Methane Content in Ground Ice and Sediments of the Kara Sea Coast

Irina Streletskaya,Dmitry Streletskiy,Alexander Vasiliev,Gleb Oblogov

doi:10.3390/geosciences8120434

Irina Streletskaya, Dmitry Streletskiy + Show 2 more

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https://doi.org/10.3390/geosciences8120434

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Abstract

Permafrost degradation of coastal and marine sediments of the Arctic Seas can result in large amounts of methane emitted to the atmosphere. The quantitative assessment of such emissions requires data on variability of methane content in various types of permafrost strata. To evaluate the methane concentrations in sediments and ground ice of the Kara Sea coast, samples were collected at a series of coastal exposures. Methane concentrations were determined for more than 400 samples taken from frozen sediments, ground ice and active layer. In frozen sediments, methane concentrations were lowest in sands and highest in marine clays. In ground ice, the highest concentrations above 500 ppmV and higher were found in massive tabular ground ice, with much lower methane concentrations in ground ice wedges. The mean isotopic composition of methane is −68.6‰ in permafrost and −63.6‰ in the active layer indicative of microbial genesis. The isotopic compositions of the active layer is enriched relative to permafrost due to microbial oxidation and become more depleted with depth. Ice-rich sediments of Kara Sea coasts, especially those with massive tabular ground ice, hold large amounts of methane making them potential sources of methane emissions under projected warming temperatures and increasing rates of coastal erosion.

Highlights

Methane emissions from permafrost are one of the topics requiring immediate attention due to potential significant implications to the Arctic and global climate system [1]
Some studies speculated that methane emissions due to subsea permafrost degradation can significantly effect the climate [2,3], while others suggest that even under the most extreme scenarios, methane release from subsea permafrost will have little to no effect on the state of the climate [4]
This paper presents data on methane content and distribution in permafrost, active layer and ground ice collected in coastal exposures of Kara Sea region

Summary

Introduction

Methane emissions from permafrost are one of the topics requiring immediate attention due to potential significant implications to the Arctic and global climate system [1]. Due to the divergent views, methane content in permafrost regions requires further investigation as general lack of field data adds to uncertainty of timing and magnitude of methane emissions from both terrestrial and subsea permafrost regions. The methane emissions from permafrost of a shelf of the East Siberian Arctic seas are expected due to high organic content of the sediments [8,9,10,11,12,13,14,15]. Not all permafrost affected soils are characterized by high methane content. Sediments of marine and lacustrine genesis of Western Siberia which were freezing epigenetically (after sedimentation ceased) are generally characterized by high

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