P - R
type: Concept

PARCA
type: Concept
in scheme: projects
definition: PARCA is a NASA project formally initiated in 1995 by combining into one coordinated program various investigations associated with efforts, started in 1991, to assess whether airborne laser altimetry could be applied to measure ice-sheet thickness changes. It has the prime goal of measuring and understanding the mass balance of the Greenland ice sheet. The main components of the program are: 1. Periodic airborne laser-altimetry surveys along precise repeat tracks across all major ice drainage basins. The first survey was completed in 1993/1994, with repeat flights along selected routes in 1995 and 1996, when flights were also made over ice caps in eastern Canada, Svalbard, and Iceland. Ice-thickness measurements along the same flight lines Localized measurements of ice thickness change in shallow drill holes. Monitoring of various surface characteristics of the ice sheet using satellite radar altimetry, SAR, passive-microwave, AVHRR, and scatterometer data. Surface-based measurements of ice motion at 30-km intervals approximately along the 2000-meter contour completely around the ice sheet, with interpolation of local relative ice motion using interferometric SAR. Shallow ice cores (10 - 200 meters) at many locations to infer recent climate history, atmospheric chemistry, and interannual variability of snow-accumulation rates, and to measure temperature and vertical ice motion at various depths. 2. Investigations of surface energy balance and factors affecting snow accumulation and surface ablation. This program is a collaborative effort with NSF, and includes the installation of automatic weather stations (AWS) at many of the drill-hole sites. 3. Estimating snow-accumulation rates by climate-model analysis of column water vapor obtained from radiosondes and TOVS data. 4. Detailed investigations of individual glaciers and ice streams responsible for much of the outflow from the ice sheet. 5. Development of a thermal probe to measure various ice characteristics at s…