Sea Ice Leads Detection Using SARAL/AltiKa Altimeter

Abstract

Sea ice leads play an essential role in ocean-ice-atmosphere exchange, in ocean circulation, geochemistry, and in ice dynamics. Their precise detection is crucial for altimetric estimations of sea ice thickness and volume. This study evaluates the performance of the SARAL/AltiKa (Satellite with ARgos and ALtiKa) altimeter to detect leads and to monitor their spatio-temporal dynamics. We show that a pulse peakiness parameter (PP) used to detect leads by Envisat RA-2 and ERS-1,-2 altimeters is not suitable because of saturation of AltiKa return echoes over the leads. The signal saturation results in loss of 6–10% of PP data over sea ice. We propose a different parameter—maximal power of waveform—and define the threshold to discriminate the leads. Our algorithm can be applied from December until May. It detects well the leads of small and medium size from 200 m to 3–4 km. So the combination of the high-resolution altimetric estimates with low-resolution thermal infra-red or radiometric lead fraction products could enhance the capability of remote sensing to monitor sea ice fracturing.

Keywords:

• Altimetry
• arctic
• leads and polynyas
• sea ice

Acknowledgements

We thanks the Center for Topographic studies of the Oceans and Hydrosphere (CTOH) at LEGOS for providing the SGDR AltiKa data. We are grateful to anonymous reviewers and the editor for the time and attention dedicated to the manuscript and for their constructive remarks.

Funding

This research is supported by the French CNES TOSCA “SICKAyS” and IDEX Tranversalité InHERA projects.