A wideband radar for high-resolution mapping of near-surface internal layers in glacial ice

©2004 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.Snow accumulation rate is an important parameter in determining the mass balance of polar ice sheets. Accumulation rate is currently determined by analyzing ice cores and snow pits. Inadequate sampling of the spatial variations in the ice sheet accumulation has resulted in accumulation rate uncertainties as large as 24%. We designed and developed a 600-900-MHz airborne radar system for high-resolution mapping of the near-surface internal layers for estimating the accumulation rate of polar ice sheets. Our radar system can provide improved spatial and temporal coverage by mapping a continuous profile of the isochronous layers in the ice sheet. During the 2002 field season in Greenland, we successfully mapped the near-surface layers to a depth of 200 m in the dry-snow zone, 120 m in the percolation zone, and 20 m in the melt zone. We determined the water equivalent accumulation rate at the NASA-U_1 site to be 34.9 +/- 5.1 cm/year from 1964 to 1992. This is in close agreement with the ice-core derived accumulation rate of 34.6 cm/year for the same period

Coherent radar ice thickness measurements over the Greenland ice sheet

This is the published version, also available here: http://dx.doi.org/10.1029/2001JD900183.We developed two 150-MHz coherent radar depth sounders for ice thickness measurements over the Greenland ice sheet. We developed one of these using connectorized components and the other using radio frequency integrated circuits (RFICs). Both systems are designed to use pulse compression techniques and coherent integration to obtain the high sensitivity required to measure the thickness of more than 4 km of cold ice. We used these systems to collect radar data over the interior and margins of the ice sheet and several outlet glaciers. We operated both radar systems on the NASA P-3B aircraft equipped with GPS receivers. Radar data are tagged with GPS-derived location information and are collected in conjunction with laser altimeter measurements. We have reduced all data collected since 1993 and derived ice thickness along all flight lines flown in support of Program for Regional Climate Assessment (PARCA) investigations and the North Greenland Ice Core Project. Radar echograms and derived ice thickness data are placed on a server at the University of Kansas (http://tornado.rsl.ukans.edu/Greenlanddata.htm) for easy access by the scientific community. We obtained good ice thickness information with an accuracy of ±10 m over 90% of the flight lines flown as a part of the PARCA initiative. In this paper we provide a brief description of the system along with samples of data over the interior, along the 2000-m contour line in the south and from a few selected outlet glaciers

A Wideband Radar for Mapping Internal Layers in the Polar Icesheets for

Determination of the mass balance of the polar ice sheets requires information on the accumulation rate. Remote sensing methods to determine the accumulation rate are essential in reducing the uncertainty associated with interpolating in situ measurements that are obtained from ice cores and pits. This is essential to reducing the 20% of uncertainty in current accumulation rate maps. Using data from surface-based radar experiments we determined optimum parameters for an airborne radar. We developed an airborne prototype and successfully demonstrated that we can map internal layers with about 1 m resolution to a depth of about 120 meters over the Greenland ice sheet. We reported the system design, construction and preliminary experimental results at the IGARSS meeting [1]. We have developed an operational radar system for routine measurement. This system operates in FM-CW and stepped-frequency pulse modes and it has 20-dB more sensitivity than the prototype radar. We also developed a radar target simulator for testing and evaluating system performance. The target simulator was constructed using fiber optic cables, microwave delay lines and RF/optical transceivers to simulate reflections from the air/snow interface, internal layers and the antenna reflection, which degrades the system's sensitivity. The simulator serves a dual purpose of optimizing the system performance in the laboratory and for internal calibration in the field. We also used a CAD package to design and simulate overall radar performance. The use of CAD package and target simulator reduced cost and time associated with the radar development. In addition, we are also able to obtain an accurate system model to deconvolve the system effects from the received signal. In this paper we will discuss detailed de..