From Dr. Roy Spencer’s Global Warming Blog
by Roy W. Spencer, Ph. D.
I sometimes see comments to the effect that recent ocean warming could be due to deep-sea hydrothermal vents. Of course, what they mean is an INCREASE in hydrothermal vent activity since these sources of heat are presumably operating continuously and are part of the average energy budget of the ocean, even without any long-term warming.
Fortunately, there are measurements of the heat output from these vents, and there are rough estimates of how many vents there are. Importantly, the vents (sometimes called “smokers”) are almost exclusively found along the mid-oceanic ridges, and those ridges have an estimated total length of 75,000 km (ref).
So, if we had (rough) estimates of the average heat output of a vent, and (roughly) know how many vents are scattered along the ridges, we can (roughly) estimate to total heat flux into the ocean per sq. meter of ocean surface.
Direct Temperature Measurements Near the Vents Offer a Clue
A more useful observation comes from deep-sea surveys using a towed sensor package which measures trace minerals produced by the vents, as well as temperature. A study published in 2016 described a total towed sensor distance of ~1,500 km just above where these smokers have been located. The purpose was to find out just how many sites there are scattered along the ridges.
Importantly, the study notes, “temperature anomalies from such sites are commonly too weak to be reliably detected during a tow“.
Let’s think about that: even when the sensor package is towed through water in which the mineral tracers from smokers exist, the temperature anomaly is “too weak to be reliably detected”.
Now think about that (already) extremely weak warmth being mixed laterally away from the (relatively isolated) ocean ridges, and vertically through 1,000s of meters of ocean depth.
Also, recall the deep ocean is, everywhere, exceedingly cold. It has been calculated that the global-average ocean temperature below 200m depth is 4 deg. C (39 deg. F). The cold water originates at the surface at high latitudes where it becomes extra-salty (and thus dense) and it slowly sinks, filling the global deep oceans over thousands of years with chilled water.
The fact that deep-sea towed probes over hydrothermal vent sites can’t even measure a temperature increase in the mineral-enriched water means there is no way for buoyant water parcels to reach up several kilometers to reach the thermocline.
Estimating The Heat Flux Into the Ocean from Hydrothermal Vents
We can get some idea of just how small the heat input is based upon various current estimates of a few parameters. The previously mentioned study comes up with a possible spacing of hydrothermal sites every ~10 km. So, that’s 7,500 sites around the world along the mid-oceanic ridges. From deep-sea probes carrying specialized sampling equipment, the average energy output looks to be about 1 MW per vent (see Table 1, here). But how many vents are there per site? I could not find a number. They sampled several vents at several sites. Let’s assume 100, and see where the numbers lead. The total heat flux into the ocean from hydrothermal vents in Watts per sq. meter (W m-2) would then be:
Heat Flux = (7,500 sites)x(100 vents per site)x(1 MW per vent)/(360,000,000,000,000 sq. m ocean sfc).
This comes out to 0.00029 W m-2.
That is an exceedingly small number, about 1/4,000th of the 1 W m-2 estimated energy imbalance from Argo float measurements of (very weak) ocean warming over the last 20 years or so. Even if the estimate is off by a factor of 100, the resulting heat flux is still 1/40th of global ocean heating rate. I assume that oceanographers have published some similar estimates, but I could not find them.
Now, what *is* somewhat larger is the average geothermal heat flux from the deep, hot Earth, which occurs everywhere. That has a global average value of 0.087 W m-2. This is approximately 1/10 of the estimate current ocean heating rate. But remember, it’s not the average geothermal heat flux that is of interest because that is always going on. Instead, that heat flux would have to increase by a factor of ten for decades to cause the observed heating rate of the global deep oceans.
Evidence Ocean Warming Has Been Top-Down, Not Bottom-Up
Finally, we can look at the Argo-estimate vertical profile of warming trends in the ocean. Even though the probes only reach a little more than half-way to the (average) ocean bottom, the warming profile supports heating from above, not from below (see panel B, right). Given these various pieces of evidence, it would difficult to believe that deep-sea hydrothermal vents — actually, an increase in their heat output — can be the reason for recent ocean warming.
Atmospheric sulfur dioxide is a pretty good proxy for the measurement of the variation of global Volcanism in longitudinal averages , (one surface eruption can peak SO2 in a big way). The problem is much of the SO2 of volcanism is absorbed by water because volcanism far more submarine than surface. One massive submarine volcanic region in the Pacific can generate enormous heat and very little atmospheric SO2 and yet acidify the ocean regionally.
So the ability to develop a grid of regional submarine volcanism using the metrics of gravitational variance, ocean acidification, Sea surface anomaly, currents etc might help but non-volcanistic ambient geothermal heating of the oceans remains the confounding factor.
the recent ocean warming ??? … as measure by what ?? the handful of moving thermometers in the ocean ? ..
the idea that you can cite a global ocean temperature with a straight face is amazing …
if the land based thermometers have siting issues (which are huge) what makes you think the ocean thermometers are any better ?
when you start with a flawed assumption (i.e. that we know how much global ocean temperatures have changed) trying to determine how it occurred is a silly exercise …
Premise is incorrect.
That references on one type of heat release from tectonics, volcanic, magmatic near surface exposures.
e.g, hot springs are known worldwide, yet ignored when considering oceanic influence. Entire bodies of freshwater are warmed by hot springs, yet for the ocean, crickets.
e.g. 2, hot springs are not single isolated occurrences. Entire states and adjoining states have hot springs spread over vast area. e.g., California, Oregon, Washington, Utah, Nevada, Arizona, Montana, Wyoming have abundant hot springs that bubble CO₂ and utterly fail to resemble smokers.
Heck, Pennsylvania, West Virginia and Virginia have hot springs as do most countries worldwide.
The real question is why hasn’t this been researched before?
Another example are the direct magma and lava flows into the sea, e.g., Hawaii, Iceland, Surtsey and many undersea volcanoes which carry significant geothermal heat to oceanic water.
All of those red dots showing volcanic activity along and near the Ring of Fire are direct and immense heat sources. Many are intermittent and quite a few are nearly continual.
A third example are magmatic emplacements near the surface. One release of this are the smokers you refer to, as is the immense land surface of geysers in Yellowstone as well as geysers worldwide.
Returning to the smokers topic, anyone who believes they have “estimated” their total is is pushing CH4 out their orifice. Neither the length, scale or scope of the Ring of Fire has ever been investigated.
Bluntly, the entire concept of oceanic water geothermal has been ignored and even now, downplayed as minimal, without evidence.
Being the climate science spectator (and low level social scientist) that I am. I have frequently asked the questions, “what is the relationship of earth’s core heat contribute to sea surface and atmospheric temperatures?’. ‘And has anyone measured the it’s variation and made correlations with other variables like the sun?’. I generally get smacked down with highly abstract and theoretical responses that conclude; none!
Yet there is no permafrost below my feet in PA nor is the seafloor anywhere on planet earth solid ice.
So in reality no one really knows how much heat is transferred ambiently through the crust into the oceans and atmosphere, nor it’s variation over time.
Relevance: We live in a world where our reality about who we are and the existential risks we face is being focused and shaped around one variable: consuming humanity. I think this is the greatest risk of human civilization. It is far better for human civilization to be organized around questions like “how do we make better stuff”, even “how do we get people to want stuff they don’t need” even “what has God said?”, than ask the question, ‘how do we reduce consumption in order to or by reducing the consuming masses?’.
This is why science is more important now than ever. Sea levels, Ocean acidification, Ocean heat, Sea ice are all points of contention in the description of how the consuming masses are putting themselves and the well being of the earth’s entire ecosystem at risk
A one variable science is no science; it’s propaganda, which is fundamentally a political and/or market tool. Yet it motivates science to answer scientific questions using actual science, in order to keep the propagandists honest and protect consuming humanity from those who want to consolidate it and rule it all.
Clearly regional variation in sea ice, sea acidification, sea surface temperature, sea level are related to multiple variables. The two primary heat sources are the Sun and the Earth itself. Macro measures like global atmospheric temperatures etc., will not help us see the variation of these ocean related variables at the regional level.
Regional variabilities and anomalies in sea ice melting, sea surface temperature, acidification (heat and submarine SO2 emissions) and sea level. point to regional heat anomalies. Ambient geothermal heating and volcanistic heating are pertinent variables to measure. Longitudinal monitoring of a sample of volcanic vents to measure global variation in volcanism maybe helpful especially if paired with gravitational variance at the crust level and seamount (submarine volcanic) level……in longitudinal time frames.
For example, if a gravitational anomaly develops under a region of an ocean, and in the same region the geothermal vents show and increase in heat output, a sea surface heat anomaly emerges with increased acidification in the same region and the resulting sea surface heat anomaly is being carried by current to a area of sea ice, then it can be demonstrated without equivocation that a variation in the emission of the earth’s heat is melting a region of sea ice. The ability to demonstrate that a region of sea ice is melting due to a regional increase in geothermal heating of the ocean is essential. Regional sea level anomalies in heat, acidification, and sea level could be investigated in the same way.
The key is to have a long term monitoring of the earth’s gravitational variance at both micro and macro scales at least for 3-4 solar cycles. My guess is if either or both the GRACE or GOCE Satellite projects were able to prove human civilization is causing accelerated sea level increases we would have ongoing continuous gravitational variance vigilance. Furthermore, we may even have a bigger piece in the puzzle in understanding how to predict earthquakes, if they are predicable… we just don’t know.
Hallo JC
I’m pretty confident that I have uncovered the mechanism that makes it possible for the small geothermal flux to have a major influence on Earths temperature.
I hope everybody will agree that the very high temperatures in deep mines are of geothermal origin, although the flux through continental crust is a mere ~65 mW/m^2
Sun only warms the upper 10-20 m of the crust.
For the wet 70% of Earths surface basically the same is true. Geothermal flux through oceanic crust is ~100 mW/m^2. Water warmed at the ocean floor has a lower density and will rise to the depth with matching density. The solar heated mixed surface layer makes it (almost) impossible to rise to the surface.
The surface temperature is the result of temperature of the deep ocean temp. plus what the sun can add, considering the daily and yearly warming and cooling cycles. This is the reason that the sun can NOT heat the oceans below 200-300 m.
Atmosphere only reduces the energy loss to space, NO warming of the surface by cold air.
https://tallbloke.wordpress.com/2014/03/03/ben-wouters-influence-of-geothermal-heat-on-past-and-present-climate/