330
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
patterned ground structure of the valley are low centred ice-wedge polygons (compare Figure I
and Table 1).
The low centred ice-wedge polygons are characterized by two different microrelief sites: the
central depression, with a water table near or above the surface, and the high border, where the
water table is distinctly below the surface. Polygon diameters range between 6-25 m, about
33% of the area are polygon walls, 67% are polygon depressions (more informations about the
investigation area and the soil properties of the investigated ice-wedge polygons can be found in
Pfeiffer et ai, 1995; Gundelwein, 1998).
Table I: Soil description of a typical ice-wedge polygon, Lake Levinson Lessing (according to Soil Survey Stuff
1994)
PolYl:on wall {site 8):
Depth (cm)
0-06
06 - 45
> 45
PolYl:on del!ression {site 7):
Depth (cm)
0-02
02 - 06
06 - 35
> 35
Methods
Methane emissions
Horizon
Oi
Bg
Cf
Horizon
Oi
Oe
Bg
Cf
Description
slightly decomposed peat, black (7 .5YR2/I), platy structure.
loamy sand, yellowish gray (2.5Y5/1), <1 vol% rock fragments,
very strong rooted. Max. thawing depth: 45 cm.
loamy sand, boundary.
Description
slightly decomposed peat, black (7.5YR2/1), platy structure.
intermediate decomposed peat, black (IOYR2II), platy structure.
loamy sand, yellowish gray (2.5Y511), very strong rooted. max. thawing depth: 35 cm.
loamy sand, < I vol% rock fragments, ice lenses, permafrost
boundary.
Methane emissions are determined by using closed chamber technique in combination with a
small circulation pump and a trace gas analyzer (TGA). The TGA works on the basis of
photoaccustic infrared spectroscopy (TGA 1302 from Bruel and Kjaer Company, Denmark).
The chambers are sealed against the soil surface by setting on waterfilled, stainless steel
frames. The measurements are conducted every 90 seconds within a period of 15 to 30
minutes, so a high resolution is possible. TGA-results are compared with results of
gaschromatograph measurements in laboratory (1-4 ppm deviation).
Measurements are repeated 4-6 times a day in the center of the polygon area at a polygon
depression (site 7) and an polygon wall site (site 8). Additionally measurements are carried out
at 16 different sites (polygon walls and polygon depressions) within a transect through the river
Valley. The daily and seasonal variations were recorded and the variations between different but
similar patterned ground structures were monitored.
To determine the influence of different water tables on methane oxidation and emission a
special field experiment was done: the water table of a polygon polygon depression was
lowered in two steps from 1 em above to 18 cm below surface, the methane emission rates
being measured simultaneously.
Soil temperatures in 5, 10 and 20 em depth, thickness of active layer, water table, air pressure
and air temperature were monitored during every measurement.
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
patterned ground structure of the valley are low centred ice-wedge polygons (compare Figure I
and Table 1).
The low centred ice-wedge polygons are characterized by two different microrelief sites: the
central depression, with a water table near or above the surface, and the high border, where the
water table is distinctly below the surface. Polygon diameters range between 6-25 m, about
33% of the area are polygon walls, 67% are polygon depressions (more informations about the
investigation area and the soil properties of the investigated ice-wedge polygons can be found in
Pfeiffer et ai, 1995; Gundelwein, 1998).
Table I: Soil description of a typical ice-wedge polygon, Lake Levinson Lessing (according to Soil Survey Stuff
1994)
PolYl:on wall {site 8):
Depth (cm)
0-06
06 - 45
> 45
PolYl:on del!ression {site 7):
Depth (cm)
0-02
02 - 06
06 - 35
> 35
Methods
Methane emissions
Horizon
Oi
Bg
Cf
Horizon
Oi
Oe
Bg
Cf
Description
slightly decomposed peat, black (7 .5YR2/I), platy structure.
loamy sand, yellowish gray (2.5Y5/1), <1 vol% rock fragments,
very strong rooted. Max. thawing depth: 45 cm.
loamy sand, boundary.
Description
slightly decomposed peat, black (7.5YR2/1), platy structure.
intermediate decomposed peat, black (IOYR2II), platy structure.
loamy sand, yellowish gray (2.5Y511), very strong rooted. max. thawing depth: 35 cm.
loamy sand, < I vol% rock fragments, ice lenses, permafrost
boundary.
Methane emissions are determined by using closed chamber technique in combination with a
small circulation pump and a trace gas analyzer (TGA). The TGA works on the basis of
photoaccustic infrared spectroscopy (TGA 1302 from Bruel and Kjaer Company, Denmark).
The chambers are sealed against the soil surface by setting on waterfilled, stainless steel
frames. The measurements are conducted every 90 seconds within a period of 15 to 30
minutes, so a high resolution is possible. TGA-results are compared with results of
gaschromatograph measurements in laboratory (1-4 ppm deviation).
Measurements are repeated 4-6 times a day in the center of the polygon area at a polygon
depression (site 7) and an polygon wall site (site 8). Additionally measurements are carried out
at 16 different sites (polygon walls and polygon depressions) within a transect through the river
Valley. The daily and seasonal variations were recorded and the variations between different but
similar patterned ground structures were monitored.
To determine the influence of different water tables on methane oxidation and emission a
special field experiment was done: the water table of a polygon polygon depression was
lowered in two steps from 1 em above to 18 cm below surface, the methane emission rates
being measured simultaneously.
Soil temperatures in 5, 10 and 20 em depth, thickness of active layer, water table, air pressure
and air temperature were monitored during every measurement.