that it happens an order of magnitude faster.”"


Owen A. Sherwood, Thomas P. Guilderson, Fabian C. Batista, John T. Schiff & Matthew D. McCarthy (02 January 2014), "Increasing subtropical North Pacific Ocean nitrogen fixation since the Little Ice Age", Nature, Volume: 505, Pages: 78–81, doi:10.1038/nature12784

http://www.nature.com/nature/journal/v505/n7481/full/nature12784.html

Abstract: "The North Pacific subtropical gyre (NPSG) plays a major part in the export of carbon and other nutrients to the deep ocean. Primary production in the NPSG has increased in recent decades despite a reduction in nutrient supply to surface waters. It is thought that this apparent paradox can be explained by a shift in plankton community structure from mostly eukaryotes to mostly nitrogen-fixing prokaryotes. It remains uncertain, however, whether the plankton community domain shift can be linked to cyclical climate variability or a long-term global warming trend5. Here we analyse records of bulk and amino-acid-specific 15N/14N isotopic ratios (δ15N) preserved in the skeletons of long-lived deep-sea proteinaceous corals collected from the Hawaiian archipelago; these isotopic records serve as a proxy for the source of nitrogen-supported export production through time. We find that the recent increase in nitrogen fixation is the continuation of a much larger, centennial-scale trend. After a millennium of relatively minor fluctuation, δ15N decreases between 1850 and the present. The total shift in δ15N of −2 per mil over this period is comparable to the total change in global mean sedimentary δ15N across the Pleistocene–Holocene transition, but it is happening an order of magnitude faster6. We use a steady-state model and find that the isotopic mass balance between nitrate and nitrogen fixation implies a 17 to 27 per cent increase in nitrogen fixation over this time period. A comparison with independent records suggests that the increase in nitrogen fixation might be linked to Northern Hemisphere climate change since the end of the Little Ice Age."

Finally, the linked reference shows that glacial meltwater typically contain significant amounts of minerals (like iron) that could in the future lead to plankton blooms and associated dead zones around Antarctica:


R. Death, J. L.Wadham, F. Monteiro, A. M. Le Brocq, M. Tranter, A. Ridgwell, S. Dutkiewicz, and R. Raiswell (2014), "Antarctic ice sheet fertilises the Southern Ocean", Biogeosciences, 11, 2635–2644, doi:10.5194/bg-11-2635-2014

http://www.biogeosciences.net/11/2635/2014/bg-11-2635-2014.pdf

Abstract: "Southern Ocean (SO) marine primary productivity (PP) is strongly influenced by the availability of iron in surface waters, which is thought to exert a significant control upon atmospheric CO2 concentrations on glacial/interglacial timescales. The zone bordering the Antarctic Ice Sheet exhibits high PP and seasonal plankton blooms in response to light and variations in iron availability. The sources of iron stimulating elevated SO PP are in debate. Established contributors include dust, coastal sediments/upwelling, icebergs and sea ice. Subglacial meltwater exported at the ice margin is a more recent suggestion, arising from intense iron cycling beneath the ice sheet. Icebergs and subglacial meltwater may supply a large amount of bioavailable iron to the SO, estimated in this study at 0.07–0.2 Tg yr−1. Here we apply the MIT global ocean model (Follows et al., 2007) to determine the potential impact of this level of iron export from the ice sheet upon SO PP. The export of iron from the ice sheet raises modelled SO PP by up to 40 %, and provides one plausible explanation for seasonally very high in situ measurements of PP in the near-coastal zone. The impact on SO PP is greatest in coastal regions, which are also areas of high measured marine PP. These results suggest that the export of Antarctic runoff and icebergs may have an important impact on SO PP and should be included in future biogeochemical modelling."


Also see Peter Ward's book "Under Green Sky Warming Extinctions":

http://www.amazon.com/Under-Green-Sky-Warming-Extinctions/dp/0061137928

While I have no proof that hydrogen sulfide bacteria are going to become a serious problem in less than multiple centuries; nevertheless, it looks like something that needs to be studied in much greater depth.

Best,
ASLR

[AbruptSLR]

Maybe I am making much to do about nothing, but the attached image from the following NOAA website indicates that 2015 had the largest extent of hypoxia zone downstream of the Mississippi River, on record (larger in area than Connecticut & Rhode Island combined):

http://www.noaanews.noaa.gov/stories2015/080415-gulf-of-mexico-dead-zone-above-average.html

[AbruptSLR]

The linked Science article indicates that abrupt melting of the ice sheets could create a positive feedback mechanisms that "… could lead to a stratification of the water column, with warm water buried underneath cold surface water."  This mechanism for stratification of the ocean is not currently included in any mainstream climate change model projection.

http://news.sciencemag.org/climate/2015/07/climate-researcher-blasts-global-warming-target-highly-dangerous


Extract: "The paper also describes an atmosphere-ocean modeling study of feedback loops caused by ice sheet melting under 2°C conditions. What they found, Hansen says, is that melting ice sheets in Greenland and Antarctica could inject enough fresh water into the seas to slow the formation of two key water masses: the North Atlantic Deepwater and the Antarctic Bottom Water formations. Both are part of the so-called Great Ocean Conveyor Belt of ocean circulation. The injection of so much cold water, they say, could lead to a stratification of the water column, with warm water buried underneath cold surface water. “Instead of emerging at the surface, much of that heat is melting the ice shelves,” Hansen says, producing more fresh water and amplifying the feedback. That is particularly striking, he added, because it’s what we’re observing right now: an increase in cold surface waters around Antarctica and Greenland, as well as increases in sea ice around some parts of Antarctica."

[AbruptSLR]

Per the following extract from NRC (2013), OMZs means Oxygen Minimum Zones, and the extract indicates that there is a potential for the abrupt reduction of ocean oxygen concentrations; however, that this risk is currently difficult to quantify, and remember that this statement was made before Hansen et al. (2015) identified the risks that abrupt ice sheet mass loss represent for potential ocean stratification.

NRC (2013), "Abrupt Impacts of Climate Change: Anticipating Surprises", The National Academies Press, Washington D.C., ISBN: 978-0-309-28773-9


Extract: "Changes in global ocean oxygen concentrations have the potential to be abrupt because of the threshold to anoxic conditions, under which the region becomes uninhabitable for aerobic organisms including fish and benthic organisms. Once this tipping point is reached in an area, anaerobic processes would be expected to dominate resulting in a likely increase in the production of the greenhouse gas N2O.  Some regions like the Bay of Bengal already have low oxygen concentrations today (Delaygue et al., 2001), but not quite low enough for denitrification to occur. Modest increases in the export of organic matter, or decreases in ventilation by the circulation, could decrease oxygen below the critical threshold for fixed nitrogen loss.

OMZs have also been intensified in many areas of the world’s coastal oceans by runoff of plant fertilizers from agriculture and incomplete wastewater treatment. These ‘dead zones’ have spread significantly since the middle of the last century and pose a threat to coastal marine ecosystems (Diaz and Rosenberg, 2008).This expansion of OMZs is due to nutrient runoff makes the ocean more vulnerable to decreasing solubility of O2 in a warmer ocean. Indeed, as warming of the ocean intensifies, the decrease in oxygen availability might become non-linear; particularly, as indicated by the expansion of the size of the oxygen minimum zone (Deutsch et al., 2011). The effect of temperature on oxygen solubility is well understood. However, it remains a major scientific challenge to model and project the changes of the magnitude and intensity of subsurface oxygen depletion because it depends on changes in ocean circulation, rates of de-nitrification, and nutrient runoff from land, and because global data coverage for chemical and biological parameters remains poor."

[Bruce Steele]

ASLR, I need to start with the disclaimer that I am a fisherman with a high school education. I have tried to understand how the processes being discussed here work in the various oceans of the world and due to the variability of the aragonite compensation depth, the calcite compensation depth and the depth at which silica dissolves the different oceans operate quite differently. The Atlantic has the deepest depths at which aragonite first, then calcite, and finally silica dissolve in the earths oceans. Silica dissolves at about 3000 meters in the Atlantic and thus represents the very deepest surface supplied organic matter can penetrate the oceans via ballasting. After that depth only deep water formation and it's associated oxygen ventilation effect oxygen content from surface supplied processes i.e. Primary productivity. Deep water masses and bottom waters below that depth ( in the Atlantic)can maintain temperature/salinity profiles as well as oxygen content for very long time periods because currents at those depths are quite slow and without interference from bacterial decomposition of surface supplied organics drawing down oxygen they can maintain T/S and oxygen for long periods...centuries . In the Pacific all of these processes are much shallower and due to a slopeing of the pycnocline , deeper West/ shallower East with the addition of eastern boundary currents and upwelling we get dissolution as well as bacterial decomposition concentrated much closer to surface water depths. Once the calcite and silica  material responsible  for ballasting is removed bacterial reduction and it's resultant drawdown on oxygen is concentrated closer to the surface.
 So some regions of the world have oxygen minima closer the surface. These same regions then will also experience a much quicker transition to hypoxic and anoxic conditions as the oceans warm and temperatures affect the ability of seawater to hold oxygen. Both surface warming and mixing as well as primary production can and will contribute to future changes in fairly short timeframes in these regions. Other regions of earth are on much different timeframes. 
 Shallow waters experiencing nutrient loading and hypoxia/ anoxia like the Gulf of Mexico can be changed back into healthy conditions with surface supplied mixing on shorter timeframes than those areas of the Pacific described above,we  just need to change terrestrial imputs.
 Those processes driving a slowdown in bottom water formation will play out on very different timeframes than western boundary current areas but their consequences are much more locked in once set into motion than dead zones in the Gulf for instance.
 I have heard Curtis Deutsch ( referenced by ASLR in last post ) speak and he is blindingly bright.
I wish.       

[Bruce Steele]

I forgot to put in a reference to  post above so here is some further info

http://oceanworld.tamu.edu/resources/ocng_textbook/chapter13/chapter13_03.htm

[AbruptSLR]

Again, I am a Civil Engineer, but as I raised this topic, I will keep trying to make sense of the future risks of hydrogen sulfide producing bacteria.  To elaborate on some of the issues raised by Bruce, I provide the following extract from NRC (2013); and I believe that the key points that this passage is making are that:

(1) It does not matter whether the deep ocean has reasonably high oxygen content for thousands of years in the future, so long as it is trapped at depth by stratification of the ocean layers at high latitude such as by cold ice sheet melt water slowing down the formation of AABW & NADW.

(2) The large portions of the ocean waters from 200m to 1000m are in the OMZ, and that this OMZ could grow rapidly with continued anthropogenic forcing, which, if it did expand upward, would create a large zone for the potential growth of hydrogen sulfide producing bacteria:

NRC (2013), "Abrupt Impacts of Climate Change: Anticipating Surprises", The National Academies Press, Washington D.C., ISBN: 978-0-309-28773-9

Extract: "The oxygen content in the surface ocean is projected to decline with warming because of the decrease in solubility of gases with increasing temperature, and changes in ventilation and biological consumption. A significant decrease in oxygen in the upper ocean between the 1970s and 1990s has already been observed at a global scale (Helm et al., 2011). Only approximately 15 percent of that decline can be attributed to a warmer mixed-layer, with the remainder being “consistent with an overall decrease in the exchange between surface waters and the ocean interior” (Helm et al., 2011). With a general weakening of ventilation rates as a result of climate change (Bryan et al., 2006), oxygen content of the global ocean is likely to further decrease (ventilation to the surface allows new input of oxygen from the atmosphere).

Of more immediate concern is the expansion of Oxygen Minimum Zones (OMZs). Photosynthesis in the sunlit upper ocean produces O2, which escapes to the atmosphere; it also produces particles of organic carbon that sink into deeper waters before they decompose and consume O2. The net result is a subsurface oxygen minimum typically found from 200-1000 meters of water depth, called an Oxygen Minimum Zone.

Warming ocean temperatures lead to lower oxygen solubility. A warming surface ocean is also likely to increase the density stratification of the water column (i.e., Steinacher et al., 2010), altering the circulation and potentially increasing the isolation of waters in an OMZ from contact with the atmosphere, hence increasing the intensity of the OMZ. Thus, oxygen concentrations in OMZs fall to very low levels due to the consumption of organic matter (and associated respiration of oxygen) and weak replenishment of oxygen by ocean mixing and circulation.  Furthermore, a hypothetical warming of 1ºC would decrease the oxygen solubility by 5 μM (a few percent of the saturation value). This would result in the expansion of the hypoxic zone by 10 percent, and a tripling of the extent of the suboxic zone (Deutsch et al., 2011). With a 2ºC warming, the solubility would decrease by 14 μM resulting in a large expansion of areas depleted of dissolved oxygen and turning large areas of the ocean into places where aerobic life disappears. In the tropical Atlantic, Pacific, and Indian Ocean, a decline in oxygen content in the subsurface waters has been confirmed with observations (Stramma et al., 2010)."

[AbruptSLR]

The attached figure (from Marshall-Speer 2012) helps to illustrate how when the formation of AABW and NADW slow-down, the ventilation of the intermediate waters (in the OMZ from 200 to 1000m depth) also slows down.  This slows down the introduction of oxygenated water to the OMZ so that the continued consumption of oxygen due to the continued rainfall of organics from the well-mixed surface waters (above 200m), results in the further reduction of oxygen concentration in the OMZ.

[Bruce Steele]

ASLR, I have no argument with the expansion of the oxygen minimum areas and my comments above also support this idea. Those areas are in those depths 200-1000 meters you state but they do not occur in all areas of the ocean, currently only .1 percent of the oceans volume are considered oxygen minimum areas. I also concur any additional stratification or slowdown in MOC or bottom water formation will result in changes for intermediate water formation and those changes will be felt in much shorter timeframes than the deep or bottom water occurring in polar waters. Intermediate waters also form in polar and sub-polar regions but are carried by currents into regions that make up the oxygen minimum areas.  I still would argue however a majority of the changes we are talking about will be in tropical , sub-tropical and to some degree temperate waters that currently constitute the oxygen minimum areas.
 You may find the following paper interesting as it makes the argument open oceans may also be changing. The timeframes for major changes need some illumination I can't deliver. Intermediate
Water processes in the Pacific take 35-50 years from formation to upwelling. I can't quantify the timeframe for the Atlantic.

    https://idw-online.de/de/news303230

From my first posting on the Carbon cycle page surface water temperatures are modeled to increase by 2.7 degrees C by 2100 under BAU. This gives some idea about how much larger the area of oxygen minimum areas may expand. Does Deutsch quantify " a large expansion "?

[AbruptSLR]

Bruce,

Regarding your question about the probable future of expansion of the OMZ by 2100 evaluate by Deutsch et al. (2011), the linked reference indicates a probable doubling in the Pacific Ocean; however, as I discuss below, new research indicates that sensitivity of the OMZ to expansion due to anthropogenic forcing may be higher than Deutsch et al. considered.

Deutsch, C., H. Brix, T. Ito, H. Frenzel and L. Thompson (2011), "Climate-Forced Variability of Ocean Hypoxia", Science 333(6040):336-339.

http://lgmacweb.env.uea.ac.uk/green_ocean/publications/ROC/Deutsch_etal_2011.pdf

Abstract: "Oxygen is a critical constraint on marine ecosystems. As oceanic O2 falls to hypoxic concentrations, habitability for aerobic organisms decreases rapidly. We show that the spatial extent of hypoxia is highly sensitive to small changes in the ocean’s O2 content, with maximum responses at suboxic concentrations where anaerobic metabolisms predominate. In model-based reconstructions of historical oxygen changes, the world’s largest suboxic zone, in the Pacific Ocean, varies in size by two-fold. This is due to climate-driven changes in the depth of the tropical and subtropical thermocline that have multiplicative effects on respiration rates in low-O₂ water. The same mechanism yields even larger fluctuations in the rate of nitrogen removal via denitrification, creating a link between decadal climate oscillations and the nutrient limitation of marine photosynthesis."

In the following reference by Brandt et al. (2015) ETNA means: eastern tropical North Atlantic; and this reference shows that current models misrepresent the intermediate circulation (and do not consider the changes in circulation induced by abrupt SLR ala Hansen et al (2015), and thus future changes in the OMZ could be larger than current models project:

P. Brandt et al. (2015), "On the role of circulation and mixing in the ventilation of oxygen minimum zones with a focus on the eastern tropical North Atlantic", Biogeosciences, 12, 489–512, doi:10.5194/bg-12-489-2015

http://www.biogeosciences.net/12/489/2015/bg-12-489-2015.pdf

Extract: "Advection by zonal jets is crucial for the establishment of the equatorial oxygen maximum. In the latitude range of the deep OMZ, it dominates the oxygen supply in the upper 300 to 400m and generates the intermediate oxygen maximum between deep and shallow OMZs.  Water mass ages from transient tracers indicate substantially older water masses in the core of the deep OMZ (about 120–180 years) compared to regions north and south of it. The deoxygenation of the ETNA OMZ during recent decades suggests a substantial imbalance in the oxygen budget: about 10% of the oxygen consumption during that period was not balanced by ventilation. Long-term oxygen observations show variability on interannual, decadal and multidecadal timescales that can partly be attributed to circulation changes. In comparison to the ETNA OMZ, the eastern tropical South Pacific OMZ shows a similar structure, including an equatorial oxygen maximum driven by zonal advection but overall much lower oxygen concentrations approaching zero in extended regions. As the shape of the OMZs is set by ocean circulation, the widespread misrepresentation of the intermediate circulation in ocean circulation models substantially contributes to their oxygen bias, which might have significant impacts on predictions of future oxygen levels."


Furthermore, as indicated by the extract from the linked reference by D. L. Arévalo-Martínez et al. (2015), "Influence of mesoscale eddies on the distribution of nitrous oxide in the eastern tropical South Pacific", Biogeosciences; mesoscale eddies add to the risk of future expansion of the OMZ:

http://www.biogeosciences-discuss.net/12/9243/2015/bgd-12-9243-2015.pdf

Extract: "Projected future deoxygenation and expansion of OMZs has been suggested to significantly increase marine N2O production. However, an increased strength of the N2O sink within the core of low-O2 waters in mesoscale eddies might also play an important role which has not been yet quantified. Hence, it is critical to understand how these prominent features of the circulation might affect N2O distribution and concentrations in order to be able to assess the variability of its sources and sinks strength."


While none of these references cite a risk of a Canfield Ocean occurring by 2100; nevertheless, even if only the tropical portions of the oceans (and local coastal hotspots) were to support concentrations of hydrogen sulfide producing bacteria by 2100, that would be very bad in my world view and would speak very poorly about the condition of the world that we are prepared to leave to our grandchildren.

Very best,
ASLR

[Bruce Steele]

Here is some pictures of what happens when hypoxia/anoxia results in a fish kill. There is a current event in hood canal -puget sound Washington State. Ugly

http://kuow.org/post/fish-and-crabs-struggle-oxygen-hood-canal-s-depleted-waters

[Bruce Steele]

This is what hypoxia looks like on a buoy in the upper reaches of Hood Canal. Hypoxia is oxygen content at less than 2 mg/liter. The graph below shows hypoxic conditions starting at 15 meters currently at this buoy so sea life deeper than those depths are forced into surface waters above that depth or they expire. Inverts that can't swim or migrate are killed first but bacterial decomposition of the dead invertebrates drive oxygen levels further down and sometimes result in anoxia or zero oxygen.

 http://orcabase.ocean.washington.edu/data_twanoh.html

Anoxia at the same buoy. Zero oxygen at ten meters about a week ago.

http://orcabase.ocean.washington.edu/profiles/hoodcanal/twanoh/ORCA1_20150829T200733_p28040.png

[Theta]

I thought I would put this link up since there is a lot of talk about anoxia and how the melting of Ice Sheets can contribute to it.

http://www.independent.co.uk/environment/gulf-stream-is-slowing-down-faster-than-ever-scientists-say-10128700.html

However, the researchers believe that Britain is still likely to become warmer due to climate change providing the Gulf Stream does not come to a complete halt – although they remain unsure how likely this is.

Calculations suggest that over the 20th century the North Atlantic meridional overturning circulation – the northward flow of warm surface water and the southward flow of deep, cold water – has slowed by between 15 and 20 per cent, said Professor Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany.

Also an article in the Guardian that states that the Gulf Stream could completely stop in a set of weeks: http://www.theguardian.com/environment/2009/nov/29/climate-change-gulf-stream-hollywood

In the Hollywood blockbuster The Day After Tomorrow, an Ice Age was set off in a single day when the Gulf Stream was disrupted. "That is silly," said Patterson. "It couldn't happen that quickly. However, previous estimates that it would take decades to switch off the Gulf Stream are not backed by our work. It could happen in a couple of months."

I have to ask, because people are saying that we could experience anoxic waters in fairly short timeframes, what timeframes are being suggested, something that occurs overnight, or perhaps over the course of a few weeks?