It is probable that I am wrong on this, but I am the sort that doesn’t take it personally when I am wrong, so why not ask the question that is in my head?
The EL Niño Southern Oscillation is pretty erratic in both warm and cold phases (El Niño and La Niña), in magnitude, in timing, and in duration. Four or five years ago I conjectured that some unknown heat source is the cause of it and that ENSO itself is just an intermediate step in the processing of huge amounts of heat energy in the equatorial Pacific. I speculated then if perhaps hydrothermal vents and/or undersea volcanoes could be the fundamental source of this heat energy. I considered this possible because of two reasons. First, I could not find any description of the causes of ENSO, just descriptions OF it – as if it just falls out of the sky each time, with no cause. Most articles seemed to assume IT was the cause. Yet its vast heat energy had to have come from somewhere, somewhere other than itself.
We do know that heat is coming up out of the vents, along with minerals that sustain weird life forms. The academic focus on these vents has been mostly centered on the sexy study of the life forms found at vents, plus studying the chemistry present and its potential benefits.
But I wondered then if the heat may be something to look at, too. No one seemed to be looking at that aspect.
The basic question was: Could the vents have irregular but somewhat cyclical heat output that has not been identified or connected with ENSO that might be underlying why and when El Niños occur?
(Even if this is wrong, it seems to me to be worth looking into it, if only to determine why it is wrong – to eliminate it as a possibility. Except no one else seemed to be even asking this question.)
Alternatively, could the ocean currents in the region vary in direction and thus direct the heat in different directions at different times (perhaps getting dispersed in some of those directions before any heat energy buildup occurs)?
Terrestrial Heat Flow
Today while looking for something entirely different, I ran across this image of four maps, with one of them being a heat flow map:
That map in the lower left really caught my attention. “Heat flow” here means the heat coming up from the Earth’s core and being able to be measured at the surface. That deep red at the edge of the Nazca tectonic plate is just about perfectly situated to be adding heat to the ocean right at the area where the El Niños begin. The upper end of it is very close to the eastern end of the El Niño phenomenon, right where the intersection is. The plate boundary going east from that intersection is called the Galapagos Rift. On most of the heat flow maps that rift seems to be where much of the heat is shown.
Two questions arise:
1. Is enough heat brought up there to affect the temperatures of the equatorial current?
2. Is it silly to think that the heat is cyclical?
As I understand it (and, folks, please educate me about this if you can) the existing theory of the El Niños involves the heat being sequestered by down-dwelling currents.
I went looking for more info on this, and it turns out there is an organization that keeps track of heat flow out of the Earth, the International Heat Flow Commission (IHFC). At their website I found this map, which in that region somewhat confirms the first heat flow map:
The IHFC has undertaken to maintain a database at http://www.heatflow.und.edu/ , which includes 23,000+ measured heat flow locations in the oceans. See this map for marine heat flow locations and values:
Okay, the image is no enlargeable, so go to the link to see it better. Note if you can that the range for the last colored (red) diamond is “180 to 500,000” ! The units are mW/m^2. Be aware that 500,000 mW/m^2 equals 500 watts/m^2. That is 50% MORE than the incoming solar radiation. Reason would argue that such a large number on that legend would not be there if there had not been at least one example with nearly that amount of heat flow.
The heat flow average for the northern hemisphere is 61.4 mW/m^2. The heat flow average for the southern hemisphere is much less, at 37 mW/m^2. (from http://geoscience.lngs.infn.it/Program/Pdf_presentations/Gosnold.pdf)
I am not a database guy, though I can do chart and basic linear analysis in Excel, but I could not do an analysis on this data because the 3D chart was limited to 4,000 data points. But I still tried to glean some information from the spreadsheet, anyway.
A sorting of the IHFC data showed that the area bounded by 77°W – 110°W and 0° – 5°N has a lot of data locations with MUCH higher heat flux than the average. And what I am positing is that perhaps this region has some very anomalous heat. And that is certainly born out by the data, though this region is not the only region that has VERY high heat flux coming out of the Earth. How high? Remember that the average heat flux in the northern hemisphere is 61.7 mW/m^2. The highest in this area is 8278 mW/m^2, with the following summary of of data locations with numbers higher than ANY in the southern Pacific, and all between 0 – 5°N and 77 – 110°:
- 3,000 to 8,278 – 5
- 2,000 to 3,000 – 4
- 1,000 to 2,000 – 30
- 334 to 999 – 194
All those 233 samples gave a mean of 0.756 W/m^2. That value is about 12 times as high as the average value for the northern hemisphere. Is that amount important? Is that amount large enough to cause an effect? Is it enough to sequester heat in Trenberth’s deeper ocean? (Perhaps the heat was already under the ocean instead of having to migrate to there. And keep in mind how small of a sample those 233 points represent, out of the IHFC’s total of . They are only a small portion of the points sampled even in that small area. Even the 2600 other less energy dense points still add heat above the average for the northern hemisphere.
BTW actually all of those locations were within an area bounded by 86° – 86°40′ and 0° – 0°55′. And the area is essentially ON the Equator – right where El Niño initializes.
Interestingly, the similar area south of the equator did not show very high values. The highest values of heat flux in the southern region down to 5°S is 333, and there are very few points measured so far, especially when compared to the area only 5° farther north. This suggests that whatever it is causing the heat flow numbers I see is itself close to the Equator but slightly north. The Galapagos Rift fits both ways: the Galapagos islands are essentially on the Equator and the rift is just north of the islands. They also happen to be measured with the highest heat flow, too. (More on the GR in a soon to come post.)
Readings evidently were not taken in close by areas, so there is presently no real way to determine how large of an area has such high heat flux values. Sampling was done at single points around the world, and though many readings were gotten there (and I do mean specifically ‘there’, as close as all those 243 measurements were taken to each other). So there would be a lot of hit or miss. And evidently no one has gone back to this area for a larger collection of data. All of those were done back in the late ’70s to the mid-’80s.
So, so far we seem to have a focused region of high heat flux coming out of the Earth itself, coincidentally at the place where the El Niño gets started with its large plume of heated surface water. And coincidentally near the Pacific Rise, where, like the Mid-Atlantic Ridge, heated magma is coming up and pressing the sides of the ridge away from each other.
Let’s look a little bit further…
At http://volcano.oregonstate.edu/book/export/html/140, I found this description:
New oceanic plates are created at mid-ocean ridges. About 2.4 cubic miles (10 cubic km) of new oceanic crust is added each year (not all of this magma is erupted by volcanoes). This is about 100 times the volume of lava erupted by Kilauea each year.
Mid-ocean ridges are divided into these groups based on their spreading rates:
- Slow: 1-5 cm/yr total opening rate
- Medium: 5-10 cm/yr total opening rate
- Fast: 10-20 cm/yr total opening rate…
…Fast-spreading mid-ocean ridges move 100-200 mm/yr. The East Pacific Rise is perhaps the best studied fast-spreading mid-ocean ridge. The ridge segment that creates the Nazca and Pacific plates moves up to 5.6 inches (142 mm) each year…
…At a fast-spreading mid-ocean ridge the magma supply rate is higher. This keeps the plates warmer and the crest of the rise does not subside.
So it just so happens that the Pacific Rise in the eastern Pacific is a fast spreading ocean ridge. One would expect from “fast spreading” and with a higher magma supply rate, that the amount of heat energy being released into the ocean water is at its highest at such places as the Pacific Rise.
Is it significant that the plates themselves also are kept warmer? Heat is heat, but is it enough?
That same site has some wonderful modeled images of the Pacific Rise. (Yes, beware of models…)
Heat Flow Diagram
Climatologist Kevin Trenberth’s top of atmosphere (TOA) heat flow diagram is shown here:
A recent paper Stephens et al 2012, The Global Character of the Flux of Downward Longwave Radiation, has revised some of the values based on more up-to-date empirical measurements:
Note the “sensible heat” flux out of the Earth itself is shown as 24 W/m^2. Then there is also latent heat of all the water evaporating, 88 W/m^2.
Trenberth shows a “Net Absorbed” of 0.9 W/m^2. Stephens shows a “Surface Imbalance” of 0.6 W/m^2. Theoretically there should BE no imbalance, not if it is a steady state planet.
If I am right in my figuring and my conjecture, this region is adding approximately the average of Trenberth and Stephens to the atmosphere above it. This would double the heat flow in that area.
Is that 0.76 W/m^2 enough to build up to an El Niño event?
If it is a matter of the currents changing, I have it on good authority that the ocean currents are driven by the wind. Do the winds anywhere nearby change directions from season to season and year to year? After all, the El Niño is named for the Christmas season, with El Niño being the baby Jesus. It is related to seasons, yes.
Does that mean that that explains it? NO. I am just tossing out an idea and hope to hear some constructive criticism. The idea may not hold water as it stands. But if it needs modification to get it right, I am all for that.
It DOES seem like the amount of terrestrial heat flow might be enough to trigger something, just in that area where the El Niño is known to rev itself up from time to time. Are they connected? That is my question.
I do NOT know enough about the currents and wind in that region and this story is long enough already. Perhaps if this idea isn’t completely bonkers I will attempt a sequel.