Preprints
https://doi.org/10.5194/egusphere-2022-1122
https://doi.org/10.5194/egusphere-2022-1122
 
19 Oct 2022
19 Oct 2022
Status: this preprint is open for discussion.

Linking scales of sea ice surface topography: evaluation of ICESat-2 measurements with coincident helicopter laser scanning during MOSAiC

Robert Ricker1,, Steven Fons2,3,, Arttu Jutila4, Nils Hutter5,4, Kyle Duncan6, Sinead L. Farrell7,2, Nathan T. Kurtz3, and Renée Mie Fredensborg Hansen8,9,10 Robert Ricker et al.
  • 1NORCE Norwegian Research Centre, Tromsø, Norway
  • 2Department of Atmospheric and Oceanic Sciences, University of Maryland, College Park, Maryland, USA
  • 3Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
  • 4Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
  • 5Cooperative Institute for Climate, Ocean and Ecosystem Studies, University of Washington, USA
  • 6Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA
  • 7Department of Geographical Sciences, University of Maryland, College Park, MD, USA
  • 8Department of Geodesy and Earth Observation, DTU Space, Elektrovej Building 328, 2800 Kongens Lyngby, Denmark
  • 9Department of Civil and Environmental Engineering, NTNU, Gløshaugen - Høgskoleringen 7a, 7491 Trondheim, Norway
  • 10Arctic Geophysics, University Centre in Svalbard (UNIS), Longyearbyen, Svalbard, Norway
  • These authors contributed equally to this work.

Abstract. Information about the sea ice surface topography and related deformation are crucial for studies of sea ice mass balance, sea ice modeling, and ship navigation through the ice pack. NASA’s Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) has been on-orbit for nearly four years, sensing the sea ice surface topography with six laser beams capable of capturing individual features such as pressure ridges. To assess the capabilities and uncertainties of ICESat-2 products, coincident high-resolution measurements of the sea ice surface topography are required. During the year-long Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition in the Arctic Ocean, we successfully carried out a coincident underflight of ICESat-2 with a helicopter-based airborne laser scanner (ALS) achieving an overlap of more than 100 km. Despite the comparably short data set, the high resolution measurements on centimetre scales of the ALS can be used to evaluate the performance of ICESat-2 products. Our goal is to investigate how the sea ice surface roughness and topography is represented in different ICESat-2 products, and how sensitive ICESat-2 products are to leads and small cracks in the ice cover. Here we compare the ALS measurements with the ICESat-2’s primary sea ice height product, ATL07, and the high-fidelity surface elevation product developed by the University of Maryland (UMD). By applying a ridge-detection algorithm, we find that 16 % (4 %) of the number of obstacles in the ALS data set are found using the strong (weak) center beam in ATL07. Significantly higher detection rates of 42 % (30 %) are achieved when using the UMD product. Only one lead is indicated in ATL07 for the underflight, while the ALS reveals mostly small, narrow and only partly open cracks that appear to be overlooked by ATL07. More research on how even small leads can be detected by ATL07 using additional validation data sets and complementing measurements, such as airborne thermal infrared imaging, would be useful to further improve the sea ice data products.

Robert Ricker et al.

Status: open (until 14 Dec 2022)

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  • RC1: 'Comment on egusphere-2022-1122', Anonymous Referee #1, 06 Dec 2022 reply

Robert Ricker et al.

Robert Ricker et al.

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Short summary
Information on the sea ice surface topography are important for studies of sea ice, and ship navigation through the ice. The satellite called "ICESat-2" senses the sea ice surface with six laser beams. To proof the accuracy of those measurements, we have carried out a helicopter flight at the same time and along the same ground track as the satellite and measured the sea ice surface topography with a laser scanner, showing that ICESat-2 can see even bumps of only few meters in the sea ice cover.