Arctic sea ice microwave signatures. A Lagrangian approach during the NSCAT mission

The drift of Arctic buoys retrieved from the International Arctic Buoy Program (IABP) data set during the flight period of the NASA scatterometer (NSCAT) is used to follow selected sea ice areas (25 km×25 km) from September 20, 1996 until June 30, 1997. The time evolution of the backscatter signatures (40° incidence angle) obtained from NSCAT measurements, at Ku-band, are compared to those of the AMI-Wind of ERS-2, at C-band. SSM/I brightness temperatures and the NASA team algorithm are used to follow the time evolution of the total and multi-year ice concentration of these areas. The IABP/POLES Surface Air Temperature Data Set provided additional information until December 31, 1996. It is shown that backscatter (σ⁰) at Ku and C-band evolve similarly for the various ice types sampled, although Ku-band is more sensitive to the aging of sea ice. The specific analysis of the passive and active signatures, following the drift of a triplet of buoys, indicates that the fluctuations of multi-year sea ice concentration cannot be related to sea ice divergence as usually assumed