The ERS1 satellite provides a high-resolution radar altimeter measurement up to 81.5¿ latitude for polar cap studies. Here we examine one particular effect of the interaction between the radar wave and the snowpack surface on height measurements. Measurements from ascending and descending tracks show systematic differences as large as 1 m. Such an artifact to be removed if it can be estimated. The difference appears to be related to the way the altimeter perceives wind-induced sculpting of the snowpack. Differences in the volume echo weight between ascending and descending passes appear to be the explanation. Seasat scatterometer allowed us to estimate independently the signal that could be inferred by wind features. Our results yield 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. ¿ 1999 American Geophysical Union