Sentinel-1 SAR observations of Iceberg A-68 during July 2017–February 2019.
We have measured the area of iceberg A68A by delineating its boundary from the Sentinel-1 SAR images. The area of iceberg A68A was 5790 km2 when it was initially formed. Its area decreased by 35 km2 in mid-August 2017 due to calving, and then remained almost constant until mid-May 2018 when another large ice chunk calved and its area dramatically decreased to 5620 km2. There was little subsequent change in the area of the iceberg until September 2018.
It is worth noting that the increase in iceberg area was measured in September 2018. 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 km2. 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. Ice shelves experience similar longitudinal stretching and thinning when they lose buttressing forces due to unpinning or iceberg calving. The observation of A68A shows that the sea ice in the northwestern region of A68A started to disappear since July 2018.
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. This suggests that an increase in the area of the iceberg due to the longitudinal stretching after August 2018.
The area of A68A at the end of January 2019 was 5620 km2, which was only 3% less than at the time of its formation.
Change in area of iceberg A-68.
Detailed analysis of area change in iceberg A-68 can be found in the paper below.
Han, H.; Lee, S.; Kim, J.-I.; Kim, S.H.; Kim, H.-C. Changes in a Giant Iceberg Created from the Collapse of the Larsen C Ice Shelf, Antarctic Peninsula, Derived from Sentinel-1 and CryoSat-2 Data. Remote Sens. 2019, 11, 404.