Fig. 1. Overview of study area. The trajectory of an ice mounted drifting buoy is shown overlaid on bathymetry. White boxes identify the location of coincident SAR images with black and white diamond symbols on the buoy track corresponding to the time of each SAR image in Table 1.

Fig. 2. Flow diagram of nested non-rigid motion processing system. I₁ and I₂ represent images 1 and 2. The gray box is an overview of the processing system with each major component described in subsequent boxes (i–iv).

Fig. 3. Motion products of image translation, masking of dynamic discontinuities, and high resolution differential motion. Panels (a) and (b) are mosaics of images 9–10 and 11–12, respectively. Grey-scale correlation map and accompanying correlation scale in panel (c) used to mark dynamic discontinuities (black dots) based on low correlations and large changes in relative motion and direction (see text for details). Circles in al panels reference buoy locations (Table 1) from which global displacement is computed. Note the sharp change in relative motion magnitude and/or direction in zoom panels (d) and (e) in close proximity to the discontinuities.

Fig. 4. Distribution of invariant shear and associated uncertainty. Panel (a) shows the estimated shear noise based on propagated position uncertainty derived from the sample SAR image pairs in Table 1. Panel (b) shows the distribution of invariant shear from these image pairs with the 4σ or 95% confidence interval chosen as the noise threshold level from panel (a). Green and red arrows match the range of invariant shear in Fig. 8.

Fig. 5. Temporal evolution of discontinuities. Correlation map and discontinuity mask shown for image pairs (a)–(f) using the same correlation scale shown in Fig. 3. The global displacement between each image pair is shown at the reference buoy (Table 1) denoted as per previous figures. The black and white box in each panel is in the same Lagrangian location throughout to serve as a reference and further represents the zoom boxes in Fig. 6.

Fig. 6. Temporal evolution of discontinuous non-rigid motion. Zoomed in composite results from Fig. 5. In addition to the correlation map, discontinuity mask, and global motion reference vector at the reference buoy, an associated local motion field is provided. Together these reveal a rich discontinuous non-rigid motion field.

Fig. 7. Wind and ice drift vector plots. Wind vectors from a buoy meteorology station being deployed during this time is shown in panel (a) with accompanying ice drift vectors in panel (b). All vectors shown are oriented relative to Fig. 1. Note: wind vectors shown in the flow direction (opposite of wind direction) to compare with the ice drift.

Fig. 8. Demonstration of composite motion products. In the upper panel, streak lines are shown using line integral convolutions (LIC) based on 400 m resolution relative motion vectors. For clarity regarding the flow direction of LIC results, motion vectors are shown at a resolution of 6.4 km commensurate with typical 5 km resolution sea ice motion products. Green and red circles denote regions of statistically significant invariant shear as per Fig. 4b. The two embedded blue boxes are references for the zoomed regions shown lower left (large zoom box) and right (small zoom box). In the large zoom box, every 4th vector is shown for motion maps at 1.6 km resolution while the highest resolution of 400 m is shown in the right panel. The absolute motion between the image pair is − 7.4 cm s^− 1 and 6.8 cm s^− 1 in the x and y directions, respectively.

Selected SAR scenes

Time shown as decimal days of the year noting that 1992 is a leap year. The column marked days is the time difference between the noted image and the previous image in units of days.