Estimating thin ice thickness around Svalbard using MODIS satellite imagery

ABSTRACT

Information about the state of the Arctic sea ice is becoming increasingly important. This paper describes an approach for automatic retrieval of daily thin sea ice thickness maps around Svalbard. The algorithm uses thermal satellite imagery from MODIS to estimate the surface temperature of the ice and further uses a thermal model of the ice surface to estimate the thickness of the sea ice. The approach is usable for thin sea ice, up to ca. 50 cm thick, during cold weather (freezing) conditions and without cloud cover present. The algorithm is compared with helicopter-borne electromagnetic ice thickness measurements. The comparison yields increasing root-mean-square deviation (RMSD) for thicker ice. The lowest RMSD found is 8.7 cm for ice thickness in the range 10 cm < h_i ≤ 20 cm. The highest RMSD found is 25.2 cm for ice thickness in the range 30 cm < h_i ≤ 40 cm. The bias shows no such trend, and the overall bias is found to be −5.5 cm. The results show that this is a promising approach, allowing monitoring of thin sea ice thickness at relatively higher spatial resolution.

KEYWORDS:

• Remote sensing
• sea ice
• MODIS
• Svalbard
• ice thickness
• Arctic

Acknowledgements

We thank M. Bratrein (NPI), and Airlift helicopter and RV Lance ship crews for their work during the expedition in March 2014, and J. King (NPI) for the processing of HEM data. The European Space Agency (ESA contract 4000110477/14/NL/FF/lf) and the Norwegian Polar Institute co-financed the HEM helicopter flights conducted during the expedition in March 2014. We also thank ESA and Norw. Space Center for ThinIce PRODEX funding, which primarily made this study possible (ESA PRODEX Arrangement (PEA) No. 4000100853).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The HEM data used in this article are available for download (King et al. 2016).

Additional information

Notes on contributors

Øystein Rudjord

Øystein Rudjord received his Master’s degree in Physics in 2006, and PhD in Astrophysics in 2010, both from the University of Oslo, Norway. In 2011, he joined Norwegian Computing Center and has since then been developing automatic algorithms for physical variable retrieval from satellite data. He has focused his research on remote sensing of cryospheric variables for applications to climate, hydrology and meteorology. Øystein Rudjord has worked on algorithms for monitoring variables related to sea ice, lake ice and snow cover using techniques based on image analysis and physical modeling.

Rune Solberg

Rune Solberg is Research Leader of Section for Earth Observation at the Norwegian Computing Center. His research focuses on the development of methods for retrieval of cryospheric variables from satellite data, in particular from multi-sensor and time-series sensor data sets.

Gunnar Spreen

Gunnar Spreen received his M.Sc. degree in Physics (Diplomphysiker) in 2004 and his Ph.D. degree in oceanography in 2008, both from the University of Hamburg, Hamburg, Germany.

He works on satellite remote sensing of Polar Regions with focus on monitoring changes of sea ice (extent, mass and dynamics) and on understanding underlying climate processes. Satellite measurements are validated using ground-based and airborne field observations, recently in particular from the 2019/2020 MOSAiC expedition. For which he serves on the project board and coordinates the remote sensing activities.

Gunnar Spreen is the head of the research group ‘Remote Sensing of Polar Regions’ at the University of Bremen, Institute of Environmental Physics, Bremen, Germany. Before, he was a research scientist at the Norwegian Polar Institute, Tromsø, Norway, and a postdoctoral scholar at the Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.

Current work addresses the development of new retrievals for sea ice parameters like leads and ice type from SAR and microwave radiometer data as well as snow on sea ice.

Sebastian Gerland

Sebastian Gerland received the Master’s (Dipl. Geophys.) degree in Geophysics from Johann Wolfgang Goethe University, Frankfurt, Germany, in 1989, and the Ph.D. (Dr. rer. nat.) degree in Marine Sediment Physics from the University of Bremen, Germany, in 1993. He was with Glaciology Groups at Alfred Wegener Institute, Bremerhaven, Germany, and at the University College of London, U.K., and worked with radioecology at the Norwegian Radiation Protection Authority, Tromsø, Norway. From 1997 to 2000 and since 2002, he has been with the Norwegian Polar Institute, Tromsø, Norway, where he is currently a Senior Research Scientist for sea ice and climate as well as the leader of the section ‘Oceans and Sea Ice.’ His research interests include Arctic sea-ice mass and energy balance, with a focus on the regions Fram Strait, Barents Sea, Svalbard, and Arctic Basin.