Satellite doppler determination of differential sea ice motion in the vicinity of the north pole∗

Abstract

Abstract During April and May 1979 multidisciplinary observations were conducted in the central Arctic Ocean from three manned ice stations to explore the nature of the submarine Lomonosov Ridge (Weber, 1979). Positions of the LOREX (Lo‐monosov Ridge Experiment) ice camps were monitored continuously using geodetic satellite doppler receivers and the U.S. Navy Navigation Satellite System. Near real‐time doppler data reduction on the ice using broadcast satellite ephemeris provided operational horizontal positions with accuracies of about ± 250 m. A precise geodetic satellite doppler reduction program has been adapted to accommodate linear station motion in a simultaneous multistation, three‐dimensional adjustment in phases using postfitted precise satellite ephemeris, if available. Complete reprocessing of the LOREX doppler data set has produced average errors of ± 48 m for single pass solution and ± 24 m for mean three‐four horizontal station positions. The station ellipsoidal heights show strongly correlated variations in excess of 5 m, with the average error of ± 0.45 m. Station velocities are also strongly correlated, with the mean of about 225 m/h and the maximum of 1,240 m/h. Total strain and hourly strain rate components of sea ice have been evaluated for a homogeneous two‐dimensional strain model. The configuration of the ice camps provides a unique solution for mesoscale strain, indicating a major change in the pattern of pack ice deformation over the Lomonosov Ridge. The total strain reflects plastic deformation, which takes place mainly in episodic events. The strain rate also indicates nearly diurnal oscillations, with amplitudes an order of magnitude smaller than those corresponding to the major deformation events.