Cryogenic displacement and accumulation of biogenic methane in frozen soils

Gleb Kraev, Ernst Detlef Schulze, Alla Yurova, Alexander Kholodov, Evgeny Chuvilin, Elizaveta Rivkina

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)

Abstract

Evidences of highly localized methane fluxes are reported from the Arctic shelf, hot spots of methane emissions in thermokarst lakes, and are believed to evolve to features like Yamal crater on land. The origin of large methane outbursts is problematic. Here we show, that the biogenic methane (δ13C ≤ -71h) which formed before and during soil freezing is presently held in the permafrost. Field and experimental observations show that methane tends to accumulate at the permafrost table or in the coarse-grained lithological pockets surrounded by the sediments less-permeable for gas. Our field observations, radiocarbon dating, laboratory tests and theory all suggest that depending on the soil structure and freezing dynamics, this methane may have been displaced downwards tens of meters during freezing and has accumulated in the lithological pockets. The initial flux of methane from the one pocket disclosed by drilling was at a rate of more than 2.5 kg C(CH4) m-2 h-1. The age of the methane was 8-18 thousand years younger than the age of the sediments, suggesting that it was displaced tens of meters during freezing. The theoretical background provided the insight on the cryogenic displacement of methane in support of the field and experimental data. Upon freezing of sediments, methane follows water migration and either dissipates in the freezing soils or concentrates at certain places controlled by the freezing rate, initial methane distribution and soil structure.

Original languageEnglish
Article number105
JournalAtmosphere
Volume8
Issue number6
DOIs
Publication statusPublished - 15 Jun 2017
Externally publishedYes

Keywords

  • Biogenic methane
  • Cryogenic migration
  • Freezing front
  • Freezing soils
  • Methane hydrates
  • Permafrost degradation
  • Transition layer
  • Yamal crater
  • Yedoma

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