CoAuthors

Sara Fleury (LEGOS, France); Kevin Guerreiro (LEGOS, France); Sascha Willmes (Trier University, Germany); Frederique Remy (LEGOS, France); Alexei Kouraev (LEGOS, France)

Sea ice is an important part of the global cryosphere. It modifies the surface albedo, provides a barrier to the exchange of energy, water and gases between ocean and atmosphere, impacts ecosystem's functioning and human activity. The Arctic sea ice cover has experienced large changes. Since the 1980's we observe an increase of summer melt time period, a decrease in ice extent and ice thickness [IPCC,2013]. Recent observations show an increase in drift speed, a growth of strain and deformation of ice fields [Rampal, 2009]. Ice motion and strain produce open water surfaces: leads and polynyas. The presence of open water within ice fields have a crucial importance for heat, water and CO2 transfer between ocean and atmosphere, for regional surface albedo, winter ice production. It also affects navigation as well as arctic animal living conditions.

In this study we investigate the performance of SARAL/AltiKa to detect leads and coastal polynyas as well as its ability to represent spatial and temporal dynamics of water openings. The approach consists first in analysis of along-track radar waveforms collocated with high-resolution Landsat imagery in order to localise ice/water transitions. We show that, in contrary to the ENVISAT RA2 altimeter, for AltiKa the peakiness can not be used for leads detection due to signal saturation over leads. We also discuss the potential of several techniques that could be used for leads and polynya studies and freeboard estimation. We further explore how altimetric results agree with MODIS leads retrievals on the regional scale.