A range correction for ICESat and its potential impact on ice-sheet mass balance studies

• Main Authors: Borsa, AA, Moholdt, G, Fricker, HA, Brunt, KM
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: eScholarship, University of California 2014
• Subjects: Climate Action; Oceanography; Physical Geography and Environmental Geoscience; Meteorology & Atmospheric Sciences; Ice Sheet; Ice Shelf; Ice Shelves; The Cryosphere
• Online Access: https://escholarship.org/uc/item/11x4x6t5

We report on a previously undocumented range error in NASA's Ice, Cloud and land Elevation Satellite (ICESat) that degrades elevation precision and introduces a small but significant elevation trend over the ICESat mission period. This range error (the Gaussian-Centroid or "G-C" offset) varies on a shot-to-shot basis and exhibits increasing scatter when laser transmit energies fall below 20 mJ. Although the G-C offset is uncorrelated over periods ≤ 1 day, it evolves over the life of each of ICESat's three lasers in a series of ramps and jumps that give rise to spurious elevation trends of-0.92 to-1.90 cm yr-1, depending on the time period considered. Using ICESat data over the Ross and Filchner-Ronne ice shelves we show that (1) the G-C offset introduces significant biases in ice-shelf mass balance estimates, and (2) the mass balance bias can vary between regions because of different temporal samplings of ICESat. We can reproduce the effect of the G-C offset over these two ice shelves by fitting trends to sample-weighted mean G-C offsets for each campaign, suggesting that it may not be necessary to fully repeat earlier ICESat studies to determine the impact of the G-C offset on ice-sheet mass balance estimates. © 2014 Author(s.).