Geochemical evidence for seabed fluid flow linked to the subsea permafrost outer border in the South Kara Sea

Petr Semenov, Alexey Portnov, Alexey Krylov, Alexander Egorov, Boris Vanshtein

Research output

1 Citation (Scopus)

Abstract

Driven by rising bottom water temperatures, the thawing of subsea permafrost leads to an increase in fluid flow intensity in shallow marine sediments and results in the emission of methane into the water column. Limiting the release of permafrost-related gas hydrates and permafrost- sequestered methane into the global carbon cycle are of primary importance to the prevention of future Arctic Ocean acidification. Previous studies in the South Kara Sea showed that abundant hydro-acoustic anomalies (gas flares) induced by seafloor gas discharge into the water column occur in water whose depth is ≥20 m. This distribution of gas flares could indicate the outer extent to which continuous permafrost restricts upward fluid flow. This paper reports on a geochemical analysis of a 1.1 m long sediment core located in an area of shallow fluid flow off of the Yamal Peninsula coast (South Kara Sea) using high-resolution seismic data. Our results reveal a thin zone of Anaerobic Oxidation of Methane (AOM), a sharp shallow sulfate-methane transition (SMT) located at a sub-bottom depth of 0.3 m, and significant temporal variation in methane discharge confirmed by the pyrite (FeS 2 ) distribution in the core sample. A concave up pore water chloride profile depicts upward fresh/brakish water advection in subsurface sediments. The terrestrial/fresh water genesis of methane from the sampled core is deduced from the stable isotopic signatures (δ 13 C and δD). We propose two mechanisms for the observed fluid flow: i) convection of thaw water from subsea permafrost; and/or ii) lateral sub-permafrost ground water discharge marking the outer extent of continuous permafrost off of the central Yamal Peninsula coast at ˜45 m water depth.

Original languageEnglish
JournalChemie der Erde
DOIs
Publication statusPublished - 1 Jan 2019

Fingerprint

permafrost
Permafrost
borders
fluid flow
Flow of fluids
Methane
methane
Water
fresh water
sediments
water depth
peninsulas
coasts
Sediments
water
flares
Gases
water column
gases
gas

Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

Cite this

@article{01b8fe9bdca845108f384e5e0c104c23,
title = "Geochemical evidence for seabed fluid flow linked to the subsea permafrost outer border in the South Kara Sea",
abstract = "Driven by rising bottom water temperatures, the thawing of subsea permafrost leads to an increase in fluid flow intensity in shallow marine sediments and results in the emission of methane into the water column. Limiting the release of permafrost-related gas hydrates and permafrost- sequestered methane into the global carbon cycle are of primary importance to the prevention of future Arctic Ocean acidification. Previous studies in the South Kara Sea showed that abundant hydro-acoustic anomalies (gas flares) induced by seafloor gas discharge into the water column occur in water whose depth is ≥20 m. This distribution of gas flares could indicate the outer extent to which continuous permafrost restricts upward fluid flow. This paper reports on a geochemical analysis of a 1.1 m long sediment core located in an area of shallow fluid flow off of the Yamal Peninsula coast (South Kara Sea) using high-resolution seismic data. Our results reveal a thin zone of Anaerobic Oxidation of Methane (AOM), a sharp shallow sulfate-methane transition (SMT) located at a sub-bottom depth of 0.3 m, and significant temporal variation in methane discharge confirmed by the pyrite (FeS 2 ) distribution in the core sample. A concave up pore water chloride profile depicts upward fresh/brakish water advection in subsurface sediments. The terrestrial/fresh water genesis of methane from the sampled core is deduced from the stable isotopic signatures (δ 13 C and δD). We propose two mechanisms for the observed fluid flow: i) convection of thaw water from subsea permafrost; and/or ii) lateral sub-permafrost ground water discharge marking the outer extent of continuous permafrost off of the central Yamal Peninsula coast at ˜45 m water depth.",
keywords = "Anaerobic oxidation of methane, Kara Sea, Methane, Permafrost, Pore water",
author = "Petr Semenov and Alexey Portnov and Alexey Krylov and Alexander Egorov and Boris Vanshtein",
year = "2019",
month = "1",
day = "1",
doi = "10.1016/j.chemer.2019.04.005",
language = "English",
journal = "Chemie der Erde",
issn = "0009-2819",
publisher = "Elsevier",

}

Geochemical evidence for seabed fluid flow linked to the subsea permafrost outer border in the South Kara Sea. / Semenov, Petr; Portnov, Alexey; Krylov, Alexey; Egorov, Alexander; Vanshtein, Boris.

In: Chemie der Erde, 01.01.2019.

Research output

TY - JOUR

T1 - Geochemical evidence for seabed fluid flow linked to the subsea permafrost outer border in the South Kara Sea

AU - Semenov, Petr

AU - Portnov, Alexey

AU - Krylov, Alexey

AU - Egorov, Alexander

AU - Vanshtein, Boris

PY - 2019/1/1

Y1 - 2019/1/1

N2 - Driven by rising bottom water temperatures, the thawing of subsea permafrost leads to an increase in fluid flow intensity in shallow marine sediments and results in the emission of methane into the water column. Limiting the release of permafrost-related gas hydrates and permafrost- sequestered methane into the global carbon cycle are of primary importance to the prevention of future Arctic Ocean acidification. Previous studies in the South Kara Sea showed that abundant hydro-acoustic anomalies (gas flares) induced by seafloor gas discharge into the water column occur in water whose depth is ≥20 m. This distribution of gas flares could indicate the outer extent to which continuous permafrost restricts upward fluid flow. This paper reports on a geochemical analysis of a 1.1 m long sediment core located in an area of shallow fluid flow off of the Yamal Peninsula coast (South Kara Sea) using high-resolution seismic data. Our results reveal a thin zone of Anaerobic Oxidation of Methane (AOM), a sharp shallow sulfate-methane transition (SMT) located at a sub-bottom depth of 0.3 m, and significant temporal variation in methane discharge confirmed by the pyrite (FeS 2 ) distribution in the core sample. A concave up pore water chloride profile depicts upward fresh/brakish water advection in subsurface sediments. The terrestrial/fresh water genesis of methane from the sampled core is deduced from the stable isotopic signatures (δ 13 C and δD). We propose two mechanisms for the observed fluid flow: i) convection of thaw water from subsea permafrost; and/or ii) lateral sub-permafrost ground water discharge marking the outer extent of continuous permafrost off of the central Yamal Peninsula coast at ˜45 m water depth.

AB - Driven by rising bottom water temperatures, the thawing of subsea permafrost leads to an increase in fluid flow intensity in shallow marine sediments and results in the emission of methane into the water column. Limiting the release of permafrost-related gas hydrates and permafrost- sequestered methane into the global carbon cycle are of primary importance to the prevention of future Arctic Ocean acidification. Previous studies in the South Kara Sea showed that abundant hydro-acoustic anomalies (gas flares) induced by seafloor gas discharge into the water column occur in water whose depth is ≥20 m. This distribution of gas flares could indicate the outer extent to which continuous permafrost restricts upward fluid flow. This paper reports on a geochemical analysis of a 1.1 m long sediment core located in an area of shallow fluid flow off of the Yamal Peninsula coast (South Kara Sea) using high-resolution seismic data. Our results reveal a thin zone of Anaerobic Oxidation of Methane (AOM), a sharp shallow sulfate-methane transition (SMT) located at a sub-bottom depth of 0.3 m, and significant temporal variation in methane discharge confirmed by the pyrite (FeS 2 ) distribution in the core sample. A concave up pore water chloride profile depicts upward fresh/brakish water advection in subsurface sediments. The terrestrial/fresh water genesis of methane from the sampled core is deduced from the stable isotopic signatures (δ 13 C and δD). We propose two mechanisms for the observed fluid flow: i) convection of thaw water from subsea permafrost; and/or ii) lateral sub-permafrost ground water discharge marking the outer extent of continuous permafrost off of the central Yamal Peninsula coast at ˜45 m water depth.

KW - Anaerobic oxidation of methane

KW - Kara Sea

KW - Methane

KW - Permafrost

KW - Pore water

UR - http://www.scopus.com/inward/record.url?scp=85064283053&partnerID=8YFLogxK

U2 - 10.1016/j.chemer.2019.04.005

DO - 10.1016/j.chemer.2019.04.005

M3 - Article

AN - SCOPUS:85064283053

JO - Chemie der Erde

JF - Chemie der Erde

SN - 0009-2819

ER -