High‐resolution radar mapping of internal layers at the North Greenland Ice Core Project

Existing accumulation maps with reported errors of about 20% are determined from sparsely distributed ice cores and pits. A more accurate accumulation rate might be obtained by generating continuous profiles of dated layers from high‐resolution radar mapping of near‐surface internal layers in the ice sheet (isochrones). To generate such profiles we designed and developed an ultrawideband radar for high‐resolution mapping of internal layers in the top 200 m of ice and tested it at the North Greenland Ice Core Project drill site. Reflection profiles of 2‐ and 10‐km length reveal horizons that we correlate with electrical conductivity measurement (ECM) recordings. Our results show that the radar‐determined depth of internal layers is within ±2 m of that in an ice core collected at a nearby location. Preliminary frequency analyses of layer reflections reveal that the reflections are strongest at the 500–1000 MHz frequency range. Long‐term accumulation rate computed from radar data is within 5% of that obtained from snow pits.