|Gravity gradient model, Mid-Atlantic Ridge; green dots are earthquakes of at least magnitude 5.5|
Credit: David Sandwell, SIO
There is a new paper in Science this week about the latest ocean topographic mapping effort. A team of researchers led by David T. Sandwell "combined new radar altimeter measurements from satellites CryoSat-2 and Jason-1 with existing data to construct a global marine gravity model that is two times more accurate than previous models." As the editor's summary stated:
Detailed topographic maps are available for only a small fraction of the ocean floor, severely limited by the number of ship crossings. Global maps constructed using satellite-derived gravity data, in contrast, are limited in the size of features they can resolve. Sandwell et al. present a new marine gravity model that greatly improves this resolution (see the Perspective by Hwang and Chang). They identify several previously unknown tectonic features, including extinct spreading ridges in the Gulf of Mexico and numerous uncharted seamounts.
|North Atlantic Ocean gravity gradient model showing plate tectonic history of rifting continents.|
Credit: David Sandwell, SIO
The paper indicated that this research will help improve the estimates of sea-floor depth in the 80% of the oceans having no depth soundings, and will greatly help scientists add to knowledge of ocean tectonic processes.
|Brittle stars and deep-sea corals cover |
a known seamount in the western Pacific Ocean.
The press release was also published at ScienceDaily.com.
The Hwang and Chang perspective mentioned in the editor's summary can be read here, though you might need a subscription to Science.
It's (not) undersea volcanoes
Whenever the topic of volcanoes under the ocean comes up, you're bound to get deniers claiming global warming is caused by undersea volcanoes. Or something along those lines. (The under-sea volcanoes notion isn't that uncommon, but it is pretty silly. It doesn't make the top 176 denier memes at SkepticalScience.com.)
A moment's reflection would stop this denier meme in its tracks. Deniers are not good at reflection.
Let's reflect on the question: is global warming or ocean acidification being caused by volcanoes? That's what Anthony Watts wonders today (archived here). He says to his readers:
One wonders how many of these newly found thousands of volcanic seamounts are producing CO2 that bubble into the ocean
Does he really wonder that or not? No-one but him probably knows because that's as far as his public wondering utterances went. He left it up to his readers to ponder and post their various comments.
Think about it. The press release that Anthony copied and pasted mentioned new discoveries of volcanic seamounts. These are mostly remnants of volcanoes.
First of all, a newly discovered seamount is not the same thing as a new seamount. The higher resolution mapping identified topographic features that were previously undetected. That's all. Most would have been there for a very, very long time.
Second of all. There is no suggestion in this work that there has been a very recent heightening of volcanic activity. Whether or not there is CO2 or anything else seeping from under the ocean, there is no reason to believe that it is any different now to what has been happening for the past thousands of years and lots of evidence that on balance, little has changed during the Holocene at least and probably much longer.
Thirdly. Even were there found to be some new volcanic activity under the ocean, or massive new source of sub-oceanic CO2, there would have to be an equally large CO2 sink that has yet to be discovered. People have calculated how much CO2 is going into the oceans, how much into land sinks and how much into the atmosphere. Plus how much has been created by humans burning fossil fuels. The sums balance pretty well. We can't pass the blame for global warming or ocean acidification onto volcanoes - above or below the ocean surface. It's us.
Fourthly. Gerlach (2011) reports that the total amount of CO2 from all volcanoes in the world averages somewhere between 0.13 to 0.44 billion tonnes a year, with a most likely range from 0.15 to 0.26 billion tonnes a year. We spew more than 35 billion tonnes a year. Volcanoes contribute barely a drop in the bucket compared to what we are adding. From the AGU:
On average, human activities put out in just three to five days the equivalent amount of carbon dioxide that volcanoes produce globally each year.
If you're interested in volcanoes in the context of global warming I recommend the Gerlach paper to start with. It has a lot of references for further reading. Terry Gerlach wrote about it at realclimate.org. There's also the USGS and AGU.
From the WUWT comments
At WUWT there is, as usual, a lot of nonsense with a few more knowledgeable comments thrown into the mix. Here's a non-representative sample.
Tim Ball confuses the source of CO2 emissions with the fact that once emitted, CO2 disperses through the troposphere and is a well-mixed greenhouse gas. For an ex-professor of any discipline, this level of ignorance is not funny:
October 2, 2014 at 4:19 pm
None of this is new. Some of us have been asking and writing about these issue for decades. The sad part is we were ignored by most, including many of the so-called skeptics.
CO2 escapes in large quantities not just from the crater but for 100s of square kilometres around the volcano. This is also detected on land based volcanoes but is effectively ignored, especially on Mauna Loa. Some of the early studies were done on Mt Etna. The porosity of the lava makes a considerable difference.
CO2 uniformly distributed in the atmosphere; what a joke, except it is not funny.
Gamecock has a bright idea. He should write a paper:
October 2, 2014 at 5:05 pm
Additionally, what impact do the undersea volcanoes have on the size of the ocean basin? Could the 1.9mm/year SLR be due to volcanoes?
Bill Taylor says he's been building straw men for years in an effort to persuade people that scientists don't know nuffin':
October 2, 2014 at 6:59 pm
as a layman i have tried to tell folks for decades that the earth spews forth gases and oil 24/7 has been doing so for eons……to claim that humans release of co2 has upset some delicate balance is utter IDIOCY………there is no delicate balance, there is a chaotic system seeking balance that can never be found……..
TRG is one of the very few who makes a reasonable point:
October 2, 2014 at 9:19 pm
If the increasing CO2 in the atmosphere is due to undersea volcanoes, does anyone have an explanation as to why it has been rising so smoothly and steadily all these years. I didn’t think so.
Sparks scoffs at the notion that atmospheric CO2 has been rising. And gets jumped on by all the informed WUWT-ers. Oops. No he doesn't.
October 2, 2014 at 9:25 pm
Rising? give some context as in capacity and potential? spill it genius!
Here's the spill for Sparks. Skip to the end to see CO2 over the past 800,000 years:
D. T. Sandwell, R. D. Muller, W. H. F. Smith, E. Garcia, R. Francis. "New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure." Science, 2014; 346 (6205): 65 DOI: 10.1126/science.1258213 DOI: 10.1126/science.1258213. (subs req'd)
Gerlach, Terry. "Volcanic versus anthropogenic carbon dioxide." Eos, Transactions American Geophysical Union 92, no. 24 (2011): 201-202. DOI: 10.1029/2011EO240001 (open access)