Arctic Ocean multiyear ice concentration changes during winters 1992-93 and 1996-97: a comparison between SSM/I estimations and scatterometer data

摘要

For the cold seasons 1992-93 and 1996-97, when extensive multiyear ice coverages were observed in the Arctic Ocean, the active microwave signatures of multiyear ice have been analysed and compared to the brightness temperatures and the multiyear ice concentration maps derived from the SSM/I. Two ways are explored for using the backscatter data obtained by the AMI-WIND, aboard ERS, and NSCAT aboard ADEOS. Firstly, the stability of the backscatter data in time is used to constitute pairs of tie points between successive images which, added to buoy positions, are at the origin of a series of interpolated ice displacement fields calculated for 8 weeks periods. Applied to the multiyear ice maps deduced from the brightness temperatures of the SSM/I at the beginning of December 1992 and 1996, these motion fields give virtual maps of the displaced multiyear ice concentration which can be compared to really calculated maps. Secondly, the backscatter data are used to isolate homogeneous areas of highly reflective ice which appear to correspond to low estimated concentrations of multiyear ice. Though the author cannot, by using backscatter data only, know the true multiyear ice concentrations, it is possible to suppose a possible source of error, due to the particular emissivities of the ice surface, in the SSM/I evaluations.