Sensitivity of AMSR-E Brightness Temperatures to the Seasonal Evolution of Lake Ice Thickness

The sensitivity of brightness temperature (T_B) at 6.9, 10.7, and 18.7 GHz from Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) observations is investigated over five winter seasons (2002-2007) on Great Bear Lake and Great Slave Lake, Northwest Territories, Canada. The T_B measurements are compared to ice thicknesses obtained with a previously validated thermodynamic lake ice model. Lake ice thickness is found to explain much of the increase of T_B at 10.7 and 18.7 GHz. T_B acquired at 18.7 GHz (V-pol) and 10.7 GHz (H-pol) shows the strongest relation with simulated lake ice thickness over the period of study (R² > 0.90). A comparison of the seasonal evolution of T_B for a cold winter (2003-2004) and a warm winter (2005-2006) reveals that the relationship between T_B and ice growth is stronger in the cold winter (2003-2004). Overall, this letter shows the high sensitivity of T_B to ice growth and, thus, the potential of AMSR-E mid-frequency channels to estimate ice thickness on large northern lakes.