CGRG Bibliography of Canadian Geomorphology
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Author : Hachem, S.; Allard, M.; and Duguay, C.R.
Date : 2006.
Title : Using MODIS Land Surface Temperature product to calculate active layer thickness of continuous permafrost.
Publication : 36th International Arctic Workshop. March 16-19, 2006. Institute of Arctic and Alpine Research, University of Colorado at Boulder, Colorado, U.S.A.
Issue :
Page(s) :
Abstract
An increase of several degrees in mean annual surface temperature, as observed recently in the Arctic affects the underlying permafrost. The atmospheric warming feedbacks the greenhouse effect by thawing permafrost which releases CO2 and CH4 from frozen organic matter (Serreze and al., 2000). Therefore it is necessary to implement a wide scale methodology to monitor permafrost evolution with respect to changing climate. Until recently, most of the permafrost studies had relied on the measurement of ground and air temperature at point locations (e.g. meteorological stations and thermistor cables). These acquisitions are precise and invaluable, but the number of sites is limited and they are not well spatially distributed. In order to decrease the level of error in spatial interpolations due to its high dependence on different soil characteristics or topography, and because the number of measurement sites can hardly be more extensive and well distributed spatially as to allow a better representation of the surface heat balance over large areas, surface temperature measurements through satellite remote sensing presents great capabilities. Satellite remote sensing provides a means of mapping/monitoring the surface heat balance at the spatial and temporal resolutions required for regional - to continental-scale permafrost investigations. Current satellite thermal infrared sensors offer the possibility to retrieve land surface temperature at moderate temporal and spatial resolutions needed for regional scale investigations. One such sensor is the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard of the Terra and Aqua satellite platforms which overpass twice a day. NASA distributes the Land Surface Temperature (LST) product retrieved from MODIS. We compared the MODIS LST daily global 1-km product from Terra with air/near-surface ground temperatures measurements from permafrost sites on tundra in northern Québec and in The North Slope of Alaska. An excellent correlation exists between air temperatures measured at 2 (or 3) m at stations in Nunavik (Northern Quebec) and on The North Slope of Alaska and radiation LST from MODIS. We calculated the average between the four LST daily measurements (Day and Night overpasses of the two satellites). Here, we use those satellite data as surface temperature to calculate the thickness of the active layer. First, we interpolate the satellite data to obtain a continuous sinusoidal equation to fill the gaps due to cloudy days. Second, this sinusoidal equation allows to calculate the freezing and thawing indices which are inserted in the Modified Stefan Equation (Hinkel and al. (1995), Nelson and al. (1997, 1998), Shiklomanov and al.(2002)) and the TTOP equation (Riseborough (2002), Smith and al. (2002), Klene and al.(2001)).
Bibliography of Canadian Geomorphology