# 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 area of Antarctica calculated from our 2005 results was \(1.3618\times 10^{7}\) km\({}^{2}\). Taking the temporal change (retreat and advance) of individual ice shelves around the Antarctica into consideration, the total Antarctic area underwent a decline from 2005 to 2010 at an average rate of \(1.62\times 10^{4}\) km\({}^{2}\)/year. In 2010, \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{5}{c}{**Length of Coastline (km)**} \\ \hline Length (km) & WS & BAS & RS & WP & IO & Total \\
2004 & 5183.83 & 13,020.01 & 7194.36 & 7416.21 & 7078.49 & 39,892.90 \\
2009 & 4750.71 & 13,868.27 & 6776.71 & 6833.04 & 7379.27 & 39,608.00 \\ Diff. 2009–2004 (MOA) & \(-\)433.12 & 848.26 & \(-\)417.65 & \(-\)583.17 & 300.78 & \(-\)284.90 \\
2005 & 4997.79 & 11,904.09 & 5900.87 & 5918.75 & 6392.62 & 35,114.13 \\
2010 & 4916.17 & 12,222.98 & 5804.99 & 5843.29 & 6493.97 & 35,281.38 \\ Diff. 2010–2005 (This study) & \(-\)81.63 & 318.88 & \(-\)95.89 & \(-\)75.47 & 101.35 & 167.25 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Deviation of coastline length in each sector (km) between MOA products (2004 and 2009) and our results (2005 and 2010). Figure 5: Coastline contours from the present algorithm for 2005, 2010, and 2017 (blue, green, and red, respectively). The deviation between the contours is very small (\(<\)10 km) in most locations, but the insets highlight the nine areas with highest deviation between 2005 and 2017. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{5}{c}{**Length of Coastline (km)**} \\ \hline  & **WS** & **BAS** & **RS** & **WP** & **IO** & **Total** \\ \hline
2005 & 4997.79 & 11,904.09 & 5900.87 & 5918.75 & 6392.62 & 35,114.13 \\
2010 & 4916.17 & 12,222.98 & 5804.99 & 5843.29 & 6493.97 & 35,281.38 \\
2017 & 4893.57 & 12,146.97 & 5897.76 & 6108.01 & 6626.55 & 35,672.86 \\ Diff. 2010–2005 & \(-\)81.63 & 318.88 & \(-\)95.89 & \(-\)75.47 & 101.35 & 167.25 \\ Diff. 2017–2010 & \(-\)22.59 & \(-\)76.01 & 92.77 & 264.72 & 132.58 & 391.47 \\ Diff. 2017–2005 & \(-\)104.22 & 242.88 & \(-\)3.11 & 189.26 & 233.93 & 558.73 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Change of coastline length in each sector (km) during 2005–2017. the measured area was \(1.3537\times 10^{7}\) km\({}^{2}\). However, by 2017 there was an increase in total area to \(1.3657\times 10^{7}\) km\({}^{2}\) at an average rate of \(1.71\times 10^{4}\) km\({}^{2}\)/year. As area change is mainly caused by the expansion or retreat of individual ice shelves, we investigated the evolution of six ice shelves. for each ice shelf, we calculated the largest area change and the highest rate of change. As shown in Figure 6, we monitored the area changes of Ronne Ice Shelf (RIS), Amery Ice Shelf (AIS), Mertz Glacier Tongue (MGT), Ross Ice Shelf (RSIS), Wilkins Ice Shelf (WIS), and Pine Island Shelf (PIS). Figure 6: Locations of six ice shelves along the Antarctic coast, which have undergone significant changes from 2005 to 2017. The green color indicates the geolocations of ice shelves around the Antarctica. The area changes of six ice shelves from 2005 to 2017 are shown below. The red shading indicates the area decreased and the blue shading indicates the area increased over this period. The contours are of the 2005 coastline from the present calculations. Data of 2005–2010 for MGT are up to end of March 2010 (i.e., after the calving of the giant iceberg C28). WIS, Wilkins Ice Shelf; PIS, Pine Island Shelf; AIS, Amery Ice Shelf; MGT, Mertz Glacier Tongue; RSIS, Ross Ice Shelf; and RIS, Ronne Ice Shelf. In Figure 6, the shape and areal change of shape of the six ice shelves between 2005-2010, 2010-2017, and 2005-2017 have been depicted by two different colors: Blue for increase of area and red for decrease. Over the 12 years from 2005, there was dominant increasing trend in the AIS, PIS, RSIS, and RIS shelves (with minor decrease in some sections). Conversely, from 2005 to 2017, the area of the WIS and MGT shelves decreased.