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
Dr Pielke, I’d like to thank you for joining the discussion. I hope you become a daily contributor.
Gavin, with regard to the mechanics of flux through the top 700m, are the structures too small to be captured by current models? How big of a problem is this?
Over the last decade something appears to have dramatically increased the mixing of 0-700m water with water to 2000m. What are current thoughts on what that something is?
[Response: I’d say that was partly due to data coverage issues – divergences in previous decades would not have been as well observed, and partly real – the long term radiative imbalance is not going to be instantly felt below 700m, and what appears to be the divergence in recent years, is probably in large part to the deep ocean catching up with the upper ocean. – gavin]
A question for Gavin in his response to 132, what happened in 2005, is that a shift to the Argo floats???? If so is it real or instrumental
[Response: The big shift is from 2002 to 2003, and while Argo was introduced in 2003, it did not dominate the OHC source data until a few years later. That doesn’t imply that there are no remaining instrumental issues, but I don’t think it is obvious that this is not real. However, corrections and how to apply them is an ongoing endeavor and so I wouldn’t stake any strong conclusions on a single year’s change. The long term trend is far more robust. – gavin]
Rob Glover @ 149 and interested parties, there is another good discussion with Dr. Pielke Sr. here:
http://skepticalscience.com/pielke-sr-and-sks-warming-estimates.html
Re: Roger Pielke @132:
…but the question we keep waiting for an answer to is how we see the heat transferred through the upper 700m. As far as I can tell, your idea of how to do this is buried somewhere in your statement about “temperature anomalies” – but you have been short on details as to exactly how this would be possible.
Are you simply stating that before we see heating below 700m we should see heating in the 0-700m layer? This would a fairly non-controversial statement, and is one plausible scenario (although others exist where heat gets to great depth without any obvious local, short-term perturbations of 0-700m temperature – e.g., a gradual overall warming). It is a long way from there to actually calculating absolute heat flux values, though.
What exactly do you mean by “see this heat be transferred”? Please be specific.
I am still waiting to hear back, but this text from the Argo website implies that monitoring the vertical, as well as the horizontal fluxes of ocean heat, is major focus of the Argo upgrade. On their website they write
“Lack of sustained observations of the atmosphere, oceans and land have hindered the development and validation of climate models. An example comes from a recent analysis which concluded that the currents transporting heat northwards in the Atlantic and influencing western European climate had weakened by 30% in the past decade. This result had to be based on just five research measurements spread over 40 years. Was this change part of a trend that might lead to a major change in the Atlantic circulation, or due to natural variability that will reverse in the future, or is it an artifact of the limited observations?
In 1999, to combat this lack of data, an innovative step was taken by scientists to greatly improve the collection of observations inside the ocean through increased sampling of old and new quantities and increased coverage in terms of time and area.
That step was Argo.”
[Response: This is not related to our discussion. Instead it refers to the geostrophic calculations of Bryden et al (2005) and the subsequent realisation that the deep ocean circulation changes were being aliased (Cunningham et al, 2007). All of these calculations are of the horizontal flow (via the geostrophic relationships), and with vertical fluxes being implied as a residual. – gavin]
From http://www.argo.ucsd.edu/ they also write on this website
“It will provide a quantitative description of the changing state of the upper ocean and the patterns of ocean climate variability from months to decades, including heat and freshwater storage and transport.”
“Currently, there are roughly 3000 floats producing 100,000 temperature/salinity profiles per year. The floats go as deep as 2000m”
If heat is transported on shorter time periods through the entire upper 700m, than I agree it could be missed in the sampling. However, if the transport is slower than can be sampled with ~33 profiles per year (~ once every 11 days) than it will be sampled.
[Response: Heat transfer will be mainly continuous, not episodic. – gavin]
Bob Loblaw – you are correct – you write
“Are you simply stating that before we see heating below 700m we should see heating in the 0-700m layer? This would a fairly non-controversial statement, and is one plausible scenario (although others exist where heat gets to great depth without any obvious local, short-term perturbations of 0-700m temperature – e.g., a gradual overall warming).”
Yes- An overall general warming would also be evident unless the anomalies are so small as to be below the precision of the instrumentation, although that would be a surprise.
The problem as i see it is of locality. The oceans are not a homogenous mixture, rather a bi-layer of current flows. The warming of the bottom occurs when a “warmer than usual” arctic current descends on its way to the bottom. To better measure this would not require the Argo floats, but rather instrumentation at the locations where the “warmer than usual” water descends in the arctic/antarctic.
Prof Pielke wrote on the 10th of Oct 2011 at 2:05 PM:
–begin included text’
Bob Loblaw – you are correct – you write
“Are you simply stating that before we see heating below 700m we should see heating in the 0-700m layer? This would a fairly non-controversial statement, and is one plausible scenario (although others exist where heat gets to great depth without any obvious local, short-term perturbations of 0-700m temperature – e.g., a gradual overall warming).”
Yes- An overall general warming would also be evident unless the anomalies are so small as to be below the precision of the instrumentation, although that would be a surprise.
–end included text
From the graph that Dr. Schmidt posted, that the global OHC from 0-2000m is smaller than the OHC for the 0-700m layer in the first third of the data ending around 1975. Two or three decades for the heat to pass through ?
sidd
sidd
The largest fraction of excess heat (Joules) associated with a TOA radiative imbalance should be observed in the upper ocean *if* the rate of “leakoff” to the deep ocean is << than the TOA radiative imbalance. This is not a difficult matter to conceptualize!
Barring evidence to the contrary, my guess is that this is a good working assumption.
If it is, then Roger is exactly correct in saying that the upper 700 meters gives a good proxy to the TOA radiative imbalance on a decadal to multi-decadal time frame. In other words, if the heat accumulation in the upper 700 meters is << than that modeled over a given time period (more than a few years), and the rate of accumulation below 700 meters cannot credibly make up for this difference, then it will become clear over a relatively short period of time that the models cannot be accurately representing the thermodynamic evolution of the atmosphere system. There will be a large large and growing energy imbalance between observations and models.
Stating differently, if a year over year large positive radiative imbalance is modeled (which I believe it is), then the rise in heat content (not surface temperature!***) in the upper 700 meters should be more or less monotonic, given the assumption that the rate of "leakoff" below 700 meters is much less than the modeled radiative imbalance.
Unless someone can produce empirical evidence that the leakoff of heat below 700 meters over decadal periods is comparable to the modeled radiative imbalance over this same period, then I must side with Roger on this issue FWIW.
Now, here is what Gavin will likely say in response: ….We still can't measure the deep ocean accurately enough to know for sure. And in the meantime we have all these other metrics that are showing things are heating up as modeled.
But I think it is clear that this is exactly why ocean heat content is so valuable. It is really the only observational check we have to see if the models are accurately depicting the thermodynamic evolution of the system. Surface temperature is simply a 2-D proxy for a 3-D physics problem. While ST may indeed be a qualitative check, it is not quantitative.
Re: Roger Pielke @ 155, 156
Thank you for taking the time to answer some of these questions.
…but again, please, exactly what is being sampled? The Argo sampling, as far as I know, provides temperature, and this is not transport. It is the result of transport (specifically, the net difference between incoming and outgoing). When I read “transport”, I think “flux”, and I still can’t see how you plan to get an absolute flux out of this.
157: OK, so we are looking at a scenario where the 0-700m layer shows an increase in temperature (a positive anomaly) before the deeper layers. Consider the following two thought experiments (again, numbers are made up):
Scenario A: a column where there is a steady downward flux of 2 W/m^2 at all depths and times, and thus temperatures are not changing with time. Flux at the surface increases to 4 W/m^2, which starts warming the surface and then heat slowly propagates downward. Gradually, temperatures increase at greater and greater depths, until eventually a new equilibrium is reached where the downward flux is 4 W/m^2 at all depths and temperatures are no longer changing with time. All depths now show a positive temperature anomaly with respect to initial conditions.
Scenario B: a column where there is a steady upward flux of 2 W/m^2 (call it –2 W/m^2 if you prefer) at all depths and times, and thus temperatures are not changing with time. Flux at the surface decreases to 0 W/m^2 (or increases from -2 to 0, if you prefer), which starts warming the surface and then heat gradually builds up at greater and greater depths. Temperatures increase at greater and greater depths, until eventually a new equilibrium is reached where the upward flux is 0 W/m^2 at all depths and temperatures are no longer changing with time. All depths now show a positive temperature anomaly with respect to initial conditions.
These two scenarios only differ in one respect: the direction of the initial heat flux. In both cases, the changes start with the upper layer switching to a +2 W/m^2 net imbalance, and the changes propagate downward in the same fashion. Thus, the temperature anomalies should follow exactly the same pattern, should they not?
These two scenarios may show different initial temperature profiles, but I expect that will depend on whether the flux is purely temperature-driven, or related to other effects e.g., salinity). On the basis of observations of temperature anomalies, can you explain how you would discriminate between these two scenarios, without additional information? In particular, can you take the identical temperature anomaly data and determine that the two scenarios start with absolute fluxes of opposite sign (i.e., direction)? If you require additional information to distinguish between the two, exactly what information would you need? (and is it available from Argo?)
> a bi-layer of current flows
What does that mean, and where is it described that way?
I again recommend looking at http://www.clas.ufl.edu/users/eemartin/GLY307411/lectures/8.%20Deep%20Ocean%20Circulation.ppt
Bob Loblaw – If the movement of the temperature anomalies were slow enough to be seen in the ~11 day profiles, they can be directly tracked.
Response: Heat transfer will be mainly continuous, not episodic. – gavin]
Gavin – How do you know this?
On your earlier response, the key text is
“In 1999, to combat this lack of data, an innovative step was taken by scientists to greatly improve the collection of observations inside the ocean through increased sampling of old and new quantities and increased coverage in terms of time and area.”
The question is whether the improved network can track heat vertical transfers.
RE: 157
Hey Harvey,
I think there is a slight error in thinking happening here. First, to get the more dense surface waters to fall the total boyancy ratio has to be fulfilled. With this ratio being a combination of temperature and density. Too warm or fresh in relation to the surrounding body of water and no sinking.
Hence, for warmer waters to sink either the surrounding water must warm or be fresher. This applies through the whole column from surface to basin bottom.
As we are aware the THC flow is dependent on the sinking mechanism. Since 2005, it has been noted that the normal Arctic sinking pattern has changed. Where the warmer saline water would pool in the Barents, creating giant columns of sinking saline water, we no longer see this pattern. Yet the THC flow rate is only slightly diminished.
This suggests the sinking mechanism has to be continuing, just not from Barent Sea pools.
So it is unlikely that you are going to find the movement of the heat moving from the surface to the bottom in bulk. Using ARGO drifting buoys won’t work either because they use salinity as a form of temperature and pressure verification/correction/reference, as well as longer cycle sampling. To get a flux sample you would likely need a system that cycles every 6-8 hours and date/time stamps the data.
To maintain the THC flow rate the initial thought is melting ice freshened the surface and dissapted the SST allowing the residual evaporate to sink taking heat with it. Well today that works till you get to about 50 meters. Now you encounter colder and less fresh water. If the surface water stops sinking the THC mechanism slows to a stop.
So how do you get the warmer water to sink below 50 meters, by making it very brine. If that is the case where ever a high amount of evaporation is occuring, there to are sinking surface waters. The complication is precipitation, it decrease salinity and SSTs. As this occurs in the temperate latitudes often we would not expect to observe sinking waters there. However, around seasonal stagnat High Pressure regions you would think we would have observations suggesting this feeds the THC, (IE: Bermuda High). (I have not seen anything suggesting this is happening.)
I believe the answer is there can only be the additional heat being sequestered in bulk, that the added density of evaporated brine can offset. In addition, the heat would have to rapidly come out of the tropical current near the poles, to maintain the THC, as the downward flow has to fill the Arctic Basin. This would suggest that very little heat is being directly deposited in the ocean. Similar to convection, a lapse rate, or adibatic/latient heat content, most heat has to rise and leave the ocean as soon as the SST/ skin layer reaches temperature parity with the water below it.
The current systems would not be able to track short residence energy if it is exiting within 10 hours of input. This suggests the need for rapid cycle independent salinity measurement device referenced to the Sea Surface Salinity (SSS) and equipped with vertical current detectors.
Cheers!
Dave Cooke
Re: Roger Pielke @162, 163.
I am getting the impression that you are either unwilling or unable to be specific. Once again, please specify how you think this is accomplished? Exactly what do you mean by “tracking”? In #160, I have given you two scenarios with identical temperature trends, but resulting from different changes in heat transfers. Can you answer the questions that I pose there?
At the moment, I am beginning to think that your claim of determining heat transfers is little more than a claim that we can see different warm bits of ocean at different places at different times, and this means that there is some heat moving around. This is a very limited description of the process and does not particularly advance the science.
…and we keep waiting for you to describe the technique to do this, which you repeatedly seem to imply exists. Are you now saying that you don’t have an answer? Have I been reading more into your claims than you have intended?
Bob Loblaw – We are talking in circles. If the heat blobs that are shown, for example, in http://www.ecmwf.int/products/forecasts/d/charts/ocean/real_time/xzmaps/ can be tracked, we can monitor where the heat anomalies move to. If the data is too sparse and/or without enough temporal resolution, they cannot be tracked.
I do not know the answer to this question, but it is one that I have requested information on. On Gavin’s hypothesis of a gradual diffusion of heat, figures such as the one above from the ECMWF suggests otherwise.
Talking of talking in circles. Re Roger senior’s comment at #166.
Earlier Roger senior noted that “We should have seen this heat be transfered through the upper 700 meters.” this to me suggests that he believes that mechanisms do not exist to transport the energy into the deep/er ocean. But now he seems to be arguing @ 166 that such a transfer is indeed taking place as per the ECMWF analysis.
As I and others have noted to track the movement of energy one requires a fixed array of sensors; Argo floats drift so they do not resample the same volume of water revery 11 days or so, and neither does another nearby Argo float (well, that is highly unlikely). When one animates the vertical cross section TAO TRITON data (see # 116 above) those data do show positive temperature anomalies moving downwards over the western equatorial Pacific during the current a La Nina, consistent with what Meehl et al. found.
How does low-oxygen, hypoxia states affect the ocean heat transport and what are the consequences for short-middle term climate feedbacks?
Ocean’s Harmful Low-Oxygen Zones Growing, Are Sensitive to Small Changes in Climate
“We found there is a mechanism that connects climate and its effect on oxygen to the removal of nitrogen from the ocean,” Deutsch said. “Our climate acts to change the total amount of nutrients in the ocean over the timescale of decades.”
Low-oxygen zones are created by bacteria living in the deeper layers of the ocean that consume oxygen by feeding on dead algae that settle from the surface. Just as mountain climbers might feel adverse effects at high altitudes from a lack of air, marine animals that require oxygen to breathe find it difficult or impossible to live in these oxygen-depleted environments, Deutsch said.
Sea surface temperatures vary over the course of decades through a climate pattern called the Pacific Decadal Oscillation, during which small changes in depth occur for existing low-oxygen regions, Deutsch said. Low-oxygen regions that rise to warmer, shallower waters expand as bacteria become more active; regions that sink to colder, deeper waters shrink as the bacteria become more sluggish, as if placed in a refrigerator.
“We have shown for the first time that these low-oxygen regions are intrinsically very sensitive to small changes in climate,” Deutsch said. “That is what makes the growth and shrinkage of these low-oxygen regions so dramatic.”
Molecular oxygen from the atmosphere dissolves in sea water at the surface and is transported to deeper levels by ocean circulation currents, where it is consumed by bacteria, Deutsch said.
“The oxygen consumed by bacteria within the deeper layers of the ocean is replaced by water circulating through the ocean,” he said. “The water is constantly stirring itself up, allowing the deeper parts to occasionally take a breath from the atmosphere.”
When oxygen is very low, the bacteria will begin to consume nitrogen, one of the most important nutrients that sustain marine life.
“Almost all algae, the very base of the food chain, use nitrogen to stay alive,” Deutsch said. “As these low-oxygen regions expand and contract, the amount of nutrients available to keep the algae alive at the surface of the ocean goes up and down.”
Understanding the causes of oxygen and nitrogen depletion in the ocean is important for determining the effect on fisheries and fish populations.
Deutsch and his team used a computer model of ocean circulation and biological processes that produce or consume oxygen to predict how the ocean’s oxygen distribution has changed over the past half century. The researchers tested their predictions using observations made over the last several decades, specifically targeting areas where oxygen concentration is already low.
How would rising global temperatures affect these low-oxygen environments?
As temperature increases, less oxygen leaves the atmosphere to dissolve in the ocean, Deutsch explained. Additionally, the shallower levels of the ocean heat up and become more buoyant, slowing the oxygen circulation to lower layers.
“In the case of a global temperature increase, we expect that low-oxygen regions will grow in size, similar to what happened at the end of the last ice age 30,000 years ago,” Deutsch said. “Since these regions change greatly in size from decade to decade due to the Pacific Decadal Oscillation, more data is required before we can recognize an overall trend.
http://www.sciencedaily.com/releases/2011/06/110617110713.htm
Low-oxygen zones where large ocean species cannot live have increased by close to 5.2 million square kilometers since the 1960s, the team found. Where this expansion intersects with the coastal shelf, oxygen-deprived waters are slipping up and over shelf floors, killing off creatures such as crabs, mussels and scallops. Such bottom-dwellers normally have a lot to eat in such rich ecosystems, but these species are sensitive to oxygen loss. Similarly, the anoxic ocean at the end of the Permian period (around 250 million years ago) was associated with elevated carbon dioxide and massive terrestrial and oceanic extinctions.
Increases in jellyfish blooms also are likely to be part of the process.
Levin says that the Pacific’s deeper currents keep its waters less oxygenated than those of the Atlantic. “It’s what we call ‘old water,’ since deeper Pacific waters haven’t been at the surface in a long time,” Levin says. Stramma thinks that some of the Pacific’s oxygen problems could also result from El Niño. But climate models predict reductions in dissolved oxygen in all oceans as average global air and sea temperatures rise, and this may be the main driver of what is happening there, she says. http://www.scientificamerican.com/article.cfm?id=low-oxygen-ocean-coastal
Oceanographer: Nitrous Oxide Emitting Aquatic ‘Dead Zones’ Contributing To Climate Change
The increased frequency and intensity of oxygen-deprived “dead zones” along the world’s coasts can negatively impact environmental conditions in far more than just local waters. In the March 12 edition of the journal Science, University of Maryland Center for Environmental Science oceanographer Dr. Lou Codispoti explains that the increased amount of nitrous oxide (N2O) produced in low-oxygen (hypoxic) waters can elevate concentrations in the atmosphere, further exacerbating the impacts of global warming and contributing to ozone “holes” that cause an increase in our exposure to harmful UV radiation.
“As the volume of hypoxic waters move towards the sea surface and expands along our coasts, their ability to produce the greenhouse gas nitrous oxide increases,” explains Dr. Codispoti of the UMCES Horn Point Laboratory. “With low-oxygen waters currently producing about half of the ocean’s net nitrous oxide, we could see an additional significant atmospheric increase if these ‘dead zones’ continue to expand.” http://www.underwatertimes.com/news.php?article_id=85403791012
a new model by Slack and Cannon is proposed in which the impact of the Sudbury bolide produced a fundamental change in the oxygen content of the oceans worldwide. This impact globally mixed shallow oxygenated and deep anoxic waters of the Precambrian ocean, creating a new suboxic state for deep seawater. This suboxic state, containing only small amounts of dissolved oxygen, prevented transport of iron from the deep ocean to continental-margin settings, ending an about 1.1 billion-year-long period of banded iron formation deposition.
When suboxic waters (oxygen essentially absent) occur at depths of less than 300 feet, the combination of high respiration rates, and the peculiarities of a process called denitrification can cause N2O production rates to be 10,000 times higher than the average for the open ocean. The future of marine N2O production depends critically on what will happen to the roughly ten percent of the ocean volume that is hypoxic and suboxic. http://www.eurekalert.org/pub_releases/2009-10/gsoa-n2g103009.php
MapleLeaf – I never said that heat could not go deeper than 700m.
On the monitoring of the warm and cool anomaly “blobs”, if their spatial structure is large enough, they will still be seen even as they move horizontally. If they are smaller and can be missed as they move, then the Argo network is not dense enough.
I would alert you to the somewhat analogous situation in thr atmosphere, where we monitor the troposphere (including its heat content) with radiosondes. Before satellites, that is all we had.
> Since 2005, it has been noted that the normal Arctic
> sinking pattern has changed.
If someone can cite a likely source for this, please do.
Folks, several of you are taking Roger Pielke’s comments way out of context! I hope this in not intentional.
The physics here is a simple matter in concept.
For illustration purposes:
If the TOA radiative imbalance is 1 W/m^2, and the downward flux of heat below 700 meters is only 0.2 W/m^2, then there must be positive flux of heat into the 0-700 integral of 0.8 W/m^2. If the TOA radiative imbalance is real, then the upper ocean cannot have a “flat” heat content unless the downward flux of heat below 700 meters=1 W/m^2 (ignoring of course the smaller reservoirs of heat and interannual weather noise for illustration purposes).
No empirical data or model output that I am aware of suggests that any downward flux of heat below 700 meters is close to the the modeled TOA radiative imbalance averaged over a decadal period. Therefore, what Roger is saying is exactly correct.
The Palmer et al., 2011 paper cited above states that the behavior of several examined models leads to the conclusion that the range of uncertainty in the absolute radiative imbalance estimates might be reduced by as much as 30% by integrating the full volume of ocean below 700 meters, but this does not change what I have just stated above. This still implies that the bulk of the radiative imbalance must be seen in the upper ocean over decadal time periods.
Maybe further research will show these assumptions must change radically. While the Palmer results suggest the need for further research, as it stands now, the simple working model I have outlined above seems like a good working assumption.
> to track the movement of energy one requires a fixed array of sensors
Or identifiable tracers detectable in blobs of water over long time spans.
Atomic bomb fallout, and persistent artificial chemicals — both of which sometimes arrive in pulses and travel with sea water, giving identifiable blobs — have facilitated this kind of work.
http://scholar.google.com/scholar?hl=en&q=thermohaline+%2Btracer
finds much.
This is interesting:
TrAC Trends in Analytical Chemistry
Volume 30, Issue 8, September 2011, Pages 1308-1319
Climate-Change Impacts on Water Chemistry
doi:10.1016/j.trac.2011.06.005
Dissolved oxygen in the bottom water of the Sea of Japan as a sensitive alarm for global climate change
Toshitaka Gamo
Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8564, Japan 29 June 2011.
“Abstract
The Sea of Japan, a semi-closed marginal sea (greatest depth ∼3700 m) in the northwestern-most Pacific Ocean, has an independent, deep convection system, which is driven by the formation and the sinking of cool, saline surface water towards the bottom in severe winters. Continuous measurement of dissolved oxygen using highly precise versions of the Winkler titration method has revealed 8–10% decreases in the bottom concentration of oxygen (O2) over the past 30 years. The temporal decrease in O2 means an imbalance between the supply of O2 from the surface and the in situ consumption of O2 in decomposing organic matter, suggesting that the change in the deep convection pattern of the Sea of Japan is probably caused by global climate change to reduce winter cooling of surface seawater.”
Re #169,
Roger senior,
“I never said that heat could not go deeper than 700m.”
I did not say that, I said:
“this to me suggests that he believes that mechanisms do not exist to transport the energy into the deep/er ocean.”
Roger senior until recently was suggesting that such a transfer/transport is unlikely because it has not been observed when Argo should have been able to detect it. Here is a reminder of what Roger senior has said about this issue here and on his blog:
Roger senior @169,
But this is what he has said on his blog:
Regardless of the conflicting statements made by Roger senior, it is good to see that he recognizes that heat can be sequestered in the deeper ocean, and that if it is then the surface temperature record is probably underestimating the amount of warming. And yes, I realize that him saying that is inconsistent with his research that claims the surface temperature record has a warm bias, especially at nighttime.
Since 1958 there is very good agreement between the radiosonde data and NCDC’s global surface air temperature data (0.13 C/decade for NCDC, compared to 0.16C/decade for RATPAC). But more to the point, Argo doesn’t have the same temporal resolution and coverage as does the MSU data.
Dave Cooke tells us in #164:
Hence, for warmer waters to sink either the surrounding water must warm or be fresher. This applies through the whole column from surface to basin bottom
Not necessarily so regarding temperature. Fresh water is most dense at 4C. Salt water, IIRC, a couple of degrees less, so still ~4C above freezing. So surface water coming into the arctic can cool off to 4C and sink through the 0-3C water below it. More 4C water being transported to the poles could lead to more heat being transported to the bottom – if the bottom was/is cooler than 4C and the salinity is equivilent.
This is the mechanism that turns lakes over before they freeze in the winter.
I have no idea whether this is a significant mechanism for warming deep currents upon polar overturning. But I thought it worth pointing out that water doesn’t have to be colder in order to sink. Depending on the deep temperature, sometimes it has to be warmer.
Just trying to figure out what the crux of the disagreement between Gavin and Roger is.
Gavin wrote in response to 155: “Heat transfer will be mainly continuous, not episodic.”
In a continuous case, heat transfer will not be directly observable from the top 700 measurements, if the same amount goes in at the top as goes out at the bottom. In an episodic case, it will in principle be observable (though still dependent on the signal to noise ratio of the measurements).
Roger argues (140) for a more episodic heat transfer: “if this transfer occurs in globs associated with mesoscale and larger ocean circulation features (as suggested in the ECMWF data), we should clearly see this movement of heat.”
I.e. Gavin argues that if approximately the same amount of heat enters the top 700 m from above, as leaves it from below, no warming signal in this layer will be observed, whereas heat is being transferred through it. Roger agrees with that (140: “If they [these fluxes] are diffuse and distributed across the upper oceans, I agree they would be hard to see in the Argo data.”), but rather thinks that the heat transfer occurs more concentrated in space, in which case it should give rise to an observable signal in the top layer.
Gavin argues that even if that were the case, the signal would not likely be observable amidst the variability (response to 140: “I have no confidence that the observations will be sufficient to distinguish the anomalous heat flux from the climatological mean with sufficient precision to be helpful.”)
Gavin and Roger may of course confirm or reject my little summary…
Re: 170
Hey Hank,
Any chance the papers behind these publicly available abstracts, blogs, or articles will help?
http://www.sciencemag.org/content/309/5742/1841.abstract
http://www.nature.com/ngeo/journal/v2/n1/full/ngeo382.html
https://www.realclimate.org/index.php/archives/2006/01/atlantic-circulation-changes/
http://www.nature.com/nature/journal/v438/n7068/full/nature04385.html
https://www.realclimate.org/index.php/archives/2005/05/gulf-stream-slowdown/
http://www.nature.com/nature/journal/v448/n7156/full/448844b.html
http://www.sciencedaily.com/releases/2008/03/080320181838.htm
As you have been about a bit I am sure you are likely aware of most of them. (Please consider that this is not the old west, I just employ a different approach. First I prefer to share or discuss an idea and then support the idea, if necessary. For me tossing about papers first seems to get in the way of sharing thoughts.) I guess your approach is the difference between a professional and the peanut gallery, sorry if it is offensive.
Cheers!
Dave Cooke
At the time I first saw this issue discussed by RP Sr. on his blog, it was in a series of emails with Josh Willis and Kevin Trenberth. I wondered at the time what this “just passing through” heat would look like in the ARGO data, but none of them gave a hint.
At the time, if I remember right, Trenberth was dubious ARGO could see it. Perhaps Josh Willis has given this some thought.
I have to say that the whole deep sequestration argument makes me a little uneasy. Roger is correct–we haven’t seen it–and to say it is there without evidence strikes me as special pleading. I distrust unobservables–they can keep you from discovering really important things.
In the end, what matters is TOA energy balance. The evidence that we are warming the planet is sufficiently strong that I don’t feel the need to oppose the denialist/complacent on every issue. After all, they have no evidence for their position.
Re: 174
Hey David Miller,
Thanks, that is something to consider when we get down to the timing and NAD penetration prior to the subduction. Generally most Gulf Stream fed waters are highly saline before entering the Arctic basin. The point you raise is likely going to effect the waters near the sea ice melt pools.
I don’t know that it will be a big issue for most of the flow we are currently discussing now. Though it might help with determining the amount of heat sequestration when we can get to the point of discussing the thermo/fluid dynamics. I was only suggesting to Harvey what I felt would help provide a empirical data set.
Others here have discussed the need for a fixed network or a high density monitoring system. With the advent of an abyssal plain siesmic sensory network being planned by SCRIPPS it might offer a platform for a piggy backed deep ocean sampling system.
Cheers!
Dave Cooke
David Cooke, I can’t read your stuff. Sorry. I’m not a scientist, I’m in the peanut gallery. You read it somewhere, that’s your answer, no worries. Enjoy. Please don’t take my questions as addressed to you when I ask for cites and sources, I understand you don’t do that.
Ray @178,
“Roger is correct–we haven’t seen it–and to say it is there without evidence strikes me as special pleading.”
I agree, apart from the “special pleading” part. Perhaps the modelling study by Meehl et al. was the first step, we now have a better idea where to look and when. Hopefully someone will run with this, it will be interesting.
Ocean Currents: Potential Impacts from melting arctic icecaps
http://climateforce.net/2011/07/08/potential-impacts-from-melting-arctic-icecaps/
Short educational video using augmented reality about ocean currents and deep ocean circulation. After watching this imagine what happens to the ocean conveyer belt and weather impacts.
Bart Verheggen – Good summary, except if there is no heat accumulation in the upper 700m as it diffuses slowly downward, we should still see a slight elevation in the temperature anomalies IF the Argo data precision is good enough. I do not know the precision of the temperature data measurements, and hope someone else can answer that.
[Response: Huh? If 0-700m temperature anomalies continue to increase, so will heat content. What are trying to say here? – gavin]
Re: Roger Pielke @166, 169
Yes, we are talking in circles. I think that is because you keep talking as if you know how to get ocean heat flux values from the Argo data, but won’t say how, and I keep asking how. Now, you have stated that you don’t have the answer, and have put your claim as a conditional “if”. That is a hugely different statement from previous ones, which implied that it was possible. But then, after admitting you don’t have the answer, you are back to talking in #169 about how you will be able to track blobs of warm or cool water if they are large enough.
I’m not going to bother asking yet again how you would do that tracking, because you’ve admitted that you don’t have the answer. As you said, we keep going in circles. As you said, we keep going in circles.
As for the link to the graph – yes, a very nice picture. That graph is for temperature anomalies, however (departures from the 1981-2005 mean). If I click on the drop-down box just about the graph, I can choose “Full Field”, and look at the actual temperatures, instead of anomalies. That is the image that is important for heat transfer, not the anomalies one. And I don’t see the same hot blobs in that graph. Full Field Map. If you think that seeing shifting patterns in anomalies allows you to track blobs of heat that represent heat flux, then I can understand why you are having so much difficulty in explaining how calculating heat flux from the Argo data would be done.
The flux of heat depends on temperature (and ocean current velocity), not anomalies.
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.
So, given that you treat heat content, changes in heat content, flux divergence, and fluxes interchangeably – and don’t seem to want to get into specifics – I will take anything further you say on the subject with an extremely large grain of salt.
To paraphrase an old, respected colleague of mine, you are just handwaving.
Re: Roger Pielke @ 183.
Oh, my, my, my. Let’s assume pure thermal diffusion. Surface at T1, 700m at T2. Temperature gradient is (T2-T1)/700, and constant with depth (i.e., the temperature itself is linear with depth). Constant heat input at surface equal to X, constant heat output at bottom equal to X. Things are at steady state, so T1 and T2 are constant, all T(z) are constant, and X is also constant. Thermal conductivity (also constant) can be determined by the ratio of the temperature gradient and the heat flux. A very simple slab thermal diffusion problem.
This simple example has constant downward diffusion (or conduction) of heat, and no changes in temperature over time. According to you, there still should be some elevation in temperature in this simple system?
If you’d like, I could show Fourier’s Law of Heat Conduction, and put my descriptive model into a mathematical model.
I’d really like to hear an explanation of the physics behind the elevation in temperature anomalies you claim will occur.
Ray #178
“In the end, what matters is TOA energy balance. The evidence that we are warming the planet is sufficiently strong that I don’t feel the need to oppose the denialist/complacent on every issue. After all, they have no evidence for their position.”
Here is a quote from the “Atmospheric Aerosol Properties & Climate Impacts Report” by the US governments Climate Change Science Program, 2009.
“ ES 3.1 Calculated change of surface temperature due to forcing by anthropogenic greenhouse gases and aerosols was reported in IPCC AR4 based on results from more than 20 participating global climate modelling groups. Despite a wide range of climate sensitivity (ie the amount of surface temperature increase due to a change in radiative forcing, such as an increase of CO2) exhibited by the models, they all yield a global average temperature change very similar to that observed over the last century. This agreement across models appears to be a consequence of the use of very different aerosol forcing values, which compensates for the range of climate sensivity. For example, the direct cooling effect of sulphate aerosol varied by a factor of six (6 ) among the models. An even greater disparity was seen in the model treatment of black carbon and organic carbon. Some models ignored aerosol indirect effects whereas others included large indirect effects. In addition, for those models that included the indirect effect, the aerosol effect on cloud brightness (reflectivity) varied by a factor of nine (9). Therefore, the fact that models have reproduced the global temperature change in the past does not imply that their future forecasts are accurate. This state of affairs will remain until a firmer estimate of radiation forcing by aerosols, as well as climate sensitivity, is available.”
Does this effect your confidence in our knowledge of the TOA energy balance
Deep Waters May Not Run Still
The currents caused by large, swirling eddies at the ocean’s surface may reach all the way to the sea floor, a new study suggests. The unexpected finding may help explain how the larvae of organisms living at isolated hydrothermal vents can be transported hundreds of kilometers to colonize new vents. And as climate change affects surface eddies, it may also reach the ocean’s depths.
As any sailor knows, conditions at the ocean’s surface can change in a moment. But most scientists presume that the environment on the sea floor is fairly stable: Temperatures hover near freezing, darkness reigns, and currents are languid and steady. Well, scratch that last one. Measurements taken at a hydrothermal vent system in the eastern Pacific indicate that currents can be highly variable, in some cases tripling in speed for an extended period, and analyses strongly suggest that eddies at the ocean’s surface are to blame.
In a field study, Diane Adams, a marine biologist at Woods Hole Oceanographic Institution in Massachusetts, and her colleagues measured the currents near the seafloor along the East Pacific Rise, a submarine ridge south-southwest of Acapulco, Mexico, that sports many hydrothermal vent systems. They suspended sensors 170 meters above the 2350-meter-deep ridge, high enough to remain unaffected by ridge-related turbulence. They also suspended traps just 4 meters above the sea floor to measure the amount of minerals spewed by the vent systems and settling back to the ocean floor, as well as to count the number of larvae produced by creatures living in the warm oasis. Because the vents usually maintain a steady flow and the creatures that live there reproduce continually, minerals and larvae fall into the traps from the cloudy waters above at fairly steady rates.
From November 2004 through April 2005, typical currents at the site flowed from the north at an average speed of about 5.5 centimeters per second, the researchers report online today in Science. Moreover, says Adams, the currents rarely rose above 10 centimeters per second. But in March 2005, currents shifted suddenly and flowed from the south at speeds that sometimes exceeded 15 centimeters per second. During the same interval, the amounts of sediment and vent-creature larvae that fell into the team’s traps dropped dramatically—indicating the cloud of minerals and larvae had been carried away, at least temporarily, as if a strong storm system had swept the stale air from a polluted valley.
Later, while searching for a possible reason for the anomalous currents, Adams and her colleagues found that a large, clockwise-spinning eddy at the ocean’s surface—one measuring about 375 kilometers across—had crossed the area at about the same time. Then the team’s computer simulations showed that eddies could trigger changes in sea floor currents matching the patterns measured by the instruments, with the best correlation occurring when the effects on deep-sea currents happened 8 days after the eddy passed overhead.
“This is a huge response at the bottom, and passage of the surface eddy probably isn’t coincidental,” says Dudley Chelton, a physical oceanographer at Oregon State University, Corvallis. “This will change the way we think about the ocean,” largely because the effects of such eddies weren’t suspected to extend so deeply, adds Cindy Van Dover, a biological oceanographer at the Duke University Marine Laboratory in Beaufort, North Carolina.
Many of the surface eddies in this region of the Pacific are generated by winds spilling westward off the coast of Central America, and those winds vary with the seasons and may become stronger or more frequent as climate changes in the future. Therefore, Van Dover says, the eddy-induced currents may offer a way for climate change to affect the deep sea sooner than expected and in a way scientists hadn’t been thinking about. Organisms that have evolved in environments that have little if any change in environmental conditions, for example, may not be able to adapt well if currents increasingly mix warm surface waters down to the seafloor.
http://news.sciencemag.org/sciencenow/2011/04/deep-waters-may-not-run-still.html
A hydrothermal vent
http://en.wikipedia.org/wiki/Hydrothermal_vent
It doesn’t let me post the content of the hydrothermal vent wikipedia entry. I thought this was very interesting read together with the rise of eddys from climate change. Eddys can make a normal hurricane explode in strength.
“The flux of heat depends on temperature”
Your physics is sloppy. Temperature changes are driven by the flux of heat (Joules). Temperature gauges are one of the instruments we use to calculate the amount of heat, and this metric also determines important things for humans like whether it feels hot or cold, or that water boils on your stove around 100 C, but fluxes of heat defintely have no clue about how they are being measured.
What I think you mean to say is that the measurement of the heat flux depends on temperature measurements.
[edit]
[Response: The principle heat flux in the ocean is advective – i.e. u*T – so it is completely accurate to state that the heat flux depends on temperature (and velocity). Diffusive heat flux depends on temperature gradients – again requiring temperature measurements. I doubt very much that anyone is measuring deep ocean heat flux directly – any such flux must be inferred. – gavin]
Bob Loblaw – The heat, even without accumulating, in Joules would still be seen as it moves downward. What you present is a constant flux layer, as is often used in the lowest layer of the atmospheric boundary layer even when it is unstably stratified and heat is transported upwards higher into the boundary layer.
I do assume that you are presenting your example as a thought experiment, and not proposing this is true (i.e. a constant flux layer) for the upper ocean. :-)
Look folks. Here is a simple assumption that makes what Roger is saying again exactly correct:
The downward flux of heat into the ocean is not constant over a semi-annual to annual basis due to weather noise and the seasonal cycle. Instead, anomolous heat would be expected to come in “globs”. During these periods of higher than average heating, we should see high temperature anomolies, and if the grid spacing is small enough, and the gauges are accurate enough, these anomolies should be able to be mapped in theory.
Repeating again in a different way so that it is perfectly clear: If the rate of “leakoff” (by whatever mechanism, turbulent or diffusive) to the deep ocean is keeping pace (averaged over decadal periods) with the incoming heat in the integral of ocean being monitored, then if measurement is good enough, these large “globs” of anomolous heat should in concept be able to be mapped and tracked over *annual time periods*.
Now if we want to estimate where these positive anomolies are moving over decadal time periods, yet the sum of the positive years plus the sum of the negative years=0, then we have two choices. Either the heat from the positive years has been lost to space, or it has leaked off to the deep ocean (ignoring other trival reservoirs of heat).
If it is being lost to space, then we must expect to see in our animation of temperature anomolies over time, that the hot anomolies primarily accumulate in the shallowest layers of of the ocean, so that an upwelling flux of heat can go back into the atmosphere and be lost to space, for instance possibly related to ENSO.
If however, our animation shows that most of the anomolies map deep in the ocean, then we might assume that these could be lost due to leakoff of heat to the deep portion of the ocean.
Ray Ladbury #178
You write,
“I have to say that the whole deep sequestration argument makes me a little uneasy. Roger is correct-we haven’t seen it–and to say it is there without evidence strikes me as special pleading. I distrust unobservables–they can keep you from discovering really important things. In the end, what matters is TOA energy balance. The evidence that we are warming the planet is sufficiently strong that I don’t feel the need to oppose the denialist/complacent on every issue.”
Can you explain why you have so much confidence in the TOA energy imbalance?
According to Trenberth, Fasullo & Kiehl 2009
“The TOA energy imbalance can probably be most accurately determined from climate models and is estimated to be 0.85 ± 0.15 W m−2 by Hansen et al. (2005) and is supported by estimated recent changes in ocean heat content (Willis et al. 2004; Hansen et al. 2005).”
Mapleleaf-
First, I stated that the Argo data density was fine enough to see the movement of the heat downward, but am now unclear on this, and look forward to an Argo specialist to give us an overview of capability in this regards.
On the other issue you raised, you wrote
“it is good to see that he recognizes that heat can be sequestered in the deeper ocean, and that if it is then the surface temperature record is probably underestimating the amount of warming. And yes, I realize that him saying that is inconsistent with his research that claims the surface temperature record has a warm bias, especially at nighttime.”
I have always recognized that heat can be transfered to greater depth. In my paper
Pielke Sr., R.A., 2003: Heat storage within the Earth system. Bull. Amer. Meteor. Soc., 84, 331-335.
http://pielkeclimatesci.wordpress.com/files/2009/10/r-247.pdf
“An assessment of the heat storage within the earth.s climate system offers a unique perspective on global change. If the heat actually remains within the earth system in the deeper ocean, for example, while the heat content of the remainder of the heat reservoirs in the earth system remains unchanged, sudden transfers of the heat between components of the system (from the ocean into the atmosphere) could produce rapid, unanticipated changes in global weather.
Similarly, relatively large warming and cooling radiative forcings (e.g., well-mixed greenhouse gases and the indirect effect of aerosols) could be in near balance at present, suggesting that sudden climate changes could occur if one of these forcings becomes dominant. On the other hand, a loss of space to a large portion of the increased radiative fluxes, as the atmosphere adjusts, such as through a change in cloud cover (e.g., Lindzen et al. 2001), would suggest that the climate system is relatively more resilient to continued anthropogenic heating effects than conventionally assumed.”
My view now is that if the heat moves to deeper depths, it would become relatively dispersed, and I do not see how it could be quickly transfered back to the surface.
On the warm nighttime bias we found, this is still a robust finding between the MSU LT data and the surface temperature data. It is an independent issue from the ocean heating.
The sequestration of the heat at depth, however, if this is accurate, does show a serious inadequacy in using the global annual average surface temperature trend as the metric to diagnose global warming.
[Response: Isn’t this where we started? – gavin]
Gavin – Regarding
Isn’t this where we started? – gavin
I have found the set of comments quite informative, so I do not feel we are back where we started. Bryan S has summarized the issue very well.
Thank you for the opportunity to interact on your weblog. Roger
Does this statement mean if heat is increasing in the deep ocean, an increase in global surface temperature is an underestimate ?
Or is Mr Pielke trying to say surface temperature trends have no relation to global warming, or do not indicate it’s happening?
Or is he simply arguing “not too worry”, there might be some unknown “natural” effects that might put the tempest back in a teapot?
Why “Either … to space, or … to the deep ocean” — hasn’t the change in the outgoing radiation been measured?
And modeled? E.g., quite recently, this posting:
18. Noise, TOA fluxes and climate sensitivity
Posted on October 7, 2011 by Isaac Held
High uncertainty is linked to the issue of the huge overturning in the Atlantic called the thermohaline circulation. Its potential collapse could be caused by freshwater inflows from Greenland ice sheet melting and changes in precipitation patterns. As insight in these changes is still limited, the likelihood of transition as well as the confidence in the assessment does not increase with temperature.
“Possible linkages of tipping elements make it even more advisable to use a risk management approach when dealing with global warming”, says Tim Lenton of the University of Exeter, UK, one of the authors. For example, a likely weakening of the thermohaline circulation in the Atlantic could lead to a warming of waters around Antarctica and shift the subpolar wind belt, inducing changes in ice sheet melting. “Those linkages are complex and are in urgent need of further exploration”, says Lenton. http://www.pik-potsdam.de/news/press-releases/kipp-elemente-im-klimasystem-forscher-verfeinern-ihre-einschaetzung
Roger A. Pielke Sr. says: “My view now is that if the heat moves to deeper depths, it would become relatively dispersed, and I do not see how it could be quickly transfered back to the surface”
Freshwater uptake lowers the amount of heat flux into the deep ocean and ocean currents transport water down and up. But the entire established transport is about to start to abruptly switch to a more passive state. We can use here the metaphor of the human blood transport and what happens when blood transport abruptly stops.
The condition means less water mixing – transport, thus creating ocean dead zones, algae blooms and jelly fish invasion.
flxible – If one is using the annual global average surface temperature trend to diagnose global warming (and cooling), but some of the heat is being sequestered in the deep ocean, the trend would be underestimated when using the surface temperature trend to monitor global warming.
This issue provides yet another reason we should move to the ocean heat content changes as the primary metric to diagnose global warming as as a check against the time integrated TOA radiative imbalance as measured from satellite.
> move to the ocean heat content changes as the primary metric
> to diagnose [global warming]
Dr. P/Gavin — would Dr. P’s term for what’s to be measured work for this?
He wrote in 2003: “Heat storage within the Earth system”
Dr. P: Would you accept this rewording?
“Would using ocean heat content changes be a satisfactory primary metric for diagnosing heat storage changes within the Earth system?”
(I do wonder about leaving out the borehole temperatures, but the researchers in that area may have their own terminology too)
Could you agree on using your own term here? It would help.*
On the “metric” I wonder — Is this an actual suggestion for the present, or a longterm wish?
What questions need to be answered to know if that can be a useful metric, and when, and how? From the peanut gallery, I’d wonder:
— How much data exists now?
— Over what time span?
(Those questions are for any data librarian or anyone else who can point to the data sets with some assurance)
Questions given the above answers:
— What are the error bars in those observations?
— How many observations, or how many years, will be needed to detect any possible trend?
— As observations and years are added, how many more are needed to have enough?
— The land surface temperature is oversampled for climatology**; what sort of instrumentation/sampling rate is needed for ocean surface temperature/ lower atmosphere over the oceans?
I’d appreciate any statistician who answers that showing the work, it would be instructive. Bob Grumbine’s example on detecting trends*** is a good example of how to take a particular data set and answer this question for that set.
________
* “If language is not correct, then what is said is not what is meant; if what is said is not what is meant, then what must be done remains undone …”
**http://www.skepticalscience.com/OfAveragesAndAnomalies_pt_2B.html
** http://moregrumbinescience.blogspot.com/2009/01/results-on-deciding-trends.html
“[…] we should move to the ocean heat content changes as the primary metric to diagnose global warming as as a check against the time integrated TOA radiative imbalance as measured from satellite.”
I wasn’t aware that there was only 1 metric.