## 4 Results and Discussion
We measured the stretching rate along the straight line connecting the points P1 and P2, and P3 and P4 from the six SAR images in Figure 4. The stretching rates were smaller than 0.008/year before July 2018 (Figure 4b-d). However, the rates increased sharply from July to September 2018, showing the value of 0.013 /year and 0.026 /year along the line P1-P2 and P3-P4, respectively (Figure 4e). This suggests that the measured increase resulted from an increase in the area of the iceberg due to the longitudinal stretching after August 2018. The area of A68A at the end of November 2018 was 5660.1 km\({}^{2}\), which was just 2% less than at the time of its formation. Figure 4: The Sentinel-1 SAR images of iceberg A68A acquired on (**a**) 15 August 2017; (**b**) 12 January 2018; (**c**) 18 May 2018; (**d**) 17 July 2018; (**e**) 16 September 2018; and (**f**) 27 November 2018. Figure 5: **(a)** Changes in the wind speed around iceberg A68A predicted by the MERRA-2; **(b)** Wind rose showing wind speed and direction for each month during July 2017–November 2018. Prior to mid-July 2018, drift speed at the center of iceberg and rotation angle were generally less than 2 km/day and \(\pm\)1\({}^{\circ}\)/day (the positive value of rotation angle indicates a counter-clockwise rotation), respectively (Figure 3b). The northern and southern part of the iceberg (the location of P1 and P2, respectively, in Figure 1) also showed very low drift speed before mid-July 2018 (Figure 3c). This was driven by strong easterly and southerly winds (Figure 5b), the high concentration of sea ice and the front of the Larsen C Ice Shelf that limited the movement and rotation of A68A. During July 2017-August 2018, the prevailing wind directions were the north and the mean wind speeds were 4-7 m/s (Figure 3c). The iceberg gradually moved northward due to southerly winds and finally emerged from the front of Larsen C Ice Shelf in July 2018 (Figure 4d). Iceberg A68A moved faster after mid-July 2018, especially in the southern part of the iceberg (Figure 3b,c), and showed nearly circular motion. A68A escaped from the bay-shaped region, but the northern part of the iceberg remains near to the Bawden Ice Rise (Figure 4e-f). Therefore, rotation in a counter-clockwise direction has only occurred (Figure 3b) even though westerly winds were becoming more and more frequent (Figures 3c and 5b). As outlined above, the movement of iceberg A68A was likely interrupted by the shallow seabed, specifically nearby the Bawden Ice Rise. The assumption of hydrostatic equilibrium cannot be valid when the iceberg is pinned to the shallow seabed. However, movement of the iceberg was only limited by the ice rise and it continued to drift. Therefore, we assumed that the ice rise had only a small effect on the hydrostatic equilibrium state of the iceberg. Freeboard changes for A68A derived from the CryoSat-2 observations are shown in Table 1. Most of the freeboard change values calculated using the CryoSat-2 observations on 8 September 2017 and 30 January 2018 as a reference (intersections 1-9 in Table 1) were positive, with an averaging change of 0.82 \(\pm\) 0.38 m/year. Calculated freeboard changes after February 2018 (intersections 10-18 in Table 1) were mostly negative, however, with an averaging change of \(-\)0.80 \(\pm\) 0.29 m/year. A positive value indicates that the freeboard is rising during the observation period, i.e., ice thickening is occurring. As an iceberg is completely detached from the grounded ice sheet and ice shelf, its thickness naturally decreases due to basal melting and surface sublimation/ablation [17; 45; 46]. CryoSat-2 SIRAL uses the Ku-band that might measure the maximum return from the snow surface on the iceberg A68A due to high densification of snow/firn layer [19]. Figure 6 shows the increase in snow depth for a region of the Larsen C Ice Shelf near iceberg A68A, as predicted by the MERRA-2 reanalysis data.