Spatio-temporal Evolution Of A Thermokarst In Interior Alaska

摘要

Landscape modifications in Arctic and subarctic regions due to warming climate conditions have been reported in recent years. This work describes the rapid development of a thermokarst in Interior Alaska over a two-year period. The research was conducted in the Caribou-Poker Creeks Research Watershed, the only research watershed in the United States underlain by discontinuous permafrost. The basin's coordinates are 65°10' N latitude and 147°30' W longitude. Within the short span of two warm summers, a portion of the study area progressed from a hummocky terrain to a well-defined channel configuration. Suspended sediment concentration and discharge measurements indicated high sediment loads following rainfall events, which play a major role in the study area's sediment transport process. Fluvio-thermal erosion detected in late spring of 2004 triggered block failures on the thermokarst's sides. The spatio-temporal evolution of a cryogenic pipe was documented during the second summer. Water flow inside the pipe caused high erosion in the soil matrix. Eroded soil sediment was transported and deposited downstream, creating a fairly smooth bed slope. Topographical surveys conducted during the two field seasons revealed an average erosion rate of 3.5 m/year.