Changes in thermal structure of permafrost active layer in a dry polar climate, Petuniabukta, Svalbard
Abstract: The relationships between meteorological conditions, permafrost active layer thickness and thermal structure were studied for a dry, polar climate site, next to Petunia− bukta (central Spitsbergen), during four successive summer seasons (2000–2003). In addi− tion to determination of the gr...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.620.509 http://www.polar.pan.pl/ppr29/PPR29-261.pdf |
| Summary: | Abstract: The relationships between meteorological conditions, permafrost active layer thickness and thermal structure were studied for a dry, polar climate site, next to Petunia− bukta (central Spitsbergen), during four successive summer seasons (2000–2003). In addi− tion to determination of the ground sedimentological and mineralogical properties, the fol− lowing parameters were measured: air temperature, air humidity (both at 2 m and 0.05 m above the ground), wind direction and velocity (at 2 m), precipitation, cloudiness, thickness of the permafrost active layer and ground temperature at 0.05, 0.1, 0.25, 0.5 and 0.75 m be− low the surface. The permafrost level was lowered 0.7 to 1.1 cm day−1 during days with tem− perature above freezing, reaching a maximum depth of 1.2 m. The temperature of the top 0.1 m of the ground reacted within one to two days to changes in air temperature. The reac− tion period of the ground temperature at 0.5 m was several days. Rainfall events were of mi− nor importance to thermal ground structure, in contrast to sites with a more marine climate. Other meteorological factors had a very small influence on the ground temperature. During summer, a well developed thermal gradient reaching over 12C m−1 was observed, followed by isothermal conditions with temperature of 0C at the beginning of fall, and reversal of the thermal gradient (−6.7C m−1) in late fall. The interannual variations were mainly due to changes in summer temperature and to the length of period with snow cover in spring, which limited the beginning of thawing. The thermal structure of active layer is governed by seasonal conditions, regardless of overall climatic change. |
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