An edge detection technique to estimate melt duration, season and melt extent on the Greenland ice sheet using passive microwave data

The melt extent, duration and melt season on the Greenland ice sheet were e stimated using an edge detection technique on passive microwave data from t he SSM/I and SMMR instruments (18/19V GHz channel) for the period 1979 to 1 997. The annual brightness temperature (Tb) time series at a pixel location that experiences summer melt has a steep rise and drop in Tb with the onse t and end of melt, respectively. A derivative-of-Gaussian edge detector is used to detect edges corresponding to the onset and end of melt. The time l apsed between the first upward and last down-ward edge on the annual Tb tim e series gives an estimate of the melt season and the time lapsed between s uccessive upward and downward edges gives the duration of melt. While the m aximum melt extent increased by 18%, the total duration of melt increased b y 3.7% and the total melt season decreased by 3.8% during the period 1979-1 997.