Feb 16 2012
Many thanks again to Anthony Watts for the opportunity to Guest Post at WUWT. There were a lot of great comments on my hypothesis that geothermal sources where the basis for the ENSO. Many who support the conventional wisdom said there was no proof of connections between ENSO cycles and earthquakes, etc. A valid point I was going to try and tackle. But I also received lots of links in the comments section to others with the same theory – and with far more work behind them.
When I looked into what has been done by others, I ran across an incredibly detailed analysis that answers most of the critics challenges. Before we get to the study, lets review more background information.
First off, there is a lot of tectonic activity in this region, including undersea hydrothermal vents, ocean ridge spreading and the nearby Galapagos hot spot:
The Galapagos hotspot has a very complicated tectonic setting. It is located very close to the spreading ridge between the Cocos and Nazca plates; the hotspot interacts with both plates and the spreading ridge over the last twenty million years as the relative location of the hotspot in relation to the plates has varied. Based on similar seismic velocity gradients of the lavas of the Carnegie, Cocos and Malpelos Ridges there is evidence that the hotspot activity has been the result of a single long mantle melt rather than multiple periods of activity and dormancy.
Clearly this area is home to an incredible diversity of geological structures. When reviewing the Cocos Plate material at Wikipedia, I ran across this study (pdf) that documents the history of the region. It is worth a read (its pretty short). In essence this region has it all: subduction zones, spreading zones and a hot spot (which created the Galapagos Islands).
So there is no doubt the region is geologically active. Put that one to rest.
I have to say, Anthony Watts picked the title of the post and zeroed in on my initial feeling this was all undersea volcanoes. But the fact is this region also has many known hydrothermal plumes, which look to be the more likely source of the cyclic nature of the ENSO. For example, the Medusa Vent was recently discovered in the region:
A new “black smoker” — an undersea mineral chimney emitting hot, iron-darkened water that attracts unusual marine life — has been discovered at about 8,500 feet underwater by an expedition currently exploring a section of volcanic ridge along the Pacific Ocean floor off Costa Rica.
Using Jason’s mechanical arms and a temperature probe, they logged water temperatures of 335 degrees Celsius (635 degrees Fahrenheit) at the vent’s opening.
In 1986, a large plume of hot, particle laden water approximately one million cubic meters in volume was discovered over the North Cleft segment of the Juan de Fuca Ridge. This plume was unique in its shape (horizontally and vertically symetric), size (100 km3) and rise height (~1km), indicating that an enormous volume of hot water had been released in a relatively short period of time.
The question is, how many plumes are there yet to be discovered? Now let’s focus in on that plume I highlighted in the previous post:
What I want folks to appreciate here is scale. Both physical scale and time scale. This hot post emerged in the 10/22/2008 data set and lasted for over 4 months! It is 100 meters below the surface and it is enormous. Here is a blow up of the hot spots with a size comparison overlayed (red circle) onto the Panama Isthmus:
This hot spot is 125-150 miles (200-240 km) wide! It dwarfs the mega plume referenced above. And it lasted for months, when it was then followed by an even larger plume. I went back to the Argo animation site and counted 14 plumes coming off this area from 2007 to 2012. That’s almost 3 mega plumes a year. And as stated before, it looks like more are coming off the coast of Panama and Peru, but are not being seen until they hit the surface (lack of Argo data in that area).
So far no one has explained how these mega plumes are caused by current and wind 100 meters below the surface. And I doubt they ever will.
Combining the 1st study linked above for this region to the mega plume work at Juan de Fuca Ridge, we begin to confirm the idea that these plumes are releasing vast amounts of heat into the ocean, which in turn effect the atmosphere (not the other way around).
One commenter stated there was no proven association between ENSO and geological activity. The study I discovered actually had references to other studies that had done this work already:
Increased seismic activity along the East Pacific Rise (EPR, Walker, 1988, 1995) and Juan de Fuca (Johnson et, al., 2001) ridges is known to precede increases in hydrothermal venting rates and corresponding SST temperature anomalies.
Going back to Juan de Fuca Ridge, which has been studied for many years, we find this:
Plotted along with the heat trend is the trend of the ratio of 3He to heat. The only source of 3He is from the degassing of magma. Early studies presumed that a 3He/Q ratio of ~0.1 units was “normal” for hydrothermal systems, …
Now this from the study on the Cocos Plate region:
Helium seawater profile data obtained during the World Ocean Circulation Experiment (WOCE) show high concentrations of Helium3 over trenches off the Mexican coast indicating increased hydrothermal venting activity within the trenches (Fig. 9). This particular profile from Pacific Marine Environmental Labs (PMEL) shows the largest anomalies directly over the trenches of the Mid-American Trench. The Galapagos rift just north of the Galapagos Islands has been a subject of study for nearly three decades by several groups (WHOI, PMEL, and RIDGE). This is the site of a documented mantle plume and there were several ongoing integrated site studies on hydrothermal vent systems.
Given all this supporting work (and there is more) I think we can conclude the following:
- The region in question is seismically active
- The region in questions is home to many hydrothermal vents, a hot spot and a spreading ocean ridge
- Studies do exist linking seismic activity to ENSO cycles
- The mega plumes discovered 100 meters down by the Argo data clearly form off the West Coast of Central and South America, and travel westward. And they are produced very regularly (not occasionally).
- The general flow of warm water is East to West (see here for animations at the surface, 100 m and 1000 m)
- Wind and waves can and do travel in different directions than the underlying currents
- The ocean floor is thin and cracked and we have a very limited understanding of how water and underlying magma interact on various scales.
We know less about the deep ocean that we do about the Earth facing side of the Moon. We only discovered Plate Tectonics within my lifetime, hydrothermal vents within my children’s short lifetimes. We are just beginning to explore the ocean’s geological wonders, which cover an area 3 times the size of the land surface of this planet.
All that is settled about science today is we still have a lot to learn, and what we know is still dwarfed by what we don’t know.
Some interesting background material:
- Nazca Plate
- Cocos Plate
- Statistical analysis of the El Niño–Southern Oscillation and sea-floor seismicity in the eastern tropical Pacific
- Hydrothermal Plumes Over Spreading-Center Axes: Global Distributions and Geological Inferences