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Methane emission peaks from permafrost environments : using ultra–wideband spectroscopy, sub-surface pressure sensing and finite element solving as means of their exploration

Pirk, Norbert (2009) In Lunds universitets Naturgeografiska institution - Seminarieuppsatser
Dept of Physical Geography and Ecosystem Science
Abstract (Swedish)
Metan är en effektiv växthusgas som har stor betydelse för det globala klimatet. Metanemissioner från
våtmarker med underliggande permafrost anses bidra väsentligt till dynamiken som styr koncentrationen av
metan i atmosfären på de nordliga breddgraderna.
Under nedfrysningen av marken hösten 2007 uppmättes ett stort utsläpp av metan vid en mätstation
på nordöstra Grönland. Mängden metan motsvarade den totala mängden emission som uppmättes under
hela sommarsäsongen. Denna rapport beskriver sökandet efter en förklaring till de oväntade mätningarna
av metan.
En mark-, vegetations- och atmosfärstransportmodell (SVAT), baserad på finita elementmetoden tillämpas för
att simulera metanemissioner med hjälp av lufttemperaturdata från... (More)
Metan är en effektiv växthusgas som har stor betydelse för det globala klimatet. Metanemissioner från
våtmarker med underliggande permafrost anses bidra väsentligt till dynamiken som styr koncentrationen av
metan i atmosfären på de nordliga breddgraderna.
Under nedfrysningen av marken hösten 2007 uppmättes ett stort utsläpp av metan vid en mätstation
på nordöstra Grönland. Mängden metan motsvarade den totala mängden emission som uppmättes under
hela sommarsäsongen. Denna rapport beskriver sökandet efter en förklaring till de oväntade mätningarna
av metan.
En mark-, vegetations- och atmosfärstransportmodell (SVAT), baserad på finita elementmetoden tillämpas för
att simulera metanemissioner med hjälp av lufttemperaturdata från Grönland under 2007. Laboratoriemetoder
utvecklas i vilka metanutsläpp från torvprov kontrolleras vid nedfrysning. För att kunna relatera det
potentiella utsläppet av metan till tryckansamling vid nedfrysning används trycksensorer. På ett annat
torvprov utförs mätningar med ultra wideband mikrovågor för att mäta gasdynamiken inuti provet utan
att tillföra yttre störningar.
Resultaten visar att SVAT-modellen inte lyckas producera ett emissionstopp då marken börjar att frysa.
Trots en markant ansamling av tryck under nedfrysningen, uppkommer inte ett metanutsläpp i experimentet
heller. Från torvprovet som behandlats utan yttre störningar, upptäcks istället en rad plötsliga metanutsläpp
då provet börjar tina. Dessa händelser registrerades väl i signalresponsen av de stimulerade mikrovågorna
samt i den uppnådda dielektriska permittiviteten. Volymen av gas, vatten och fast material bestäms med en
dielektrisk mixing modell. Resultaten visar att denna metod är användbar för mätning av rörelseprocesser
av gas i torv. (Less)
Abstract
Methane is an effective greenhouse gas of vital importance to global climate. Methane emissions from
permafrost dominated peatlands contribute significantly to the dynamics of the high-latitude atmospheric
methane concentration.
During the freezing period of autumn 2007 a large methane emission peak was recorded at a peatland in
northeast Greenland. The integral of this abrupt peak was equivalent to the emissions of the entire summer
season. The present work seeks to explain this unexpected methane burst.
A soil-vegetation-atmosphere transfer (SVAT) model based upon the finite element method is applied to
simulate the methane emission driven by air temperature data from Greenland 2007. Laboratory experiments
are developed in which... (More)
Methane is an effective greenhouse gas of vital importance to global climate. Methane emissions from
permafrost dominated peatlands contribute significantly to the dynamics of the high-latitude atmospheric
methane concentration.
During the freezing period of autumn 2007 a large methane emission peak was recorded at a peatland in
northeast Greenland. The integral of this abrupt peak was equivalent to the emissions of the entire summer
season. The present work seeks to explain this unexpected methane burst.
A soil-vegetation-atmosphere transfer (SVAT) model based upon the finite element method is applied to
simulate the methane emission driven by air temperature data from Greenland 2007. Laboratory experiments
are developed in which the methane emissions from peat samples are monitored as they freeze. In order
to relate the potential methane burst to the pressure build-up at freezing, sub-surface pressure sensors
are employed. On another sample ultra-wideband microwave measurements are performed to capture gas
dynamics inside the sample in a non-invasive manner.
It is found that a methane emission peak at the onset of freezing is not comprised in the SVAT model.
Despite a significant pressure build-up, the methane discharge at the onset of freezing does not appear in
the experiment either. Instead, a set of sudden methane bursts from the non-invasively treated sample are
detected at the onset of thawing. Their occurrence is well captured in the signal response of the stimulated
microwaves as well as in the attained dielectric permittivity. The volumetric content of gas, water and solid
material is determined by the use of a dielectric mixing model. The results demonstrate the feasibility of
ultra-wideband spectroscopy for gas movement processes in peat soils. (Less)
Please use this url to cite or link to this publication:
author
Pirk, Norbert
supervisor
organization
year
type
H1 - Master's Degree (One Year)
subject
keywords
finite element solving, permafrost, ultra-wideband spectroscopy, sub-surface pressure sensing, methane emission, physical geography, geography
publication/series
Lunds universitets Naturgeografiska institution - Seminarieuppsatser
report number
174
language
English
id
1857577
date added to LUP
2011-03-22 08:52:34
date last changed
2011-12-20 10:44:36
@misc{1857577,
  abstract     = {Methane is an effective greenhouse gas of vital importance to global climate. Methane emissions from
permafrost dominated peatlands contribute significantly to the dynamics of the high-latitude atmospheric
methane concentration.
During the freezing period of autumn 2007 a large methane emission peak was recorded at a peatland in
northeast Greenland. The integral of this abrupt peak was equivalent to the emissions of the entire summer
season. The present work seeks to explain this unexpected methane burst.
A soil-vegetation-atmosphere transfer (SVAT) model based upon the finite element method is applied to
simulate the methane emission driven by air temperature data from Greenland 2007. Laboratory experiments
are developed in which the methane emissions from peat samples are monitored as they freeze. In order
to relate the potential methane burst to the pressure build-up at freezing, sub-surface pressure sensors
are employed. On another sample ultra-wideband microwave measurements are performed to capture gas
dynamics inside the sample in a non-invasive manner.
It is found that a methane emission peak at the onset of freezing is not comprised in the SVAT model.
Despite a significant pressure build-up, the methane discharge at the onset of freezing does not appear in
the experiment either. Instead, a set of sudden methane bursts from the non-invasively treated sample are
detected at the onset of thawing. Their occurrence is well captured in the signal response of the stimulated
microwaves as well as in the attained dielectric permittivity. The volumetric content of gas, water and solid
material is determined by the use of a dielectric mixing model. The results demonstrate the feasibility of
ultra-wideband spectroscopy for gas movement processes in peat soils.},
  author       = {Pirk, Norbert},
  keyword      = {finite element solving,permafrost,ultra-wideband spectroscopy,sub-surface pressure sensing,methane emission,physical geography,geography},
  language     = {eng},
  note         = {Student Paper},
  series       = {Lunds universitets Naturgeografiska institution - Seminarieuppsatser},
  title        = {Methane emission peaks from permafrost environments : using ultra–wideband spectroscopy, sub-surface pressure sensing and finite element solving as means of their exploration},
  year         = {2009},
}