# Automatically Extracted Antarctic Coastline Using Remotely-Sensed Data: An Update
## 4 Results and Analysis
### Changes of Coastline in the Regions Around Six Ice Shelves
The change of area of each ice shelf for each of the three periods is shown in Table 7. Area decline for individual ice shelves peaked between 2005 and 2010 at the WIS (4836 km\({}^{2}\)), while the least decline occurred between 2010 and 2017 at the MGT (67 km\({}^{2}\)). Conversely, the most significant increase of area for individual ice shelves happened in the RIS (3887 km\({}^{2}\)) during 2010-2017, and the smallest expansion happened in the AIS (698 km\({}^{2}\)) during 2005-2010. Different ice shelves retreat at different rates, triggered by minor or significant collapse as well as the speed of ice flow. The rate of retreat is modulated by the ice shelf configuration and conditions of mass balance [26]. Based on the breakup time and the calved area, we give a detailed analysis of some decreasing ice shelves from 2005 to 2017. One of the retreating ice shelves, the WIS, is located on the southwestern side of the Antarctic Peninsula. As shown in Table 6, it has been one of the fastest retreating ice shelves around Antarctica, especially from 2005 to 2010. It experienced a series of breakup events in 2008, revealing a number of different mechanisms for ice shelf disintegration [27]. In March 2008, it lost more than 400 km\({}^{2}\) in a sudden collapse, and a further breakup of 160 km\({}^{2}\) in the same area occurred in May during austral winter, as reported in [28]. In December 2008, new rifts developed, leading to a further breakup. As shown in Table 6, the area of WIS decreased by 4836 km\({}^{2}\) from 2005 to 2010, and by a further 1900 km\({}^{2}\) from 2010 to 2017. The ice shelf loss from 2005 to 2010 occurred at a much faster rate than that from 2010 to 2017. This is consistent with the series of breakup events in 2008, which accelerated the rate of loss. The total change rate is \(-\)561.33 km\({}^{2}\)/year. The large loss of area from the WIS supports a strong projection for a potential catastrophic loss of this ice shelf [28]. The MGT is a highly crevassed glacier in George V Land of East Antarctica. The ice velocity of the MGT typically exceeds 100 m/year [29]. The major calving event for the MGT occurred in February, 2010. An ice tongue about 78 km long and 36 km wide protruded 100 km out into the Southern Ocean, and broke away from the main body of the MGT to form a giant iceberg in February 2010 [30]. As shown in Figure 6, the coastline change between 2005 and 2010 captured this significant shape change. The length of the MGT decreased from 319.0 km in 2005 to 124.4 km in 2010, and then expanded slightly to 127.1 km in 2017. The area of the MGT decreased by 2582 km\({}^{2}\) from 2005 to 2010, and by 2649 km\({}^{2}\) from 2005 to 2017. The total change rate is \(-\)220.75 km\({}^{2}\)/year. In another study, ASAR WSM data acquired on 9 January 2010 was used to extract the area of the disintegrated iceberg, which is estimated to be 2572 km\({}^{2}\)[31]. This is in good agreement with the results presented here (2582 km\({}^{2}\)). The difference is likely due to the spatial resolution between the two data sets. The PIS is a large ice stream, and the fastest changing glacier in the West Antarctica [32]. Therefore, its stability is of paramount importance to sea level rise and the mass balance of the West Antarctic Ice Sheet [33]. According to Table 6, its area decreased by 852 km\({}^{2}\) from 2005 to 2010, then increased by 3174 km\({}^{2}\) from 2010 to 2017. However, the loss pattern varies between different parts of the PIS, even for the same period. For example, from 2005 to 2010, there was expansion of PIS in some parts totaling 857 km\({}^{2}\), and breakups in other parts with a total lost area of 1709 km\({}^{2}\). This local response pattern