Variability in surface reflectance of the Greenland ice sheet (1982-2005) using satellite remote sensing

Data from space born sensors, the Advanced Very High Resolution Radiometer (AVHRR) and the Moderate Resolution Imaging Spectroradiometer (MODIS) are used to investigate albedo trends over the entire Greenland ice sheet for the period 1982-2005. Data from the two sensors is merged in order to performing an extended trend analysis, as the current publicly available AVHRR data only cover the period from 1982-1999. Satellite derived albedo measurements are compared with in-situ automatic weather station albedo values in order to assess sensor biases and inter-calibrate the datasets. Comparing AVHRR and MODIS with in-situ observations yields mean biases of -0.032 and -0.050 and root mean square errors of 0.093 and 0.075, respectively. Dataset inter-calibration is attempted using the mean biases as offsets and by calibrating each albedo image to the dry snow constant. Dataset in-homogeneity issues are not entirely resolved; therefore trend analysis is performed separately for each data record. AVHRR registers statistically significant mean albedo reductions as large as 0.08 over the southern ice sheet and ice sheet periphery. Albedo remained unchanged over the interior dry-snow region. MODIS period data reveal additional reductions, with albedo decreasing more than 0.08 along the ice sheet margins during the early melt season (i.e., April 1- June 31). Investigation of albedo-temperature correlation yields statistically significant values at the 99% level as great as -0.8 along ice sheet margins, where melting strongly influences albedo.NASA grant NNG04GH70GOhio State University Undergraduate Honor’s Research Scholarshi