Wavelet analysis of microwave satellite data is used to obtain daily sea ice drift information for both the northern and southern polar regions. This technique provides improved spatial coverage over the existing array of Arctic Ocean buoys and better temporal resolution currently available with other satellite sensors. Examples of derived ice-drift maps for the Arctic illustrate large-scale circulation reversals over a period of a few days. Comparisons of satellitederived ice motion with ice displacements derived from buoys give good quantitative agreement.
Early estimates of ice drift were obtained from ship records, manned ice stations, and reconnaissance aircraft. The ARGOS system on NOAA satellites, for example, can relay data from buoys and determine locations to an accuracy of a few hundred meters about ten times a day (Thorndike, 1986). A network of automatic data buoys to monitor synoptic-scale fields of pressure, temperature, and ice motion throughout the Arctic Basin. the Arctic Ocean Buoy Program, was established in 1978 to support the Global Weather Experiment. The basic objective is to maintain a network of drifting buoys in the Arctic Ocean with which to provide data needed for real-time operations and meteorological and oceanographic research. Sequential satellite images obtained from the Advanced Very High Resolution Radiometer (A VHRR) have also been used to determine ice motion through ice feature tracking (Emery et al., 1991). Emery et al. combined the automated maximum cross-correlation method with a spatial filtering technique to retrieve coherent ice motion vectors in cloud contaminated imagery. Nonetheless, AVHRR images are obscured by cloud cover and low light levels limiting their usefulness. Since 1987 the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) has been providing global maps of radiometric brightness from which sea ice extent, concentration and type are derived routinely for operational and research purposes.
