The connection between global warming and the changes in ocean heat content has long been a subject of discussion in climate science. This was explicitly discussed in Hansen et al, 1997 where they predicted that over the last few decades of the 20th Century, there should have been a significant increase in ocean heat content (OHC). Note that at the time, there had not been any observational estimate of that change (the first was in 2000 (Levitus et al, 2000)), giving yet another example of a successful climate model prediction. At RC, we have tracked the issue multiple times e.g. 2005, 2008 and 2010. Over the last few months, though, there have been a number of new papers on this connection that provide some interesting perspective on the issue which will certainly continue as the CMIP5 models start to get analysed.
The most recent paper was a new study from NCAR out last week that looked into what happens to OHC in models when there are occasional 10 year periods with no trends in global surface temperatures (Meehl et al, 2011).
It is well-known (or at least it should be) that simulations for late 20th C and early 21st Century do not produce monotonically increasing temperatures at the annual or decadal time-scale. For the models used in AR4, the decadal trends expected under estimates of present day forcings are roughly N(0.2,0.14) (i.e. a Gaussian distribution centered on 0.2 ºC/decade with a standard deviation of ~0.14ºC/decade. This implies that one would expect an 8% probability of getting surface temperature trends less than zero in any one decade.
The Meehl et al study looked at the changes in ocean heat content during these occasional decades and compared that to the changes seen in other decades with positive surface trends. What they found was that decades with cooling surface temperatures consistently had higher-than-average increases in ocean heat content. This makes perfect sense if there is internal decadal variability in the fluxes that connect the deeper ocean to the surface ocean (which of course there is). An anomalous downward heat flux reduces the ocean surface temperature (and hence global surface temperature), which generates an anomalous heat flux into the ocean from the atmosphere (because the flux into the ocean is related to the difference between atmospheric and ocean temperature). And this of course increases total OHC.
A related study from the UK Met. Office looked at the relationship between the ocean heat content changes in the top 700m and the total ocean heat content change in models (Palmer et al, 2011). They found that (unsurprisingly) there is more variability in the top 700m than in the whole ocean. This is important to quantify because we have better estimates of the upper ocean OHC change than we do of changes in the whole ocean. Observational studies indicate that the below-700m increases are not negligible – but they are poorly characterised (von Schuckmann et al, 2009). The Palmer study indicates that the uncertainty on the decadal total OHC change is about 0.15 W/m2 if one only knows the OHC change for the top 700m.
So what can we infer about the real world from these tests? First, we can conclude that we are looking at the right quantities. Total OHC changes are a good measure of the overall radiative imbalance. Second, there is likely to be a systematic issue if we only look at the 0-700m change – this is a noisy estimate of the total OHC change. Third, if the forcings are close to what we expect, we should anticipate that the deeper ocean (below 700m) is taking up some of the slack. There are of course shorter term sources of variability that also impact these measures (OHC changes associated with ENSO, solar irradiance variability over the solar cycle) which complicate the situation.
Two further points have come in comment threads recently that are related to this. The first is whether the changes in deep ocean heat content have any direct impact other than damping the surface response to the ongoing radiative imbalance. The deep ocean is really massive and even for the large changes in OHC we are discussing the impact on the deep temperature is small (I would guess less than 0.1 deg C or so). This is unlikely to have much of a direct impact on the deep biosphere. Neither is this heat going to come back out from the deep ocean any time soon (the notion that this heat is the warming that is ‘in the pipeline’ is erroneous). Rather, these measures are important for what they tell us about the TOA radiative imbalance and it is that which is important for future warming.
The second point is related to a posting by Roger Pielke Sr last week, who claimed that the Meehl et al paper ‘torpedoed’ the use of the surface temperature anomaly as a useful metric of global warming. This is odd in a number of respects. First, the surface temperature records are the longest climate records we have from direct measurements and have been independently replicated by multiple independent groups. I’m not aware of anyone who has ever thought that surface temperatures tell us everything there is to know about climate change, but nonetheless in practical terms global warming has for years been defined as the rise in this metric. It is certainly useful to look at the total heat content anomaly (as best as it can be estimated), but the difficulties in assembling such a metric and extending it back in time more than a few decades preclude it from supplanting the surface temperatures in this respect.
Overall, I think these studies show how we can use climate models to their best advantage. By looking at relationships between key quantities – those that can be observed in the real world and those that are important for predictions – we can use the models to interpret what we are measuring in the real world. For these cases the inferences are not particularly surprising, but it is important that they be quantified. Note that the assumption here is akin to acknowledging that since the real world is more complicated than the (imperfect) models, inferences in the real world should at least be shown to work in the models before you confidently apply them to reality.
However, it is the case that none of these studies prove that these effects are happening in the real world – they are merely suggestive of what we might strongly expect.
References
- S. Levitus, J.I. Antonov, T.P. Boyer, and C. Stephens, "Warming of the World Ocean", Science, vol. 287, pp. 2225-2229, 2000. http://dx.doi.org/10.1126/science.287.5461.2225
- G.A. Meehl, J.M. Arblaster, J.T. Fasullo, A. Hu, and K.E. Trenberth, "Model-based evidence of deep-ocean heat uptake during surface-temperature hiatus periods", Nature Climate Change, vol. 1, pp. 360-364, 2011. http://dx.doi.org/10.1038/nclimate1229
- M.D. Palmer, D.J. McNeall, and N.J. Dunstone, "Importance of the deep ocean for estimating decadal changes in Earth's radiation balance", Geophysical Research Letters, vol. 38, pp. n/a-n/a, 2011. http://dx.doi.org/10.1029/2011GL047835
- K. von Schuckmann, F. Gaillard, and P. Le Traon, "Global hydrographic variability patterns during 2003–2008", Journal of Geophysical Research: Oceans, vol. 114, 2009. http://dx.doi.org/10.1029/2008JC005237
RE: 197
Hey prokaryotes,
Okay two questions…
First; How is the Arctic water column being freshened? Keeping in mind how sea ice forms. The temperature drop of the incoming Gulf Stream water causes the salt or brine to precipitate out leaving a large pool of fresh water floating on the more saline and slightly cooler waters below. Cooler air blows across the pool of fresher water where it begins to freeze forming “cup or pot” ice blocks that capture frozen precipitation. They become unbalanced and roll to expose their bottom and another “cup” forms. The winds blow the “cups” together where they form rafts. The rafts, converge forming plates, and eventually they form “shelves”.
So if we reverse the process, does the fresher melt water act differently then, then former less warm or saline slowly freezing tropical inflow, very unlikely.
Secondly, how would freshened melt water in the column, sink to the bottom, if the temperature differences between it and the more saline Arctic Ocean even out, by the time it falls to around 50 meters depth? If we have incoming tropical water that is say three times as saline and 7 deg. C warmer then the fresh water in residence, it will likely fall through the first 50 meters and with very little mixing. As the more saline waters fall they radiate out most of their heat, warming the fresher surface and melt waters. The fresher waters absorbing the added heat at depth, rise. (The difference in salinity forms a boundary layer, reducing mixing, while rising to the surface.) Here at the surface the warmed fresh water is exposed to frigid wind and air temperatures in Winter, extracting the absorbed warmth and refreezes.
In the meantime the more saline tropical waters still sink further with less heat then before. These incoming tropical waters are still more density then the surrounding 70-100 meter waters. Their balance of heat is slightly higher, as they were not resident on the surface as long, as in a non-freshed sea surface. (The added salinity, in a warming climate or under the influence of a long resident Blocking High, causes the tropical waters to became, say three times more saline then a sea surface not so warmed.) Hence, with a slightly greater density they overcome the added boyancy, the higher SST heat they absorbed, would cause. Taking slightly higher then normal heat, (a few degrees), with them to the Arctic Basin.
Finally as the cooled tropical waters fall to the Arctic Basin floor they slightly transfer a portion of their addtional heat to the waters they fall through, which slowly dissapates. It does not look like freshened water reaches the bottom.
Did I miss-understand your point?
(Oh, it is very likely that in an a hypoxic or anoxic environment there would be a large increase in anaerobic oganisms creating a lot of sulfur compounds as they dined on the aerobic dead from above, characteristic of Desulfuromonadales (more likely in the ocean due to greater concentration of ocean bottom manganese and iron compounds found there). Though denitrification is evident where there is sufficient carbon resources and large populations of Paracoccus or E. Coli as would be more common on land or in fresh water. (c/o wikipedia anaerobic resperation, “examples of resperation types” table, Sad to say no proper references appear available.))
Cheers!
Dave Cooke
In contrast to what I wrote in my little summary at 175, the disagreement between Roger and Gavin doesn’t seem to be on whether the heat transfer is concentrated in space (both seem to agree that it is), but rather on whether the heat transfer is continuous or episodic in time (Gavin thinks it’s the former; Roger doesn’t say) and on whether the data precision is sufficient (Gavin thinks it isn’t; Roger doesn’t say).
For a while the same amount of heat may enter the top 700 m from above, as leaves it from below. As a result, no warming signal in this layer will be observed, whereas heat is being transferred through it. A constant temperature is thus not proof that no heat has transferred through the layer.
A longer summary of the discussion between Roger and Gavin -and what I make of it- is on my blog: http://ourchangingclimate.wordpress.com/2011/10/12/ocean-heat-content-transfer-of-heat-through-the-top-700-metres-gavin-schmidt-vs-roger-pielke-sr/
@ 189
Gavin, you missed my point completely (which was highlighted in the part you edited)! I tried to illustrate the point by intentionally taking a sentence out of context, and then trying to make hay to “show up” a commentor.
I then explained my slight of hand trick (in the part you edited) in order to make a point to a specific commentor (and you). You were not being fair to Pielke Sr. by not giving him the benefit of the doubt. You guys did not seem to even try to understand his points.
You have done this so many times over the years, and it is quite distasteful. This type of tactic is why climate science has suffered so much in the eyes of the public in recent years.
The last EOS that I recieved, I noticed that Pielke Sr. is on the editorial board of the AGU. I doubt he has gotten there by being a idiot and not being competant to deal in very basic physics.
[Response: I do not think that Roger is an ‘idiot’ nor do I think he is ‘incompetent’ – where do you get this stuff from? What I edited out was you attacking another commenter – who wasn’t actually wrong. Stick to arguing about science, stop trying to ‘show up’ other commenters, and please don’t make up insinuations about my opinions that you know nothing about. – gavin]
Hank Roberts –
Regarding
“Would using ocean heat content changes be a satisfactory primary metric for diagnosing heat storage changes within the Earth system?”
The answer is yes. I have heard Jim Hansen say the same thing at one of NRC (2005) committee meetings. This is a suggestion for the present (2003 and later when the Argo network obtain their planned coverage and into the future.
P.S. I disagree that the land temperatures are well sampled, but that is an issue for a different thread.
Yor related questions are clearly presented and answers needed.
Bart Verheggen
Regarding
“…whether the heat transfer is continuous or episodic in time (Gavin thinks it’s the former; Roger doesn’t say) and on whether the data precision is sufficient (Gavin thinks it isn’t; Roger doesn’t say).”
I expect the transfers, to whatever extent they are occuring, are in coherent blobs, as illustrated at the ECMWF site – http://www.ecmwf.int/products/forecasts/d/charts/ocean/real_time/.
As to precision, I do not know the answer to that question, but it needs to be answered.
P.S. Enjoyed reading your weblog; I have bookmarked it.
Om my earlier answer to Hank Roberts, there is a typo – it should read
“Would using ocean heat content changes be a satisfactory primary metric for diagnosing heat storage changes within the Earth system?”
The answer is yes. I have heard Jim Hansen say the same thing at one of NRC (2005) committee meetings. This is a suggestion for the present (2003 and later) when the Argo network obtained their planned coverage, and into the future.
Thank you Dave Cooke for the detailed explanation and to make clear that there is very minimal heat flux to the deep ocean. Though it seems there is some heat going down and distributed on it’s path to surrounding layers(How much exactly?), but much less then my earlier post might have suggested (in response to Roger’s comment).
What we did not discussed yet is the effect of the biological pump:
climate change may affect the biological pump in the future by warming and stratifying the surface ocean. It is believed that this could decrease the supply of nutrients to the euphotic zone, reducing primary production there. Also, changes in the ecological success of calcifying organisms caused by ocean acidification may affect the biological pump by altering the strength of the hard tissues pump. This may then have a “knock-on” effect on the soft tissues pump because calcium carbonate acts to ballast sinking organic material
http://en.wikipedia.org/wiki/Biological_pump
I wonder for how much heat transport to the deep ocean, sinking organic material accounts for?
Related
Decadal fluctuations in ocean salinity, nutrients, chlorophyll, a variety of zooplankton species, and fish stocks in the Northeast Pacific have been unexplained for many years. They are often poorly correlated with the most widely used indicator of large-scale climate variability in the region: the Pacific Decadal Oscillation (PDO). Researchers Emanuele Di Lorenzo of the Georgia Institute of Technology and Niklas Schneider of the University of Hawaii recently defined a new pattern of climate change—the North Pacific Gyre Oscillation (NPGO)—and showed that its variability is significantly correlated with the previously unexplained fluctuations of salinity, nutrients, and chlorophyll. http://planetforward.org/idea/new-climate-mode-of-variability-links-ocean-climate-and-ecosystem-change/
Marine algae live in the upper layers of the ocean but rely on nutrients that circulate up from lower layers. Rising temperatures mean the different layers mix less with each other, so fewer nutrients reach the algae.
In the oceans, ubiquitous microscopic phototrophs (phytoplankton) account for approximately half the production of organic matter on Earth. Analyses of satellite-derived phytoplankton concentration (available since 1979) have suggested decadal-scale fluctuations linked to climate forcing, but the length of this record is insufficient to resolve longer-term trends. Here we combine available ocean transparency measurements and in situ chlorophyll observations to estimate the time dependence of phytoplankton biomass at local, regional and global scales since 1899. We observe declines in eight out of ten ocean regions, and estimate a global rate of decline of ~1% of the global median per year. Our analyses further reveal interannual to decadal phytoplankton fluctuations superimposed on long-term trends. These fluctuations are strongly correlated with basin-scale climate indices, whereas long-term declining trends are related to increasing sea surface temperatures.
http://thinkprogress.org/romm/2010/07/29/206497/nature-decline-ocean-phytoplankton-global-warming-boris-worm/
Sensitivities of marine carbon fluxes to ocean change
Throughout Earth’s history, the oceans have played a dominant role in the climate system through the storage and transport of heat and the exchange of water and climate-relevant gases with the atmosphere. The ocean’s heat capacity is ≈1,000 times larger than that of the atmosphere, its content of reactive carbon more than 60 times larger. Through a variety of physical, chemical, and biological processes, the ocean acts as a driver of climate variability on time scales ranging from seasonal to interannual to decadal to glacial–interglacial. The same processes will also be involved in future responses of the ocean to global change. Here we assess the responses of the seawater carbonate system and of the ocean’s physical and biological carbon pumps to (i) ocean warming and the associated changes in vertical mixing and overturning circulation, and (ii) ocean acidification and carbonation. Our analysis underscores that many of these responses have the potential for significant feedback to the climate system. Because several of the underlying processes are interlinked and nonlinear
. A potentially more significant impact of changes in the hydrological cycle on the oceanic CO2 uptake can arise at high latitudes in the North Atlantic: Here, reduced surface salinities, together with higher SSTs, would lower the density of surface waters and thereby may inhibit the formation of deep waters. This lowering in turn would reduce meridional pressure gradients and tend to slow down the thermohaline-driven part of the meridional, overturning circulation.
The abiotic solubility pump is caused by the solubility of CO2 increasing with decreasing temperature. In present climate conditions, deep water forms at high latitudes. As a result, volume-averaged ocean temperatures are lower than average sea-surface temperatures. The solubility pump then ensures that, associated with the mean vertical temperature gradient, there is a vertical gradient of dissolved inorganic carbon (DIC). This solubility-driven gradient explains ≈30–40% of today’s ocean surface-to-depth DIC gradient (7).
A key process responsible for the remaining two thirds of the surface-to-depth DIC gradient is the biological carbon pump. It transports photosynthetically fixed organic carbon from the sunlit surface layer to the deep ocean. Integrated over the global ocean, the biotically mediated oceanic surface-to-depth DIC gradient corresponds to a carbon pool 3.5 times larger than the total amount of atmospheric carbon dioxide (8) and has a mean residence of a few hundred years. Hence, small changes in this pool, caused, for example, by biological responses to ocean change, would have a strong effect on atmospheric CO2. Counteracting the organic carbon pump in terms of its effect on air–sea CO2 exchange is a process termed the carbonate counter pump (9), also known as the alkalinity pump. The formation of CaCO3 shell material by calcifying plankton and its sinking to depth lowers the DIC and alkalinity in the surface ocean, causing an increase in CO2 partial pressure. It is worth noting that the organic and inorganic carbon pumps reinforce each other in terms of maintaining a vertical DIC gradient, whereas they are counteractive with respect to their impact on air–sea CO2 exchange.
Although the range of potential changes in the solubility pump and chemical responses of the marine CO2 system is known reasonably well, our understanding of biological responses to ocean change is still in its infancy. Such responses relate both to possible direct effects of rising atmospheric CO2 through ocean acidification (decreasing seawater pH) and ocean carbonation (increasing CO2 concentration), and indirect effects through ocean warming and changes in circulation and mixing regimes. These changes are expected to impact marine ecosystem structure and functioning and have the potential to alter the cycling of carbon and nutrients in the surface ocean with likely feedbacks on the climate system.
Increased thermal stratification due to rising SST affects both nutrient supply and mixed-layer light intensities. In the tropics and midlatitudes, where thermal stratification restricts vertical mixing, typically low surface nutrient concentrations limit phytoplankton growth. Ocean warming will further reduce mixing, diminishing the upward nutrient supply and lowering productivity (Fig. 4Upper). At higher latitudes, phytoplankton is often light-limited because intense vertical mixing circulates algal cells over deep mixed layers, resulting in lower mean light intensity along a phytoplankton cell’s trajectory and hence lower net productivity. In these regions, ocean warming and a greater influx of fresh water, mostly from increased precipitation and melting sea ice, will contribute to reduce vertical mixing which may increase productivity
As sea-surface warming reduces deep-ocean ventilation, this slowdown will lower the supply of oxygen to the ocean interior (59). This process, which has been termed “ocean deoxygenation” (60), is expected to cause an overall decrease in deep-ocean oxygen content, including an expansion of oxygen-minimum zones (61, 62). Suboxic and anoxic conditions favor processes such as denitrification and anaerobic ammonium oxidation, leading to the loss of bioavailable nitrogen in the ocean, with possible implications for marine primary production. Provided that the ocean’s nitrogen inventory ultimately determines the amount of carbon biologically sequestered in the ocean, reducing the nitrogen inventory would provide a positive feedback to the climate system. http://www.pnas.org/content/106/49/20602.full
More at: https://www.realclimate.org/index.php/archives/2007/11/is-the-ocean-carbon-sink-sinking/
The planet’s deep oceans at times may absorb enough heat to flatten the rate of global warming for periods of as long as a decade even in the midst of longer-term warming….
The study, based on computer simulations of global climate, points to ocean layers deeper than 1,000 feet (300 meters) as the main location of the “missing heat” during periods such as the past decade when global air temperatures showed little trend. The findings also suggest that several more intervals like this can be expected over the next century, even as the trend toward overall warming continues….
“This study suggests the missing energy has indeed been buried in the ocean,” [coauthor Kevin] Trenberth says. “The heat has not disappeared, and so it cannot be ignored. It must have consequences.”
These potential consequences include accelerated warming in the coming decade and melting of the West Antarctic Ice Sheet. Let’s take these two in order.
The heat may have been carried deep into the ocean by overturning circulations, which can plunge surface water from the subtropical regions into the ocean’s depths. The burying of warmer water also corresponds with La Nina weather patterns, which are born from cooler-than-average surface water temperatures in the tropical Pacific. And over the last decade, La Nina conditions have dominated, Trenberth said.
That the heat is buried in the ocean, and not lost into space, is troublesome, Trenberth said, since the heat energy isn’t likely to stay in the ocean forever, perhaps releasing back into the atmosphere during a strong El Nino, when sea surface temperatures in the tropical Pacific are warmer than average.
“It can come back quite fast,” he said. “The energy is not lost, and it can come back to haunt us, so to speak, in the future.” http://thinkprogress.org/romm/2011/09/23/327298/hottest-decade-deep-oceans-warming-may-be-on-its-way/
Is the North Pacific Gyre Oscillation related to the recent increase in late summer snow cover in the Montana Rockies? The last 2 years have seen a great improvement in skiable lines. The Stanton Glacier for example was nearly all bare ice in late Sept 2007 but almost completely firn in early Oct 2010 with coverage at least 200 m into what had been rock.
Re: Bryan S @ 189
Um, no, your physics is sloppy. Let’s go back to the simple slab – steady state, constant temperature, linear with depth. Let’s presume that the flux at the top surface is received by absorption of radiation, and the same flux (i.e. same quantity) of heat is lost at the bottom by radiation. Conduction through the slab occurs at this same heat flux value.
So, we have a flux of heat, and we have no changes in temperature with time. So a flux of heat can’t possibly require that there be a change in temperature, can it? Conversely, there is a gradient in temperature (with depth), and that gradient is the reason that heat is conducted, so I think it’s safe to say that the flux of heat depends on temperature. To get changes in temperature, you need to have flux divergence – i.e., a flux that is not constant with depth – the rate of heating depends on the difference between what goes in and what goes out..
(Of course, if you can move mass, you can move heat without a temperature gradient. Just pick the object up and put it down somewhere else, and the heat it contains has been transferred.)
The math is in comment 120 (but don’t forget to look at #123 and #128 while you’re at it).
[Captcha is “tofhou velocity”. Is that what you get when your kid throws the tofu across the room?]
Re: Roger Pielke @ 190
Yes, another thought experiment. One that clearly has transfer of energy (heat conduction), yet there are no changes in temperature with time.
…and yet you still seem to think that “the heat, even without accumulating, in Joules would still be seen as it moves downward.”
I will try again: how will it be seen? It won’t be because there is a temperature anomaly or a change in temperature, because all temperature anomalies will equal zero and all rates of temperature change with time are zero – we’re in a steady state. We look at the system at time t1, and then look at it again at time t2, and it looks exactly the same. We decide to leave it for a week, or a month, or a year. We know that buckets of heat have passed through the slab, but every time we look at the temperature field, it still looks exactly the same. You agree that heat is being transferred. How do you “see” it?
This is the crux of our disagreement. To me, it appears that you think that every transfer of heat will be accompanied by a visible feature in in the temperature field. This simply isn’t true. We may see visible features moving around in the temperature field, and they certainly may, nay should be related to transfers of heat, but it is not a requirement.
And thus, you can’t quantify the local transfer of heat in absolute terms by just looking at the changing patterns of the temperature field. If all you have is temperature data, then clearly you can look at net difference in transfers (the flux divergence, which translates to changes in heat content), but this is not the absolute flux at that point. Clearly, you can integrate heat content to the edges of the field, and determine fluxes at the boundaries (e.g., if the bottom is zero, then the only place left for heat to get in is the surface), but that still doesn’t tell you the absolute fluxes at any single point in the interior regions.
Go back to the thought experiment in #127 – two different patterns of heat flux (but the same pattern of flux divergence), and identical changes in temperature with time. That in itself should tell you that you can’t distinguish absolute heat flux from just that temperature data – the same “seeing” can be (at least) two different situations.
What it comes down to, is that you need more information on the system to do what you seem to think you can do.
RE: “This study suggests the missing energy has indeed been buried in the ocean,” [coauthor Kevin] Trenberth says. “The heat has not disappeared, and so it cannot be ignored. It must have consequences.”
What effect will this study have on Paleoclimate reconstructions? Or is the suggestion that this is some kind of new phenomenon or process that has not happened in the past?
Bob Loblaw – You write
“As for the comments about radiosondes: a key element is that they provide horizontal velocity data as well as temperature and humidity (and pressure). They rise through the air (and this rate of ascent is calculated from the pressure changes, combined with temperature data to get density so that pressure altitude can be converted to linear altitude). They follow the air currents horizontally, though, so there is velocity information.
…but you also go on to say that radiosondes allow us to measure heat content. This is not heat flux. Without a measurement of the vertical velocity of air (not the balloon), I suspect it would be difficult to use radiosonde data to determine heat fluxes (in 3-D, at least). Feel free to explain how it would be done, if you think it is possible, but I won’t bother asking because I don’t expect an answer. You can go back to my first post on the subject (#101) to review the kinds of measurements required to measure heat flux in the atmosphere, if you want.”
Argo measures temperature profiles. Using this information, currents can be diagnosed from the resulting pressure field derived from the hydrostatic relationship. Vertical velocity can be derived from balance equations analogous to what we do in the atmosphere (e.g. the omega equation). A big difference with the atmosphere, of course, is that the equation of state is different (its not ~an ideal gas). However, the physics is very parallel; for example, the methodology to compute the geostrophic flow.
Heat can be calculated from the Argo data by weighting the temperatures over the layers (mass) that are sampled. This has units in Joules, and if the temporal and spatial resolution is good enough, it can be tracked, even when there is no local change of temperature.
I hope ths finally clarifies.
RE: 208
Hey prokaryotes,
I do not consider “sea snot” or “marine snow” to be a primary heat transport to the bottom. Though as a carbon, sugar transport it is an important means of reducing surface water carbon and removing it from the top 100 meters of the ocean.
As to an energy conveyance it is coincidental with seasonal phytoplankton blooms and due to seasonality unlikely to drive denitification in the deep trenches. However, the deep trench waters which have been “warmed” by geothermal contact and displaced by the “newer” THC inflow, goes into circulation of the Pacific depths. As this hypoxic, denitrifacted, sulfate bearing waters reach geographic features, such as sea mounts or continental banks they flow up and carry the fully digested inorganics into the aerobic environment. Until such time they round and mix with the oxygen rich Antarctic saline waters and flow into the S. Atlantic.
Point being as suggested before until such time advection or horizontal flow stops it is unlikely we would see universal full column stratification.
Cheers!
Dave Cooke
Hey All,
If I may be so bold, it is likely if a thermal pulse has occurred it should leave a telltale current or turbulace which we cannot currently detect. As for Dr. Trenberth’s observation for every “goes into there must be a goes out of”, it is likely correct. Deep ocean heat added via the THC rather then sinking to the bottom of the Pacific deep sea trenches, skirts across the top to continue its flow to emerge near coastlines and the Western Antarctic range.
If on the otherhand the input occured near the equator it likely gets advected to the polar regions where it melts sea ice. If instead it is occuring under stagnant Blocking Highs in the Temporate zone it would likely amplify convective activity both warming the atmosphere and result in both more intense Low pressures and enhanced rainfall amounts. If instead the Blocking Highs were to occur close to the polar circles they would both enhance the insolation there and increase the surface salinity, until seasonal loss of insolation cooled the surface sufficently to cause a seasonality to the THC flow to emerge. The end result appears to be that which suddenly goes in, likely suddenly comes out. Similar to the radiant heat exchange of a high albedo surface to a low albedo surface.
Given that it is likely both thoughts are correct, they are just different viewing points of the same data. As to one being more dominate then the other, the fast in and out. It is this exchange which creates weather and it is the long term weather patterns which create climate. As a Professor once shared in class, “Change the weather change the climate”. Hmmm, puts a whole different slant on the 1960’s weather control experiments…
Cheers!
Dave Cooke
Bob Loblaw #210, #211
Your steady state conduction example with heat energy driven through a linear temperature differential from the top to the bottom of the ‘slab’ is correct.
Temp 1 at the top of the slab and Temp 2 at the bottom of the slab can remain the same with time and a steady heat flux occur dependent only on (T1 – T2) and the conduction coefficient of the medium.
However if you move the masses in the slab by mechanical mixing then your steady state is no more.
Given my quotation of Berényi Péter in #143 which suggests that mechanical mixing is the major method of heat transfer in the oceans – not steady state conductivity: (sorry for the long quotation but it all seems important)
Quote:
“Needless to say heat conductivity of seawater is so low, that by conduction alone (with no macroscopic flow) it would take ages for heat to get down to the abyss from the surface.
There are parts of MOC that work as a heat engine indeed. Downwelling of cold saline water in polar regions is such an exception. However, if there were no other processes at work in other regions, the abyss would eventually get saturated with very cold water of high salinity and downwelling would stop altogether. Or rather, it would switch to the much slower rate permitted by geothermal heating alone.
We should also note this part of the so called thermohaline circulation does not add heat to the abyss, but removes it from there.
Currently deep water production is restricted to two distinct regions of the oceans. One is where the North Atlantic joins the Arctic ocean, the other is along the Antarctic coastline. In theory it could also happen in the North Pacific, but in fact it does not, for the salinity is too low there and the coastline is not cold enough.
Details of the physics are somewhat different in the North and the South though. The North Atlantic Drift carries ample quantities of warm, highly saline water into the Arctic ocean (the high salinity is leftover of evaporation), which cools down there and when it gets next to freezing (the most dense state of seawater), it sinks. It is an intermittent process, restricted to “chimneys” (of diameter ~100 km and lifetime of several weeks) in the open ocean. Please note the heat carried to the polar region this way is lost to the atmosphere entirely, the cold saline water sinks to the bottom without it. This heat subsequently is radiated out to space, as that is the only heat reservoir around which is colder (-270°C).
Antarctica is a special place. No warm current gets near to the continent, so salinity of seawater there is inherently lower than in the Northern Atlantic. On the other hand along the coastline, especially in winter, extremely cold gale force katabatic winds descend from the plateau creating polynyas (open water expanses) by blowing sea ice away.
High chilly winds coupled with open water provide for vigorous cooling of water masses (because total area of air-sea interface is huge, think of sea spray) and as sea ice starts to form, salinity also increases by brine exclusion. Cold dense water then descends to the abyss along the continental slope. At the underside of great Antarctic ice shelves even super-cooled water is formed. Its potential temperature is below freezing, that is, it only stays fluid because of pressure, it would freeze if raised to the surface.
In general abyssal water of Antarctic origin is somewhat colder but less salty than its Arctic cousin.
But still, we need an energy source to keep the engine going. In other words, abyssal waters have to be warmed up and diluted in order to be able to raise somewhere and make room for more cold, dense polar water.
The process that does exactly that is supposed to be deep turbulent mixing, driven by external mechanical energy sources like tides and winds.
Tidal forcing is a considerable source of mixing, but it is deterministic and independent of all other forcings on climate. It is also cyclic, not exactly, but close enough. The Metonic cycle (the period the National Tidal Datum Epoch [NTDE] of the U.S. is based on) is 19 years long. Or more precisely it is 235 synodic months which is 1h 38′ longer than 19 tropical years. The nodal cycle of lunar orbit happens to be only slightly shorter than that (18.5996 years).
It means if one is looking for trends in deep turbulent mixing, it is best to consider multiples of the Metonic cycle. Epochs shorter than that (like 6 years) are to be considered as a last resort only if one does not have data with longer timespan. Even then some caution is in order, to filter out tidal effects on trends as much as possible (the same is true for sea level studies).
The other source is internal waves excited by winds. One can see that distribution of wind power is extremely uneven on the surface of Earth.
It is concentrated in three regions, the Southern ocean, the Norh Pacific and the Norh Atlantic. Of these winds in the south are the most intense by far (and surprisingly mild over the continents).
The only problem remaining is that in the open ocean turbulent mixing is measured to be at least an order of magnitude smaller than needed to maintain the observed flows in MOC.
The solution seems to be there are narrow regions where topography of the bottom is very complex, like over mid ocean ridges or certain rugged continental slopes where deep turbulent mixing can be up to two, sometimes even three orders of magnitude higher than average. However, these sites are poorly known and most are not even identified yet.
So, the very energy source driving MOC and making thermohaline downwelling possible is not well constrained. It is also one of the (many) weak points of GCMs (General Circulation Models). This process is represented in them only through parametrization and even if we knew much better the process going on in real oceans, their too coarse resolution could not accommodate to the small scale vigorous and probably intermittent mixing which characterizes it.
Anyway, the take home message is that MOC (Meridional Overturning Circulation), consequently heat exchange between the surface and abyss is not driven by temperature differences, but external mechanical energy sources.”
Endquote
Bob, Could you comment on this?
> Proc
> It doesn’t let me post the content of the hydrothermal vent wikipedia entry.
Links. They work.
Use links rather than reposting stuff in full that you found elsewhere.
Please.
Proc, re the Trenberth quote you reposted, have you thought about the question already raised? Look back at https://www.realclimate.org/index.php/archives/2011/10/global-warming-and-ocean-heat-content/comment-page-1/#comment-216152
In #212 barn E. rubble (watch much Flintstones? Don’t want to use your real name?) asks:
What effect will this study have on Paleoclimate reconstructions? Or is the suggestion that this is some kind of new phenomenon or process that has not happened in the past?
I think the key difference is that we’re modeling a long-term process and trying to make corrections based on what happens over a very short time period. Paleoclimate changes took place over many thousands of years, so with rare exception (think PETM) the environment didn’t get as far out of equilibrium as it is now. In any case, we don’t have year-by-year resolution of changes from paleoclimate times to compare to todays record.
What we’re discussing here is how much of the radiative imbalance has ended up in the deep ocean sooner than initially expected. My feeling is that in the long run this is pretty much irrelevant. On a century to millenial period temperature will equilibrate so the radiative imbalance disappears. The only important questions are the charney sensitivity (how much do we warm for a doubling of CO2?) and the local/regional effects the warming temperatures have.
barn E. rubble – Or is the suggestion that this is some kind of new phenomenon or process that has not happened in the past?
The climate model is simulating La Nina-like periods, which is when heat is deposited down deep. I’m sure you are aware this is observed in the real world – such as the cool (negative) phase of the Interdecadal Pacific Oscillation. Most of the heat (in the model runs) is being deposited down to the deep in the Southern Ocean, which is what is being observed in the real world. See Sutton & Roemmich (2011).
As for paleoclimate reconstructions – the last great CO2-induced(?) global warming, the PETM saw the polar seas and deep ocean warm. In fact the last time atmospheric CO2 was around what it is now (approx 400ppm), during the Pliocene, the deep ocean and polar seas warmed too. Sea level eventually ended up around 25 metres higher than present.
The “skeptics” haven’t laid out their rationale for long-term cooling of the oceans. Certainly the physics-based climate models, and both past and present observations disagree with them.
“Let’s presume that the flux at the top surface is received by absorption of radiation, and the same flux (i.e. same quantity) of heat is lost at the bottom by radiation. Conduction through the slab occurs at this same heat flux value. So, we have a flux of heat, and we have no changes in temperature with time.”
Please assume that your conversation partners have advanced beyond this level of understanding. Pielke is an AGU fellow. I really think he gets this!
If you will make this presumption, my guess is that the discussion will turn out to be much more fruitful. Otherwise it comes across as snark.
As I understand Prof. Pielke’s scheme: We have measurements of pressure, temperature, salinity for a set of points (x,y,z,t). Then with the continuity equations+(linearized?) Navier-Stokes we solve for the velocity field (in the presence of a free surface (with the mechanical wind stress, precip-eval mass flux, and energy flux imposed on this surface ?). In general, we should set up the transport equations for temperature and salinity fluxes independently together with the corresponding forcing gradients of temperature and chemical potential, and if we were really going to do it right, with the Onsager cross coefficients put in, but it might suffice to treat heat and salinity as carried entirely by the mass flow in a sort of Boussinesq treatment, where the effect of temperature and density affects the flow through small changes in density ?
That last phrase in my post above should read “but it might suffice to treat heat and salinity as carried entirely by the mass flow in a sort of Boussinesq treatment, where temperature and salinity affect the flow through small changes in density ?
@80 I said “.What is the best metric for measuring global warming or cooling.? I submit that the Hadley global SST fits the bill as well as anything.The Oceans occupy 70% of the surface and SST’s while not perfect avoid the problems raised by the UHI effect and more importantly they avoid the problem caused by the fact that the land temperature data does not measure the enthalpy of the system which is the really significant number.Since the sea is 100% saturated with H20 the changing temperature is a good relative measure of the change in enthalpy.”
In addition the thermal inertia of the oceans smooths out some of the short term noise in the system.
After all the succeeding posts it is obvious that we don’t know enough about the factors controlling the OHC to use it as as a useful metric. We can’t even measure it very well .Perhaps the best estimate would be from Global MSL by subtracing all the other contributors and getting the thermal expansion. The deep oceans do however provide a convenient dumping ground for the errors in the GCMs – a bit like dark matter for the standard model cosmologists.
Hank your link only brings up the 1st page, not the exact comment.
Roger Pielke, Sr. #213.
You say currents “can” be inferred, and heat transfer “can” be calculated. When will your paper be coming out? It should be very interesting.
Proc, link (works for me) should go to
grypo says: 3 Oct 2011 at 9:28 AM
specifically Gavin’s inline response answering query about that Trenberth quote.
Using a Tamino style two box linearized model with global forcings from GISS for 1880–2007 to explain the variance in the GISS global temperature product for the same interval, versions with a parameter to represent a linear increase do better than versions without a trend. The slope is about 0.13–0.23 K/century; this might be explained as due to the slowdown in THC/MOC (due to deep ocean heat uptake) which is otherwise unaccounted for in such simple models.
Re Hank, in regards to the study i found this explanation:
During these hiatus periods, simulations showed that extra energy entered the oceans, with deeper layers absorbing a disproportionate amount of heat due to changes in oceanic circulation. The vast area of ocean below about 1,000 feet (300 meters) warmed by 18% to 19% more during hiatus periods than at other times. In contrast, the shallower global ocean above 1,000 feet warmed by 60% less than during non-hiatus periods in the simulation.
“This study suggests the missing energy has indeed been buried in the ocean,” Trenberth says. “The heat has not disappeared, and so it cannot be ignored. It must have consequences.”
A pattern like La Niña
The simulations also indicated that the oceanic warming during hiatus periods has a regional signature. During a hiatus, average sea-surface temperatures decrease across the tropical Pacific, while they tend to increase at higher latitudes, especially around 30°S and 30°N in the Pacific and between 35°N and 40°N in the Atlantic, where surface waters converge to push heat into deeper oceanic layers.
These patterns are similar to those observed during a La Niña event, according to Meehl. He adds that El Niño and La Niña events can be overlaid on top of a hiatus-related pattern. Global temperatures tend to drop slightly during La Niña, as cooler waters reach the surface of the tropical Pacific, and they rise slightly during El Niño, when those waters are warmer.
“The main hiatus in observed warming has corresponded with La Niña conditions, which is consistent with the simulations,” Trenberth says.
The simulations were part of NCAR’s contribution to the Coupled Model Intercomparison Project Phase 5 (CMIP5). They were run on supercomputers at NCAR’s National Science Foundation-supported Climate Simulation Laboratory, and on supercomputers at Oak Ridge Leadership Computing Facility and the National Energy Research Scientific Computing Center, both supported by the Office of Science of the U.S. Department of Energy. http://www.sciencedaily.com/releases/2011/09/110918144941.htm
Though now i wonder what James Hansen has to say about this and how this can be plotted to real world observations.
This are the “consequence” of the natural variability…
The regular nature of these hiatus decades in the climate model, indicate that they are simply periods of natural variability, which occur even in the presence of a long-term warming trend. This is supported by historic observations (Figure 1), which shows roughly decade-long hiatus periods in upper ocean heat content during the 1960s to 1970s, and the 1980s to 1990s.
The natural variability ‘flip-side’ to these hiatus decades, are periods where there is greater-than-average surface warming (see inset in Figure 2). So at some point in the very near future we can probably expect surface temperatures to gather up a head of steam, and begin rising at a rapid rate. http://www.skepticalscience.com/news.php?n=1018
Proc, are you a modeler yourself? I’m wondering because it seems Gavin is a bit less definite about saying what’s going on than you are.
gator – In terms of your comment,
“You say …… heat transfer “can” be calculated. When will your paper be coming out? It should be very interesting.”
see Jim Hansen’s comment on this
http://pielkeclimatesci.files.wordpress.com/2009/09/1116592hansen.pdf
“Contrary to the claim of Pielke and Christy, our simulated ocean heat storage (Hansen et al., 2005) agrees closely with the observational analysis of Willis et al. (2004). All matters
raised by Pielke and Christy were considered in our analysis and none of them alters our conclusions.
The Willis et al. measured heat storage of 0.62 W/m2 refers to the decadal mean for the upper 750 m of the ocean. Our simulated 1993-2003 heat storage rate was 0.6 W/m2 in the upper 750 m of the ocean. The decadal mean planetary energy imbalance, 0.75 W/m2, includes heat
storage in the deeper ocean and energy used to melt ice and warm the air and land. 0.85 W/m2 is the imbalance at the end of the decade.
Certainly the energy imbalance is less in earlier years, even negative, especially in years following large volcanic eruptions. Our analysis focused on the past decade because: (1) this is the period when it was predicted that, in the absence of a large volcanic eruption, the increasing greenhouse effect would cause the planetary energy imbalance and ocean heat storage to rise above the level of natural variability (Hansen et al., 1997), and (2) improved ocean temperature measurements and precise satellite altimetry yield an uncertainty in the ocean heat storage, ~15% of the observed value, smaller than that of earlier times when unsampled regions of the ocean
created larger uncertainty.”
So this part is generally accepted, unless you disagree with Jim and I on this.
Hank Roberts, if you follow the links you find the authors of the article and no i’m not a modeler myself. I simply looked up the study details and posted them here. And my post do not necessarily reflect my opinion on a matter, but it helps me to learn and understand better.
Re: Ken Lambert @216.
First your comment about the slab model vs. the actual ocean. I never intended to imply that the pure conduction/diffusion model was a good one for the ocean – it’s just a starting point for attempting to understand how Dr. Pielke thinks we “see” heat transfer. (Alas, it does not seem to be having its intended result.)
Clearly the ocean has movement, but let’s take your statement “However if you move the masses in the slab by mechanical mixing then your steady state is no more”. This is not necessarily true – at least by the way I define “steady state”.
Let’s extend the theoretical slab model – let it be a fluid, and add a slow cirulation regime that goes left to right across the top, down the right side, right to left across the bottom. and back up the left side. Heat accumulates during the move across the top, is carried downward on the right side, is released at the bottom, and the fluid returns back up the left side.
In comparison to the earlier slab, we now also have heat transfer associated with the circulation, instead of just conduction/diffusion. Now, let’s assume that it is all in a constant state of motion and flux: through time, there are no changes in velocity, temperature, or heat flux at any point in the system (but the there is heat flux – it’s just constant, not zero). I would still call this a “steady state”, because every time I look at it I see the same conditions. Mathematically, the fields of temperature, flux, or velocity all show a derivative with respect to time of zero.
If you prefer to say that this is not steady state, because there is motion, then that’s just a difference in terminology between you and me. When I say “steady state”, I’m not saying position is constant, just velocity – nothing is accelerating.
Now, let’s presume the following: we’re looking at the two slabs independently, and all we have to look at is the temperature measurements. We’ll find that we have a hard time sorting out just what the heat flux values are in either system. For the fixed one (no motion – and we know for sure there is no motion), then all we need to add to our knowledge is the thermal conductivity at each point and we can use the temperature gradient at each point to get the flux at each point… For the second problem, with motion, we need to also know the velocities at each point, plus the heat capacity at each point, and then we can get the fluxes. And all this will be true whether the system is steady state or not.
So, my point is that if you only have records of temperature, you can get heat content changes (call it flux divergence if you will), but not absolute fluxes. Whether you have motion or not, in order to get fluxes you need more information, and in the case of motion you need a lot more than for the case with no motion.
Does that clarify my views?
Now, for the lengthy quote. First, I’m a landlubber, not an oceanographer. I do atmospheres and soils for science. Oceans are for recreation. I cannot comment on the accuracy of the circulation regime that is described in the quote, but the mechanics do not look unreasonable to me. Yes, thermal conduction/diffusion would be smaller than heat transfer through circulation. This is also the case in the atmosphere, where forced turbulence and free convection do all the heat transfer. Yes, I can easily imagine that much of the motion is forced by non-thermal issues. One thing I did not see in that quote was a discussion of sediment loading – the amount of sediment in river or glacial water affects its density. Whether sediment is important compared to salinity, etc., I do not know, but sediment load and density change as sediment settles out of water. (It turns out I’ve done a bit of rivers and glaciers for science, too).
Beyond that, is there something in particular you are wondering about in that quoted text?
re: Roger Pielke @ 213.
“I hope ths finally clarifies.”
You’re starting something… At least you’ve identified the need to have some additional information beyond the temperature field. We finally have velocity showing up. And that is an essential ingredient in being able to determine any absolute flux values – you simply can’t do it by looking at the temperature alone.
…but since we’re both comfortable in the atmospheric regime – let’s look at atmospheric sensible heat flux. Conduction is also irrelevant there – if heat was transferred only by conduction, we’d see maximum air temperature at 2m height that would happen many hours after the peak surface temperature. Close to the ground, turbulent (mechanical) mixing is the key, and drives the rate of energey transfer. That turbulence can be forced (i.e., wind), or free convection if the surface heats enough.
Now, to calculate heat transfer (let’s stick to the vertical direction), you can usually get a good estimate if you know the time-averaged temperature gradient, but you need to be able to estimate the appropriate turbulent transfer coefficient (analagous to a thermal conductivity). To get that transfer coefficent, you usually combine the time-averaged wind speed gradient (gives the shearing stress that drives the turbulence), but you also need to account for the temperature gradient in the form of a stability correction (stable or unstable conditions). In the lower atmosphere (close to the surface, say tens of metres), suitable time-averaging periods are in the order of an hour.
…but these methods based on time-averaged temperature and wind speed values do suffer from error sources. The definitive method, without resorting to approximations of transfer coefficients, it to collect high frequency, instantaneous, simultaneous measurements of both temperature and vertical velocity, and time-average the cross-product to get time-averaged fluxes.
I have no doubt that it is theoretically possible to do the same approximations or measurements in the ocean. I also have no doubt the the frequency and accuracy of the measurements required to do it will be different from the atmosphere, because the rates of motion will be vastly different. (And note that the frequency is quite different between the method that uses time-averaged temperature vs. the instantaneous readings).
What I don’t believe is that you can get the absolute fluxes just by looking at the temperature field alone. And that’s what you appear to have been saying in most of your posts.
re: Bryan S @ 221
“Please assume that your conversation partners have advanced beyond this level of understanding. Pielke is an AGU fellow. I really think he gets this!”
I was attempting to define a simple model we could agree on, to discuss how it works, so that we could hopefully move on to our apparent disagreements on the complex ocean system and what it takes to measure absolute heat fluxes (not storage!)
“If you will make this presumption, my guess is that the discussion will turn out to be much more fruitful. Otherwise it comes across as snark.”
So be it. I accept that it is quite possible that Dr. Pielke knows of a sufficiently advanced technology that allows calculation of absolute heat fluxes in the ocean, but all he has been saying so far is “you can see it”, and I’m having a difficult time distinguishing that from magic.
Re: Roger Pielke @ 232
Well, I’d hate to try to speak for Jim Hansen, but I’ll guess that when he’s asked a question about “heat transfer”, he wouldn’t start taking about “heat content” instead. They are related (if not siblings, then at least kissing cousins), but they aren’t the same thing.
If the heat transfer is concentrated in space in the down-welling of the overturning circulations, then 99% of the Argo floats are irrelevant, the energy is moving into the deep ocean only where the down-welling occurs.
The net effect would be that the 0-700 m layer warms from below, but not much because the relative size of the 0-700 layer is small compared to the deep ocean, but maybe enough to compensate for warming on the surface driven by climate change.
In this model the deep ocean equilibrates with the atmosphere before the 0-700 m level. In net, since both the top and the bottom are warming at (for the sake of argument) at the same rate there is no net heat transport across the 0-700 m level
Captcha iingfo pyrolysis. Light it off.
RE: 219
“David Miller says: barn E. rubble (watch much Flintstones? Don’t want to use your real name?) asks:”
Perhaps I should of thot of something more clever like, Mike Smith or better, David Muller. Obviously if it sounds like a ‘real’ name it has to be, right?
RE: “In any case, we don’t have year-by-year resolution of changes from paleoclimate times to compare to todays record.”
Actually, there are those that think they do. Not just seasonal but weekly and even daily resolution.
William Patterson, University of Saskatchewan,:
“What we’re getting to here is palaeoweather,” Patterson says. “We can reconstruct temperatures on a sub-weekly resolution, using these techniques. For larger clams we could do daily.”
You can find them here:
http://geochemistry.usask.ca/bill.html
-barn
RE: 238
Hey Eli,
To me that makes more sense. Though to deny there is some subduction in the ITCZ would be counter-intutive. It is this issue where the greatest difference between the ARGO studies and TRITON/PIRATA sea buoy data differ. Earlier Rob Painting suggested that Dr. Trenbreath and subsequient models demonstrated definitive heating in the 0-700 meter range below 20deg. N/S. Looking at the fixed buoys in the 10deg. N/S range since about 1994 show variation about the mean, with individual trends tracking the ENSO, PDO and NAO phases.
To me this would suggest validation that the circulations of one maybe related to the other. Going the next step to define the depth can be modeled in the tropopause. The circulations of the two different layers are not interdependent, but are related to closed system processes in high resolution. When we move back (decrease resolution and increase surface area), we begin to see large scale influences.
When we look at the large scale it becomes evident there is a high degree of advected transport with little vertical diffusion. This begins to focus us to the fact change (deltaT) or flux should be lateral with the heat content increasing in bredth not depth.
Looking at the TAO data seems to confirm that there are some localized trending of penetration at depth. However, overall we are looking at normal variation even as the warming sea surface area seems to increase.
That heat is transported to the deep ocean polar basin can best be measured by the temperature difference in sea area covered by higher SSTs, minus the following Polar componets or heat pathways; convective wv plumes, plus radiative surface emission, plus the polar sea ice volume melt with the remaining heat content in the polar seas being diffused into the Polar oceans. The increased heat content of the Polar ocean near the top of the Arctic basin depth, (Near the Arctic submarine ridge depth, stretching from Greenland to Scandinavia), defines the additional heat that can be sequestered; (as the boyancy of the salinity/temperature ratio should result in a near linear constant, except near the 4C-2C values (or above the 700m depth), David Miller brought up).
I suspect the greatest indicator of higher seasonal input will be balanced by higher seasonal sea ice melt, regardless the latitude. This should suggest a total flux value of zero, until, year round sea ice is gone. (It appears there is a need to account for the larger polar surface area emission/convective flow historical data set, which we apparently do not currently have a good handle on…)
If we can correlate the warming SST area to Sea Ice Melt volume there may be an avenue to simplify the modeling, (at least in low resolution). Afterall is that not what most of this thread is about?
Cheers!
Dave Cooke
RE 232: “So this part is generally accepted, unless you disagree with Jim and I on this.”
Mayhem Torpedoes Science
Baring his chest, Roger taunts all comers, “Me and my older brother Jim are the biggest and the baddest …in all the worldddd!!”
“Stinkin’ papers”, he stomps around the ring, his grip forcing and knotting the ropes into a flow field visualization.
Waving, he assures the artless onlookers, “I am the smartest raccoon I know!!!!”
http://www.youtube.com/watch?v=Fmvh36hWyEI
Roger is dead on.
Bob Loblaw
Good discussion Bob. Sounds like a global fixed array of ocean sensors, all reporting at the same instant. What grid spacing in both vertical and horizontal would you suggest?
Perhaps the makers of the Asian aerosols could cough up the money for such an enterprise – they are the only ones left who have any.
also mentioned at Eli’s, hat tip to someone well-informed who posted mention of an upcoming Loeb et al. paper at Spencer’s sea temp thread a while ago:
http://www.irc-iamas.org/files/GEB_Report_IRC2011.doc
IRC working group Global Energy Balance (GEB) Annual Report 2011
Martin Wild and Norman Loeb (WG Co-chairs)
“… this working group, entitled “Towards an improved understanding of the Global Energy Balance: absorption of solar radiation”. This proposal has been accepted in April and a PhD student has been assigned to start working September 1. The project aims at reducing the uncertainties in the absorption of solar radiation within the climate system, through the use of the information contained in worldwide surface radiation measurements in combination with satellite products….”
Thanks for the vote of confidence, Ken, but as I’ve said, I do atmospheres and soils, not oceans. So my suggestion would be to ask someone with more ocean experience.
In the fine tradition of overextending myself, however, I can tell you what question I would ask if I were really tasked with providing an answer:
What exactly is the purpose of the network?
– if the desire is to track global ocean heat storage, then measuring fluxes is doing it the hard way. It’s much easier to just look at the final result (temperatures) and do the sums. It seems that Argo is quite capable of this. If you want to know if your “need a penny, take a penny” jar is accumulating pennies or losing them, you don’t need sit all day watching to track every transaction – you just need to count the pennies at the start and end of the day.
– if you really want to get global coverage on details of fluxes, then the network of instrumentation has to be fine enough (in both time and space) that you don’t miss important fluxes, and that requires knowledge of the circulation regime. Of course, you don’t know those details until you set up an instrumentation network to figure it out, so… Perhaps someone else already knows the answer to this. I know I don’t.
– if you want to gain greater understanding of ocean fluxes in key areas, but don’t want to do it on a global scale, then you pick one or a few locations of interest and focus your resources on those areas. Even in the atmosphere, which is a lot easier to get to than the oceans, I’m not aware of detailed flux measurements carried out on a global scale. Temperature, humidity, winds, pressure, etc., yes (surface obs and radiosonde networks), and lots of other sampling networks for radiation, gases, etc., but not a full 3-D network of fluxes. It’s a lot more common to select one spot for detailed analysis. NASA had a “Mission to Planet Earth” a number of years back that did this for several ecosystems – one of which was the BOREAS project. These intensive field campaigns were a kind of strategic attack approach, fighting the battle for understanding on a small, localized scale.
My guess is that those more knowledgable in the ocean field of study could tell you more about what networks or studies exist and what they are capable of.
Yes, i agree with you necessary steps should be taken in order to reduce global warming or man will have to pay for all of this
Bob Loblaw@245
I have read some of the papers on Ocean Heat Content measurement by Argo and have never been able to tease out how the Argo floats moving with the currents ‘en mass’ are able to accurately detect temperature changes in a particular ’tile’ of ocean.
I can see how a fixed array could do it – if the oceans were ’tiled’ on a fixed X-Y-Z grid with a temperature sensor measuring each tile at the same instant T1 then you would get a snapshot at T1 and then at subsequent times T2 etc subsequent snapshots on each tile summing the whole ocean.
With Argo, floats follow currents and the same ’tile’ of ocean might not have a float measuring it at all because the float has travelled with he same mass of water to another ’tile’ where two or more floats might have gathered. Current Argo spacing is roughly 300km x 300km so a ’tile’ is 90000sqkm down to 2000m.
For example if floats report at all different times how do we know that the same temperature/mass of water in a current is not being measured at different times as the float travels with it – and no change is detected.
Now with 3000 floats, these effects might be statistically corrected, however the snapshot issue is not clear.
Forgive me for thinking aloud – I am sure the ocean experts have an answer for this.
typo: “what happens to OHC in models when there is are occasional 10 year periods”
[Response: Fixed. thanks. – gavin]
Ken Lambert @ 247:
From looking at the Argo web page, I would interpret each profile as being a snapshot at one time and location, with each profile being at a new location. Although a fixed grid and fixed times would make interpolation easier, I don’t see the random nature of the location and timing of profiles as being an insurmountable problem. You basically have a collection of profiles, giving a sampling of temperature vs. depth at various times, and each individual profile represents data that can be used to deterine heat content in that profile. Integrate over space to get a regional heat content, and then deduce regional changes in heat content from the integrated field. Accuracy will depend on sufficient sampling density and suitable integration/interpolation schemes.
A fixed location would let you look at local heat content changes directly, which could then be integrated regionally. (This would be similar to using temperature anomalies in the surface records.) Different sort of analysis, different sources of error, but regional totals still require some sort of integration/interpolation scheme.
I could see the apparent random movement of Argo floats causing problems in a couple of ways – leaving gaps (but they seem to have a plan to deal with that), or if for some strange reason the random movement (following ocean currents at depth, so it isn’t really random) some how caused a bias in readings. In order for a bias to affect the calculated changes over time, it would need to be a bias that grows in time, though.
I suppose we could look for a paper that presents ocean heat content calcuations to see if they say how they did it. :-)
Re: 249
Hey Bob,
There is likely a bias wrt circulation. Objects in a slower moving current resist the accelleration of a parallel moving faster current. Unless, as the probe rises to the surface it emerges in the middle of the faster current. The difference would not be unlike the behavior you may see in a weather ballon equipped with a radiosonde in the vacinity of a gradient/front. Without a controlled craft capable of a specific trajectory you would be limited as to what your sample actually represents.
(Note: Imparted spin of the probe could provide some insight. It would likely require the additiion of a gyro, along with a gps and a chron.)
Cheers!
Dave Cooke