ASIRAS airborne radar resolves internal annual layers in the dry-snow zone of Greenland
We present data from the European Space Agency's Airborne SAR/Interferometric Radar Altimeter System (ASIRAS), flown during the CryoVex 2004 field calibration/validation campaign, and new, high-resolution depth profiles of snow density measured in the field by neutron scattering. We combine these data to calculate the depth of internal reflecting horizons in the ASIRAS data. The high resolution density data allow us to identify annual layers in the snow density profile, and correlate their peaks with the reflecting horizons. We use the thickness of the annual layers combined with the density profile to determine the spatial and temporal pattern of snow accumulation along the radar track, for a period of 6 years from 1995–2002. Our mean-annual accumulation rate is 0.47 ± 0.09 ma−1 water equivalent, in agreement with the value determined from a core taken in this location in 1992. Similarly, our inter-annual variability shows the same trends as recent model estimates over the entire ice sheet. Because ASIRAS was designed to mimic as closely as possible the characteristics of the SAR/Interferometric Radar Altimeter (SIRAL), the principal payload of CryoSat, the detection of internal layering with ASIRAS illuminates the possibility of detecting internal layers with a space-borne radar, and thus the possible application of this technique to the dry-snow zones of Antarctica, Greenland, and smaller ice bodies.