## 4 Results and Discussion  
The area of iceberg A68A was 5786.3 km\({}^{2}\) when it was initially formed (Figures 1 and 3a). Its area decreased by 35 km\({}^{2}\) in mid-August 2017, when ice pieces broke away (Figure 4a), and then remained almost constant until mid-May 2018. In mid-May 2018, another large ice chunk calved (Figure 4c) and the area of A68A dramatically decreased to 5620 km\({}^{2}\). There was little subsequent change in the area of the iceberg until September 2018 in which the area slightly increased by approximately 30 km\({}^{2}\). Large ice chunks were concentrated on the northern part of the iceberg, with little separation of debris in other parts (Figure 4a,c). Calving occurs by the extension of cracks on the top and bottom surfaces of icebergs, which can be caused by increases in air and sea surface temperatures, wind, and current drag forces, and via interaction with the surrounding topography [17, 40]. However, the observed trends in air temperature predicted by the MERRA-2 reanalysis data did not match changes in iceberg area (Figure 3a). As A68A was surrounded by sea ice throughout the observation period, we did not compare changes in iceberg area with sea surface temperature. In August 2017 and May 2018, when the large ice chunks calved from A68A, southerly winds blew at 6-12 m/s (Figure 5), which were strong enough to move the iceberg north and to break the surrounding packed sea ice [41]. However, the iceberg hardly moved as the iceberg collided with the coastline of the Larsen C Ice Shelf and the shallow seabed near the Bawden Ice Rise (Figure 1). This created ice fragments in the northern part of the iceberg via crack extension on the top and bottom surfaces. Figure 2: CryoSat-2 SAR Interferometric (SARIn) mode profiles on iceberg A68A overlaid on the Sentinel-1A SAR image acquired on 8 September 2017. The freeboard changes of the iceberg were calculated at the intersections of the different profiles which have a time difference of more than 180 days. It is worth noting that the increase in iceberg area was measured in September 2018. This was likely caused by error in the visual digitization of SAR images or by an actual increase in surface area due to the longitudinal stretching of the iceberg. The digitizing errors calculated as the standard deviations of the repeatedly measured iceberg areas from the same images through visual inspection were small, ranging from 2.7 to 7.8 km\({}^{2}\). There were no significant calving events after mid-May 2018. Longitudinal stretching of ice mass is possible if external restraining forces on its boundaries are small or not present [42; 43]. Ice shelves experience similar longitudinal stretching and thinning of ice. The effect of the longitudinal stretching on the iceberg area is not significant. Figure 3: **(a)** Changes in the area of iceberg A68A and 10-m air temperature around the iceberg predicted by the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2); **(b)** Changes in the drift speed at the center of iceberg A68A and its rotation angle; **(c)** Changes in the drift speed at the location of P1 and P2 of iceberg A68A, and monthly mean wind speed and prevailing wind direction (0\({}^{\circ}\) = from south, 90\({}^{\circ}\) = from west, 180\({}^{\circ}\) = from north, 270\({}^{\circ}\) = from east) around the iceberg predicted by the MERRA-2. The vertical error bars in **(c)** represent the standard deviation of wind speeds for each month. when they lose buttressing forces due to unpinning or iceberg calving [44]. The observation of A68A shows that the sea ice in the northwestern region of A68A started to disappear since July 2018 (Figure 4). We suspect that this reduced the external restraining forces on the iceberg and caused longitudinal stretching in the horizontal direction. The horizontal stretching can occur around the iceberg.