East Siberian Shelf methane
LAPTEV SEA WORKSHOP
The Russian research estimates that methane venting to the atmosphere from the ESAS "is on par with previous estimates of methane venting from the entire World Ocean." There is potentially an enormous amount of methane below the ESAS. "Remobilization to the atmosphere of only a small fraction of the methane held in East Siberian Arctic Shelf (ESAS) sediments could trigger abrupt climate warming."
A Laptev Sea science workshop in 2010 confirms the extreme danger of East Siberian shelf subsea floor methane.
Subsea permafrost in the Central Laptev Sea H Kassens et al
The Arctic comprises some of the most sensitive elements of the global environment, which are considered to respond rapidly to climate change.The north Siberian margin today is comprised of a permafrost landscape that has undergone major changes during Quaternary times.
Moreover, there is evidence from modern data that the stability of the permafrost is in threat due to global warming. Such a change of the permafrost in the future is of major climatic relevance, considering a potential release of gas hydrates that are now trapped in the frozen ground.
During ensuing postglacial global sea-level rises the region gradually changed from a terrestrial permafrost landscape into shallow marine shelf environments.
Geochemical, micropaleontological, and sedimentological data obtained through sediment coring and drilling not only reveal the strong influence of this transformation process on the shelf environment for the time since the last glacial period, they also clearly confirm the existence of permanently frozen, and ice-bearing sediments below a soft, marine sediment package of Holocene age.
Geochemical studies on subsea permafrost of the Western Laptev Sea S Wetterich et al
The coring reached a maximal depth below sea level (b.s.l.) of 77 m n the core C2 located furthest from the coast (~12km from the coast). Borehole temperature logging showed increasing ground temperatures seawards from about -12 °C in C1 on land up to -1 °C in the marine cores, pointing to thermal
degradation of relict terrestrial permafrost under marine influence. Hydrochemical and stable water isotope data from ground ice in ice-bonded deposits or from pore water in cryotic deposits reveal clear evidence for chemical degradation of relict terrestrial permafrost under subsea conditions.
The marine influence acts downwards via conductive heat transfer, via pressure-gradient and via concentration-gradient diffusion of warm, saline and isotopically heavy sea water into the ground. Accordingly, relict terrestrial permafrost shows low ionic contents (measured as electrical conductivity, EC)
that increase under marine influence to values much more than 10 mS cm-1. The respective stable water isotopes (δ18O, δD) of relict terrestrial permafrost are generally lighter than -15‰ for δ18O and -150‰ for δD. In all four marine cores, the infiltration of marine waters into underlying former terrestrial permafrost following the Holocene sea transgression is mirrored by abrupt shifts in hydrochemical and stable isotope parameters in transition zones between degrading and non-degraded permafrost
Subsea permafrost at the Buor Khaya Peninsula, Eastern Laptev Sea PP Overduin et al.
Thermal abrasion of coastlines can lead to thermal destabilization of permafrost by inundation. This is a concern, since warming of subsea permafrost may
mobilize carbon stored in or beneath the permafrost, including gas hydrates of greenhouse gases. The predicted response of coastal erosion to increased
summer air temperatures, thermokarst subsidence, increased sea-water temperatures and reduced sea ice extent will lead to more rapid inundation of
terrestrial permafrost. We investigate subsea permafrost in the near-shore zone of the western coastline Buor Khaya Peninsula in the Laptev Sea, a zone
strongly influenced during the open water season by the Lena River ... nearshore zone and the rate of degradation of the top of the ice-bearing permafrost.
Initial observations from the field suggest that a relatively steep shoreface profile is underlain by a rapidly
degrading ice-bearing permafrost table. Electrical conductivity, depth and temperature of the water were measured over the course of a summer storm event. The storm shifted water beneath the halocline shoreward, resulting in episodic step changes in bottom water temperature and salinity closer to shore.
Satellite images before and after the storm show its effectiveness in suspending material in the near-shore zone.
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