Before the daily checks on the ice quality through MODIS starts for a new melt season, I surveyed the Laptev Sea for a weird scintillation pattern. I saw it first in ’12. The pattern returned in ’13.
For some reason, it wasn’t visible spring ’14. But this time it’s back.
I’ve found some geological survey maps that gave an idea of the interesting seabed in that region. After bringing a somewhat schematized version in CAD, I was able to locate the main scintillation zone. On the map below the ’12 pattern is contained within the complicated blue line. The hatched green swath shows the location on 31 March this year:
The orientation is taken from MODIS, with N in the lower left corner. In that corner the Gakkel Ridge is indicated. The continued tectonic force, originating in the diverging oceanbed plate boundary, stretches right into the Siberian mainland. A brush of rifts and horsts extends from Siberia into the deep Eurasian Basin.
A lot of these structures are covered by recent sedimentary deposits from the Lena and Yana rivers. Still, the scintillations seem to occur mainly over an old terrace that stretches right into the Yana river delta. The terrace is topped by a tundra soil about 12 to 15 m below present sea level. It was flooded some 9000 years ago.
My hypothesis is that, visible through the described geological situation, the scintillation indicates methane releases from the ancient tundra soil. The release is triggered by summer warming of the shallow sea. It continues right into the freezing season, scarring ice formation in ranges of circular features.
I won’t argue that the effect is anywhere close to the ‘burp’ that is at time to be expected from clathrate deposits along the continental slopes. It probably resembles the same process as tundra decomposition on land. It is an interesting detail within a larger phenomenon of methane release from most tundra areas.
Nevertheless, there’s a chance that the tectonic forces in this specific region may add to the loss of permafrost and might provide escape routes for deeper clathrate formations. That may be one of the origins for the methane vents that Semiletov and Shakhova have been reporting over the last couple of years.
I would welcome mapped information where they have actually seen these vents, as MODIS doesn't reveal them in ice free summer waters.