Influence of fire events on permafrost, Yubileynoe Gas Field, West Siberia
Abstract
The study area is located in the Subarctic region of Western Siberia at Nadym and Pur Rivers interfluve. The mean monthly air temperature of the coldest month is -25…-27oC and of the warmest month is 8…10oC. The mean annual air temperature is increasing at 0.03…0.06oC per year. The mean annual precipitation is 550…600 mm. The continuous permafrost up to 50-70 m thick have temperature of -1..-3oC. The study site is located 40 km west of Noviy Urengoy City. The study site is dominated by typical forest-tundra, where the cup-mossy larch-birch light forests neighbors with typical tundra, and the boreal fir-larch forest spread across minor river valleys. Ecosystems of the study area experience strong technogenic stress from the large gas-producing enterprise "Yubileinoe" which is situated nearby. A polygonal peatland with 2-2.5 m peat at the southern bank of Nashe-to Lake was disturbed by fire in July, 2005. The fire event lasted for 2 days have burned vegetation dominated by semifrutex, sedges, mosses, and underlaying peat. Following years the succession rates were rather slow. The peatland surface is elevated relative to the surrounding drained lake basin (hasyrey) and free of snow in winter. After the disturbance of the thermo-insulating layers (peat, moss and vegetation cover) the activation of frost-cracking was observed, especially strong at completely burnt areas on sandy loam. The second site of the hasyrey has experienced the fire in the middle of July, 2007. It is located within the plain watershed with drainage hollows. The Arctic birch, semifrutex and cup-mosses were dominating in the vegetation cover of hillocky tundra. The vegetation cover has experienced slow succession after the fire. In August, 2008, we found the semifrutex, sedges and cotton-grass growing sparsely between the burnt bare hillocks. The wetness of the territory increased. As a result of vegetation cover and mosses disturbance, the thermoinsulation have decreased and the frost cracks of 2007/08 winter were 5 m long and 2…5 cm wide. The thermal borehole located at the site reflected in the temperature changes after the fire event. Temperature changes at 10-30 m in 2006-07 were close to those observed in 2007-08. The temperature increase below 10 m depth (at and below the depth of the zero annual amplitudes) was 0.35oC at 10 m depth, 0.15oC at 15 m, and 0.02oC at 30 m depth. The disturbance of vegetation and peat layer and associated moisture increase allowed temperature fluctuations to penetrate deeper. The activation of frost cracking combined with the penetration of summer heat in grounds was evident.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.C13C0633G
- Keywords:
-
- 0702 CRYOSPHERE / Permafrost;
- 0768 CRYOSPHERE / Thermal regime