Archive for the ‘Arctic’ Category

Robert Sohn of Wood’s Hole: the 1999 Arctic seafloor volcanic explosions are NOT responsible for rapid sea ice melting

July 2nd, 2008 2 comments
In personal email correspondence with me, geophysicist Robert A. Sohn, the lead scientist on the international team that reported last week about powerful explosive volcanic activity in 1999 in the deep Arctic Ocean seafloor has strongly rejected the wild speculation – thrown up by Investors Business Daily (“Are Volcanoes Melting Arctic?“) and  rapidly picked up by the gullible “skeptical” blogosphere – that such volcanic activity has any responsibility for the recent disturbingly rapid summer melting and thinning of the Arctic Ocean sea ice.
Science journals and other news services last week ran stories last week about the June 26, 2008 report in prestigious Nature magazine about the July 2007 Arctic Gakkel Vents Expedition (AGAVE), financed by the U.S. National Science Foundation and NASA, to explore a region of the deep (4 kilometers below the Arctic Ocean) and remote Gakkel Ridge, a portion of the largely unexplored mid-ocean ridge system that runs through the Arctic Ocean and which was the site of seismic activity in 1999.  Rob Sohn, of the Woods Hole Oceanographic Institution, led the expedition and was lead author on the paper, along with 21 co-authoring scientists from nine institutions in four countries. 
The expedition found evidence of apparently “spectacularly” large explosive volcanic eruptions, at depths previously thought impossible.  According to one report, Sohn said that “These are the first pyroclastic deposits we’ve ever found in such deep water, at oppressive pressures that inhibit the formation of steam, and many people thought this was not possible,” and that “This means that a tremendous blast of CO2 was released into the water column during the explosive eruption.” 
According to another report, Sohn, who is an expert on mid-ocean ridges, said: “The scale and magnitude of the explosive activity that we’re seeing here dwarfs anything we’ve seen on other mid-ocean ridges,” that the volume of gas and lava that appears to have blasted out of the Gakkel volcanoes is “much, much higher” than that seen at other ridges (“Jets or fountains of material were probably blasted one, maybe even two, kilometers up into the water”), and that “it is a good thing there is four kilometers of seawater on top of the Gakkel Ridge as the eruptions would have been ‘highly problematic’ had they occurred on dry land”.
This is the information that has quickly been spun rather wildly – especially as some noted that Arctic sea ice began to thin more rapidly since 1999 –  even though a responsible observer would have noted that the international team stated that such explosions have been part of “a widespread, and ongoing, process”, and “The scientists say the heat released by the explosions is not contributing to the melting of the Arctic ice, but Sohn says the huge volumes of CO2 gas that belched out of the undersea volcanoes likely contributed to rising concentrations of greenhouse gases in the atmosphere. How much, he couldn’t say.”
In response to queries by commenters at the New York Times “Dot Earth” blog, an July 1 Andy Revkin posted a brief survey of scientists regarding what Andy called an “eruption of assertions” that the recent startlingly rapid summer melting and thinning of Arctic Ocean sea ice might be due not to climate change but to “all the heat from the recent discovered volcanoes peppering the Gakkel Ridge, one of the seams in the deep seabed”. 
Andy’s post (“What’s Up With Volcanoes Under Arctic Sea Ice“) and the questions of commenters prompted me to do a bit of digging on my own.  Fortunately, I was able to get ahold of Rob Sohn, to whom I directly the following questions
Perhaps you might care to weigh in on the discussion re: the 1999 eruptions?
In particular:
  • how much CO2 was released? 
  • would any/a significant portion of the CO2 released gone directly to the surface?
  • was the release reflected in atmospheric CO2 measurements?
  • how high did the debris column likely go?
  • would it be possible that any of the heat released would have created a column of hot water significantly light enough to rise to the surface?
  • even if not, could such a below surface hot spot have slowed downward heat flux, producing a greater upward heat flux?

 In response, Rob stated:

Tom, we are still trying to figure out how much CO2 was released – not an easy question given that we got to the scene of the crime long after the CO2 was gone. We are also still trying to understand the dynamical aspects of the explosions in terms of what happened in the overlying water column.

We doubt that the events perturbed the overlying pack ice because of the incredible damping from 4 km of water between the volcanoes and the ice. At most we believe the explosive plume reached about halfway through the water column, but there may have been some transient heat flux to the underside of the ice right above the volcanoes.

One thing that is certain, however, is that these events were not capable of causing any significant melt-off on the basin scale. Some have asserted that these events are linked to the diminishing ice cover in the Arctic, and that simply cannot be true.  Wishful thinking, perhaps, but not grounded in scientific fact.

In any case we need to do a lot more work to understand these explosions and their impact on the water column and surrounding seafloor, and the fact they are located in the remote Arctic is a big problem.

Thanks for your interest in my research.


(emphasis added)

Personal communication; July 2, 2008.

It sounds to me that Rob, while noting that this and other deep sea volcanic activity is CANNOT be responsible for any significant melting of Arctic sea ice, that it might be possible that the massive 1999 eruptions had a “transient” local effect.

[UPDATE:]  In a follow up email, I asked Rob “What do you think happened to the CO2 though – could a substantial portion have bubbled directly to the surface?  I imagine this is a question that you’ll get from others, too.”

Rob responded:

Tom, unfortunately it takes a while to answer these questions. The first step is to estimate the amount of CO2 that was discharged. We are working on that, and I hope to have decent estimates by end of summer. Then we have to try and understand how this CO2 (and other volcanic products) interacts with the overlying water column. …. Our paper last week has touched off a lot of interest inside the scientific community, and I believe it will help stimulate the necessary research. But it will all take time.

I can see how it would be frustrating for the public because it takes a lot longer to answer the key questions than it does to formulate them. Federal funding for this kind of basic research has been stagnant and in many cases declining, which makes it all the harder to advance the field.  One possible positive side effect of all the interest we’ve generated
would be to increase awareness about the need for this kind of research.

Best regards, Rob