## 4 Results and Discussion
The snow depth in this region continued to increase during the entire observation period, except for January-February 2018 when a small reduction was observed. The linear fitting of the changes in snow depth shows that the rate of increase rate was 0.82 \(\pm\) 0.06 m/year. Therefore, the increase in the freeboard of iceberg A68A (using the 8 September 2017 and 30 January 2018 reference values) was likely the result of increased snow depth on the ice surface and not ice thickening, and the thickness of the iceberg possibly remained constant until January 2018. The decrease in the freeboard of A68A after February 2018 indicates that the iceberg thinning rate was greater than the rate of snow depth increase. In other words, the thickness of A68A has decreased dramatically since February 2018. This likely reflects warm seawater during the Antarctic summer, and an increase in the relative velocity of the iceberg resulting from drift in winter (Figure 3b) promoted the basal melting [17; 45]. The longitudinal stretching of the iceberg after August 2018 could also contribute to the decrease in the freeboard as it is accompanied by ice thinning [44]. Assuming that CryoSat-2 observations reflect the maximum radar returns from the snow surface on the iceberg, the averaging rate of thickness change during February-November 2018 was calculated as \(-\)12.89 \(\pm\) 3.34 m/year from Equation (1) based on an averaging snow depth change of 0.82 \(\pm\) 0.06 m/year. The thickness changes of the iceberg could be influenced by the changes in firm densification and basal melting. The effect of the changes in firm densification on the freeboard change is much smaller than basal melting of iceberg [45]. [PERSON] et al. [39] showed that the change in firm compaction in the West Antarctic ice shelves is \(-\)2.7 cm/year. Therefore, the thinning of iceberg A68A was mainly attributed to basal melting. Assuming that the ice thinning rate and thickness (300 m from Bedmap2) were constant over the whole iceberg, the volume loss of the iceberg caused by both calving and basal melting was approximately 1.12 \(\times\) 10\({}^{5}\) tons. According to the Sentinel-1 observations, A68A was still located near the Bawden Ice Rise as of the end of November 2018, and it is rotating without significant movement (Figure 4). This is probably because the western part of the iceberg is not free to move past the ice rise. It is not easy to predict when A68A will drift away from the ice rise. However, as summer approaches, its rate of thinning will increase, which will make the ice rise less effective. A68A might also move further out to ocean when strong westerly winds blow, after which it will drift at a much faster rate, and its area and thickness will decrease more rapidly. Although we observed changes over a period of only 1.5 years, the initial evolution of iceberg A68A could be analyzed, characterized by drift that was limited by complex terrain and the surrounding sea ice. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**No.** & **Date** & **Freeboard (m)** &
\begin{tabular}{c} **No.** \\ **Intersections** \\ \end{tabular} & **Dates** & **Freeboard (m)** \\ \hline  
\hline \hline \end{tabular}
\end{table} 
Table 1: The freeboards of iceberg A68A at the intersections of different CryoSat-2 profiles shown in Figure 2.  
Figure 6: Monthly averaged snow depth on glaciated area around iceberg A68A predicted by the MERRA-2. N is the number of data points.