lAnnual CycleActive Layer DepthConc

lAnnual CycleActive Layer DepthConclusionsSurface-Atmosphere exchange mechanisms are critical to understanding changes in Arctic Environment.Tiksi Arctic Observatory has a micrometeorological flux tower and is equipped with 5 surface heat flux plates, 2 active layer thermistor strings and severalsets of soil temperature sensors in various closely spaced (30 m) locations. Because of the inhomogeneity of the surface in the vicinity of the tower, thisplacement of sensors allow comparison of the seasonally varying temperature structure for sites with different active layer moisture content.In this study we focus on the fall freeze-up period beginning with the onset of continuous air freezing temperatures below 0C at the surface, followed by azero curtain period, and ending with the declining temperatures at the top of the permafrost. The term zero curtain refers to the effects of latent heatmaintaining soil temperatures near 0ºC over an extended period until freezing (or thawing) of the water in the active layer is complete.We analyze the influence of morphological characteristics on the occurrence and duration of zero-curtain effect (such as active layer thickness and, soilwater content) and the consequent spatial variation observed by the Tiksi sensors