Monitoring of Active Layer and Permafrost Disturbances caused by “low frequency traffic” at Kapp Linné,– Svalbard, Norway. H. Jonas Åkerman1, Patrik Klintenberg2 & Patrik Bremborg3 1. Department of Earth and Ecosystem Sciences, Lund University, Lund, Sweden 2. Desert Research Institute of Namibia. Windhoek. 3. The Swedish Mapping, Cadastre and Land Registration Authority, Stockholm INTRODUCTION The active layer, has been monitored in the vicinity of Kapp Linne’, (78o03’42’’N, 13 o37’07’’E) Svalbard since 1972. These measurements are in the Circum Polar Active Layer Permafrost Monitoring (CALM) program. In addition to the long term monitoring program special case studies have been performed. Tractor traffic over an ice wedge polygon system have triggered and enhanced thermokarst processes. The mean active layer in the polygon area varies between 1,92m and 0,38m with the deepest in the exposed, well drained raised beach ridges and the shallow sites in the bogs. The summer mean air temperature 1972-2006 is +3,7oC. The average DDT is 399.6 oC. There is no clear over all trend in the summer climate during the monitoring period but a clear division between the period from 1972 to 1983, which had a decreasing summer temperature, and 1984 to 2004, which show an increase in the air temperature.
Fig. 1. Panorama of the investigation site, July, 1994. View towards S.
Fig. 5. Ice wedge of the same system, 300m S of the investigation site
CALM site AL1
Figure 4. The studied thermokarst is affecting a part of an ice wedge polygonal pattern. The large scale ice wedge polygonal pattern is found upon a beach ridge system which also have a soil wedge pattern developed in the active layer (Åkerman 1980). METHODOLOGY. The depth of the active layer has been monitored in a standard 100x100m site according to CALM methodology at CALM site AL3 less than 500 m from the site of the thermokarst (Fig. 4). Figure 4 and 5 show the simple procedure used for measuring Active layer depth and surface subsidence.
One exception is where tractor and snow scooter traffic over an ice wedge polygon system have triggered and enhanced thermokarst processes and disturbances in the vegetation cover. Generally for the area, the active layer variations during the investigation period have not yet reached a depth at which the ice wedges proper are influenced. The marginal is however only a few centimeters. However, at the site where the tractor tracks are passing the ice wedge system the surface disturbances have caused an increased active layer depth, a thawing of the ice rich layers, including the wedge ice, following surface subsidence and an accelerated thermokarst process. The process was clearly initiated during the increased “traffic” during installations works of a power line in 1974. After this initial period the thermokarst process has clearly followed the variations in the summer climate. This means a slowing down during the cooler summers in the 70-ties and early 80ties and an acceleration during the late 80-ties and 90-ties. The intensification is very clear for the last decade, with its warmer summers, and goes parallel with other observations of increased non-anthropogenic thermokarst activity in the area.
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Fig. 2. Position of the study area
Figure 6. Subsidence over the wedge caused by anthropogenic surface disturbances.
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Figure 7. Active layer depth at the nearby CALM bog site Al3.
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Fig. 3. The area around Kapp Linné. The Fyrsjöen catchment area is indicated. The study site is shown by a square. Air photo, NIR, by Norsk Polarisnstitutt, Aug. 18th 1990. Original scale 1:15 000
OBSERVATIONS. The observed changes in the depth of the active layer during the period 1984 -2006 show a good correlation with the summer climate (Fig. 7). There is also a good correlation the amount of soil water in the active layer - especially at the bog site and at the bottom of the active layer at the end of the summer. This is the case also at well drained raised beach ridges with areas of ice and soil wedges (Fig. 8). Signs of thermokarst are few in the flat strandflat area dominated by raised beach ridges. However the increasingly wet bog areas are slowly loosing a majority of the earlier rather common palsa like mounds (Åkerman 1980, 1982)
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Figure 8. Annual progression (1972-2000) of surface subsidence across the ice wedge polygon furrow inserted. (about 40cm/28year at the maximum). CONCLUSION. The thermokarst process was clearly initiated during the increased “traffic” during installations works of a power line in 1974. After this initial period the thermokarst process has followed the variations in the summer climate with an increased active layer depth but also a subsidence in the polygon furrow. REFERENCES Råheim E, (ed.) 1992. Registration of vehicular tracks on the Svalbard archipelago: Norsk Polarinstitutt, Oslo 1992 Richard, W.E. & Brown, J. 1974. Effect of Vehicles on Arctic tundra. Environmental Conservation nr. 1, vo.l 1 55-62. Lausanne CORRESPONDENCE:
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