Today Perennially Puzzled Bob Tisdale is puzzled about ocean heat. Going by what he's written today (archived here), he knows less about ocean heat transport than I do. And I know very little about the subject.
This article isn't anything more than a bit of a hodge podge of material relating to ocean heat transport. It's prompted by Perennially Puzzled Bob's article. I'm aware that a lot of HotWhopper readers know a lot more about the subject than me, so feel free to point out errors or add to the discussion.
Bob Tisdale asks a (very long) question:
If Manmade Greenhouse Gases Are Responsible for the Warming of the Global Oceans……then why do the vertical mean temperature anomalies (NODC 0-2000 meter data) of the Pacific Ocean as a whole and of the North Atlantic fail to show any warming over the past decade, a period when ARGO floats have measured subsurface temperatures, providing reasonably complete coverage of the global oceans?
Let's have a look. Here is the ocean heat content with data from NODC/NOAA. First the change in ocean heat content in the different oceans and globally.
|Data source: NODC/NOAA|
|Data source: NODC/NOAA|
Let's move up and just look at the top 700 metres. Here is a chart tracking the heat content of the different oceans.
|Data source: NODC/NOAA|
|Data source: NODC/NOAA|
Most of the increased heat globally in the top 700 metres is down to the Indian Ocean heating up.
Back to Bob Tisdale's question:
...why do the vertical mean temperature anomalies (NODC 0-2000 meter data) of the Pacific Ocean as a whole and of the North Atlantic fail to show any warming over the past decade...
Bob expands on his question:
Or, in other words, why is the warming of the global oceans (0-2000 meters) over the past 10 years limited to the Indian and South Atlantic Oceans, when carbon dioxide is said to be a well-mixed greenhouse gas, meaning all ocean basins should be warming?
He seems to think that CO2 being a well-mixed greenhouse gas (which it is) means that everywhere on Earth will warm at the same rate. He's wrong. Air moves, oceans move, heat is transported around the world in different ways at different times.
The real question is "how does heat move around?" And more specifically in relation to the world's oceans: "how does heat move around in the oceans?". Bob seems to think that oceans heat up like this:
However the oceans have a life of their own. Think how deep 700 metres is, then think just how deep 2000 metres is. That's two kilometres or, for the metrically challenged, 1.24 miles. And it's all sea water. Water isn't static. The oceans aren't static. Water moves in the oceans.
I found this chart in a paper by Lynne Talley from Scripps, which is a simplified view of the global overturning circulation.
|Figure 1. Schematic of the global overturning circulation (“GOC”). Purple (upper ocean and thermocline), red (denser thermocline and intermediate water), orange (IDW and PDW), green (NADW), blue (AABW), gray (Bering Strait components; Mediterranean and Red Sea inflows). Updated from Talley et al. (2011), based on Schmitz (1995), Rahmstorf (2002), and Lumpkin and Speer (2007). Source: Talley 13.|
That's not the whole story by a long shot. But it gives some idea of how water moves within and between the different oceans, coming up for air (so to speak) and moving to depths. The Talley paper in Oceanography gives a lot of detail and is quite technical. If you're up for that level of discussion I can recommend it.
If you are new to the subject (like me) and want a simpler overview, I found a PowerPoint presentation that has some neat diagrams. It's a start. From that as I understand it, most of the heat transport between the oceans and the surface is wind-driven. At depth within the oceans it's a different story of course.
Here is some more information, which looks to be from a Columbia lecture. It describes directions of flows as well as the mechanisms of heat exchange:
Meridional heat and freshwater transfer: The ocean and atmosphere work together to move heat and freshwater across latitudes, as required to maintain a quasi-stationary climate pattern. The wind-driven and thermohaline ocean circulation accomplish this task for the ocean, by moving warm waters poleward, colder water toward the Equator. On average the ocean meridional heat flux is higher or at least equivalent to that of the atmosphere between the equator and 30° latitude, with the atmosphere becoming dominate at higher latitudes. Ocean currents of differing salinity also move freshwater from place to place to close the global hydrological budget. For example, salty water flows away from the evaporative subtropics to be replaced with lower salinity water from the tropics.
Fluxes across the sea-atmosphere interface: Heat exchange between ocean and atmosphere is a product of a number of processes: solar radiation heats the ocean; net long wave back radiation cools the ocean; heat transfer by conduction and convection between the air and water generally cools the ocean as does evaporation of water from the ocean surface
Any imbalance of the heat or freshwater budgets due to sea-atmosphere fluxes is compensated by transfer of heat and freshwater by ocean currents. Generally heat transport across latitudes is from the tropics to the polar regions, but in the South Atlantic Ocean the oceanic heat transport is directed towards the equator. This is due to the thermohaline circulation - as warm upper kilometer water is carried northward, across the equator, offsetting the southward flow of cooler North Atlantic Deep Water near 3000 m. Much of the heat lost to the atmosphere in the North Atlantic is derived from this cross equatorial heat transfer. The flux of freshwater in the North and South Atlantic is southward, as freshwater excess of the Arctic is brought into off set the net evaporation and influx of salty water from the Indian Ocean
If this is more than you bargained for, you can blame Bob Tisdale for prompting me to look into the topic with his dumb question at WUWT. I'd have thought he would know better given he's often going on about water moving around when he pontificates about ENSO. The odd thing is that Bob refers to some recent papers that go a fair way to explaining the accumulation of heat within the deeper ocean. Bob says the data shows differently, but he's wrong. Maybe he didn't understand the papers or maybe he did and he's counting on the fact that a lot of his readers won't bother reading them.
These are the papers Bob referenced:
The picture emerging is one where the positive phase of the PDO from 1976 to 1998 enhanced the surface warming somewhat by reducing the amount of heat sequestered by the deep ocean, while the negative phase of the PDO is one where more heat gets deposited at greater depths, contributing to the overall warming of the oceans but cooling the surface somewhat. The Paciﬁc Ocean appears to account for the majority of the decadal variability [Chen et al., 2008]. Nevertheless, the events in the Paciﬁc undoubtedly also affect the Atlantic, Indian, and Southern Oceans as the system acts collectively to equilibrate to these changes in the ﬂow of energy.I note that Bob only looks at the top 2,000 metres. (The deepest part of the Pacific is the Mariana Trench which goes down almost 11 kilometres at its deepest.) I don't know how far down in the Pacific Ocean the heat referred to by Trenberth and Fasullo gets to. But there sure is a lot of water in which heat can accumulate.
If you were expecting easy answers, I'm sorry. When it comes to quantifying every bit of heat and exactly how and where and when it moves through the Earth system it gets a bit tricky, especially when dealing with the deep ocean, which isn't easy to monitor directly. The scientists are doing a stellar job. Bob Tisdale and the denialati at WUWT not so much. (By the way, Bob Tisdale is a greenhouse effect denier too.)
From the WUWT comments
Phil's Dad thinks it might be underwater volcanoes and says:
December 19, 2013 at 3:35 am
Any idea why the Indian and South Atlantic are warming and the rest not? Volcanic chains?
Ronald says there are no such thing as ocean currents transporting water and heat and there is no such thing as thermohaline circulation:
December 19, 2013 at 4:56 am
Anomalies are nice but not the point. Heat is sitting in the ocean and heat is temperature just like cold and every thing in between. So warm water is heat and that cant go under cold water because of it being lighter than cold water. By giving it a fancy name it masks the problem of the case. And by doing so they cane take it a way from reality.
Dan points out that Bob's charts don't conflict with the papers from actual scientists (unlike Bob's questions and conclusions) and says:
December 19, 2013 at 5:23 am
You say that “Kevin Trenberth and associates say the recent series of La Niña events are causing the Pacific Ocean to warm at depths below 700 meters”.
Looking at your derived analysis of the 700-2000m depth temperatures, it would appear you are proving Trenberth to be correct, with a cooling surface and warming ocean underlayer. Is my understanding correct?
Correct me if I am wrong,from my understanding of Trenberth’s analysis, I think that the warming down to 2000m is insufficient to account for the anticipated energy imbalance, and hence it is hypothesised that the warming is also taking place at depths below 2000m?
Old'un goes off topic and all alarmist, saying that the shift to clean energy will be a killer:
December 19, 2013 at 7:07 am
...Sadly, blind belief in CAGW is already driving the UK down a calamitous path of high energy costs, deaths from fuel poverty and probable black-outs. To paraphrase John Maynard Keyne’s comment on stock markets, our leaders seem intent on remaining irrational for longer than the Nation will be able remain solvent.
Talley, L.D. 2013. Closure of the global overturning circulation through the Indian, Pacific, and Southern Oceans: Schematics and transports. Oceanography 26(1):80–97, http://dx.doi.org/10.5670/oceanog.2013.07