Something Swirling in the Sea

January 20th, 2017 by Kathryn Hansen

Almost every volcano is interesting from a scientific perspective, but there are just too many eruptions for us to cover every single one. Instead we tend to focus on eruptions that have the potential to affect people. Or, occasionally our satellites return images that simply look so unique that we find the time to cover them. The plume recently ejected from Alaska’s Bogoslof Volcano was noteworthy for both reasons.

Bogoslof, which has been erupting since mid-December 2016, gave rise to a compelling two-tone plume. Are materials being ejected from a vent that is still under water? (Most of the volcano is below the surface of the sea.) The volcano’s interaction with seawater explains the white steam. But if the vent is not yet above water, then how did such a large, dark plume of ash reach so high in the atmosphere? Scientists at the Alaska Volcano Observatory continue to monitor the remote volcano and perhaps answers will be forthcoming as the eruption evolves.

Also intriguing are the swirls of blue visible in the image above. The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured the image on January 7, 2017. My first thought was that the color was caused by a bloom of phytoplankton. The milky blue color looked about right. And iron from eruptions have previously been shown  to provide the nutrients needed for blooms to flourish. But when I asked the experts, the general consensus was that while you can’t rule out a bloom, there was another more likely explanation for the swirls.

According to ocean scientist Norman Kuring of NASA’s Goddard Space Flight Center:

“Phytoplankton don’t normally bloom in the Bering Sea during winter because there’s not a lot of sunlight and because winter storms deepen the mixed layer which also keeps the plankton more in the dark. Wave action can resuspend bottom sediments, and that may be happening farther east along the Aleutian chain in the January 7 image where the water is relatively shallow. Bogoslof Island is beyond the shelf break, however, so bottom resuspension is less likely. Ash in the water seems most probable…. I wouldn’t expect the Bering Sea to be nutrient limited in the winter, so I don’t expect an ash-based phytoplankton boost.”

In short, the swirls are probably ash in the water. The phenomenon is not unprecedented. We have previously published images of the occurrence here and here. But as Kuring reminds us, “the only way to know for sure would be to sample the water directly.”

 

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One Response to “Something Swirling in the Sea”

  1. Daniel B Kester says:

    Good eye, Kathryn Hansen,

    Given the location of your anomaly, under the Northern Lights, is it possible that Earth’s magnetosphere has some influence on particles suspended in the water?
    I couldn’t begin to state accurately what the composition of volcanic as is, but, there are probably some metals in there. Perhaps gravity vs. magnetic pull +/- electronic charge of solar wind would contribute to these particles staying in a state of suspension rather than settling to the sea bottom…?

    OR, if the volcanic activity is under water, could this be condensation in the atmosphere above that heat source? That would be consistent with a plume of steam, but on a lower scale of emission due to heat generated/water depth ratio. It is possible, based on that theory, this would not be visible from the surface (horizontally). I would be only visible from above…

    I enjoyed your article!

    dan