ERS-1 SAR backscatter changes associated with ice growing on shallow lakes in Arctic Alaska

Spatial and temporal backscatter intensity (σ°) variations from ice growing on shallow lakes during the winter 1991-92 near Barrow, NW Alaska have been quantified for the first time using ERS-1 C-band SAR data acquired at the Alaska SAR facility. A field and laboratory validation program, including measurements of the thickness and structure-stratigraphy of the ice indicates that σ° values are strongly dependent on whether the ice freezes to the lake bottom, or remains afloat. Backscatter intensity decreases significantly when the ice grounds on the bottom. Strong backscatter from floating ice is attributed to a specular ice-water interface and vertically oriented tubular bubbles. During the spring thaw, backscatter undergoes a reversal; σ° values from ice that was grounded increase, while σ° values from ice that was afloat decrease. This phenomenon has not previously been reported