The Layers of Meaning in Levitus

Guest Post by Willis Eschenbach

There have been a lot of electrons sacrificed on the altar of the discussion of the Levitus ocean heat content data. The oddity seems to be that the deep ocean is gaining heat faster than the upper ocean. Here’s a typical graphic showing the issue:

global ocean heat content levitusFigure 1. Changes in the ocean heat content for two layers, 0-700 metres and 0-2000 metres. Values are pentadal (5-year) centered averages. SOURCE: NOAA/NODC

This week I got to ruminating about this graphic, and a number of similar graphics I’d seen. And yesterday I realized that it wasn’t showing what I thought it was showing. Let me illustrate what I mean.

I’ll start with an overview of the oceanic heat content (OHC) of the three layers that are provided by NOAA. These cover 0-100, 0-700, and 0-2000 metres depth. Figure 2 shows that data.

changes in ocean heat content noaa layersFigure 2. Annual changes in oceanic heat content for the 0-100, 0-700, and 0-2000 metre layers. 

Now, my problem was that when I looked at graphs like Figures 1 & 2, I thought that the deepest layer was gaining heat the fastest. And there’s been a lot of discussion about how that could be, and much speculation about the reason for the big increase in the deeper layers from 2001 onwards.

But yesterday I thought hey, wait a minute … those layers of the ocean overlap! They are not separate layers, they all extend to the surface.  So what we’re seeing in the deep 2000 metre level data is to some extent affected by what’s happening in the other levels. Yeah, I know, I should have seen it earlier, but I’m not gonna pretend.

The good news is that we’re measuring ocean heat content (OHC), so it’s very different from temperature. We can simply subtract the changes in the 700 metre level OHC from the 2000 metre level OHC changes, and what is left is the change in heat content for the layer from 700 metres down to 2000 metres. Can’t do that with temperature. Figure 3 shows the same OHC data as in Figure 2, except split out into distinct and separate layers, at the same scale. as Figure 2.

changes in ocean heat content separate layersFigure 3. Changes in oceanic heat content. The exact same data was used as in Figure 2, except it was split into three separate layers rather than three overlapping layers.

I was quite surprised by this result. Once I split the information up so that I could see the changes in each of the layers separately, much of the apparent change post-2001 disappeared. In Figure 2 there’s not a lot of change in 2001.

I also found it interesting that for most of the time covered by the study, all three layers picked up about the same amount of heat. Only in the last decade has the middle layer (100-700 m) picked up a bit more heat than the other two layers. I hadn’t expected them to warm and cool generally in unison as we see above.

Finally, I calculated the change in temperature for each of the levels. The nice thing about the ocean is that the temperature and heat content are mathematically related by the fact that it takes about 4 megajoules to warm a tonne of water by 1°C. This lets us convert from heat content to temperature and back as needed.

Remember that the three layers have very different volumes. So a terajoule of energy added to the shallow 0-100 metre layer will warm it more than the same terajoule of energy added to the more voluminous 700-2000 metre layer. Fortunately, NOAA also provided the ocean depths on a 1° x 1° grid, so we can calculate the volume of each of the layers. Once we know the volumes, we can calculate the temperature changes. Figure 4 shows the same data as in Figure 3, except expressed as a temperature change rather than as a change in heat content.

changes in sea surface and subsurface tempsFigure 4. Measurements of ocean temperatures at the surface and three sub-surface layers.

There are several interesting things about this plot of the temperature measurements.

First, as one might hope, we have relatively good agreement between the sea surface temperature (SST) and topmost layer (0-100 m). However, the annual and inter-annual swings in the upper 100 metres are larger than those at the surface … which seems somewhat strange to me. I’d have expected the surface to change more than the bulk.

Next, as we’d expect, the nearer to the surface, the greater the changes in temperature.

Finally, I’ve marked the eruptions of El Chichon and Pinatubo for future reference. I’ll come back to this in a subsequent post. For now, note that there is no visible effect of the volcanoes on any of the five different measurements of ocean temperatures. As near as we can tell from these measurements, the effect of the volcanoes on the ocean was below the limit of detection.

So … now that we have had a better overview of what’s happening to the various layers under the sea, are the changes in ocean heat content surprising?

I’d say not particularly. Yes, the middle layer (100-700 m) started warming in 1995. And yes, the lower layer (700-2000 m) followed suit starting in about 2001. But neither of these seem particularly surprising. I don’t have any explanation for them, but they do not seem to be unusual. It is possible, for example, that they represent the sub-surface changes associated with the gradual shift of the Pacific Decadal Oscillation from the positive to the negative phase. We know very little about the ocean depths, including how much we’d expect them to vary. And the records are short, too short to even show two PDO changes. It is clear, however, that the changes in heat content are not caused by CO2, at least directly.

Finally, we have to consider that the changes in the deeper layers may be an artifact. One obvious possible source is the integration of the Argo data into the Levitus analysis. The first Argo floats went in during the early nineties, and were added progressively over the next two decades. It is at least conceivable that some or all of the recent changes in the deeper layers are an artifact of the change in measuring methods.

Best regards to all,

w.

NOTES:

The data is from NOAA , except the ERSST and HadISST data, which are from KNMI.

The NOAA ocean depth data is here.

The R code to extract and calculate the volumes for the various Levitus layers is here.

Advertisements

  Subscribe  
newest oldest most voted
Notify of
simon abingdon

Fig 2 and 3 y-axis: 5.0E and -5.0E should read 0.5E and -0.5E.

simon abingdon

My mistake. I see the exponent for the 5.0 is 22 and not 23.

Otter

Gah! A quick glance on Tom’s page and I thought it said ‘Leviticus’ 😛 Now, please, I do NOT intend a discussion on that subject, I just wanna note: the was ONE person in history, who was able to calm storms… 😛
Back to trenbreth’s failure….

simon abingdon

At the same time the expansion of the scale of the y-axis outside the central bands is visually very misleading.

Tim

So if I’m right in interpreting your diagrams, each of the layers follows the trends in global temperature with an increasing lag and decreasing sensitivity dependent on depth. So in future we can expect to see 0-100m temps go down, whilst lower depths continue to rise before falling again somewhere around the mid-century period.

Tim

I should have said follows the trends in global air temperature…

M Courtney

Am I correct in observing that there are sharp troughs in the 0-100m temperature anomaly and that these troughs coincide with El Nino events?
If so, can I ask if the temperature anomaly rise (that is the extra heat) in the air at that time is balanced?
I am curious as to whether the extra atmoshperic heat from the ocean causes any positive feedbacks or whether the heat is lost somewhere else; downwards into the greater water volume or into phase changes or into the biosphere or…
All that can be ruled out if the heat balances.

Greg Goodman

Nice one Willis.
One observation from your figure 3: it seem like the two deeper layers are in sync (which is a little surprising to me but seems clear enough) however, the 0-100m layer seems to have a lead of about 3 years over the other two. This could be assessed more accurately by cross-correlation preferably on annual data not pentads of course.
The phase lag would be a useful parameter to extract in relation to things like Hansen ‘in the pipe line’ warming claims.

Greg Goodman

Your suggestion of bias due to Argo seems important. There does not seem to be a physical explanation for where the heat could come from to cause a substantial rise in 100-700m without 0-100m rising. Little solar energy can penetrate that deep before getting absorbed.
That this anomaly occurs in the period where Argo starts to come in does point a finger.

pochas

Why is deep ocean water cold in the first place? Anybody?

lgl

M Courtney
“Am I correct in observing that there are sharp troughs in the 0-100m temperature anomaly and that these troughs coincide with El Nino events?”
No, they coincide with La Nina events. El Nino is warming both the ocean and the atmosphere.

DirkH

Nice!
Now the comparison of pre ARGO and post ARGO mass deployment data is probably open for a lot of Winston Smith-style history rewritings; but the interesting thing is the misleading “layering” used by the government agencies with the N in their name.

Greg Goodman

Willis: “Finally, I’ve marked the eruptions of El Chichon and Pinatubo for future reference. I’ll come back to this in a subsequent post. For now, note that there is no visible effect of the volcanoes on any of the five different measurements of ocean temperatures. As near as we can tell from these measurements, the effect of the volcanoes on the ocean was below the limit of detection.”
Not at all sure I’d agree with that. There is a quite significant drop in 0-100m OHC after El Chichon, that could be interpreted as oceans compensating for loss of solar input with climate feedbacks acting so as to correct the deficiency. You have posted a lot on your ‘governor’ idea, this may be a manifestation of just that sort of negative feedback.
Mt Pinatubo is less clear but there is a less drop and then of course the huge dip caused by 1998 El Nino. I’m a little surprised not to see a more obvious positive excursion for SST around 1998 but that may well be an artefact of these damn running means again. In your last thread I pointed out how they were inverting precisely that event.
I _strongly_ suggest any closer look at changes on the sub-decadal time-scale is done with a non distorting filter on the annual data, otherwise you will end up discussing the aberrations caused by the filter and not what the data does.
Since both the shallow OHC and SST is available with higher resolution , that is obviously the way to go.
This is well worth looking at since, if what I have suggested is happening (climate governor compensating for volcanoes) then the major excuse for exaggerating CO2 with hypothetical +ve feedbacks disappears.
I’ve been suggesting this for a couple of years.
And if climate can handle a major stratospheric eruption, there a damn good chance it can counteract a slow gradual increase in CO2.
There’s at least one published paper that shows an increased likelihood of El Nino a couple of years after major eruptions.
Some of Bob Tisdale’s plots of basin by basin changes in SST and OHC would also support this idea if only he would stop ‘detrending’ SST without explaining where that energy went.
My impression is that 8 to 10 years after a major eruption, the climate has compensated and the net result is near zero. To that extent, I would agree with your statement but I don’t think volcanoes are undetectable on the annual scale.
Following eruptions, winters are milder , summers cooler, OHC compensates for lost solar input. Initial cooling of SST is followed by more or less equal warming period and La Nina recovers OHC lost to compensate earlier Ninos.
That’s a rough sketch and may not fit exactly but I think that is closer than the official line of exaggerated volcanic cooling compensated for by exaggerated CO2 warming. On model which has blatantly failed in the first decade with negligible volcanic activity.

Willis said, “As near as we can tell from these measurements, the effect of the volcanoes on the ocean was below the limit of detection.” More like barely at the level of detection. I was comparing the lower stratosphere by hemisphere with OHC trying to make a quick Black body shell example. With the lags between hemispheres, you can separate regionally to follow the volcanic aerosol impact.
http://redneckphysics.blogspot.com/2013/05/ocean-heat-content-versus-stratospheric.html
That and a buck will get you a cup of coffee, but it is kind of neat how useful the satellite data is.

Greg Goodman

Capt. Dallas, that plot of stratosphere tends to beck up my previous post. The stratosphere also shows a similar rebound after each volcanic event before falling back to a lower ‘steady state’.
This shows that climate is reactive and not just sitting back waiting for the dust to settle. Official line is just that. There is a few years where ash/aerosols etc block sun and it eventually fades away.
Such data show that premise to be incorrect and that climate has a reactive response to such events.

cRR Kampen

” The oddity seems to be that the deep ocean is gaining heat faster than the upper ocean. Here’s a typical graphic showing the issue:”
That a layer of water 2000m deep will take up more heat than a layer 700m deep, methinks.

cRR Kampen

“Why is deep ocean water cold in the first place? Anybody?”
Density. And remember, sea water has highest density at freezing point (that is: near -2° C) and not at +4° C like destilled water.
The cold water on the ocean floors is the result from freezing sea-ice nearing wintertime. Sea-ice is sweet water; while forming cold currents of brine drop down to the bottom to gradually spread out over the entire oceanfloor. Further reading: thermohaline circulation.

Robert of Ottawa

I wonder what would happen if these heat content numbers were expressed as joules/meter cubed?
Which has the larger volume – 0-100 meters, 100 – 700 or 700 -2000. I’d suspect the 100-700 but I don’t know.

Bill Yarber

Willis
I like the way you think, simplify things and clearly articulate & illustrate your findings. Well done!
You should have indicated the three volumes: 0-100, 100-700 & 700-2,000 and converted that to mass, compensating for density due to temperatures. I think that will clearly illustrate & justify the heat transfer lag times. Do we have any credible knowledge about deep ocean currents below 700 meters? I would assume the “mixing” in the varicous layers varies greatly.
Bill

Greg Goodman, of course it is reactive. Most of the albedo, clouds/snow, is response driven. If you want to avoid all the noise, then you go back to the radiant physics basics, black body cavity and radiant “shell”. That response of the stratosphere to the deep ocean heat content is perfectly predictable.

M Courtney

lgl says at May 10, 2013 at 4:40 am
Right, so the troughs are La Nina events then. Does the slight uptick in the 100-700m range account for that heat then or is the heat going somewhere else? Of course, the deeper ocean has more thermal capacity than the tinnere upper layer.
The heat budget change still seems worthy of investigation as those negative peaks are so clear. Are they showing the transport of heat down to the depths? Or are they showing transport of heat elsewhere?
If La Nina’s can move Trenberth’s missing heat downwards then it is missing no more. All that’s left to do is to work out how man is causing La Ninas and we would be able to get published.

Greg Goodman

Me says:
“Your suggestion of bias due to Argo seems important. There does not seem to be a physical explanation for where the heat could come from to cause a substantial rise in 100-700m without 0-100m rising. Little solar energy can penetrate that deep before getting absorbed.”
Looking at this again, that was incorrect. Figure 4 shows temp of surface laying is warmer, so there’s no contradiction with heat energy increasing in 100-700m faster than surface layer.
Heat is being lost from surface layer to 100-700m at the same time as heat in coming in from solar. That would seem to be about in balance since 2003, so middle layer is warming while surface layer 0-100m is remaining fairly constant.
So that does hang together. That does not mean we can assume any of this is free from error and bias, however,

jlurtz

Until we understand how the cumulative, say fifty years, of Solar activity affects the Trade Winds and the Indonesian bulge, and then understand how the Pacific Ocean currents move from the bulge, we will not understand how the Pacific Ocean is heated at depth.
As per the “experts”, [paraphrase] “it is not well understood how the surface currents merge with the deep currents”. Remember the deep oceans are not static, they are in motion. The only static areas are in the North/South Pacific Gyres and the Southern Atlantic Gyre. But, as the Sun moves to the Tropic of Cancer or the Tropic of Capricorn, these areas move.
Why doesn’t the NOAA research the “Hot Indonesian Bulge”, I’m sure they can get monies if they say it could be causing “Climate Change” due to “Global Warming” due to “CO2” from “Man”.

Steve K

“But neither of these seem particularly surprising. I don’t have any explanation for them, but they do not seem to be unusual.”
Absolutely hilarious.

Owen in GA

Interesting, looking at figure 4, surface and 0-100 m begin their rise somewhere around 1976-8, then the 100-700 m begins its rise around 1994, then the deeper layer begins rising around 2002-2004. It seems to me that would indicate that there is a time constant delay and the ocean layering in the models are 1) too simple of a layer structure, and 2) too short a time constant for the energy transfer. It looks as though the 100-700 m layer lags the surface to 100 m layer by about 15 years, and the 700-2000 m layer lags it by almost 10 years. This indicates a very complex energy transport that simply isn’t reflected in the models.
I recognize that there is not enough time in the time-series to really say a whole heck of a lot about “climate” from this as the good deep data is only about 10 years long. We haven’t even begun to see all the cycles in this data. Then there is the whole notion of someone “adjusting” the data to match climatology that will pervert the whole time-series. We also have virtually no coverage of the deep areas under the polar sea ice, what exactly is happening up there?

chris y

A number that is almost never reported is the total heat content of the oceans, rather than the change.
The oceans contain about 1.3×10^18 tons of water. Each ton has been heated from -273C to 0C, giving 2.7×10^8 J/ton. The heat of fusion to melt it gives another 3.3×10^8 J/ton. Ignoring the additional 4C rise gives total heat content of about 6×10^8 J/ton.
That gives a total heat content in the oceans of about 7.8×10^26 J.
The 5×10^22 J anomaly over the last 55 years for the majority of the ocean volume is a change of about 64 parts per million in total heat content.

Katherine

Just how reliable are the pre-Argo OHC measurements given how little of the ocean was sampled? Aren’t those figures just so much WAG, especially those for depths down to 2000 m?

lgl

M Courtney
I have collected a few grahps here http://virakkraft.com/OHC-SSST-OLR.pptx
The way I read this is
– Most of the energy ‘generated’ by an El Nino is sent to space.
– Except for the post-2000 ARGO miracle SSST 0-100m is following SST (it’s well mixed and should do so)
– 100-700m lags the surface by around 2 yrs (again except the ARGO miracle)
– As long at the SST is above a long term average the deeper layers temp will rise slowly, a low pass filter (lagged)
So, where can I find XBT- only OHC data covering at least up to 2005?

Thanks, Willis. Great post.
I noticed you used 1960-1970 for base years. They help to show how the data diverge with time, which is great.
FYI, if you had used 1955 to 2010 for example, you’d also note in a comparison like your Figure 2 how the 0-700 meter and 0-2000 meter data align themselves from 1970 to 2003 and then diverge once the ARGO floats are in place. The NCDC still has lots of work to do with that dataset.
Regards

chris y: Regarding your May 10, 2013 at 6:48 am comment, I’d like to suggest that you write it up, add some more detail and present it as a guest post to Anthony.
Regards

bwanajohn

Willis,
This was a “well, duh!” moment for me. I, too, had not seen the overlap in layers. As soon as I read your opening lines, I had a pretty good idea of what to expect when you plot the data in a more meaningful fashion. I look at data all day everyday and should have seen the problem a long time ago. Thanks for making my AHA! OHC makes a lot more sense to me now.

Owen in GA says: “Interesting, looking at figure 4, surface and 0-100 m begin their rise somewhere around 1976-8, then the 100-700 m begins its rise around 1994, then the deeper layer begins rising around 2002-2004. It seems to me that would indicate that there is a time constant delay…”
You’re assuming, of course, that the data below the surface prior to the ARGO era has any value (keep in mind it’s been adjusted beyond recognition) and that the increase around 2002-2004 in the deeper layer isn’t an artifact of the additional coverage with, and the adjustments to, the ARGO data.
Regards.

Philip Peake

Pochas: water is odd in that it gets more dense as it cools, up to about 4C, then it starts to get less dense. So water at around 4C sinks to the bottom. Water from melting ice at the poles will continually feed the depths.
The actual temperature for maximum density depends upon the salt content, its ~4C for pure water.

pochas

cRR Kampen says:
May 10, 2013 at 5:33 am

pochas: “Why is deep ocean water cold in the first place? Anybody?”
cRR Kampen: “Density. And remember, sea water has highest density at freezing point (that is: near -2° C) and not at +4° C like destilled water.
The cold water on the ocean floors is the result from freezing sea-ice nearing wintertime. Sea-ice is sweet water; while forming cold currents of brine drop down to the bottom to gradually spread out over the entire oceanfloor.”

And so, shouldn’t this be the first place to look when trying to assess changes in heat content of cold deep ocean water? Specifically, wouldn’t a decrease in the amplitude of the circumpolar freeze/thaw cycle affect the inflow of cold deep ocean water into the reservoirs? And in theory CO2 does have most of its effect at high latitudes, by reducing cooling rates.

Curious George

The bottom of oceans is filled by the densest, cool water – therefore, from a certain depth down the temperature should never change. Do we know what that “certain” depth is? Is it near 2000 m?
The graphs are plotted for “oceans”. Is it only for areas of oceans that are at least 2000 m deep, or does it include continental shelves as well?

David in Texas

The sun is not heating the interior of the earth. The interior of the earth is hot because of radioactive decay. (It would have long since cooled from gravitational heating.) Can we assume that heat flow from the center of the earth out is uniform and constant in space and time? Anyone? References?

Katherine says: “Just how reliable are the pre-Argo OHC measurements given how little of the ocean was sampled? Aren’t those figures just so much WAG, especially those for depths down to 2000 m?”
I believe your second question answers the first.

HR

Hello Willis,
Looking for a mechanism?
There is a new paper at JoC
http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00281.1
It’s paywalled but this presentation seems to contain the relevant information.
http://www.tims.ntu.edu.tw/download/talk/20120917_2280.pdf
It describes a mechanism for centennial variability in the antarctic/Southern Oceans which impacts heat content of global oceans at depth. In 1975 a maximum was reached in the amount of very cold Antarctic Bottom Water being produced and since then this has declined (and looks likely to continue for several decades if the mechanism is right). This would suggest the apparent warming at depth maybe due to a weakening of the impact of this cold water. It’s worth reading all this because midway it starts to explain the impact this variability has on the position of AABW and NADW. And in the conclusion seems to suggest the impact is felt at mid depth (below 1000m).
Maybe you could repeat your analysis for the different ocean basins to see whether it is the Atlantic that is mainly contributing to these trends?

Thanks Willis, excellent post.
Yes, overlapping ranges confuse the issue and create an illusion to infuse life into the “missing heat” monster.

pdtillman

Willis:
Thanks for the prompt and thoughtful analysis. Something pros like Trenberth should have done before starting to politick.
Best regards,
Pete Tillman
Professional geologist, amateur climatologist

Owen in GA

Bob Tisdale:
The adjustments to ARGO have me scratching my head. I don’t see anything in the engineering documents for ARGO that would indicate the system should have a cold bias, but someone adjusted it to correct for that. That someone needs to have a serious, introspective look at their integrity, because this looks like making changes to experimentally collected data for the purpose of supporting ones hypothesis. I was always told that was a punishable error worthy of having all ones papers pulled and grants withdrawn. Apparently, that does not apply in Climate Science(tm). If they suspect some units are reporting bad data, they should go collect those units, bring them back to the lab, and check their calibration! If the calibration is good then there is no need to make adjustments, but if the calibration is bad, remove that unit’s readings from the series! You have to assume the data is good until you have actually, physically verified a malfunction.
As to the old bucket and drop sensors, I concur that they were too few and too sparse to give anything like an accurate look into what was going on at depth. There is a definite apples to comets comparison going on in deep ocean analysis.
My point in the first point was a bit of a dig at the paper that was reported on WUWT a few months ago that showed a climate model that modeled the ocean as a two tiered reservoir with a rather fast time constant. This data (if it has any validity at all) seems to indicate that the ocean heat transport model is far more complicated. I would suggest that even these 3 layers are inadequate and probably need to be broken up farther and compared, but without getting to the raw ARGO data and doing some very laborious rebinning into ever smaller delta depth/pressure/density segments, then checking the time delays, that hypothesis could not be tested.

Curious George

@David in Texas: The average flow of heat from the Earth’s interior is estimated at 70 mW per square meter. It is not uniform in space nor in time – volcanoes, hot spots. I don’t know how accurate that estimate is.

chris y

re Bob Tisdale-
” I’d like to suggest that you write it up, add some more detail and present it as a guest post to Anthony.”
Thanks for the note of encouragement! I don’t know if there is enough to justify a complete post. I’ll think it over.
By the way, I’ve thoroughly enjoyed your e-book “Who Turned on the Heat?”. Very enjoyable reading with lots of drawings.

Doug Proctor

The first thing the relative energy content of shallow and deep data suggest to me is that the data AS CREATED is flawed, i.e. the conversion of Argo temp-salinity to energy is incorrect. Because we are not graphing data but calculations involving data.
The second is that we are seeing a natural cycle in how the oceans transferr heat that is outside of conventional understanding. We know that the oceans overrturn, so that surface waters eventually go deep and deep come to the surface. Our understanding is that this takes a long time, perhaps 300 years. Perhaps we are serriously wrong, We also think that the overturning is a continuous process; again, perhaps we are wrong and the overrturning is cyclic and sudden. If overturning can be or is fast and sudden, it would explain swift temp changes globally explained by neither CO2-atmospheric circulation models nor solar-cloud theories.
The third is that we are looking at the merging of two datasets that shouldn’t be merged, the Argo and the pre-Argo data. Again, calculations and not data: it could be the original data sources are not actually sampling the same though they appear to be.
This is anotherr Trenberth Event, a Positive TE: a deep heating that is bypassing the shallow that should not be seen but is. It actually has caused a Negative TE: we should be seeing more of a shallow heating than we are. The TE response is interresting because together the explanations are contradictory: not seeing what was modeled, the shallow heating, is taken to mean not that the models are inadequate or flawed, but that we are being “tricked” by nature. Seeing what was not modelled, the deep heating, means the models are not inadequate or flawed, but that they are VINDICATED by other yet-unknown means. Nature is reassuring us that we are right to be worried.
Trenberth Events are extraordinary events that reveal our social need to be certain and “right”, a need that taps into an extraordinary ability to find rationalizations where justifications are missing.

Richard M

As I looked at the graphs I could see the heat gained from the 1999-2001 La Niña. It first warmed the 0-100 depth and proceeded downward. It would be interesting to investigate OHC changes vs. the ENSO (La Niña) index to see if that changes over time. Might produce some interesting insights.
For example, if a La Niña warms the oceans and we see more of them during a negative PDO then we should see an overall warming of the oceans. However, since most of this data was collected during the positive PDO phase it seems counterintuitive.

Willis Eschenbach

chris y says:
May 10, 2013 at 6:48 am

A number that is almost never reported is the total heat content of the oceans, rather than the change.
The oceans contain about 1.3×10^18 tons of water. Each ton has been heated from -273C to 0C, giving 2.7×10^8 J/ton. The heat of fusion to melt it gives another 3.3×10^8 J/ton. Ignoring the additional 4C rise gives total heat content of about 6×10^8 J/ton.
That gives a total heat content in the oceans of about 7.8×10^26 J.
The 5×10^22 J anomaly over the last 55 years for the majority of the ocean volume is a change of about 64 parts per million in total heat content.

Thanks, Chris, you raise good points.
I get slightly different numbers, though. Sea water has a specific heat of about 4 megajoules per tonne. So to raise a tonne of water from -273 to 0°C require 273 * 4e+6, or 10.9e+8 joules. You give this as 2.7e+8 joules.
Also, the Levitus data contains the total volume of the ocean. They have it at 1.56e+9 cubic km, where you are using the canonical value I’ve used for years, 1.3e+18 cubic metres. In addition, you have to increase this by about 3.3% to get tonnes, so the total weight of the ocean is 1.62e18, about 25% larger than the figure you give.
So at the end, I get a heat content of 1.62e+18 tonnes times 10.9e+8 tonnes, or 1.8e+27. This is about 2.3 times the value you obtained.
However, that’s just the math. Your point is correct. We are talking about very small changes in OHC. I’m not sure how relevant that is or what that might imply, however. I’ll have to think this over.
Best to you,
w.

Bart

It seems to me that measuring the heat content of the overall oceans in general is a very coarse measurement which doesn’t really tell you a whole lot. I would think more informative measures would be the layered heat content in upwelling and downwelling areas separately. That tells you how much heat is being carried down, and how much is coming up.

DocMartyn

The most recent papers hows more heating from 300-700m than from 0-300m
http://i179.photobucket.com/albums/w318/DocMartyn/deepoceanJPEG_zpsc6585990.jpg
The blow up shows that in 0-300m there is a change of 3 measured units and in the 0-700m, there are 7.5 units. Thus, 4.5 units represent 300-700m. Hence, the rate of warming is greater in the colder body than the warmer body.

Willis Eschenbach

cRR Kampen says:
May 10, 2013 at 5:33 am (Edit)

“Why is deep ocean water cold in the first place? Anybody?”

Density. And remember, sea water has highest density at freezing point (that is: near -2° C) and not at +4° C like destilled water.

Thank, cRR. This is a common misconception which others have repeated above. At the pressure and salinity at the ocean bottom, sea water continues to get denser all the way down, and is densest at freezing (which as you point out is a couple degrees below zero because of the salinity).
w.

@Curious George 8:38 am
The graphs are plotted for “oceans”. Is it only for areas of oceans that are at least 2000 m deep, or does it include continental shelves as well?
A very astute question. Because the Argo floats ‘hibernate” below1000 m for about 90% of their cycle, that corals the Argo floats preferentially into deep water. So shallow seas must be undersampled by consequence. Also isolated deep water seas with choke points could be undersampled or oversampled because entry or escape is hindered.
There was a Feb 25, 2013, WUWT article: http://wattsupwiththat.com/2013/02/25/ocean-temperature-and-heat-content/
In the comments, Willis added map of ARGO locations that reported in the past 30 days from 3-Feb-2012. http://wattsupwiththat.com/2013/02/25/ocean-temperature-and-heat-content/#comment-1233606
I made comments on the areas I thought undersampled and oversampled, with the hypothesis that water depth and sub sea barriers were in part to blame.
http://wattsupwiththat.com/2013/02/25/ocean-temperature-and-heat-content/#comment-1234165

…The density of points in the Sea of Japan is remarkably high compared to the Southern Caribbean and Gulf of Mexico and the Philippian Sea. Is it evidence of a trap? There is also a surprising gap between the Philippines and Papua New Guinea, one of the deepest average depths in the Pacific. (more…)