Introduction To The NODC Ocean Heat Content Anomaly Data For Depths Of 0-2000 Meters
The National Oceanographic Data Center (NODC) recently posted a new Ocean Heat Content (OHC) anomaly dataset on its website. It is available on annual and quarterlybases, along with the data for its standard and documented dataset that covers depths of 0-700 meters. I looked for but was not able to find any papers (in any state of publication) that supported the new OHC data for 0-2000 meters. We’ll just have to wait and see how the NODC intends to present this dataset.
The data for the depths of 0-700 meters is, of course, documented in the paper Levitus et al (2009) “Global ocean heat content (1955-2008) in light of recent instrumentation problems”. Refer to Manuscript. It was revised in 2010 as noted in the October 18, 2010 post Update And Changes To NODC Ocean Heat Content Data. As described in the NODC’s explanation of ocean heat content (OHC) data changes, the changes result from “data additions and data quality control,” from a switch in base climatology, and from revised Expendable Bathythermograph (XBT) bias calculations.
COMPARISON OF GLOBAL OHC ANOMALIES: 0-700 METERS VERSUS 0-2000 METERS
Figure 1 compares the quarterly NODC OHC anomaly data for the depths of 0-700 meters and 0-2000 meters on a global basis. As noted on the illustration, the most obvious divergence between the two datasets occurs during the ARGO era. This is the period when ARGO floats became the dominant means of sampling of ocean temperatures and salinity at depth.
Figure 1
If we limit the comparison to the period from 1970 to 1999, Figure 2, we can see that there is basically no difference in the linear trends. There are minor differences from year to year, but the two datasets appear to be basically the same. Why?
Figure 2
There are extremely few observations prior to the year 2000 at depths greater than 1000 meters. This is illustrated in Figure 3. (Note that NOAA Climate Prediction Center Data Distributionwebpage breaks down the temperature profiles into depths of 0-250 meters, 250-500 meters, 500-1000 meters and 1000-5000 meters. Those depths don’t agree with the depths presented by the NODC for its Ocean Heat Content anomaly data.)
Figure 3
And Animation 1 shows a series of annual maps of the locations of temperature profiles from 1979 to 2005 for the depths 1000-5000 meters. As illustrated, there is also very little spatial coverage at these depths until the introduction of the ARGO floats.
Animation 1
As a reference, Figure 4 shows the number of temperature profiles for depths of 250 to 500 meters. There were between 2000 to 5000 temperature profiles per month between the late 1970s and the late 1990s at these depths before the ARGO floats were deployed. Note that the TAO/TRITON project (red curve) shows temperature profiles that were initially for the equatorial Pacific (coordinates approximately 8S-9N, 137E-95W). Those buoys were deployed for the study of El Niño and La Niña events. The locations were later expanded to include portions of the Tropical Atlantic and Indian Oceans under the PIRATA and RAMA projects. Refer to the TAO Project Global Arraywebpage. So while there are a good number of temperature profiles for the TAO project, they are limited in their location.
Figure 4
Figure 5 illustrates the difference between the two NODC Global Ocean Heat Content (OHC) datasets, where the 0-700 meter data has been subtracted from the 0-2000 meter data. Also referring back to Figure 3, the difference between the two datasets seems to increase in concert with the number of temperature samples at depths greater than 1000 meters. It appears as though the divergence of the 0-2000 meter dataset from the 0-700 meter data since around 2000 could be caused by the increased number of samples at depth and the increased spatial coverage of the ARGO floats, as shown in the animations. The impacts on short-term and long-term trends of the increased number of samples at depths greater than 700 meters and the impact of the increased area of observations should be determined. (A study such as that is well beyond my capabilities.) Maybe it will be documented in the NODC paper that accompanies the 0-2000 meter dataset.
Figure 5
Keep in mind, before the ARGO era, there were very few ocean temperature observations at any depth in the Southern Hemisphere south of about 40S. For example, Animation 2 is a gif animation of maps that illustrate the locations of temperature profiles for depths of 0-250 meters, 250-500 meters, 500-1000 meters, and 1000-5000 meters for the year 1995.
Animation 2
And Animation 3 shows the same series of temperature profile maps but for the year 2005.
Animation 3
A COUPLE OF QUESTIONS FOR READERS
Were the Expendable Bathythermograph (XBT) probes with wire lengths of 760 meters the most commonly used XBT probes before the ARGO era? Is this the reason the NODC originally limited the depth to 700 meters for the Ocean Heat Content anomaly data? Does anyone recall a paper that presents this? I had always assumed the depth of 700 meters was selected due to the number of and locations of observations, but I have never seen it stated in a paper.
LONG-TERM TRENDS PER OCEAN BASIN
When I originally prepared the graphs for this post, I could find no reason to present the long-term trends for the individual ocean basins of the 0-2000 meter data. The reason being, in some respects, the NODC OHC data for 0-2000 meters appears to me to simply be a 0-2000 meter OHC dataset spliced onto a 0-700 meter dataset. But on further thought, my failure to present the data might be thought by some as an attempt on my part to hide something. So Figure 6 (0-2000 meters) and Figure 7 (0-700 meters) are long-term trend comparisons of the Ocean Heat Content anomalies for the individual ocean basins as presented by the NODC. The most obvious similarity is that the long-term trends of the North Atlantic Ocean Heat Content are significantly higher than other ocean basins in both datasets, and in both, the North Atlantic Ocean Heat Content peaked in 2004. After that, there are significant declines. One would think this would lead researchers to examine the effects of the Atlantic Multidecadal Oscillation and Meridional Overturning Circulation on North Atlantic Ocean Heat Content observational data, yet, as far as I know, this is an area unexplored by climate scientists.
Figure 6
#########################
Figure 7
ARGO-ERA TRENDS PER OCEAN BASIN
The ARGO-era (2003 to present) linear trends per ocean basin for the depths of 0-2000 meters and 0-700 meters are shown in Figure 8 and 9, respectively. Like the trends for the 0-700 meter data, the South Atlantic and Indian Ocean are the only basins with significantly positive linear trends for the 0-2000 meter Ocean Heat Content data. And also like the trends 0-700 meter data, the linear trends of the 0-2000 meter Ocean Heat Content anomalies in the North Atlantic and South Pacific are negative. The linear trends for those two ocean basins are less negative for 0-2000 meter depths than they are for 0-700 meter depths, indicating that the declines at depths of 0-700 meters are greater than the increases at the 700-2000 meter depths. Considering there is less than a decade of ARGO-era data with “full” coverage, there is no need to speculate about the cause. Note also that the trend for the North Pacific OHC anomalies is basically flat for the 0-2000 meter data, and that the same holds true for the 0-700 meter data.
Figure 8
#########################
Figure 9
CLOSING COMMENTS
The undocumented (as of this writing) NODC 0-2000 meter Ocean Heat Content dataset appears as though it was prepared to show that Global Ocean Heat Content continues to rise during the ARGO era, and that it is intended to counter the argument that Global Ocean Heat Content has flattened during the ARGO era as shown in the NODC 0-700 meter dataset.
Due to the extremely limited number of observations at depths of 1000-5000 meters (shown in Figure 3 and in the animations), the 0-2000 meter Ocean Heat Content dataset should be used with great caution. It appears to me to be an ARGO-era 0-2000 meter Ocean Heat Content dataset spliced onto a long-term 0-700 meter dataset. For this reason, I, personally, would not expend the effort to analyze the long-term (pre-ARGO era) 0-2000 meter NODC OHC data beyond what has been presented in this post.
Each time I see the claim (based on many assumptions) by anthropogenic global warming proponent scientists that the rise in ocean heat content at depth “will come back to haunt us” I wonder why those same scientists have not bothered to attempt to document how much of the rise in OHC from the 1970s to the early 2000s (0-700 meters) was caused by the deep oceans upwelling warmer anomalies from past decades, other than the fact that there’s no data for them to do so. Could they believe that multidecadal variability is limited to Sea Surface Temperatures and does not impact temperatures at depth? Or is their intent to have the unsuspecting public believe it?
hotrod (Larry L) says:
October 24, 2011 at 5:03 pm
I feel your pain with the color, sounds like my color impairment is identical to yours.
Thanks Mom 🙂
Thanks for changing color codes Bob, I have a similar problem, when I am out plant collecting, I usually take an offsider who can pick red out at distance… Excellent post
They need to throw out everything before Argo or at least separate them as they are attempting to relate separate things. It appears the warming best correlates with the increase in the measurements.
ARGO only dives to 2000 meters so displaying it on a 1000-5000 meter chart is deceiving. The average depth of the ocean is 4000 meters so ARGO vertical coverage doesn’t even reach halfway to the average depth. Horizontal coverage isn’t too bad theoretically with a nominal spacing of 300 kilometers but since they drift freely they end up bunching up in stagnant areas and miss the interesting currents.
Excellent analysis once again, Bob.
I can’t understand how all that extra energy could get down to the 700-2000m level before showing up in the 0-700m level first. Surely there would either be a large blip in the 0-700m prior to the rising in the 0-2000m, or a very large drop in the 0-700 as the 0-2000 was rising.
I think you’re right in thinking that they’ve just spliced the temps of the prior years from the 0-700m, but they should have communicated that. To not do so is “alarmist”, IMV.
John Eggert says:
October 24, 2011 at 5:37 pm
“I’ve been wrestling with a question over the last number of weeks. The question is: Why is the ocean so cold?”
I’ve been trying to tell people the answer to that question for a long time. The average temperature of the global ocean is 3.9C and the only possible way for it to get that way is for the average surface temperature to be 3.9C.
A period of time of oh say 100,000 years is sufficient for even slow-ass conduction to equalize the bottom temperature with the surface temperature. This gives some perspective on the earth’s average temperature over a full glacial/interglacial cycle.
It’s fair to say that the current climate is thin skin of temporary warmth floating on a bucke of icewater. Imagine something that might disturb the mix rate between shallow surface layer (about 10% of the ocean volume has a temperature greater than 3C) such that more of that 3C frigid deep rises to the surface. Can you spell instant end to the Holocene Interglacial?
John Eggert says:
October 24, 2011 at 5:37 pm
“If we are to follow Dr. Pielke sr’s view, we should be looking at energy content, not flux. And looking at energy content brings us closer to the land of the dragons, because the top 14 meters of the ocean has the same mass as the entire atmosphere and I believe water is a better store of energy. As I said. It is a struggle.”
The ocean has over 1000 times the heat capacity of the atmosphere. Pressure reaches 1 bar, by the way, at 10 meters not 14. Don’t go diving without knowing that.
Pound for pound water has about 4 times the heat capacity of air. Given that 71% of the earth’s surface is water it works out that the first 3.2 meters of the ocean has the same heat capacity of the entire atmosphere. The average depth of the ocean is 4000 meters so it has over 1000 times the heat capacity of the atmosphere.
I’m not sure why you’re afraid of saying the answer to the question of why the ocean is so cold. The answer is scary but that’s no reason to avoid it. There’s only one possible answer and it doesn’t take a rocket scientist to figure it out.
Dave Springer says:
October 24, 2011 at 6:42 pm
I’ve been trying to tell people the answer to that question for a long time. The average temperature of the global ocean is 3.9C and the only possible way for it to get that way is for the average surface temperature to be 3.9C.
__________________________
Just curious. How much would you think that vulcanism plays into the temp of the oceans? IS there even a way to estimate something like that?
Bill Illis says:
October 24, 2011 at 5:07 pm
“That leaves the Earth 1.87 10^22 joules short or about 1.16 watts/m2 short. Space anyone? The energy is still missing.”
The answer is pretty darn simple, actually. The ocean is largely uneffected by greenhouse gases. Greenhouse gases work by slowing radiative heat loss. The ocean, unlike land, loses only 20% of the solar energy it absorbs radiatively. The great majority is lost through evaporation. CO2 doesn’t do jack diddly squat to slow down evaporative heat loss.
I think you’ll find the numbers work out rather nicely when you plug this revelation about the oceanic heat budget into the equation.
Dave Springer says:
October 24, 2011 at 6:42 pm
“The average temperature of the global ocean is 3.9C and the only possible way for it to get that way is for the average surface temperature to be 3.9C.”
Dave: That is a succint summary of my question: Is it possible for the mean ocean temperature to be lower than the mean surface temperature? If so, what is the mechanism of heat transfer that moves the energy out of the ocean while keeping the surface temperature of the ocean higher than the mean without transfering some of that energy downward into the depths. Ouch. My brain hurt just from writing that.
Jeff D says:
October 24, 20118:
“Just curious. How much would you think that vulcanism plays into the temp of the oceans? IS there even a way to estimate something like that?”
My quick and dirty guess is about 0.2 W/m² calculated as follows:
800 k temperature at bottom of crust
275 k temperature at bottom of ocean
525 k delta T
5000 m distance
1.7 W/(m.K) Thermal conductivity of basalt
0.1785 W/m² Rate of addition of heat to the ocean
(525/5000*1.7)=0.1785 = 0.2 rounded to appropriate sig figs.
If one considers 0.2 W/m² to be trivial, turn it into a total energy by multiplying by time and total ocean area. Use 1 billion years as a start for time. If you don’t like the rounding, truncate.
I could be wrong.
Cheers
JE
Jeff D says:
October 24, 2011 at 6:57 pm
“Just curious. How much would you think that vulcanism plays into the temp of the oceans? IS there even a way to estimate something like that?”
Neglible unless you’re an organism that thrives near deep thermal vents. The earth loses about 3 milliwatts/m2 of internal heat IIRC. If it were much faster than that the mantle would no longer be molten. That isn’t enough energy to make any measurable difference in ocean temperature.
John Eggert says:
October 24, 2011 at 7:17 pm
“Is it possible for the mean ocean temperature to be lower than the mean surface temperature?”
No.
Dave Springer says:
October 24, 2011 at 6:54 pm
“Pressure reaches 1 bar, by the way, at 10 meters not 14. Don’t go diving without knowing that.”
Dave: What is 10 / 0.7? Why did I divide by 0.7? Hint. I was talking about mass, not pressure.
Cheers!
JE
John Eggert says:
October 24, 2011 at 7:27 pm
“My quick and dirty guess is about 0.2 W/m² calculated as follows:”
I’m impressed. The more in depth calculation is 0.1 W/m2 and whatever source I recall saying it was a few milliwatts/m2 was off by quite a bit.
The ocean loses about 200 W/m2 at the surface so a tenth of a watt added at the bottom is stll insignificant in comparison.
Much more interesting is what happens on the surface of Venus where the interior is molten but the rocks on the surface are covered by 80 bar of CO2 which doesn’t conduct heat upward with anywhere near the efficiency of water. This changes the reduces the gradient in the crust substantially and is, contrary to urban Venusian greenhouse legend, what keeps the surface hot enough to melt lead. The greenhouse effect on Venus ends above the thick clouds that blanket the planet and make the surface as dark as the bottom of the Marianis Trench.
“Dan in California says:
October 24, 2011 at 4:25 pm
Somebody please check my numbers.”
See
http://www.engineeringtoolbox.com/specific-heat-fluids-d_151.html
The specific heat capacity of sea water at 36 F is 3.93 kJ/kgK and not 1.8 kJ/kgK. However this should not radically change your bottom line.
(I did a different calculation for a different post to answer the following question: IF we for the moment assume the air temperature were to potentially go up by 2 degrees C, but IF we then assume ALL this heat goes into the ocean instead, how much would the ocean warm up? Using mct(air) = mct(ocean), I get an answer of 0.0018 C is the increase in the temperature of the ocean.)
Gavin in a discussion with Dr Pielke claims that the heat deeper than 700 meters has acculmulated through a fast diffusive process that can not be sampled by Argo (every 11 days). This is simply nonsense. Strudies of borehole temperature logs on land have revealed the transfer of heat over the last two hundred years has been slow and has now only reached depths of 150 meters in 150 years.
http://esrc.stfx.ca/pdf/2002GL015702.pdf
Maybe somebody can explain to me what mechanism would allow heat to reach 2000 meters from the less than 1 mm skin depth of infrared penetration in less than 11 days.
Maybe somebody can explain to me what mechanism would allow heat to reach 2000 meters from the less than 1 mm skin depth of infrared penetration in less than 11 days.
Infrared penetration is irrelevant. The mechanism is that a warmer atmosphere impedes evaporation and therefore warms the oceans.
Downwelling currents could take ocean heat to the deep oceans without Argo detecting it.
Not that I think this is happening to the degree necessary.
I think Argo is giving us the correct answer. There has been no warming since 2002, excepting the Indian Ocean. Where the largest ocean to land heat transport occurs on Earth and it is known to be highly variable from the historical record.
In support of my monsoon theory, I’ll note that where the Indian Ocean OHC dips down in 2005 was when Western India had the highest monsoon rains ever recorded
Phily Bradley.
You are not paying attention. The warmists are now claiming that Argo shows that the missing heat is below 700 meters. Gavin claims that it is accumulating so fast that that Argo with an 11 day sampling period can not detect the heat flux responsible for the buildup. We all know that the documented overtuning of heat due to processess such as the gulfstream burying heat deep into the ocean at high laititudes is a relatively slow process that should be easily picked up by the ARGO’s eleven day sampling rate. I think Gavin has stuck his head out too far this time. I look for a retreat when physicist’s familar with thermodynamics cut his head off.
Thanks Bob for this excellent and thought-provoking update. The Indian and South Atlantic (SA) oceans stand out with increasing Argo-era OHC while the remaining oceans apparently cool. Looking at your ENSO SST animations, La Nina events pile up warm water in the western Pacific and this extends to south east Asia, possible influencing the Indian ocean. So is Indian Ocean warming a side effect of La Nina?
You have previously pointed to the Atlantic as the only place where there is a significant cross-equatorial current – the south-to-north South Equatorial current (north of the equator becoming the Carribean current). Is this current connected with the North Atlantic drift, such that a weakening in the North Atlantic drift might also weaken the South equatorial current? Thus the South Atlantic may be keeping its warmth rather than exporting it across the equator.
I have suggested previously that the strength of the North Atlantic drift might correlate with the AMO – evidence for this includes Barents sea temperatures (to 150m) which correlate closely with the AMO (refer to the Levitus 2009 paper cited in this post):
http://wattsupwiththat.com/2009/10/08/new-paper-barents-sea-temperature-correlated-to-the-amo-as-much-as-4%C2%B0c/
Dave Springer says:
October 24, 2011 at 6:42 pm
I’ve been trying to tell people the answer to that question for a long time. The average temperature of the global ocean is 3.9C and the only possible way for it to get that way is for the average surface temperature to be 3.9C.
———————————————————————
You are not alone Dave, your statement reminded me of this interesting paper.
http://greenhouse.geologist-1011.net/
The Shattered Greenhouse: How Simple Physics Demolishes the “Greenhouse Effect”.
Timothy Casey B.Sc.(Hons.): Consulting Geologist
“Notwithstanding 100 years of apparently constant mean temperature from Arrhenius to Burroughs, we may determine that the observed temperature at the altitude corresponding to the centre of absorbing mass is 4ºC or 277ºK. This, via the reasoning above, extends to an observed average absorbing mass temperature for planet earth of 4ºC or 277ºK.”
Two entirely different approaches, T. Casey calculates the above from the absorbing portion of land mass, and air column, and you from logic, considering the average ocean temperature. The resulting agreement to within 0.1°C seems pretty amazing to a school dropout like me.
‘Or is their intent to have the unsuspecting public believe it?’
Bang on the money there, a good percentage perhaps even the majority of climate science is about the politics not the science. PR and headlines grasping , helped by a ‘friendly press ‘ , seems to be a standard consideration of research in this area .
Rick C,
Gotta a link for that?
phlogiston says: “So is Indian Ocean warming a side effect of La Nina?”
Glad you caught that. Sometimes I will leave observations unwritten in a post with hope that a reader will initiate a conversation. It was what I was trying to illustrate with the OHC animations included toward the bottom of the ARGO-era OHC post a couple of months ago:
http://bobtisdale.wordpress.com/2011/03/25/argo-era-nodc-ocean-heat-content-data-0-700-meters-through-december-2010/
You wrote: “You have previously pointed to the Atlantic as the only place where there is a significant cross-equatorial current…”
I hate to contradict you, but I discuss the North and South Equatorial Currents and the Equatorial Countercurrents in the Pacific as parts of ENSO posts.
You asked, “Is this current [the Caribbean Current] connected with the North Atlantic drift, such that a weakening in the North Atlantic drift might also weaken the South equatorial current?”
The Caribbean Current is part of the North Atlantic Gyre, while the North Atlantic Drift is an offshoot of the North Atlantic Gyre. Also, I would assume a change in the North Equatorial Current and South Equatorial Currents in the Atlantic would influence one another, though I’m not sure how strong the Equatorial Countercurrent is in the Atlantic. A couple of questions for you for your research: since the equatorial currents are wind driven, do the trade winds vary independently in the North and South Hemispheres or are they both driven primarily by ENSO? Local sea level pressures (weather) would impact them, but which is the primary driver?
You wrote, “Thus the South Atlantic may be keeping its warmth rather than exporting it across the equator. “
Or the ACC may have carried warm anomalies from the South Pacific to the South Atlantic or…
philip Bradley says: “Infrared penetration is irrelevant. The mechanism is that a warmer atmosphere impedes evaporation and therefore warms the oceans.”
Please supply links to papers that document this using observational data. Your hypothesis sounds very odd to me.