Different ERS altimeter measurements between ascending and descending tracks caused by wind induced features over ice sheets

The ERS1 satellite provides a high-resolution radar altimeter measurement L IP to 81.5 degrees latitude for polar cap studies. Here we examine one part icular effect of the interaction between the radar wave and the snowpack su rface on height measurements. Measurements from ascending and descending tr acks show systematic differences as large as 1 m. Such an artifact to be re moved if it can be estimated. The difference appears to be related to the w ay the altimeter perceives wind-induced sculpting of the snowpack. Differen ces in the volume echo weight between ascending and descending passes appea r to be the explanation. Seasat scatterometer allowed us to estimate indepe ndently the signal that could be inferred by wind features. Our results yie ld a map of the effect of wind on radar altimetric measurement. Finally, we consider the possibility of long-term variations in altimeter measurements caused by climatic changes.