My Bookmarks on Science & Technology, Climate Change, Astrobiology, Genetics, Evolution

July 3, 2008 – Original Source: Dot Earth, The New York Times
By Andrew C. Revkin

It’s worth posting the voices of a few more scientists to address persistent questions here about a possible connection between retreating Arctic Ocean sea ice and seabed volcanic activity two miles below — including a Vesuvius-size eruption in 1999.

The bottom line? There is almost no chance of a significant influence, despite the huge outflow of heat and gases along the Gakkel Ridge, according to these scientists, including Robert Reves-Sohn of Woods Hole and Vera Schlindwein, a geophysicist at the Alfred Wegener Institute and one of the authors of the Nature paper that described the apparent explosive eruption. Ignatius Rigor of the University of Washington notes that the animation from the University of Colorado illustrating my earlier post — like his own ice studies — is a simulation drawing on limited buoy data, so specific features (like a transient blob of open water in 1999) are not cast in stone.

A good starting place is a YouTube video describing the volcanic activity in the area and the research there — narrated by Dr. Reves-Sohn, the lead author of the Nature paper. The video’s punchline may be disturbing to those who also worry that possible oil deposits in the Arctic Ocean seabed could spur a North Pole resource race. I’ll provide a hint at the end of this post.

Here’s what Dr. Reves-Sohn said, in an e-mail response to me and a batch of his colleagues I’d copied, after I asked them all whether there’s any chance of surface effects from such Arctic deep-sea eruptions. He says a brief disruption can’t be ruled out because satellite imagery from the period in 1999 when the volcano was most active is incomplete:

Once it became apparent that the 1999 seismic swarm at 85E on the Gakkel Ridge was associated with large volcanic explosions, and that the jets of hot gas and molten lava may have reached upwards well into the overlying water column, I began to search for satellite imagery of the region to see if there was any direct evidence that the overlying ice had been affected. I wasn’t thinking about a basin-wide phenomenon, as that doesn’t make sense from the standpoint of ocean physics (as several people have pointed out), but rather a localized effect.

Unfortunately, we did not have good satellite coverage of this region back in 1999. The situation seems to have improved somewhat subsequently, but back then the only satellite imagery I could find (with help from a friend who is an expert) was visible band imagery, and during the key time periods the 85E region of Gakkel was completely obscured by cloud cover. If we had had infrared or other bands that penetrate clouds, we might have had a shot at making a definitive observation. If anyone knows of existing satellite imagery that images the ice cover in our study region during the 1999-2000 time period, I would love to know about it.

My perspective is thus that on the basin-wide scale there is no chance that these volcanic eruptions/explosions had anything to do with changes in ice cover, for the reasons described by Peter Winsor et al. We do not know, however, if the events might have caused a small, localized disturbance to the overlying ice, because we do not have the observational evidence to say one way or the other, and because we simply do not understand the dynamical aspects of the explosive events well enough at this point. Most likely the explosions were not energetic enough to perturb the overlying ice, but we can’t say we know that for sure. We still have a lot to learn about this kind of explosive activity in the deep-sea.

Best regards, Rob

Dr. Schlindwein sees almost no chance of surface disruption from the eruptions:

I am currently working on a reconstruction of the Gakkel volcanic episode from 1999-2007 integrating seismicity data and water column observations and I have started to look at sea ice images as well. We know pretty well when the 1999 eruption took place; it will be easy to check for effects on the sea ice. I doubt there will be such effects:

In 2001, the volcano at 85E was still erupting explosively, although in a less vigorous mode (Schlindwein et al., GRL, 2005). The associated event plume in the water column is well surveyed and described in Edmonds et al. (Nature 2003). That plume of relatively “warm” water – temperature anomaly less than 1/10 degree – reaches a minimum water depth of about 1700 m, its center being around 2500 m water depth. These data make it very evident that the sea ice is not influenced by the heat released from the ongoing eruption.

Peter Winsor of Woods Hole
also provided more detail on why he sees no chance of changes in sea ice from the volcanism far below:

The 1999 event was still visible in CTD profiles [a sequence of measurements of water conductivity, temperature, depth] in 2007 along the Gakkel Ridge as a thin layer (50-200 m thick) with slightly warmer temperatures (~0.01 – 0.001 C warmer). The layer is at about 2600 m depth, some 600-800 m off the sea floor and has some particles in it (just barely detectable).

Heated water from such events rises vertically and mixes with ambient waters much like a smoke stack in winter until they reach equilibrium density with surrounding water masses at which they spread out horizontally. We have solid measurements that this water spread out horizontally around ~2600 m depth.

As Jamie [Morison] mentioned, water at 300 m depth is much warmer, has a greater heat content and is continuously present but is still on average unable to contribute to any larger heat flux to the underside of the ice, due to the strong stratification of the upper Arctic. Any resemblance of weaker ice cover in 1999 over the Gakkel area is purely coincidental, nothing else.

There is one thread that can still offer hope to those insisting that there must be some surface consequence from all that deep heat, and it comes from Igor Polyakov of the University of Alaska, Fairbanks. He said some Russian colleagues mentioned another possible incident in the 1990s when Arctic surface ice seemed to change in relation to seabed volcanic activity. He has sent a query to scientists at the Arctic and Antarctic Research Institute in St Petersburg. Here’s what Dr. Polyakov told me:

I recall a seminar at AARI (St.-Petersburg, Russia) which happened many years ago (around 1995) , when an AARI scientist reported a peculiarity in central-basin ice cover which he associated with volcano activity. Similar to what you are talking. I remember that during the seminar people were skeptical but maybe this gentleman was right? [Dr. Polyakov said Wednesday night that a query is on its way….]

The punch line in Dr. Sohn’s video presentation relates to the huge deposits of metals that can form around hydrothermal vents…. Anyone up for an Arctic Rush?


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