# Automatically Extracted Antarctic Coastline Using Remotely-Sensed Data: An Update
## 4 Results and Analysis
### Temporal Change of Coastline  
Figure 5 shows the maps of the Antarctic coastline from 2005, 2010, and 2017 data with detailed information. Based on visual interpretation of maps in the five sectors, the most significant changes occurred in the BAS, while the WS experienced modest changes. The extracted coastlines were used to precisely calculate the total length of the coastline and area of the Antarctic continent using ArcGIS software environment in the Stereographic_South_Pole projected coordinate system. The length of each sector and the total length of the Antarctic coast are presented in Table 5. The rate of change of the total length from 2005 to 2010 was +33.4 km/year, and from 2010 to 2017 was +55.9 km/year. The rate of cumulative change from 2005 to 2017 was 46.5 km/year. In 2005, the area of the Antarctic was \(1.3618\times 10^{7}\) km\({}^{2}\) and it decreased to \(1.3537\times 10^{7}\) km\({}^{2}\) in 2010 at a rate of \(-16\),137.46 km\({}^{2}\)/year. In 2017, the area increased to \(1.3657\times 10^{7}\) km\({}^{2}\), which is larger than the area of 2005. The rate of cumulative change from 2005 to 2017 is +1627.75 km\({}^{2}\)/year. As shown in Table 5, the length of the coastline reveals an overall increasing trend during 2005-2017, by 558.73 km in total. However, with some regional variability leading to the increase or decrease of length of the coastline in each sector, the largest change of length occurred in the BAS sector during 2005-2010 and the smallest occurred in the WS sector during 2010-2017. Only two sectors (WS and IO) showed a monotonic change of the length; increase in IO and decrease in WS. The other three sectors (BAS, RS, and WP) underwent increases and decreases. The East Antarctica encompasses the IO and WP sectors and the length of coastline in these two sectors increased to 6626.55 km and 6108.01 km in 2017, respectively. By analyzing the spatial change of ice shelves, we found that this increment is mainly due to the breakup of ice shelves (such as Amery Ice Shelf and Shackleton Ice Shelf) in these two sectors, which exposed more parts of ice sheet to the sea water and therefore increased the length of the outer border of the ice sheet. Detailed information is presented in Section 4.4. In order to confirm the length change of coastline, we also calculated the differences between MOA in 2004 and 2009, as well as the differences between our extraction results in 2005 and 2010 (Table 6). From the MOA coastlines, the total length decreased by 284.90 km. However, the length of the coastline in the BAS and IO sectors increased while the length in the WS, RS, and WP sectors decreased between 2004 and 2009. On the other hand, based on our results (between 2005 and 2010), the direction of the change of length (increase/decrease) is the same in each sector as in the MOA data, though our results consistently exhibit less changes than the MOA data. The increase of 167.25 km in the total Antarctic coastline length from 2005 to 2010 in our results disagrees with a reduction of 284.90 km from 2004 to 2009 from the MOA data. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & & & **Distance Distribution** & & & & & \\ \hline Distance (m) & a & b & c & d & e & f & g & h & i & Total \\
[0, 100] & 954 & 917 & 825 & 975 & 999 & 977 & 787 & 892 & 983 & 8309 \\
[100, 200] & 40 & 52 & 62 & 20 & 1 & 23 & 143 & 94 & 17 & 452 \\
[200, 300] & 6 & 25 & 49 & 5 & 0 & 0 & 41 & 14 & 0 & 140 \\
[300, 400] & 0 & 6 & 37 & 0 & 0 & 0 & 25 & 0 & 0 & 68 \\
[400, 600] & 0 & 0 & 27 & 0 & 0 & 0 & 4 & 0 & 0 & 31 \\ Mean (m) & 34.58 & 37.46 & 71.26 & 20.68 & 21.39 & 23.56 & 71.39 & 43.56 & 19.47 & 38.15 \\ St. Dev. (m) & 33.46 & 51.31 & 105.36 & 26.62 & 16.03 & 25.23 & 74.21 & 47.79 & 23.18 & 55.93 \\ Maximum (m) & 285.45 & 325.24 & 586.27 & 242.24 & 105.65 & 180.00 & 411.96 & 266.60 & 178.53 & 586.27 \\ Minimum (m) & 0 & 0 & 0 & 0 & 0 & 0.05 & 0.05 & 0.06 & 0.04 & 0.00 \\ \hline \hline \end{tabular}
\end{table}