Are deep oceans the answer to the 'missing heat' question?
Most of us are probably aware of the "missing heat" - the fact that climate scientists can't account for where all of the global energy imbalance is going, which Kevin Trenberth called a "travesty". There have been suggestions that much of the heat is going into the deep oceans where we don't have adequate measurements.
Purkey & Johnson 2010 reconstructed ocean heat warming down to abyssal depths and found significant amounts of heat building up at the bottom of the ocean. http://journals.ametsoc.org/doi/abs/10.1175/2010JCLI3682.1
Now there's a new paper in press, "Deep ocean warming assessed from altimeters, Gravity Recovery and Climate Experiment, in situ measurements, and a non-Boussinesq ocean general circulation model", Song, Y. T., and F. Colberg (2011). http://www.agu.org/contents/journals/ViewPapersInPress.do?journalCode=JC
You need an AGU membership to read it, but here's the abstract:
Observational surveys have shown significant oceanic bottom-water warming, but they are too spatially and temporally sporadic to quantify the deep ocean contribution to the present day sea-level rise (SLR). In this study, altimetry sea surface height (SSH), GRACE ocean mass, and in-situ upper-ocean (0-700m) steric height have been assessed for their seasonal variability and trend maps. It is shown that neither the global mean nor the regional trends of altimetry SLR can be explained by the upper-ocean steric height plus the GRACE ocean mass. A non-Boussinesq ocean general circulation model (OGCM), allowing the sea-level to rise as a direct response to the heat added into the ocean, is then used to diagnose the deep-ocean steric height. Constrained by sea-surface temperature data and the top-of-atmosphere (TOA) radiation measurements, the model reproduces the observed upper-ocean heat content well. Combining the modeled deepocean steric height with observational upper-ocean data gives the full-depth steric height. Adding a GRACE-estimated mass trend, the data-model combination explains not only the altimetry global mean SLR but also its regional trends fairly well. The deep ocean warming is mostly prevalent in the Atlantic and Indian Oceans, and along the Antarctic Circumpolar Current, suggesting a strong relation to the oceanic circulation and dynamics. Its comparison with available bottom-water measurements shows reasonably agreement, indicating that deep-ocean warming below 700 m might have contributed 1.1 mm/year to the global mean SLR or one-third of the altimeter-observed rate of 3.11±0.6 mm/year over 1993-2008.
Basically it's consistent with Purkey and Johnson that there's a significant amount of heat somehow reaching the deep oceans. What do you think - is this the answer to the 'missing heat' question?
2011-01-14T12:17:03Z
FGR - same reason 'skeptics' made such a big deal about the 'missing hot spot', even though it's not an anthropogenic signal. They'll latch onto any possible argument that there could be anything wrong with the AGW theory. It doesn't have to make sense, the word "missing" is sufficient for them, just like "hide" in "hide the decline".
bob3262011-01-14T13:44:49Z
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Thanks for the heads up -- it looks like a fascinating study. From a quick glance it doesn't appear to be *the* answer to the "missing heat" question, but it's a start. I'll give it a proper read here a little later.
In searching your link for the Song&Colberg study I came across another paper on deep ocean warming by Kouketsu et al. titled, "Deep ocean heat-content changes estimated from observation and reanalysis product and their influence on sea level change." The abstract states:
"We calculated basin-scale and global ocean decadal temperature change rates from the 1990s to the 2000s for waters below 3000 m. Large temperature increases were detected around Antarctica, and a relatively large temperature increase was detected along the northward path of Circumpolar Deep Water in the Pacific. The global heat content (HC) change estimated from the temperature change rates below 3000 m was 0.8 × 1022 J decade−1; a value that cannot be neglected for precise estimation of the global heat balance. We reproduced the observed temperature changes in the deep ocean using a data assimilation system, and examined virtual observations in the reproduced data field to evaluate the uncertainty of the HC changes estimated from the actual temporally and spatially sparse observations. From the analysis of the virtual observations, it is shown that the global HC increase below 3000 m during recent decades can be detected using the available observation system of periodic revisits to the same sampling sections, although the uncertainty is large."
The heat content of 0.8*10^22 J/decade equates to roughly 0.04 Wm-2 at the TOA, which is significant but does not solve the missing heat problem. They do note in their conclusion that the measurements in the >3000 region are sparse and non-uniform, and ultimately call for more and better research into this area.
For starters the missing hot spot is an indication of a strong water vapour feedback. The fact that it is not there shows the climate system is not behaving the way the climate models say it should behave.
I doubt that the missing heat is store below 700m in the oceans. There are far too many uncertainties in measuring OHC below 700m. Plus you would also have to explain how it arrived from the top of the oceans to such a depth without leaving any signals as it passed through the layers of the oceans.
Lastly, the "missing heat" is a figment of Trenbreth's failed computer models. It is not there because his computer models of the earth`s energy imbalance is wrong.
"Considering that these calculations on which the TF analysis is based involve an explicit matching to the estimate of H one cannot possibly regard FTOA = 0.9 W/m2 as a purely empirical result without assigning error bars so large that the “missing energy” is lost in them. This is the basis of our opinion that missing energy is most likely an artifact due to the acceptance, or imposition, of the modeled value FTOA = 0.9 W/m2."
TF=(Trenberth and Fasullo (2010) Tracking Earth’s Energy, Science 328 p316-317.) H= Hansen et al. (2005) Earth’s Energy balance: Confirmation and implication, Science 308 1431-1435.)
The net inward energy flux at the top of the atmosphere (FTOC) has to almost equal to FOHC, the rate of change of ocean heat content. If there is a difference then there is an energy imbalance and thus missing energy. In order to believe that there is missing energy one has to believe that there is no uncertainties in the FTOC. But there are huge uncertainties with FTOC. The uncertainties in FTOA CERES values are estimated to be 2σ = 4.2 W/m2 [N. Loeb et al., J. Climate 22 (2009) 748].
One of the reason why climate scientists are certain that the FTOC value is correct is because Hansen calculated that value in 2005 and it matched historically the FOHC. But if you look at the OHC data there is a huge spike in OHC at the exact time when the method of calculating OHC was introduced. Alarms bells should always ring off when that happens. Josh Willis has said that there are many uncertainties in the pre Argo OHC data. So yes it does match, but given the huge uncertainties in the pre Argo OHC, one should not have too much confidence in this historical matchup.
First, I never can quite understand why everyone gets bugs in their pants about the "missing heat." The heat is going somewhere. Either out into space or into the oceans. We just have to figure out where and have the tools (and it was the lack of tools which trembath considered to be the tragedy) to verify.
Nailing the energy balance is only a secondary corroboration of the general warming trend. It is nice to have to satisfy some of the naysayers and it helps verify climate models.
That said using the thermal expansion of water is a reasonable way to deduce the temperature rise in the icy depth. Hard to get enough data points otherwise. So yes, this indicates the depths as the sink for the missing heat, but in of itself, I don't think the paper, based on the abstract, is sufficient. It needs to be corroborated.
Perhaps that is where the warmer waters come from during El Nino and therefore there is greater release of carbon dioxide during those periods of time which then forces the air temperature to increase.
The heat isn't missing, we just have not figured out where it has been going. The same goes for CO2 concentrations; we can measure the levels but we haven't figured out conclusively which forces which.
Considering our lack of information in the deep oceans and how the oceans do transport water vertically, having answers as to how much heat is stored down there will certainly help us account for the missing heat. I think these studies are definitely good starts, but like FGR said, it will need further research and corroboration, esp. to silence the deniers. Thanks for the heads-up.
(BTW, I find it hilarious that Richie in his "retort" question above said that he doesn't think the oceans are storing heat, because there's no evidence. Isn't that kind of what we're saying, that we don't have much information?)