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:
Figure 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.
Figure 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.
Figure 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.
Figure 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.
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Fig 2 and 3 y-axis: 5.0E and -5.0E should read 0.5E and -0.5E.
My mistake. I see the exponent for the 5.0 is 22 and not 23.
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….
At the same time the expansion of the scale of the y-axis outside the central bands is visually very misleading.
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.
I should have said follows the trends in global air temperature…
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.
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.
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.
Why is deep ocean water cold in the first place? Anybody?
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.
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.
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.
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.
” 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.
“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.
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.
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.
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.
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,
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”.
“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.
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?