MABEL photon-counting laser altimetry data in Alaska for ICESat-2 simulations and development

Kelly M Brunt,Thomas A Neumann,Jeffrey L Kavanaugh,Mahsa S Moussavi,Jason M Amundson,Kaitlin M Walsh,William B Cook,Thorsten Markus

doi:10.5194/tc-10-1707-2016

Abstract

Abstract. Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) is scheduled to launch in late 2017 and will carry the Advanced Topographic Laser Altimeter System (ATLAS), which is a photon-counting laser altimeter and represents a new approach to satellite determination of surface elevation. Given the new technology of ATLAS, an airborne instrument, the Multiple Altimeter Beam Experimental Lidar (MABEL), was developed to provide data needed for satellite-algorithm development and ICESat-2 error analysis. MABEL was deployed out of Fairbanks, Alaska, in July 2014 to provide a test dataset for algorithm development in summer conditions with water-saturated snow and ice surfaces. Here we compare MABEL lidar data to in situ observations in Southeast Alaska to assess instrument performance in summer conditions and in the presence of glacier surface melt ponds and a wet snowpack. Results indicate the following: (1) based on MABEL and in situ data comparisons, the ATLAS 90 m beam-spacing strategy will provide a valid assessment of across-track slope that is consistent with shallow slopes (< 1°) of an ice-sheet interior over 50 to 150 m length scales; (2) the dense along-track sampling strategy of photon counting systems can provide crevasse detail; and (3) MABEL 532 nm wavelength light may sample both the surface and subsurface of shallow (approximately 2 m deep) supraglacial melt ponds. The data associated with crevasses and melt ponds indicate the potential ICESat-2 will have for the study of mountain and other small glaciers.

Highlights

Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) is a NASA mission scheduled to launch in 2017
We determined the full width at half maximum (FWHM) for each of the beams, which ranged from 0.19 m in beam 5 (532 nm) to 0.31 m in beam 43 (1064 nm)
What we can say is that if the Advanced Topographic Laser Altimeter System (ATLAS) signalphoton density and signal-to-noise ratios are within 30 % of its measurement requirements, ATLAS can be used to measure surface slopes over both relatively flat ice-sheet interior conditions and steeper glaciers, such as the Lower Taku Glacier, and identify melt ponds

Summary

Introduction

Cloud, and land Elevation Satellite-2 (ICESat-2) is a NASA mission scheduled to launch in 2017. ICESat-2 is a follow-on mission to ICESat (2003–2009) and will extend the time series of elevation-change measurements aimed at estimating the contribution of polar ice sheets to eustatic sea level rise. ICESat-2 will carry the Advanced Topographic Laser Altimeter System (ATLAS), which uses a different surface detection strategy than the instrument onboard ICESat. While the measurement goals of ATLAS remain as described in Abdalati et al (2010), some of the details have evolved (Markus et al, 2016). ATLAS is a six-beam, photon-counting laser altimeter (Fig. 1). ATLAS will use short (< 2 ns) 532 nm (green) wavelength laser pulses, with a 10 kHz repetition rate, which yields a ∼ 0.70 m along-track sampling interval, and a ∼ 17 m diameter footprint. An accurate assessment of ice-sheet surface-elevation change based on altimetry is de-

Results

Discussion

Conclusion