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Ocean heat content: latest numbers

Filed under: — gavin @ 16 August 2006

Net ocean heat content changes are very closely tied to the net radiative imbalance of the planet since the ocean component of the climate system has by far the biggest heat capacity. Thus we have often made the point that diagnosing this imbalance through measurements of temperature in the ocean is a key metric in evaluating the response of the system to changes in CO2 and the other radiative forcings (see here).
In a paper I co-authored last year (Hansen et al, 2005), we compared model results with the trends over the 1993 to 2003 period and showed that they matched quite well (here). Given their importance in evaluating climate models, new reports on the ocean heat content numbers are anticipated quite closely.

Recently, a new preprint with the latest observations (2003 to 2005) has appeared (Lyman et al, hat tip to Climate Science) which shows a decrease in the ocean heat content over those two years, decreasing the magnitude of the long-term trend that had been shown from 1993 to 2003 in previous work (Willis et al, 2004) – from 0.6 W/m2 to about 0.33 W/m2. This has generated a lot of commentary in some circles, but in many cases the full context has not been appreciated.

With any new data sets there are a number of questions that must always be asked: Are the measurements really representing what is claimed? (in particular, are there sampling or definitional problems?). Do related data provide some support for the results? If correct, what are the potential causes? and, most importantly, what part of the changes are related to predictable deterministic effects? This last question brings up the issue of model evaluation, because of course, the models can only be expected to reproduce the deterministic long-term component.

Given some of the ongoing discussion, it obviously still needs to be pointed out that year-to-year fluctuations in any of the key metrics of planet’s climate are mostly a function of the weather and cannot be expected to be captured in climate models, whose ‘weather’ is uncorrelated with that in the real world. So claims that two years worth of extra data of any quantity somehow prove or disprove climate models are simply erroneous. Clearly, life would be simpler without weather ‘noise’ cluttering up the system, but this is something that just needs to be dealt with. Dealing with it means paying more attention to long term changes than to short term fluctuations and making sure that enough ensemble simulations are made with the models to isolate the signal from the noise.

Going back to the data, are there any potential problems? Well, as addressed by the authors, this time frame is the period when the ARGO floating profilers really start to be important in improving the coverage of data (look at the difference in coverage in their figure 8 between 2002 and 2005). The profilers have clearly been the best thing to happen to ocean observations in decades. Not using the profilers gives a smaller recent change – but with increased error bars because of the deterioration of the sampling. Additionally, some parts of the ocean, particularly the Arctic are still not being sampled sufficiently. These effects may yet prove to be part of the story.

What about any supporting data? One problem is that if the ocean has lost heat at the suggested rate, then the thermal exapansion part of recent sea level rise should have decreased (i.e. sea level should have dropped). Overall, sea level however has continued to rise unabated according to the altimeter satellites. The only way to reconcile the results would be to have had a sharp compensating increase in freshwater from the ice sheets adding to sea level (from 0.7 mm/yr to 2.9 mm/yr). This is conceivable (though unlikely), but clearly would not be good news!

If however, we assume that the data are reasonably accurate, what could be going on? Some of the changes are clearly due to ocean circulation changes – an increased advection of warm water from the sub-tropical Atlantic to the North for instance, but the biggest contribution are the changes seen in the sub-tropical South Pacific. The heat can either have been subducted below the 700m level (the bottom depth for this analysis), advected sideways (no real evidence for that though), or lost through the surface (either to the atmosphere, or directly out to space). The third possibility is thought the most likely.

This in turn can have had a number of possible causes: ‘natural’ tropical variability – for instance, the winter (DJF) tropical Pacific cooled over these two years, possibly as part of larger-scale ENSO variability. Alternatively, it may be due to a change in the forcings. Possible candidates are an as-yet-unquantified increase in aerosol forcings from Asian sources. These haven’t been included in simulations since the data on emissions aren’t yet in.

On a larger point, the radiative imbalance in the AR4 models is a function of how effectively the oceans sequester heat (more mixing down implies a greater imbalance) as well as what the forcings are. Therefore, there is a variation in that modelled value across the models – some of which are smaller than our reported figure (all are significantly positive though).

A slightly more subtle (and slightly more valid) criticism is that the reported magnitude of decadal variability in the OHC numbers is larger than is seen in most coupled models. Some recent work has shown that sampling may play a role here, but it wouldn’t necessarily be surprising if this was so. Even in our paper last year we stated that earlier reported decadal variations were not well simulated. There is obviously much that remains to be understood about annual to decadal variability, however, it must be remembered that it is only on the longer time scales that we expect the forced signal to dominate over the internal ‘noise’. On this basis the ocean heat content changes remain a good validation of the climate model simulations.

107 Responses to “Ocean heat content: latest numbers”

  1. 1
    Steve Sadlov says:

    RE: “The third possibility is thought the most likely.”

    My guess at this point would be wind. During the measurement period, perhaps the combo of wind, fetch and, timing of wind events versus sun angles, did the trick. Chaos … etc.

  2. 2
    Craig Gaydos says:

    I know nothing about climate science, but just reading your post I wonder if it is possible that the decrease in measured ocean heat content is mostly a factor of having better tools (the ARGO floating profilers)? That is, could it be possible that measurements in previous years, with lower quality measuring devices, consistently overstated the heat content?

  3. 3
    Bryan Sralla says:

    Gavin, thank you for that thourough early analysis. As you point out, we should all be cautious over the next few months to see if these results are robust. Notwithstanding the continued rise in sea level (which Josh Willis has just commented on the Climate Science site), lets assume for a moment that this loss of heat is confirmed, and this heat is not still in the deep ocean (no evidence of this). I honestly do not understand assigning this magnitude of heat loss to “natural tropical variability”. Can you ellaborate? 21% loss of the heat that was accumulated between 1955-2003, in just two years? This will need some good research to show why natural variablity would be this large over these time spans. Would not such a finding largely invalidate the heat budget equations as they are now understood? The Levitus and Pielke papers show that averaged out for these types of time intervals (>1 year), this analysis provides a snapshot of the net radiative imbalance at the top of the atmosphere. There has virtually been no dispute about this from the community (that I have read about). How can this actual radiative imbalance be negative, even for these short(2 year) periods of time?

    The real question in my mind is, given the continued increase in GHG forcing, what could have allowed such a loss of heat? If we isolate the ocean for diagnosis, there is a rather short list of suspect forcings and feedbacks (ie changes in shortwave reaching ocean surface possibly from strong negative aerosol feedbacks, net positive rate change in loss of longwave from the ocean (which would have implications for the positive WVF), net positive heat loss through evaporation without balancing compensation (with other implications for positive WVF). Another voodoo possiblity would be a net change in shortwave reaching the top of the atmosphere. No evidence of this either, but lets get all of them out on the table.

    If this heat has been lost to space, and the models have not accounted for it, it would seem to me that it must have an effect on the model “projections” because the non-equalibrium forcing has changed (the system has been reset at a lower temperature).

  4. 4
    Timothy says:

    Re: #1 The short answer is: Yes.

    Nevertheless, the best estimate is still that the heat content went down – but only over a couple of years. The trend for the whole period is still positive.

  5. 5
    Hank Roberts says:

    In earlier threads I”ve posted links to several studies showing increasing abysal temperatures (Nordic sea, and north Pacific). You say above “sea level however has continued to rise unabated according to the altimeter satellites. The only way to reconcile the results would be to have had a sharp compensating increase in freshwater …”

    Isn’t deeper mixing so the abyss is warming sooner another explanation that would keep ocean expansion the same overall?

    I am just a reader, no competence in the science, don’t know if the magnitudes are at all comparable for mixing and warming/cooling.

  6. 6
    Joseph O'Sullivan says:

    Thanks providing the full context. The paper is very new and it takes some time for the scientific community to examine closely and to judge how important it is.

    Its hard for someone with some but not a lot of scientific training (like myself) to fully understand how significant a study is without hearing from scientists.

    If the measurements are shown to be very accurate and they represent a change in heat content of the oceans, is the magnitude of the change significant? Is the reduction in heat content itself significant?

  7. 7
    Paul says:

    Could there have been a lare net transfer of energy from the oceans to the atmosphere during 2004-05 due to the very active tropical storm seasons in the Northern Hemisphere?

  8. 8
    Eric (skeptic) says:

    year-to-year fluctuations in any of the key metrics of planet’s climate are
    mostly a function of the weather and cannot be expected to be captured in climate
    models, whose ‘weather’ is uncorrelated with that in the real world.

    Seasonal weather is correlated since it is mostly a function of energy inputs. Seasonal weather patterns are also correlated (between models and the real world) to an increasing extent and there is a high degree of correlation between circulation changes based on SST’s between the models and the real world.

    What is lacking is mainly the correlation between the models and real world in local and regional weather but this is also ever improving as the model time and spatial resolution improves. The ability of the models to forecast weather is neither possible nor necessary, but the models must have adequate weather feature modeling to determine a realistic horizontal and vertical water vapor pattern to be able to model the warming effects of that water vapor.

  9. 9
    sidd says:

    There are similar sharp decreases shown in Fig. 1 of Levitus (GRL,2005) in the middle
    sixties and early eighties. Are the reasons for these also understood ?

    Also, why is radiative loss to space considered more likely than more heating of the depths ?


  10. 10
    Fergus Brown says:

    As this is my first post to you, firstly let me congratulate you on an excellent site, which I regularly recommend to my fellow forum members on Netweather.TV.
    I posted Climate science on the subject of the undersampled Arctic, and Roger Pielke kindly responded, but said that, as the Arctic was only 10% of the oceans, the sample difference would probably not be significant. Evidently, though, if the NOAA/NESDIS anomaly graphics are to be believed, whilst being ‘small’ in area, the size of the anomalies would surely raise the overall temperature by a measurable/ quantifiable amount; it was not the remit of the paper to include this, but shouldn’t such an adjustment be taken into account in a discussion of its implications?
    Secondly, you mention the possibility of a large freshwater influx over the past three years as a possible explanation. From recent research, I would suggest that this is entirely plausible; I could cite several examples of substantial increases (runoff, glacier melt, precipitation, sea-ice loss) which, collectively, amount to a real net increase in the Arctic freshwater budget. If this water is finding its way into the ocean areas sampled, we really could be in trouble with the THC. What do you think?
    Fergus Brown.

  11. 11
    Bryan Sralla says:

    Re: #9 These are really excellent questions. Lyman and Willis took a look at both of these and comment on them in their paper. The earlier heat changes had long been suspect due to sampling. Lyman asserts that the 1960’s change is subject to a much larger error, but both the one in the 1980’s and most recent are statistically significant. I would suggest that the reasons for these are not understood at this time.

    In respect to heat transport to the deeper ocean, Lyman also took a look at heat changes below 750 meters, and the cooling signal was still quite strong. This does not invalidate the deep ocean hypothesis, but with no viable mechanism proposed to transport this heat, it looks unlikely at this time to be the answer.

  12. 12
    Mark Shapiro says:

    Icecaps are melting faster now in the Arctic, Antarctica, Greenland, and glaciers. So some heat is being transferred to the cryosphere. How much?

    Latent heat to melt ice: 355,000 joules/kg x 1,000 kg/cubic meter x 10^9 cubic meter/cubic km
    = 3.55 x 10^17 joules to melt one cubic kilometer of ice.

    Thus, melting 1,000 cubic km absorbs 3.55 x 10^20 joules.

    That’s 1% of Lyman’s heat loss (if the arithmetic and logic are right). Then there is more heat to warm all that ice, first to melting point and then to the average temperature of the ocean. This accounts for some of the heat loss, sea level rise, and decreasing salinity at high latitudes. Plus, the remaining ice may also be warming.

    The cryosphere is small relative to the oceans, but not relative to Lyman’s drop in heat content.

  13. 13
    Wacki says:

    These Argo probes are very interesting.

    What is the maintenance like on those things? How long does the battery last? How long can they go without any servicing?

  14. 14
    John Fasullo says:

    Gavin- Interesting summary.

    Clearly more analysis will clarify the uncertainties in the ocean heat estimates – which are very large and, I believe, may be understated in the Lyman et al paper since they address random but not systematic sources of error. Having done a variety of global-ocean heat flux calculations recently, I can say with confidence that the systematic error, even if VERY small, can rectify significantly onto the global heat integral when integrating to depths of 700m. It is likely that the systematic error will shift as new data are incorporated into their analyses (you’ll note that they get nearly ALL of their cooling below 200 m!)

    It is also worth mentioning that the results of this study (which imply a recent ~0.5 PW ocean cooling) are, in my view, entirely inconsistent with the best available fluxes at TOA – CERES retrievals- which actually show a NET INCREASE in the net downward flux at TOA of at least 0.4 PW (depending on which sensor is used) between the 2001-2 and 2003-4 periods. The error bars on the CERES retrievals, particularly when all 4 sensors are available are significantly less than the (reported) error bars on the ocean heat content data in the Lyman et al work.

    Accounting for this anomalous ~1 PW sink WITHIN the climate system between the 2001-2 and 2003-4 periods I think will prove to be a bit of a reach, don’t you think?

  15. 15
    Rhampton says:

    Recent Cooling of the Upper Ocean
    by John M. Lyman, Josh K. Willis, and Gregory C. Johnson
    Submitted 26 May 2006
    to Geophysical Research Letters
    Accepted 31 July 2006

    …The recent cooling of the upper ocean implies a decrease in the thermosteric component of sea level. Estimates of total sea level [Leuliette et al., 2004;], however, show continued sea-level rise during the past 3 years. This suggests that other contributions to sea-level rise, such as melting of land-bound ice, have sccelerated. This inference is consistent with recent estimates of ice mass loss in Antarctica [Velicogna and Wahr, 2006] and accelerating ice mass loss on Greenland [Rignot et al., 2006] but closure of the global sea level budget cannot yet be achieved.

    New satellite observations from the Gravity Recovery and Climate Experiment (GRACE; launched in March, 2002 and administered by NASA and Deutsches Zentrum für Luft-und Raumfahrt, GRACE will map Earth’s gravity field approximately once every 30 days during its lifetime) should soon provide sufficient observations of the redistribution of water mass to more fully describe the causes of recent sea-level change.

    Finally, the estimates presented here are made possible only by recent improvements in the global ocean observing system. The sharp decrease in error since 2002 is due to the dramatic improvement of in situ sampling provided by the Argo array of autonomous profiling CTD floats, and the real-time reporting of Argo data made it possible to extend the estimate through 2005. Characterization of the error budget, which is of paramount importance in the estimate of such globally averaged quantities, was made feasible by the long-term maintenance of high quality altimeter missions such as TOPEX/Poseidon and Jason.

    The issues relating to sea level rise and the global water budget can only be addressed when the record of satellite gravity measurement from GRACE achieves adequte duration. GRACE, Argo, and satellite altimetry are core components of the global ocean observing system. Failure to maintain any one of these observing systems would seriously impair our ability to monitor the World Ocean and to unravel its importance to the climate system.


    Greenland’s ice loss accelerating rapidly, gravity-measuring satellites reveal
    University of Texas at Austin, August 10, 2006

    …The loss of ice has been occurring about five times faster from Greenland’s southeastern region in the past two years than in the previous year and a half. The dramatic changes were documented during a University of Texas at Austin study of Greenland’s mass between 2002 and 2005.

    The study was published today in the journal Science. Related results on the significant loss of ice from Antarctica were published in Science in March by other researchers participating in the Gravity Recovery and Climate Experiment (GRACE) mission. The GRACE mission is funded by NASA and the German Aerospace Center, and led by Aerospace Engineering Professor Byron Tapley at the university.

  16. 16
    Josh Willis says:

    Dear Gavin (and all commentors), Thanks to you all for your interest in and discussion of our manuscript.

    For those that are interested, I have posted some further discussion of the sea level budget and the possibility of errors caused by the introduction of Argo data on Roger Pielke Sr.’s Climate Science weblog.

    Gavin, thanks for the thorough discussion you provided at the outset. I did want to make a minor comment about your post, though. I don’t think I would put the increase of the freswater input into the “unlikely” category. As I mention in the post linked above, adding up the various reports of melting rates found in the literature, you can arrive at rates of freshwater input as high as 2 mm/yr. Considering the error bars on all of these estimates, I don’t think that is too far removed from our rate of total minus thermosteric sea level rise of 2.9 mm/yr between 2000 and 2005.

    [Response: Hi Josh, Thanks for dropping by. My use of ‘unlikely’ was really in relation to the change from 0.7 mm/yr to 2.9 mm/yr in such a short time. That is a rather large increase and prior to it being raised as a possibility here is not a magnitude of rapid change I had ever heard considered before this. However, this issue should be decidable with available data. First off, we have the altimeter data which should be able to validate the relative changes in steric height implied by the heat content changes on a regional (or zonal mean) basis (maybe you’ve done that already?). Secondly, salinity measurements should be able to assess the amount of freshwater inputs for this period relative to the years before, though these have probably not yet been collated. On another tack, it should be possible to track the heat anomalies month by month (at least in the basin mean) – that would make it clearer where the heat is going/coming from. Unconnected subsurface anomalies would be a sign of a problem, while advected anomalies and surface generated anomalies shoul dbe easy to spot. – gavin]

  17. 17 says:

    Potential Causes

    …reason is subducted below the 700m level…

    As Dr. James E Hansen descibed it(2004)

    The ocean’s surface begins to warm, but before it
    can heat up much, the surface water is mixed down and replaced by colder
    water from below.

    Mixed down from the water streams of the ocean current.
    I think this process the decrease in heat could be a mix of water fluctuation caused from melted/fresh(cold) water streams and the ozean current .

    Isn’t heat also compensated from the fact of still rizing sea levels(expanding ozean floods coast land)?

    And maybe weather anomalys have also a impact (eg. air movement caused from hurricanes).
    Transporting warmer air to higher areas – cooling the surface.

  18. 18
    Ike Solem says:

    Re #7 and hurricane-driven heat transfer: I tried to look up differences in tropical convection heat transfer to the atmosphere between high-hurricane and low-hurricane years and couldn’t find a clear answer, other then that the topic is complex. Hurricanes do have a deep surface mixing effect that normal tropical convection doesn’t produce, and that would be expected to result in greater transfer of heat to the atmosphere, but it gets complicated in a hurry; see the realclimate discussion of the Walker circulation for example, as well as the link between hurricanes and sea surface temps.

    Re #9 and space loss vs. deep ocean loss: It does seem that if radiation to space was the loss, you’d see a correlated increase in the temperature at the top of the troposphere, which is some -73 C. If loss to the deep ocean was responsible, well the data doesn’t go below 700m. Undersampling in the Arctic could be far more important then the 10% cited by Pielke because the polar regions are where deep water formation (sinking of cold, salty water) occurs; this drives the deep circulation and also oxygenates the deep ocean. Warmer water hold less dissolved gases (the classic example is to shake up a can of warm cola and a can of cold cola, and open both at the same time – try it!); that includes both O2 and CO2. If a warming deep ocean starts releasing CO2…

    In this respect, the continuing hypoxic trend off the Oregon coast is important. See ; “Marine ‘Dead Zone’ Off Oregon Is Spreading”; that’s the 5th time in 5 years (my previous post on this topic linked to the 2004 event). Here’s the brief report:

    “A fundamental new trend in atmospheric and ocean circulation patterns in the Pacific Northwest appears to have begun, scientists say, and apparently is expanding its scope beyond Oregon waters… This year for the first time, the effect of the low-oxygen zone is also being seen in coastal waters off Washington,”

    Re#10 and the freshwater input: That will require better data, according to the authors of this paper. I cut and pasted some sections out of their preprint that relate to this:

    “This suggests that other contributions to sea-level rise, such as melting of land-bound ice, have accelerated. This inference is consistent with recent estimates of ice mass loss in Antarctica [Velicogna and Wahr, 2006] and accelerating ice mass loss on Greenland [Rignot et al., 2006] but closure of the global sea level budget cannot yet be achieved. New satellite observations from the Gravity Recovery and Climate Experiment (GRACE; launched in March, 2002 and administered by NASA and Deutsches Zentrum für Luft-und Raumfahrt, GRACE will map Earth’s gravity field approximately once every 30 days during its lifetime) should soon provide sufficient observations of the redistribution of water mass to more fully describe the causes of recent sea-level change…..

    …..The issues relating to sea level rise and the global water budget can only be addressed when the record of satellite gravity measurement from GRACE achieves adequate duration. GRACE, Argo, and satellite altimetry are core components of the global ocean observing system. Failure to maintain any one of these observing systems would seriously impair our ability to monitor the World Ocean and to unravel its importance to the climate system.”

    What I think they are referring to is the widely noted failure of NASA to keep up Earth system satellite research programs. Perhaps pressure on Congress to earmark funds for an Earth System branch at NASA would be the best strategy for making sure the data continues to be collected. One of my advisors once told me “Science is politics.” Darn it – she was right.

  19. 19
    Lynn Vincentnathan says:

    I’m not sure I totally understand this post, but if the ocean has cooled slightly as part of natural fluctuation “noise,” and if last year’s hurricane season (with Katrina, et al.) happened during this natural cooling fluctuation, and if the ocean is on a general track of getting warmer, then we probably have much much worse to expect in future hurricanes….

  20. 20
    Mark Hadfield says:

    RE 16

    I think it’s not a good idea to try to link the global upper ocean heat content result to hurricanes. The recent cooling, if real, is largest at 400 m depth or so where it is less than 0.1 degC. The implied global average heat flux is ~1 W/m2. These are not large numbers compared to the seasonal and interannual variations for any given region. Eg see the map in LWJ06’s Fig 2, which shows regional heat content changes, expressed as fluxes, on the order of +/- 50 W/m2.

  21. 21
    Mark Hadfield says:

    My last comment was actually addressing #19, by Lynn Vincennathan, not #16.

  22. 22 says:

    Re# 19
    Id like to point out, Katrina´s strengh and growth was intesified by a Loop Current (Eddy). And this year there is again such an Eddy.

    And i just found this news bit U.S. Study Links Global Warming, Hurricane Intensity

  23. 23
    pat neuman says:

    Re 10. … THC. What do you think?


    I haven’t thought much about the THC although I’ve expressed doubt about seeing large regional cooling if it did shut down or change direction, mainly because global warming is so rapid that any cooling effect with time would be dampened by warming factors going on.

    After reading you’re comment, I’m wondering about how much influence on ocean temperatures there was as a result of the thawing of the Larsen B ice shelf (was about 220 meters thick … 2,717 square kilometers) …
    Are there still parts of Larsen B floating around?

  24. 24
    Stephen Berg says:

    “Establishing A Connection Between Global Warming And Hurricane Intensity

    Climate change is affecting the intensity of Atlantic hurricanes, and hurricane damage will likely continue to increase because of greenhouse warming, according to a new study. It provides for the first time a direct relationship between climate change and hurricane intensity, unlike other studies that have linked warmer oceans to a likely increase in the number of hurricanes.


  25. 25
    Stephen Berg says:

    To continue with my previous comment, I’ve created an image which compares a graph of Atlantic tropical storm systems to a graph of global surface air temperature anomalies from 1851 to 2004:

    The top graph, with a description, can be found on the National Hurricane Center site:

    The bottom graph, with a description, can be seen at the UK Climate Research Unit site:

    It seems as if there is a lag of roughly a decade between the warming air and greater numbers of tropical storm systems, but a correlation seems discernible.

    What are your thoughts on this?

  26. 26
    Karl Sanchez says:

    Re #18 Hi Ike, I live on the Oregon coast where this dead zone is happening. Here’s an item offering anecdotal evidence that this phenomena has been around some time and isn’t anything to be concerned about,

    I’ve been living here not quite 3 years now, so I can’t comment, but the only times I’ve seen ocean water look so ugly–like green pond scum, but in motion–are associated with effluent being dumped into the ocean without being properly treated. Yes, and it’s smellier than usual too. SSTs are higher here now too, and oldtimers are saying that the summer wind and weather patterns are different. The real unfortunate part of this is the area where this is happening is one of several along the Oregon coast we’re trying to have proclaimed marine sanctuaries.

    Upwelling to me implies greater thermal mixing that should result in SSTs decreasing, but ours are rising, and the experts all seem perplexed.

  27. 27
    sidd says:

    Re: comment # 14

    May I have a reference for the CERES TOA data ?


  28. 28
    Lawrence McLean says:

    Can the delta values be really trusted?

    From my reading, it seems that we are seeing a spread of the warm water sea life. Have there been any findings that contradict the trend (of spreading warm water sea life)? If there has not, then any assertions of confidence with the delta values should be withheld.

    I would be suprised if the increased flow of cold water from the melting polar icecaps could decrease the total heat content of the oceans, given the amount of additional heat that must be in the oceans that is causing the coral bleaching episodes throughout the tropics. It may turn out to be the case, however, my gut feel is that something is wrong with the measurements (now or more likely then!)

  29. 29
    Bryan Sralla says:

    Re: #23. There is a new paper by Carl Wunsch which also expresses doubt about a collapse in the THC

  30. 30
    Ravi Nathan says:

    Could the intense hurricane activity of 2004 and 2005 explain the reduction in oceanic heat content over the 2003 to 2005 period?

  31. 31
    Lynn Vincentnathan says:

    This is a bit off-topic, but I’ve read about the ocean off Oregon, where it is oxygen-depleted with large marine animal die out. They are saying it is due to changes in currents or upwelling of low oxy waters.

    Could it also be due to anoxia happening when methane clathrates melt — the methane combines with oxygen, forming CO2 and such, depleting the oxygen. Or is it too early (& not warm enough yet) for that?

    I understand this has happened in past severe GW episodes, mainly in the oceans.

    I also read that there could be massive releases of hydrogen sulfide caused by the warming, toxic levels — but how warm would it have to get for that?

  32. 32
    ike solem says:

    Re#26, Hi Karl. So called ‘dead zones’ exist in other areas as well; a better term is oxygen minimum zones. A well-studied example is the oxygen minimum zone that develops off the west coast of South America and is generally thought to be due to the high nutrient inputs and the very productive fisheries in the region; in addition in this region the bottom waters tend to stay oxygenates – the zone develops in the mid-ocean depths. An image of this system can be seen at Similar zones exist off the Arabian peninsula, and they are important areas for studying nitrogen cycling.

    In contrast, the Oregon zone appears to be linked to low O2 levels in upwelling subarctic bottom water; you are correct in that high effluvient outflow would also produce such effects, but that would look more like the Peruvian system. It is certainly possible that both effects are occuring in synergy.

    Regarding the anectodal article that you linked to, there are a couple of issues involved here. Terry Thompson (the author) is a retired commercial fisherman and I doubt that he’s was out taking measurements of bottom water dissolved O2 from his boat. Surface water anoxia, as you point out, can happen due to effluvia and the 50’s were not exactly an environmentally conscious era – paper/pulp mill effluvient in particular is known to cause fish kills. From his article: “I have my own memories of the 1950s. I recall seeing whiting floating in Yaquina Bay, gasping for air. This wasn’t a rare occurrence. People who lived here will remember the dead fish that littered the beaches.” See also . Political activisim is fine, but attacking science for political reasons is not.

    From ScienceDaily:
    “The lack of wide-scale ocean monitoring makes determining the size and movement of the dead zone difficult, although some new instrumentation being used this year by OSU scientists is helping. Dissolved oxygen sensors have been deployed on the sea floor both close to shore and in 260 feet of water off Newport, some of which are sending data in near real-time.”

    So, enough about that. To revisit the role of global ocean hypoxia and hydrocarbon formation, (yes they are related), see this site:

    Bryan Sralla had this to say about my previous comment on this issue:
    “Ike, I am glad you are finally talking about hydrocarbons. FYI, the Middle East hydrocarbon source rocks were deposited in the Tethys Sea. This was a shallow inland sea, that generated restricted anoxic marine source rocks. The massive carbonate reservoirs of the Middle East oilfields are mainly shallow water karsted and fractured dolomites. You are so far off base on this, that it is really hard to even begin to take what you said seriously. Wrong tectonic setting, wrong source rock environment, wrong reservoirs, wrong structural setting. Try again! Global ocean stratification forming oilfields? I have never heard of this in my career as a petroleum geologist. There is way too much junk science on this website.”

    Ummm – perhaps it is time for an apology for the ‘junk science’ comment?

  33. 33
    Bryan Sralla says:

    My comments were indeed needlessly harsh, and for that, you have my apology. To the valuable Real Climate website, I also retract my statement about the “junk science”. Although my interpretations of some data may differ, it will be my intention to attempt a more diplomatic tone in the future.

    Old crusty, tough guys like Bill Gray have always been my heros in science though, but I see that these kinds of tactics have their drawbacks and occasionally hurt feelings. I will do better.

  34. 34
    ike solem says:

    Thanks for the response, Bryan. However it was less the tone of your comments and more their lack of scientific accuracy that I was concerned with. If you link to the last link in my post, you will find the following statement; there are many such examples available and any decent petroleum geologist would agree with this:

    “Examples of modern sapropel formation within the oxygen minimum zone beneath upwelling high productivity surface waters can be found on the continental slope of the Arabian Peninsula and in the California borderlands. Upwelling in the northwest Indian Ocean provides sufficient surface productivity to provide an excess of organic matter to sediments on the continental slope of the Arabian Peninsula where the oxygen minimum zone intersects the slope. Off California, the combined effects of sluggish circulation in semi-isolated basins, continental margin depths within the oxygen minimum zone, and high surface water productivity all contribute to accumulation of laminated, organic-rich sediments in the Santa Barbara basin.

    Anoxic sediments have been widespread in the past and are of great economic importance as source rocks for hydrocarbon deposits. Expansion and intensification of the oceanic oxygen minimum zone, probably during times of reduced thermohaline circulation, is one mechanism that seems to account for many sapropels. Deep basins connected only by shallow connections, which resulted in restricted bottom circulation, were especially common during early stages of continental rifting that formed the Atlantic basin.”

    As you point out, the Mideast oilfields source rocks were produced in the Tethys Sea; to quote,

    “This was a shallow inland sea, that generated restricted anoxic marine source rocks. The massive carbonate reservoirs of the Middle East oilfields are mainly shallow water karsted and fractured dolomites. You are so far off base on this, that it is really hard to even begin to take what you said seriously. Wrong tectonic setting, wrong source rock environment, wrong reservoirs, wrong structural setting.”

    However, my comment was strictly related to the conditions under which source rock would form, not the myriad other factors that allow for the development of productive oilfields – the porosity, the presence of cap rocks, etc. What I’d like to see is an acknowledgement of the scientific inaccuracy of your ‘unnecessarily harsh criticism”.

  35. 35
    Jerry Steffens says:

    Lyman, et al’s result would seem to fly in the face of previously compiled SST data, which shows no letup in the rising trend of SSTs during this period, e.g., Fig. 12 at
    (Note that SURFACE cooling is indicated in Fig. 4 of Lyman, et al.)

  36. 36
    Bryan Sralla says:

    Re: #34 If you or anyone else would like, I would really enjoy continuing our discussion of petroleum geology off line. Petroleum source rocks and geochemistry are facinating, but really not the subject of this thread.

    For a massive source of published, peer-reviewed work on the subject, I would suggest an associate membership in the American Association of Petroleum Geologists. The AAPG Bulletin is published online each month, and is a world-class source for technical papers involving petroleum systems. I look forward to visiting with you further via e-mail.

  37. 37

    The set of Comments and the original posting on Real Climate have advanced the discussion of the signficance and the issues associated with the observed recent upper ocean cooling. I have just two comments here:

    The 60S-60N averaged sea surface temperatures have been relatively flat since 2001 as shown in a personal communication from NOAA, that should be widely available soon. The current value is significantly lower than it was in 1998.

    Secondly, unlike the global average surface temperature trend, which has a lag with respect to radiative forcing, there is no such lag when heat content is measured in Joules (see The upper ocean heat content in mid 2005 was about equal to that in mid 2001. This means that the heat content was “reset” to this earlier value, whereas the multi-decadal global climate model projects a more-or-less monotonic increase in ocean heat content. There clearly is a problem with the models and the IPCC-type understanding of the human- and natural-climate forcings and feedbacks.

    [Response: Well, according to the Hadley/Reynolds analysis, SST has risen from 1998 onwards, and so I’m not sure what the NOAA analysis has done differently (see for yourself). Obviously though on any short time scale of a few years, there is significant local variability as would be expected from a dynamic ocean environment. I don’t know why that appears to be a surprise. I agree that the models tend to show less decadal ocean variability than observed (given the obvious caveats on the observational side), but absolutely disagree that this implies that longer term estimates are off. The model used in Hansen et al (2005) for instance, does not have a good representation of ENSO variability – conceivably leading to this underestimate of decadal variability, but other models do a better job and it would be good to see what their variability looked like in this metric. By the way, it is the same quantity whether it’s measured in total Joules or converted to W/m^2. The latter makes it much more convenient to compare to the radiative imblance, and so is the way I prefer to think about it. – gavin]

  38. 38
    Steffen Christensen says:

    Hello, everyone. Interesting discrepency. I wonder if the original paper describes how interpolation was done over the missing data – I apologize in advance, as I haven’t access to the paper. Slide 7 of the PowerPoint deck over at shows the global data coverage of Argo as of 30 September 2005. As you can plainly see, North of 60 there is only data basically for the Greenland and Norwegian Seas. The data from the large Barents, West Siberian, East Siberian, Chukchi and Beaufort Seas, the Baffin Bay and the Denmark strait as well as the polar Arctic Ocean appear not to exist. Normally this couldn’t influence the results overmuch, as the Arctic Ocean is only ~10% of the polar ocean. But if we consider the mean polar temperature anomalies (see for a map), the missing data seem to be experiencing much greater warming then the sampled North Polar data, at the ocean surface at least. The Beaufort Sea and areas north appear particularly striking, with some of the highest mean temperature anomalies observed on the planet, around 1.5 oC for the region. Compare this with the modest surface temperature changes of ~0.5 oC for the sampled region, and you the sense of my post. (It’s not my idea, tho’ – credit goes to Fergus Brown, post #10 over at RealClimate: In terms of power integrated over area, only northern Eurasia has a higher regional warming in absolute terms – which suggests to me that sea surface warming in the Arctic west of the Canadian archipelago might change the total sea energy balance by quite a bit. Any thoughts? (crossposted to Roger Pielke’s Climate Science blog at

  39. 39
    Hank Roberts says:

    The geologists are interested in, and talking about, the way oil used to be formed in the past; the marine biologists are saying that developing conditions can kill off a lot of organisms, and that would cause sedimentation making layers rich in organic material — at present, in a very different world.

    I don’t see any contradiction. Looking at the difference between limestone and dolomite tells us whether calcium shells of the organisms was soluble at the depth and temperature where the sediment was laid down at the time. The issue today is what happens today.

    Someone above said methane reacts with oxygen to make carbon dioxide in water.

    I believe that reaction takes much longer than bubbles require to reach the surface; the methane released in these bubble sites or in rapid events like underwater landslides) either dissolves in water or reaches the atmosphere in a matter of minutes, according to what was posted here earlier.

  40. 40
    Jerry Steffens says:

    Re #34
    My mistake: When one looks at ANNUALLY averaged SSTs, e.g., at (the link given in Lyman, et al.), rather than multi-year averages, the disagreement disappears. (The Washington data indicates a drop of 0.02 degrees C between 2003 and 2005.)

  41. 41
    Fergus Brown says:

    My thanks to Bryan Sralla, Pat Neuman and many others, who responded to my somewhat naive questions(#10). The Wunsch paper in particular (see #29), being from an oceanographic perspective, was instructional. A striking comparison can be made by reading Schlesinger et. al. (Illinois)’Assessing the Risk of a Collapse of the Global Thermohaline Circulation’ (sorry, no link), or the recent paper published by Curry et. al. (WHOI) in Science magazine.
    Let’s agree that a simple ‘Global Conveyor’ is an inadequate, even misleading model of circulation. Let’s also agree that the Laurentide ‘hosing’ of the Atlantic was not a causal agent in the YD. We still end up with a bucketful of freshwater. Curry suggests an Arctic-Atlantic flux of 5000km3/an mean 1965-95, + 19000Km3 from the three ‘salinity anomalies’ in that period. This must be having an effect on the ocean circulation, on the upper levels, if nowhere else. Therefore, it must be having an effect on the climate. So, two more naive questions: What effect do you think this is having? and; What are the current AOGCMs which incorporate the Polar regions (I am certain there is one) showing as a consequence (in climate terms) of this, assuming it were a forcing mechanism?
    I’m not married to the idea of thermohaline weakening or even less, shutdown; at the moment, the numbers don’t add up. But I do wonder how seriously the models, and thus the humans who interpret them, are taking this.
    Once again, thank you for letting me contribute to your discussions.

  42. 42
    Josh Willis says:

    Re #14.

    John, thanks for the comments. It is certainly true that a very small temperature bias that is not random from instrument to instrument, but instead is the same over a large number of profiles can create systematic error in global estimates of ocean heat content. However, we felt that by testing the different datasets independently, as I discussed in post to Roger Pielke’s blog that was linked in #16. Since tossing all of the Argo data, or using ONLY Argo data to make the estimate did not get rid of the cooling, we felt that it was not a result of systematic bias.

    I would also comment that it is important not to read too much into the depth v. temperature change figure. Having the peak in the cooling occur at depth rather than at the surface is not that suprising considering how that figure was calculated. Remember, this represents a global averaged of temperature changes over many regions of the ocean that are governed by vastly different dynamics. The peak in the cooling, for instance, (about 400m) coincides with the depth of the thermocline in the subtropical Pacific. The ocean moves heat around internally in complicated ways, and the 1-D view provided in figure 4 is simply not sufficient to descirbe its global heat budget. In other words, the ocean is not a simple 1-D slab that diffuses temperature anomalies down from the surface.

    Finally, you are correct that 1 pW heat sink in the climate system would be problematic. My understanding of the CERES TOA fluxes, however, were that the 1-sigma error bars were still on the order of 2.4 W/m^2, or about 1 pW. This is still a bit too large to be contradictory to our ocean cooling findings, I think. Perhaps you have newer references or info. on the satellite data, though. If you do, I would love to hear more.

  43. 43
    Pekka Kostamo says:

    Another type of observation is that there seems to be a virtual plague of droughts world-wide. Too little precipitation has cut agricultural production in the U.S. and in Europe, Australia and southern Africa. The Amazonas is drying too. Abnormally high rains have been reported only in North Korea, Ethiopia and Poland, but these areas seem to me very small. Grain market prices have risen 20% and the stocks are reaching new lows.

    Is this just biased news reporting, or is there something else?

    Colder sea surface, less evaporation, less rain would be logic, but should be visible on satellite surface temperature measurements. It is the surface temperature that has immediate impact.

    Best regards,

  44. 44
    Karl Sanchez says:

    Thanks Ike for your response, and Bryan too.

    Questions, wouldn’t increasing ocean acidification impact formation of carbonate-based rock? What would this altered rock strata look like to a future geologist? Lastly, several articles I’ve read regarding current and near future grain production say yields are likely to drop because of an impending el nino; is this correct, or are these writers just trying to continue the bull market in food commodities?

  45. 45
    Nigel Goddard says:

    Re #12: Perhaps the ice isn’t all melting, which would throw off your calculation. There have been reports of increased shedding of ice from Greenland and I think Antarctica. Sea level can go up without the ice melting.

  46. 46
    Jeff Weffer says:

    It is not surprising for there to be SST variability. If you ever see a good time series animation of SSTs, you will know that there is significant movement of water and temperatures within the world’s oceans (like there is with polar ice extents.)

    Here is a good animation of the Pacific over the past year (August 05 to August 06 centred over the El Nino formation region.)

    Here is a really good hi-resolution animation of the gulf stream over a one-year period (takes a while to load but worth it.)

    These animations should tell you that you shouldn’t get worked up about one little area of the acean warming for a period of time. Carribean temperatures cooling slightly over a 2 year period is normal given the nearly chaotic heat transfer that occurs in a system as large as the world’s oceans (the biggest surface system there is of course.) A few bouys in the North Atlantic showing warmer temperatures compared to the measurements of 30 years ago is not “evidence” etc.

  47. 47
    Steve Sadlov says:

    Why did you censor a simple NWS Anchorage ice desk forecast? That’s pretty crass. Amazing.

    [Response: Ummm…. maybe an apology is due? – gavin]

  48. 48
    Steve Sadlov says:

    Sorry, got the threads mixed up.

  49. 49

    Gavin- Regarding # 37, from the latest NOAA OI.v2SST analysis, the 60S to 60N SST anomalies are 2005 +0.247C; 2004 +0.217C; 2003 +0.235C; and 2002 +0.222C. Those values are quite flat.

  50. 50
    pat neuman says:

    re: 43

    Adding to the virtual plague of droughts world-wide:
    Western China Endures Worst Drought In 50 Years
    (AFP) Aug 17, 2006:

    My guess on why was shown at RC a few weeks ago in comment #12 …
    Wayne, if it’s true as you indicated in 9, that upper air temperatures are increasing at a much stronger rate than near the surface, it seems to me the departure would explain at least part of what seems to be a large increase in world area having minimal rainfall and drought… at: