Sub-permafrost methane seepage from open-system pingos in Svalbard
<p>Methane release from beneath lowland permafrost represents an important uncertainty in the Arctic greenhouse gas budget. Our current knowledge is arguably best developed in settings where permafrost is being inundated by rising sea level, which means much of the methane is oxidised in the w...
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doaj-b4c7751474f84f94b7022d0fc13e8fbf2020-11-25T04:01:24ZengCopernicus PublicationsThe Cryosphere1994-04161994-04242020-11-01143829384210.5194/tc-14-3829-2020Sub-permafrost methane seepage from open-system pingos in SvalbardA. J. Hodson0A. J. Hodson1A. Nowak2M. T. Hornum3M. T. Hornum4K. Senger5K. Redeker6H. H. Christiansen7S. Jessen8P. Betlem9S. F. Thornton10A. V. Turchyn11S. Olaussen12A. Marca13Department of Arctic Geology, University Centre in Svalbard (UNIS), 9171 Longyearbyen, NorwayDepartment of Environmental Science, Western Norway University of Applied Sciences, Røyrgata 6, 6856 Sogndal, NorwayDepartment of Arctic Geology, University Centre in Svalbard (UNIS), 9171 Longyearbyen, NorwayDepartment of Arctic Geology, University Centre in Svalbard (UNIS), 9171 Longyearbyen, NorwayDepartment of Geosciences and Natural Resource Management, University of Copenhagen, 1350 Copenhagen K, Copenhagen, DenmarkDepartment of Arctic Geology, University Centre in Svalbard (UNIS), 9171 Longyearbyen, NorwayDepartment of Biology, University of York, York, YO10 5DD, UKDepartment of Arctic Geology, University Centre in Svalbard (UNIS), 9171 Longyearbyen, NorwayDepartment of Geosciences and Natural Resource Management, University of Copenhagen, 1350 Copenhagen K, Copenhagen, DenmarkDepartment of Arctic Geology, University Centre in Svalbard (UNIS), 9171 Longyearbyen, NorwayDepartment of Civil and Structural Engineering, University of Sheffield, Sheffield, S10 2TN, UKDepartment of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, UKDepartment of Arctic Geology, University Centre in Svalbard (UNIS), 9171 Longyearbyen, NorwaySchool of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK<p>Methane release from beneath lowland permafrost represents an important uncertainty in the Arctic greenhouse gas budget. Our current knowledge is arguably best developed in settings where permafrost is being inundated by rising sea level, which means much of the methane is oxidised in the water column before it reaches the atmosphere. Here we provide a different process perspective that is appropriate for Arctic fjord valleys where local deglaciation causes isostatic uplift to out pace rising sea level. We describe how the uplift induces permafrost aggradation in former marine sediments, whose pressurisation results in methane escape directly to the atmosphere via groundwater springs. In Adventdalen, central Spitsbergen, we show how the springs are historic features responsible for the formation of open-system pingos and capable of discharging brackish waters enriched with high concentrations of mostly biogenic methane (average 18 <span class="inline-formula">mg L<sup>−1</sup></span>). Thermodynamic calculations show that the methane concentrations sometimes marginally exceed the solubility limit for methane in water at 0 <span class="inline-formula"><sup>∘</sup></span>C (41 <span class="inline-formula">mg L<sup>−1</sup></span>). Year-round emissions from the pingos are described. During winter, rapid methane loss to the atmosphere occurs following outburst events from beneath an ice blister. During summer, highly variable emissions occur due to complex surface processes at the seepage point and its inundation by surface runoff. In spite of this complexity, our observations confirm that sub-permafrost methane migration deserves more attention for the improved forecasting of Arctic greenhouse gas emissions.</p>https://tc.copernicus.org/articles/14/3829/2020/tc-14-3829-2020.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
A. J. Hodson A. J. Hodson A. Nowak M. T. Hornum M. T. Hornum K. Senger K. Redeker H. H. Christiansen S. Jessen P. Betlem S. F. Thornton A. V. Turchyn S. Olaussen A. Marca |
spellingShingle |
A. J. Hodson A. J. Hodson A. Nowak M. T. Hornum M. T. Hornum K. Senger K. Redeker H. H. Christiansen S. Jessen P. Betlem S. F. Thornton A. V. Turchyn S. Olaussen A. Marca Sub-permafrost methane seepage from open-system pingos in Svalbard The Cryosphere |
author_facet |
A. J. Hodson A. J. Hodson A. Nowak M. T. Hornum M. T. Hornum K. Senger K. Redeker H. H. Christiansen S. Jessen P. Betlem S. F. Thornton A. V. Turchyn S. Olaussen A. Marca |
author_sort |
A. J. Hodson |
title |
Sub-permafrost methane seepage from open-system pingos in Svalbard |
title_short |
Sub-permafrost methane seepage from open-system pingos in Svalbard |
title_full |
Sub-permafrost methane seepage from open-system pingos in Svalbard |
title_fullStr |
Sub-permafrost methane seepage from open-system pingos in Svalbard |
title_full_unstemmed |
Sub-permafrost methane seepage from open-system pingos in Svalbard |
title_sort |
sub-permafrost methane seepage from open-system pingos in svalbard |
publisher |
Copernicus Publications |
series |
The Cryosphere |
issn |
1994-0416 1994-0424 |
publishDate |
2020-11-01 |
description |
<p>Methane release from beneath lowland permafrost represents an
important uncertainty in the Arctic greenhouse gas budget. Our current
knowledge is arguably best developed in settings where permafrost is being
inundated by rising sea level, which means much of the methane is oxidised
in the water column before it reaches the atmosphere. Here we provide a
different process perspective that is appropriate for Arctic fjord valleys
where local deglaciation causes isostatic uplift to out pace rising sea
level. We describe how the uplift induces permafrost aggradation in former
marine sediments, whose pressurisation results in methane escape directly to
the atmosphere via groundwater springs. In Adventdalen, central
Spitsbergen, we show how the springs are historic features responsible for
the formation of open-system pingos and capable of discharging brackish
waters enriched with high concentrations of mostly biogenic methane (average
18 <span class="inline-formula">mg L<sup>−1</sup></span>). Thermodynamic calculations show that the methane
concentrations sometimes marginally exceed the solubility limit for methane
in water at 0 <span class="inline-formula"><sup>∘</sup></span>C (41 <span class="inline-formula">mg L<sup>−1</sup></span>). Year-round emissions from the pingos
are described. During winter, rapid methane loss to the atmosphere occurs
following outburst events from beneath an ice blister. During summer, highly
variable emissions occur due to complex surface processes at the seepage
point and its inundation by surface runoff. In spite of this complexity, our
observations confirm that sub-permafrost methane migration deserves more
attention for the improved forecasting of Arctic greenhouse gas emissions.</p> |
url |
https://tc.copernicus.org/articles/14/3829/2020/tc-14-3829-2020.pdf |
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